Summary of the searches for squarks and gluinos using √s = 8 TeV pp collisions with the ATLAS experiment at the LHC

JHEP10(2015)054 Published for SISSA by Springer Received:July 21, 2015 Accepted:September 9, 2015 Published:October 8, 2015 Summary of the searches for squarks and gluinos using √s= 8 TeV pp collisions with the ATLAS experiment at the LHC The ATLAS collaboration E-mail: [email protected] Abstract: A summary is presented of ATLAS searches for gluinos and firstand secondgeneration squarks in final states containing jets and missing transverse momentum, with or without leptons or b-jets, in the √s= 8 TeV data set collected at the Large Hadron Collider in 2012. This paper reports the results of new interpretations and statistical combinations of previously published analyses, as well as a new analysis. Since no significant excess of events over the Standard Model expectation is observed, the data are used to set limits in a variety of models. In all the considered simplified models that assume R-parity conservation, the limit on the gluino mass exceeds 1150 GeV at 95% confidence level, for an LSP mass smaller than 100 GeV. Furthermore, exclusion limits are set for left-handed squarks in a phenomenological MSSM model, a minimal Supergravity/Constrained MSSM model, R-parity-violation scenarios, a minimal gauge-mediated supersymmetry breaking model, a natural gauge mediation model, a non-universal Higgs mass model with gaugino mediation and a minimal model of universal extra dimensions. Keywords: Supersymmetry, Hadron-Hadron Scattering ArXiv ePrint: 1507.05525 Open Access, Copyright CERN, for the benefit of the ATLAS Collaboration. Article funded by SCOAP3. doi:10.1007/JHEP10(2015)054 JHEP10(2015)054 Contents 1 Introduction 1 2 SUSY models 3 2.1 Phenomenological models 4 2.1.1 A phenomenological MSSM model 4 2.1.2 Minimal Supergravity/Constrained MSSM and bilinear R-parity-violation models 5 2.1.3 Minimal gauge-mediated supersymmetry breaking model 5 2.1.4 Natural gauge mediation model 6 2.1.5 Non-universal Higgs mass models with gaugino mediation 6 2.1.6 Minimal Universal Extra Dimensions model 7 2.2 Simplified models 7 2.2.1 Direct decays of squarks and gluinos 7 2.2.2 One-step decays of squarks and gluinos 9 2.2.3 Two-step decays of squarks and gluinos 9 2.2.4 Gluino decays via third-generation squarks 11 3 The ATLAS detector and data sample 13 4 Monte Carlo simulated samples 14 5 Object reconstruction and identification 16 6 Analysis strategy 17 7 Experimental signatures 19 7.1 Final states with high-pTjets, missing transverse momentum and no electrons or muons 20 7.2 Final states with high-pTjets, missing transverse momentum and at least one electron or muon 24 7.3 Final states with high-pTjets, missing transverse momentum and at least one hadronically decaying tau lepton 27 7.4 Final states with many b-jets and missing transverse momentum 27 8 Systematic uncertainties 28 9 Results for the new signal regions 29 10 Combination strategy 30 – i – JHEP10(2015)054 11 Limits in SUSY models 32 11.1 Limits in phenomenological models 35 11.1.1 A phenomenological MSSM model 35 11.1.2 Minimal Supergravity/Constrained MSSM and bilinear R-parityviolation models 35 11.1.3 Minimal gauge-mediated supersymmetry breaking model 38 11.1.4 Natural gauge mediation model 38 11.1.5 Non-universal Higgs mass model with gaugino mediation 38 11.1.6 Minimal Universal Extra Dimension model 38 11.2 Limits in simplified models 40 11.2.1 Direct decays of squarks and gluinos 40 11.2.2 One-step decays of squarks and gluinos 42 11.2.3 Two-step decays of squarks and gluinos 46 11.2.4 Gluino decays via third-generation squarks 50 12 Conclusions 56 A Extension of the ˜g→t¯ t˜χ0 1simplified model to include decays with offshell top quarks 57 B Summary of selection criteria 58 C 0-lepton Razor analysis details 58 C.1 The Razor variables 60 C.2 Signal regions 65 C.3 Control and validation regions for SM background processes 67 The ATLAS collaboration 83 1 Introduction Supersymmetry (SUSY) [1–9] is a generalization of space-time symmetries that predicts new bosonic partners for the fermions and new fermionic partners for the bosons of the Standard Model (SM). If R-parity is conserved [10–13], SUSY particles (called sparticles) are produced in pairs and the lightest supersymmetric particle (LSP) is stable. The scalar partners of the leftand right-handed quarks, the squarks (˜qLand ˜qRwhich mix to form two mass eigenstates ˜q1and ˜q2, ordered by increasing mass), and the fermionic partners of the gluons, gluinos (˜g), could be produced in strong interaction processes at the Large Hadron Collider (LHC) [14] and decay via cascades ending with a stable LSP. The rest of the cascade would yield final states with multiple jets and possibly leptons arising from the decay of sleptons (˜ `), the superpartners of leptons, or W,Zand Higgs (h) bosons originating from the decays of charginos (˜χ±) or neutralinos (˜χ0), where the charginos and neutralinos – 1 – JHEP10(2015)054 are the mass eigenstates formed from the linear superpositions of the superpartners of the charged and neutral electroweak and Higgs bosons. In the Minimal Supersymmetric extension of the Standard Model (MSSM) [10–13,15], there are four charginos, ˜χ± 1and ˜χ± 2, and four neutralinos, ˜χ0 i(i= 1 to 4, ordered by increasing mass); unless stated otherwise, this is assumed in the following. In a large variety of models, the LSP is the lightest neutralino (˜χ0 1), which interacts weakly and is a possible candidate for dark matter [16]. Undetected ˜χ0 1LSPs would result in substantial missing transverse momentum (Emiss T, with magnitude Emiss T). Significant Emiss Tcan also arise in R-parity-violating (RPV) scenarios in which the LSP decays to final states containing neutrinos or in scenarios where neutrinos are present in the cascade decay chains of the produced SUSY particles. Significant mass splitting between the top squark (stop) mass eigenstates ˜ t1and ˜ t2is possible due to the large top Yukawa coupling.1Because of the SM weak isospin symmetry the mass of the left-handed bottom squark (sbottom, ˜ bL) is tied to the mass of the left-handed stop (˜ tL), and as a consequence the lightest sbottom (˜ b1) and stop (˜ t1) could be produced via the strong interaction with relatively large cross-sections at the LHC, either through direct pair production or in the decay of pair-produced gluinos. The ATLAS experiment [17] performed several searches for supersymmetric particles in Run 1. No statistically significant excesses of events compared to the predictions of the Standard Model were observed. Therefore the results were expressed as model-independent limits on the production cross-sections of new particles and limits in the parameter space of supersymmetric or simplified models. The large cross-sections of squark and gluino production in strong interaction processes offer sensitivity to a broad range of SUSY models. This paper provides a summary of the results from inclusive searches for gluinos and firstand second-generation squarks performed by ATLAS, using data from proton-proton (pp) collisions at a centre-of-mass energy of 8 TeV collected during Run 1 of the LHC. The results for direct production of third-generation squarks are reported elsewhere [18]. In addition to summarizing already published searches for squarks and gluinos, this paper presents new signal regions, new interpretations and statistical combinations of those searches, as well as an additional search using the Razor variable set [19], thus improving the sensitivity to supersymmetric models. In order to differentiate strongly produced SUSY events from the SM background, the searches typically require high Emiss Tdue to the presence of the LSP and possibly neutrinos, several high-pTjets and large deposited transverse energy. They are further classified according to the presence of leptons and b-jets. A first class of searches applies a veto on leptons [20–22], a second considers final states containing electrons and muons [23– 25], and a third requires tau leptons in the final state [26]. A fourth class of searches concentrates on final states containing multiple b-jets [27]. The paper is organized as follows. Section 2summarizes the SUSY signals in the strong production of gluinos and light-flavour squarks. Section 3describes the ATLAS experiment and the data sample used, and section 4the Monte Carlo (MC) simulation samples used for 1The masses of the ˜ t1and ˜ t2are the eigenvalues of the stop mass matrix. The stop mass matrix involves the top quark Yukawa coupling in the off-diagonal elements, which typically induces a large mass splitting. – 2 – JHEP10(2015)054 background and signal modelling. The physics object reconstruction and identification are presented in section 5. A description of the analysis strategy is given in section 6, and the experimental signatures are presented in section 7. A summary of systematic uncertainties is presented in section 8. Results obtained using the new signal regions with selections similar to those used in previous publications as well as the new analysis using the Razor variable set are reported in section 9. The strategy used for the combination of the results from different analyses is discussed in section 10. Limits in phenomenological and simplified models are presented in section 11. Section 12 is devoted to a summary and conclusions. 2 SUSY models Since no superpartners of any of the SM particles have been observed, SUSY, if realized in nature, must be a broken symmetry with a mechanism for breaking the symmetry taking place at a higher energy scale. It is difficult to construct a realistic model of spontaneously broken low-energy supersymmetry where the SUSY breaking arises solely as a consequence of the interactions of the particles of the MSSM [28–30]. Therefore, it is often assumed that the SUSY breaking originates in a “hidden” sector, and its effects are transmitted to the MSSM by some unknown mechanism. Various such mechanisms have been proposed, such as gravity-mediated SUSY breaking (SUGRA) [31–36], gauge-mediated SUSY breaking (GMSB) [37–42] and anomaly-mediated SUSY breaking (AMSB) [43,44]. As a result, these models consider only a small part of the parameter space of the more general MSSM. In such SUSY models, the particle spectrum is typically specified by fixing parameters at the high scale. In order to translate this set of parameters into physically meaningful quantities that describe physics near the electroweak scale, it is necessary to evolve them using their renormalization group equations. Another approach to constraining SUSY at the electroweak scale is to use simplified models [45,46] which are based on an effective Lagrangian that only describes a small set of kinematically accessible particles, interactions, production cross-sections and branching ratios. The simplest case corresponds to considering one specific SUSY production process with a fixed decay chain. Several classes of phenomenological and simplified models, as well as a minimal Universal Extra Dimensions (mUED) scenario [47,48], covering different combinations of physics objects in the final state, are considered in this paper. Unless otherwise specified, R-parity is assumed to be conserved and the lightest neutralino, ˜χ0 1, is taken to be the LSP. The phenomenological models include a scenario for the phenomenological MSSM (pMSSM) [49– 51], minimal Supergravity/Constrained MSSM (mSUGRA/CMSSM) [31–36], bilinear Rparity violation (bRPV) [52], a minimal gauge-mediated supersymmetry breaking model (mGMSB) [37–42], natural gauge mediation (nGM) [53], and a non-universal Higgs mass model with gaugino mediation (NUHMG) [54]. The simplified models presented here include the pair production of gluinos or firstand second-generation squarks with various hypotheses for their decay chains (direct, one-step or two-step decay), as well as gluino decays via real or virtual third-generation squarks. Direct decays are those where the considered SUSY particles decay directly into SM particles and the LSP, e.g., ˜q→q˜χ0 1. – 3 – JHEP10(2015)054 One-step (two-step) decays refer to the cases where the decays occur via one (two) intermediate on-shell SUSY particle(s), e.g., ˜q→q˜χ± 1→qW ˜χ0 1(˜q→q˜χ± 1→qW ˜χ0 2→qWZ ˜χ0 1). In gluino decays via third-generation squarks, gluinos undergo a one-step decay to a stop or sbottom such as ˜g→t˜ t→tt˜χ0 1, or decay directly to final states containing top or bottom quarks, for example ˜g→tt˜χ0 1if the stop is off-shell. In these simplified models, all supersymmetric particles which do not directly enter the production and decay chain are effectively decoupled, i.e. with masses set above a few TeV. The list of models considered is not comprehensive, and the searches presented here are sensitive to a larger class of decay patterns, mass combinations and hierarchies. 2.1 Phenomenological models 2.1.1 A phenomenological MSSM model In the pMSSM scenario, no specific theoretical assumption is introduced at the scale of Grand Unification Theories (GUT), or associated with a SUSY breaking mechanism. A short list of experimentally motivated considerations is used to reduce the 120 parameters of the MSSM to 19 real, weak-scale parameters: •R-parity is exactly conserved, •there are no new sources of CP violation beyond that already present in the quark mixing matrix, •Minimal Flavour Violation [55] is imposed at the electroweak scale, •the first two generations of squarks and sleptons with the same quantum numbers are mass-degenerate, and their Yukawa couplings are too small to affect sparticle production or precision observables. The remaining 19 independent parameters are: 10 squark and slepton masses, the gaugino masses (M1,M2,M3, associated with the U(1)Y, SU(2)L, SU(3)Cgauge groups, respectively), the higgsino mass parameter (µ), the ratio (tan β) of the vacuum expectation values of the two Higgs fields, the mass of the pseudoscalar Higgs boson (mA), and the trilinear couplings for the third generation (Ab,Atand Aτ) [49]. In the pMSSM model considered here only the left-handed squarks of the first two generations, the two lightest neutralinos ˜χ0 2and ˜χ0 1, and the lightest chargino ˜χ± 1are assumed to be within kinematic reach. Three gluino masses are considered, m˜g= 1.6, 2.2 and 3.0 TeV, while the masses of all other SUSY particles are kinematically decoupled with masses set to 5 TeV. The parameter tan βis set to 4. The model is further specified by four parameters: m˜qL,µ, and M1and M2, from which m˜χ0 1,m˜χ0 2and m˜χ± 1can be calculated. Either M1is fixed to 60 GeV and M2is varied independently, or M1is varied and M2is set to (M1+m˜qL)/2. Left-handed squarks can be pair produced only via t-channel gluino exchange. They can undergo a direct ˜qL→q˜χ0 1decay, or one-step decays: ˜qL→q+˜χ0 2→q+Z/h +˜χ0 1or ˜qL→q+˜χ± 1→q+W±+˜χ0 1. Here the lightest Higgs boson his assumed to have the SM – 4 – JHEP10(2015)054 ˜g ˜qL ˜qL ˜χ0 2 ˜χ± p p q ˜χ0 1 Z/h q ˜χ0 1 W± Figure 1. Example of a one-step decay topology of the left-handed squark in the phenomenological MSSM. decay branching fractions, and its mass is set to 125 GeV. The ˜χ± 1always decays to W± and ˜χ0 1(figure 1). The branching fraction to a left-handed squark via the one-step decay with ˜χ0 2(˜χ± 1) is ∼30% (65%). The branching fraction of the ˜χ0 2→h˜χ0 1decay is between 70% and 90% depending on m˜qL. 2.1.2 Minimal Supergravity/Constrained MSSM and bilinear R-parityviolation models The mSUGRA/CMSSM model is specified by five parameters: a universal scalar mass (m0), a universal gaugino mass (m1/2) , a universal trilinear scalar coupling (A0), all defined at the grand unification scale, tan β, and the sign of the higgsino mass parameter (µ). The dependence of the SUSY particle mass spectrum on these five parameters is such that all masses increase with increasing m1/2, while squark and slepton masses also depend on m0. In the mSUGRA/CMSSM model studied here the values tan β= 30, A0=−2m0and µ > 0 are chosen, such that the lightest scalar Higgs boson mass is approximately 125 GeV in a large fraction of the (m0,m1/2) parameter space studied. The bRPV scenario uses the same parameters as the mSUGRA/CMSSM model, but Rparity violation is allowed through the bilinear terms2iLiH2, whose coupling parameters are determined by a fit to neutrino oscillation data [56] under the tree-level dominance scenario [57]. In this scenario, the ˜χ0 1LSP decays promptly to Wµ,Wτ,Zντor hντ (where the W/Z/h boson can either be onor off-shell) with branching fractions which are weakly dependent on m0and m1/2and are typically on the order of 20–40%, 20–40%, 20–30% and 0–20%, respectively. 2.1.3 Minimal gauge-mediated supersymmetry breaking model In gauge-mediated SUSY breaking models, the LSP is a very light gravitino ( ˜ G). The mGMSB model is described by six parameters: the SUSY-breaking mass scale felt by the low-energy sector (Λ), the mass of the SUSY breaking messengers (Mmess), the number of SU(5) messenger fields (N5), tan β,µand the gravitino coupling scale factor (Cgrav) which determines the lifetime of the next-to-lightest SUSY particle (NLSP). Four parameters are fixed to the values previously used in refs. [58–60]: Mmess = 250 TeV, N5= 3, µ > 0 and Cgrav = 1. With this choice of parameters the production of squark and/or gluino pairs is 2In this notation, Liindicates a lepton SU(2)-doublet superfield, the Higgs SU(2)-doublet superfield H2 contains the Higgs field that couples to up-type quarks, and the iparameters have dimension of mass. – 5 – JHEP10(2015)054 Figure 2. Example of a gluino-pair production followed by the two possible decay chains within the nGM scenario. expected to dominate over other SUSY processes at the LHC. These SUSY particles decay into the NLSP, which subsequently decays to the LSP. The experimental signatures are largely determined by the nature of the NLSP: this can be either the lightest stau (˜τ), a selectron or a smuon (˜ `), the lightest neutralino (˜χ0 1), or a sneutrino (˜ν), leading to final states usually containing tau leptons, light leptons (`=e, µ), photons, or neutrinos, respectively. 2.1.4 Natural gauge mediation model In the nGM scenario, which assumes general gauge mediation [61,62], the phenomenology depends on the nature of the NLSP [63,64]. Various models assume that the mass hierarchies of squarks and sleptons are generated by the same physics responsible for breaking SUSY (for example refs. [65,66]). Typically in these models the third generation of squarks and sleptons is lighter than the other two, and together with the fact that sleptons only acquire small masses through hypercharge interactions in gauge mediation, this leads to a stau NLSP. In the model considered here, it is also assumed that the gluino is the only light coloured sparticle. All squark and slepton mass parameters are set to 2.5 TeV except the lightest stau mass, m˜τ, which is assumed to be smaller. The parameters M1and M2 are also set to 2.5 TeV, while all trilinear coupling terms are set to zero. The value of µis set to 400 GeV to ensure that strong production dominates in the parameter space studied. This leaves the gluino mass M3and the stau mass m˜τas the only free parameters. The chosen value of the µparameter sets the masses of the ˜χ± 1,˜χ0 1and ˜χ0 2, which are almost mass-degenerate. The only light sparticles in the model are the stau, a light gluino, higgsino-dominated charginos and neutralinos, and a very light gravitino LSP. Therefore, the strong production process allowed in this model is gluino-pair production followed by the three possible decay chains: ˜g→g˜χ0 1,2→g˜ττ →gττ ˜ G, ˜g→q¯q˜χ0 1,2→q¯q˜ττ →q¯qττ ˜ G and ˜g→qq ˜χ± 1→qqντ˜τ→qqνττ˜ G(figure 2), where the final-state quarks are almost exclusively top or bottom quarks. A range of signals with varying gluino and stau masses is studied. The lightest Higgs boson mass is specifically set to 125 GeV. 2.1.5 Non-universal Higgs mass models with gaugino mediation The NUHMG model is specified with parameters m0= 0, tan β= 10, µ > 0, m2 H2= 0, and A0chosen to maximize the mass of the lightest Higgs boson. The ranges of the two remaining free parameters of the model, m1/2and m2 H1, are chosen such that the NSLP is a tau sneutrino with properties satisfying Big Bang nucleosynthesis constraints [54]. The – 6 – JHEP10(2015)054 Diagram Production Parameters Mass relation Branching ratio Result figure 3(a) ˜q˜q m˜q, m˜χ0 1m˜q> m˜χ0 1BR(˜q→q˜χ0 1) = 1 figure 18 figure 3(b) ˜g˜q m˜g, m˜χ0 1m˜q= 0.96 m˜g> m˜χ0 1BR(˜q→q˜χ0 1) = 1 figure 20(a) BR(˜g→˜qq)=1 m˜q, m˜gm˜χ0 1= (0,395,695) GeV If m(˜g)> m(˜q): figure 20(b) BR(˜q→q˜χ0 1) = 1, BR(˜g→˜qq)=1 If m(˜q)> m(˜g): BR(˜g→qq ˜χ0 1) = 1, BR(˜q→˜gq) = 1 figure 3(c) ˜g˜g m˜g, m˜χ0 1m˜g> m˜χ0 1BR(˜g→qq ˜χ0 1) = 1 figure 19 figure 3(d) ˜g˜g m˜gm˜χ0 1= 0 BR(˜g→g˜χ0 1) = 1 figure 21(a) m˜χ0 1m˜g= 850 GeV figure 21(b) Table 1. Simplified models of squark and gluino production with direct decays to ˜χ0 1. For each model the diagram of the decay topology, the model parameters and assumptions about mass relations and branching ratios are listed. The last column refers to the experimental results presented in section 11.2. Horizontal dashed lines separate different mass or branching ratio assumptions within a model. squared mass terms of the two Higgs doublets, m2 H1and m2 H2, are defined at the unification scale. This model is characterized by significant cross-sections for ˜qand ˜gproduction. The gluino decays mainly to a light quark/squark pair q˜q(≈50%), but also to t˜ t(≈30%) or b˜ b(≈20%), while the squark multi-step decays typically involve charginos, neutralinos and/or sleptons. 2.1.6 Minimal Universal Extra Dimensions model The mUED model is the minimal extension of the SM with one additional universal spatial dimension. In this non-SUSY model, the Kaluza-Klein (KK) quark excitation’s decay chain to the lightest KK particle, the KK photon, gives a signature very similar to the supersymmetric decay chain of a squark to the lightest neutralino. The properties of the model depend on two parameters: the compactification radius Rcand the cut-off scale Λ. This cut-off is interpreted as the scale at which some new physics underlying the effective non-renormalizable UED framework becomes relevant. The Higgs boson mass is fixed to 125 GeV. 2.2 Simplified models The details of the simplified models considered are given below and summarized in tables 1–3. 2.2.1 Direct decays of squarks and gluinos Simplified models with direct decay of the pair-produced strongly interacting supersymmetric particles assume the production of gluino pairs with decoupled squarks, light-flavour – 7 – JHEP10(2015)054 triggers or combinations of triggers were used: Emiss Ttriggers, multi-jet triggers, combined Emiss T+jet, lepton+Emiss Tor lepton+jet+Emiss Ttriggers, single-lepton or dilepton triggers. Details of the trigger selections used in the published ATLAS searches included in this paper are not discussed here and can be found in the corresponding publications [20–27]. 4 Monte Carlo simulated samples The simulated event samples for the SM backgrounds are summarized in table 4, together with the choices of Monte Carlo generator, cross-section calculation, set of tunable parameters (tune) used for the underlying event and parton distribution functions (PDFs). The Powheg-Box+Pythia t¯ tsample is used for all analyses except for the analysis that requires high jet multiplicities (at least seven to at least ten jets) and large missing transverse momentum [22], which uses the Sherpa t¯ tsample. The Sherpa Drell-Yan samples have a lepton filter requiring p`1(`2) T>9 (5) GeV and |η`1(`2)|<2.8. This filter prevents its use in analyses requiring the presence of soft leptons in the final state. Such analyses instead use Alpgen samples with a lepton pTthreshold at 5 GeV. When using the baseline Powheg-Box+Pythia top quark pair production sample, in some of the analyses events are reweighted in bins of pT(t¯ t) to match the top quark pair differential cross-section measured in ATLAS data [73,74]. The exact usage of MC simulated samples together with the additional samples used to assess modelling uncertainties are detailed in the corresponding publication of each analysis. Signal samples for the pMSSM, mSUGRA, mGMSB, nGM and mUED models, as well as the samples for the simplified models of gluino-mediated top squark production (for m˜g−m˜χ0 1>2mt) are generated with Herwig++ 2.5.2 [106]. Samples for all the other simplified models are generated with up to one extra parton in the matrix element using Madgraph 5 1.3.33 interfaced to Pythia 6.426. The MLM matching scheme [107] is applied with a scale parameter that is set to a quarter of the mass of the lightest sparticle in the hard-scattering matrix element, with a maximum value of 500 GeV. The signal samples used for the bRPV and NUHMG models are generated with Pythia 6.426. For the gluino-off-shell-stop model in the region m˜g−m˜χ0 1<2mt, the production of gluino pairs is generated with Madgraph 5 1.3.33. The events are subsequently combined with separately generated gluino decays ˜g→f¯ f0f00 ¯ f000b¯ b˜χ0 1based on the full matrix element amplitude (also using Madgraph), preserving spin-dependent distributions. A summary of the studies related to event generation in this model can be found in appendix A. Potential effects of the gluino lifetime (displaced decays, hadronization), which are strongly model dependent, have been neglected. The ATLAS underlying-event tune AUET2B [80] is used for Madgraph 5 and Pythia 6 samples while the UE-EE-3C tune [108] is used for Herwig++ samples. The parton distribution functions from CTEQ6L1 [81] are used for all signal samples. For all except the mUED sample, the signal cross-sections are calculated to next-toleading order in the strong coupling constant, including the resummation of soft gluon emission at next-to-leading-logarithmic accuracy (NLO+NLL) [109–113]. In each case the nominal cross-section and its uncertainty are taken from an ensemble of cross-section – 14 – JHEP10(2015)054 Process Generator Cross-section Tune PDF set order in αs W(→`ν)+jets Sherpa 1.4.1 [75] NNLO [76]Sherpa default CT10 [77] Z/γ∗(→``)+jets Sherpa 1.4.1 NNLO [76]Sherpa default CT10 Drell-Yan Sherpa 1.4.1 NNLO [78]Sherpa default CT10 (8 < m`` <40 GeV) Z/γ∗(→``) + jets Alpgen 2.14 [79]NNLO [78] AUET2 [80] CTEQ6L1 [81] +Herwig 6.520 [82,83] (10 < m`` <60 GeV) + Jimmy [84] γ+jets Sherpa 1.4.1 LO Sherpa default CT10 t¯ tPowheg-Box 1.0 [85–87]NNLO+NNLL [88,89]Perugia2011C CT10 +Pythia 6.426 [90] [91,92] t¯ tSherpa 1.4.1 NNLO+NNLL Sherpa default CT10 Single top t-channel AcerMC 3.8 [93]NNLO+NNLL [94] AUET2B [95] CTEQ6L1 +Pythia 6.426 s-channel, Wt mc@nlo 4.03 [96,97]NNLO+NNLL [98,99] AUET2B CT10 +Herwig 6.520 t¯ t+W/Z boson Madgraph 5 1.3.28 [100]NLO [101–103] AUET2B CTEQ6L1 +Pythia 6.426 Dibosons WW,WZ,ZZ,Sherpa 1.4.1 NLO [104,105]Sherpa default CT10 Wγ and Zγ Table 4. The Standard Model background Monte Carlo simulation samples used in this paper. The generators, the order in αsof cross-section calculations used for yield normalization (leading order (LO), next-to-leading order (NLO), next-to-next-to-leading order (NNLO), next-to-next-toleading logarithm (NNLL)), tunes used for the underlying event and PDF sets are shown. For the γ+jets process the LO cross-section is taken directly from the MC generator. predictions using different PDF sets and factorization and renormalization scales, as described in ref. [114]. For the mUED model, the cross-section is taken at leading order from Herwig++. For the mSUGRA/CMSSM and NUHMG samples, Susy-Hit [115] and Sdecay 1.3b [116], interfaced to the Softsusy 3.1.6 spectrum generator [117], are used to calculate the sparticle mass spectra and decay tables, and to ensure consistent electroweak symmetry breaking. The decays of tau leptons are simulated directly in the generators in the case of event samples produced with Sherpa,Herwig++ 2.5.2 and Pythia 8.165, while in all other cases Tauola 2.4 [118,119] is used. Standard Model background samples are passed through either the full ATLAS detector simulation [120] based on Geant4 [121], or through a fast simulation using a parameterization of the performance of the ATLAS electromagnetic and hadronic calorimeters [122] and Geant4 elsewhere; the latter applies to W/Z/γ+jets samples with boson pT<280 GeV and Powheg-Box+Pythia t¯ tsamples. All SUSY signal samples are passed through the fast simulation, with the exception of the mSUGRA/CMSSM model samples which are produced with the Geant4 simulation. The fast simulation of SUSY signal – 15 – JHEP10(2015)054 events was validated against full Geant4 simulation for several signal models. Differing pile-up (multiple pp interactions in the same or neighbouring bunch-crossings) conditions as a function of the instantaneous luminosity are taken into account by overlaying simulated minimum-bias events (simulated using Pythia 8 with the MSTW2008LO PDF set [123] and the A2 tune [95]) onto the hard-scattering process and reweighting events according to the distribution of the mean number of interactions observed in data. 5 Object reconstruction and identification This paper summarizes different analyses which are combined to improve the sensitivity to a variety of possible topologies originating from the production and decay of squarks and gluinos. Although different event selections are used among these analyses, they share common definitions of the reconstructed objects. Analysis-specific exceptions to these definitions are detailed in the corresponding publication of each analysis. The reconstructed primary vertex of the event is required to be consistent with the beamspot envelope and to have at least five associated tracks with pT>400 MeV. When more than one such vertex is found, the vertex with the largest Pp2 Tof the associated tracks is chosen. Jet candidates are reconstructed using the anti-ktjet clustering algorithm [124,125] with a radius parameter of 0.4. The inputs to this algorithm are topological clusters [126, 127] of calorimeter cells seeded by those with energy significantly above the measured noise (topoclusters). The local cluster weighting (LCW) calibration method [127,128] is used to classify topoclusters as being either of electromagnetic or hadronic origin, and based on this classification it applies energy corrections derived from MC simulations and measurements in data. The jets are corrected for energy from pile-up using the method suggested in ref. [129]: a contribution equal to the product of the jet area and the median energy density of the event is subtracted from the jet energy [130]. Further corrections, referred to as the jet energy scale (JES) corrections, are derived from MC simulation and data and used to calibrate on average the energies of jets to the scale of their constituent particles [127,131]. Only jet candidates with pT>20 GeV and |η|<4.5 after all corrections are retained. To remove events with jets from detector noise and non-collision backgrounds, events are rejected if they include jets failing to satisfy the “loose” quality criteria described in ref. [127]. A neural-network-based algorithm [132] is used to identify jets containing a b-hadron (b-jets). It uses as inputs the output weights of several algorithms exploiting the impact parameter of the inner detector tracks, secondary vertex reconstruction and the topology of band c-hadron decays inside the jet. The algorithm used has an efficiency of 70% for tagging b-jets, determined with simulated t¯ tevents [133]. For this efficiency, the algorithm provides a rejection factor of approximately 140 for light-quark and gluon jets, and of approximately 5 for charm jets [134]. Candidate b-jets are required to have pT>40 GeV and |η|<2.5. Electrons are reconstructed from energy clusters in the electromagnetic calorimeter matched to tracks in the inner detector [135] and are required to have pT>10 GeV and |η|<2.47. The preselected electron candidates are required to pass a variant of the “medium” selection [135], which was modified in 2012 to reduce the impact of pile-up. – 16 – JHEP10(2015)054 Photon candidates, which in the analyses presented are used only for the measurement of the missing transverse momentum, are required to have pT>10 GeV and |η|<1.37 or 1.52 <|η|<2.47, to satisfy photon shower shape and electron rejection criteria [136], and to be isolated. Muon candidates are formed by combining information from the muon spectrometer and inner tracking detectors [137]. The preselected muon candidates are required to have pT>10 GeV and |η|<2.4 or 2.5, depending on the analysis. Reconstruction of hadronically decaying tau leptons starts from jets with pT> 10 GeV [138], and an ηand pT-dependent energy calibration to the tau energy scale for hadronic decays is applied [139]. Tau lepton candidates must have one or three associated track(s) with a charge sum of ±1, and satisfy pT>20 GeV and |η|<2.5. The “loose” and “medium” working points [138] are used and correspond to efficiencies of approximately 70% and 60%, independent of pT, with rejection factors of 10 and 20 against jets misidentified as tau candidates, respectively. After these selections, ambiguities between candidate jets with |η|<2.8 and leptons (electrons and muons) are resolved as follows. First, any such jet candidate lying within a distance ∆R=p(∆η)2+ (∆φ)2= 0.2 of a preselected electron is discarded; then any lepton candidate within a distance ∆R= 0.4 of any surviving jet candidate is discarded. In analyses requiring the presence of one lepton (electron or muon) in the final state, electrons are also required to be well separated from muon candidates with ∆R(e, µ)>0.01. If two preselected electrons are found within an angular distance ∆R(e, e)=0.05 of each other, only the electron with the higher pTis kept. Finally, in the analyses that require the presence of at least one or two opposite-sign leptons in the final state, any event containing a preselected electron in the transition region between the barrel and endcap electromagnetic calorimeters, 1.37 <|η|<1.52, is rejected. The measurement of the missing transverse momentum vector is based on the transverse momenta of all electron, photon, jet and muon candidates, and all calorimeter energy clusters not associated with such objects [140]. Fully calibrated electrons and photons with pT>10 GeV and jets with pT>20 GeV are used. Energy deposits not associated with these objects are also taken into account in the Emiss Tcalculation using an energy-flow algorithm that considers calorimeter energy deposits as well as ID tracks [141]. In the Emiss T measurement tau leptons are not distinguished from jets and it has been checked that this does not introduce a bias in any kinematic variables used in the analyses. Corrections derived from data control samples are applied to account for differences between data and simulation for the lepton trigger and reconstruction efficiencies, momentum/energy scale and resolution, and for the efficiency and mis-tag rate for tagging jets originating from b-quarks. 6 Analysis strategy A search for squarks and gluinos under various decay mode assumptions necessitates many different event selections targeting the wide range of experimental signatures. This section summarizes the common analysis strategy and statistical techniques that are employed in – 17 – JHEP10(2015)054 all searches included in this paper. Signal regions (SRs) are defined using the Monte Carlo simulation of the signal processes and the SM backgrounds, and are optimized to maximize the expected significance for each model considered. To estimate the SM backgrounds in a consistent and robust fashion, corresponding control regions (CRs) are defined for each of the signal regions. They are chosen to be non-overlapping with the SR selections in order to provide independent data samples enriched in particular background sources. The CR selections are optimized to have negligible SUSY signal contamination for the models under investigation, while minimizing as much as possible the systematic uncertainties arising from the extrapolation of the CR event yields to the expectations in the SR. Crosschecks of the background estimates are performed using several validation regions (VRs) selected with requirements such that these regions do not overlap with the CR and SR selections, again with a low probability of signal contamination. Several classes of profile likelihood fits that utilize the observed numbers of events in the various regions are employed in the analyses [142]. In some analyses, the shape of a final discriminating variable in the SRs is also used. A background-only fit is used to determine the compatibility of the observed event yield in each SR with the corresponding SM background expectation. This fit uses as constraints only the observed event yields or the shape of the discriminating variable distributions from the CRs associated with the SR, but not the SR itself. It is assumed that signal events from physics beyond the Standard Model (BSM) do not contribute to these yields. The numbers of observed and predicted events in each of these CRs are described using Poisson probability density functions. The systematic uncertainties and the MC statistical uncertainties on the expected values are included in the fit as nuisance parameters which are constrained by Gaussian distributions with widths corresponding to the sizes of the uncertainties considered and Poisson distributions, respectively. Correlations of a given nuisance parameter across the various regions, between the various backgrounds, and possibly the signal, are taken into account. The product of the various probability density functions forms the likelihood, which the fit maximizes by adjusting the inputs to the fit and the nuisance parameters. The inputs to the fit for each of the SRs are the number of events observed in each of the CRs, and the corresponding number of events expected from simulation, the extrapolation factors obtained from the simulation which relate the number of predicted SM background events in their associated CR to that predicted in the SR, and the number of events predicted by the simulation in each region for the other background processes. The background fit results are cross-checked in validation regions. The data in the validation regions are not used to constrain the fits; they are only used to compare the results of the fits to statistically independent observations. A model-independent fit is used to set upper limits on the number of BSM signal events in each SR. This fit proceeds in the same way as the background-only fit, except that the number of events observed in the SR is added as an input to the fit, and the BSM signal strength, constrained to be non-negative, is added as a free parameter. The observed and expected upper limits at 95% confidence level (CL) on the number of events from BSM phenomena for each signal region (S95 obs and S95 exp) are derived using the CLS prescription [143], neglecting any possible signal contamination in the control regions; an uncertainty on S95 exp is also computed from the ±1σuncertainty on the expectation. These – 18 – JHEP10(2015)054 limits, when normalized by the integrated luminosity of the data sample, may be interpreted as upper limits on the visible cross-section of BSM physics (hσi95 obs), where the visible crosssection is defined as the product of production cross-section, acceptance and efficiency. The model-independent fit is also used to compute the one-sided p-value (p0) of the backgroundonly hypothesis which quantifies the statistical significance of an excess. Model-dependent fits are used to set exclusion limits on the signal cross-sections for specific SUSY models. Such a fit proceeds in the same way as the model-independent fit, except that signal contamination in the CRs is taken into account as well as the yield in the signal region and, in some analyses, the model shape information. Correlations between signal and background systematic uncertainties are taken into account where appropriate. The systematic uncertainties on the signal expectations originating from detector effects and the theoretical uncertainties on the signal acceptance are included in the fit. The impact of the theoretical uncertainties on the signal cross-section is shown on the limit plots obtained (section 11). Numbers quoted in the text are evaluated from the observed exclusion limit based on the nominal signal cross-section minus its 1σtheoretical uncertainty. Background-only and model-independent fit results are presented in this paper only for new analyses or signal regions which are not available in earlier ATLAS publications. In the context of this publication, model-dependent exclusion fits for various simplified and phenomenological models are combined to include results from different searches for each model individually, in order to maximize the expected exclusion reach for each model. Where possible a full statistical combination of non-overlapping searches is applied, as explained in section 10. 7 Experimental signatures This paper summarizes and combines the results of several individual inclusive squark and gluino analyses previously published by the ATLAS experiment. Each of these searches uses one or more sets of signal regions targeting specific experimental signatures which originate from different squark or gluino decay modes and mass hierarchies. Several extensions to the previously published searches in the form of additional signal regions are also included, along with one new analysis channel. The full list of searches and their signal regions used in this paper is presented in table 5, together with the corresponding references. The details of the signal region selections for all searches listed in table 5can be found in appendix B. The details of the control and validation region selections, together with the strategies used for the estimation of the background processes, can be found in the corresponding publications. The new analysis and extended signal regions, which are also presented in table 5, are discussed in more detail in the subsequent subsections. Each signal region is referred to with an acronym, listed in table 5, indicating the analysis origin, so for example the ‘2jl’ region from the 0-lepton + 2–6 jets + Emiss Tanalysis is referred to as ‘0L 2jl’. The correspondence between the searches and the various models probed is provided in table 6and a summary of the limits in simplified models presented in the respective papers is given in table 7. The 0-lepton + 2–6 jets + Emiss Tand 1-lepton (soft+hard) + jets + – 19 – JHEP10(2015)054 Short analysis name and corresponding reference Acronym Signal region name Monojet [21] MONOJ M1, M2, M3 0-lepton + 2–6 jets + Emiss T[20] 0L 2jl, 2jm, 2jt, 2jW, 3j, 4jW, 4jl-, 4jl, 4jm, 4jt, 5j, 6jl, 6jm, 6jt, 6jt+ 0-lepton + 4–5 jets + Emiss T(?) 0L 4jt+, 5jt 0-lepton + 7–10 jets + Emiss T[22] MULTJ 8j50, 9j50, 10j50 (multi-jet+flavour stream), 7j80, 8j80, (multi-jet+flavour stream), 8j50, 9j50, 10j50 (multi-jet+MΣ Jstream) 0-lepton Razor (•) 0LRaz SRloose, SRtight 1-lepton (soft+hard) + jets + Emiss T[23] 1L(S,H) 3-jet/5-jet/3-jet inclusive (soft lepton), 3-jet/5-jet/6-jet (hard lepton) 1-lepton (hard) + 7 jets + Emiss T(?) 1L(H) 7-jet 2-leptons (soft) + jets + Emiss T[23] 2L(S) 2-jet (soft dimuon) 2-leptons (hard) + jets + Emiss T[23] 2LRaz ≤2-jet/3-jet 2-leptons off-Z [24] 2L-offZ SR-2j-bveto, SR-2j-btag, SR-4j-bveto, SR-4j-btag, SR-loose Same-sign dileptons or 3-leptons + jets + Emiss T[25] SS/3L SR3b, SR0b, SR1b, SR3Llow, SR3Lhigh Taus + jets + Emiss T[26] TAU 1τ(Loose, Tight), 2τ(Inclusive, GMSB, nGM, bRPV), τ+l(GMSB, nGM, bRPV, mSUGRA) 0/1-lepton + 3b-jets + Emiss T[27] 0/1L3B SR-0l-4j-A, SR-0l-4j-B, SR-0l-4j-C, SR-0l-7j-A , SR-0l-7j-B, SR-0l-7j-C, SR-1l-6j-A, SR-1l-6j-B, SR-1l-6j-C Table 5. List of analysis names referring to the experimental signatures addressed, with references to the appropriate publications; their acronyms; and all signal region names. The new analysis is denoted with (•), while the extended signal regions are denoted with (?). The details of the signal region selections for all searches listed in the table can be found in appendix B. Emiss Tstatistical combination, referred to as (0+1)-lepton combination, is used to probe the models for which both analyses have comparable sensitivity. 7.1 Final states with high-pTjets, missing transverse momentum and no electrons or muons Several searches to address final states without electrons or muons, containing high-pT jets and missing transverse momentum, have been performed in ATLAS. These searches are split according to the jet multiplicity into three categories: searches with at least one, two to six and seven to ten jets. They are presented in table 5as Monojet, 0-lepton + 2–6 jets + Emiss T(extended with two additional signal regions) and 0-lepton + 7–10 jets +Emiss T, respectively. Events with reconstructed electrons or muons are vetoed in these searches. A new search using kinematic variables, known as Razor variables [19], which provide longitudinal and transverse information about each event (listed as 0-lepton Razor in table 5), has also been performed and is included in the results presented in this paper. – 20 – JHEP10(2015)054 (0+1)-lepton MONOJ 0L MULTJ 0LRaz 1L(S,H) 1L(H) 2L(S) 2LRaz 2L-offZ SS/3L TAU 0/1L3B Model combination pMSSM X mSUGRA/CMSSM X X X X X X mSUGRA/CMSSM with bRPV X X X X X X mGMSB X X nGM X X X NUHMG X mUED X X X X X ˜q˜qproduction, ˜q→q˜χ0 1X X X ˜g˜gproduction, ˜g→qq ˜χ0 1X ˜q˜gproduction, ˜q→q˜χ0 1, ˜g→qq ˜χ0 1X ˜g˜gproduction, ˜g→g˜χ0 1X ˜q˜qproduction, ˜q→qW ˜χ0 1X ˜g˜gproduction, ˜g→qqW ˜χ0 1X X X ˜q˜qproduction, ˜q→q(``/`ν/νν)˜χ0 1X X X X ˜g˜gproduction, ˜g→qq(``/`ν/νν)˜χ0 1X X X X X X ˜q˜qproduction, ˜q→q(ττ/τν/νν)˜χ0 1X ˜g˜gproduction, ˜g→qq(ττ/τν/νν)˜χ0 1X ˜q˜qproduction, ˜q→qWZ ˜χ0 1X X ˜g˜gproduction, ˜g→qqWZ ˜χ0 1X X X ˜g˜gproduction, ˜g→t¯ t˜χ0 1(off-shell stop) X X X X ˜g˜gproduction, ˜g→˜ t1t,˜ t1→t˜χ0 1X X ˜g˜gproduction, ˜g→˜ t1t,˜ t1→b˜χ± 1X X ˜g˜gproduction, ˜g→˜ t1t,˜ t1→c˜χ0 1X X ˜g˜gproduction, ˜g→˜ t1t,˜ t1→bs X X ˜g˜gproduction, ˜g→tb˜χ0 1X ˜g˜gproduction, ˜g→b¯ b˜χ0 1(off-shell sbottom) X X ˜g˜gproduction, ˜g→˜ b1b,˜ b1→b˜χ0 1X Table 6. Searches used to probe each of the phenomenological models described in section 2.1 and simplified models described in section 2.2. – 21 – JHEP10(2015)054 Analysis acronym Process 95% CL limit Assumptions 0L [20] ˜g˜g, ˜g→g˜χ0 1, ˜g→qq ˜χ0 1m˜g>1330 GeV m˜χ0 1= 0 GeV ˜q˜q, ˜q→q˜χ0 1m˜q>850 GeV m˜χ0 1= 0 GeV, mass degenerate ˜q ˜q˜q, ˜q→q˜χ0 1m˜q>440 GeV m˜χ0 1= 0 GeV, single flavour ˜q ˜g˜g, ˜g→qqW ˜χ0 1m˜g>1100 GeV m˜χ0 1= 0 GeV ˜q˜q, ˜q→qW ˜χ0 1m˜q>700 GeV m˜χ0 1= 0 GeV ˜g˜g, ˜g→˜ t1t,˜ t1→c˜χ0 1m˜g>1100 GeV m˜ t1= 400 GeV, m˜χ0 1=m˜ t1−20 GeV MULTJ [22] ˜g˜g, ˜g→t¯ t˜χ0 1m˜g>1100 GeV m˜χ0 1<350 GeV ˜g˜g, ˜g→qqW ˜χ0 1m˜g>1000 GeV m˜χ0 1<200 GeV ˜g˜g, ˜g→qqW Z ˜χ0 1m˜g>1100 GeV m˜χ0 1<300 GeV 1L(S,H), ˜g˜g, ˜g→qqW ˜χ0 1m˜g>1200 GeV x= ∆m(χ± 1,˜χ0 1)/∆m(˜g, ˜χ0 1)=1/2, m˜χ0 1= 60 GeV 2L(S), ˜q˜q, ˜q→qW ˜χ0 1m˜q>700 GeV x= ∆m(χ± 1,˜χ0 1)/∆m(˜q, ˜χ0 1) = 1/2, m˜χ0 1<200 GeV 2LRaz [23] ˜g˜g, ˜g→qq`ν ˜χ0 1m˜g>1320 GeV m˜χ0 1= 100 GeV ˜q˜q, ˜q→q`ν ˜χ0 1m˜q>840 GeV m˜χ0 1= 40 GeV ˜g˜g, ˜g→˜ t1t,˜ t1→c˜χ0 1m˜g>1200 GeV m˜ t1= 200 GeV, m˜χ0 1=m˜ t1−20 GeV ˜g˜g, ˜g→qqW Z ˜χ0 1m˜g>1140 GeV m˜χ0 1<200 GeV 2L-offZ [24] ˜g˜g, ˜g→qq(``/`ν/νν)˜χ0 1m˜g>1170 GeV m˜χ0 1= 50 GeV ˜q˜q, ˜q→q(``/`ν/νν)˜χ0 1m˜g>780 GeV m˜χ0 1= 50 GeV SS/3L [25] ˜g˜g, ˜g→t¯ t˜χ0 1m˜g>950 GeV ˜g˜g, ˜g→˜ t1t,˜ t1→sb m˜g>850 GeV ˜g˜g, ˜g→qqW ˜χ0 1m˜g>860 GeV m˜χ0 1<400 GeV ˜g˜g, ˜g→qqW Z ˜χ0 1m˜g>1040 GeV m˜χ0 1<520 GeV ˜q˜q, ˜q→qW Z ˜χ0 1m˜q>670 GeV m˜χ0 1<300 GeV ˜g˜g, ˜g→qq(``/`ν/νν)˜χ0 1m˜g>1200 GeV m˜χ0 1<660 GeV ˜q˜q, ˜q→q(``/`ν/νν)˜χ0 1m˜g>780 GeV m˜χ0 1<460 GeV TAU [26] ˜g˜g, ˜g→qq(ττ/τν/νν)˜χ0 1m˜g>1090 GeV nGM model, ˜τis NLSP 0/1L3B [27] ˜g˜g, ˜g→t¯ t˜χ0 1m˜g>1340 GeV m˜χ0 1<400 GeV Table 7. The 95% CL exclusion limits obtained in published ATLAS searches listed in table 5for the indicated processes and related assumptions. A dedicated search for ˜c˜cpair production [144] excludes charm squark masses up to 490 GeV for m˜χ0 1<200 GeV (95% CL). The monojet (MONOJ) analysis, originally designed to search for direct production of top squarks (˜ t), each decaying into a charm quark and a neutralino ( ˜χ0 1) [21], targets final states characterized by at least one high-pTjet (with pT>150 GeV and |η|<2.8) and large missing transverse momentum. Signal regions have been specifically optimized for models with a very small mass difference (≤20 GeV) between the top squark and the neutralino. The event selection makes use of the presence of initial-state radiation (ISR) jets to identify signal events, and the squark-pair system is boosted, leading to large Emiss T. Three signal regions which are based only on different selection criteria related to the jet pTand Emiss Thave been used to bring additional sensitivity to models with very small mass differences between SUSY particles. These signal regions do not impose any criteria to specifically select events originating from the top squarks and as such they can be used to select events in which squarks are produced in pairs and decay directly via ˜q→q˜χ0 1with a small ˜q–˜χ0 1mass difference. – 22 – JHEP10(2015)054 Signal region name 0L 4jt+ 0L 5jt Number of jets ≥4 5 Emiss T/mNj eff ≥0.30 0.15 mincl eff [GeV] ≥2200 1900 Table 8. Additional 0L signal regions optimized to increase the sensitivity of the search for lefthanded squarks within the pMSSM. The 0-lepton + 2–6 jets + Emiss T(0L) search [20] targets final states where each initial squark yields one jet and Emiss Tand each initial gluino yields two jets and Emiss T. Additional decay modes can include the production of charginos via ˜q→q˜χ± 1and ˜g→q¯q˜χ± 1, where the subsequent decay of these charginos to a Wboson and ˜χ0 1can lead to final states with larger jet multiplicity. The search strategy is optimized for various squark and gluino masses, for a range of models. Fifteen inclusive signal regions are characterized by increasing the minimum jet-multiplicity from two to six (for jets with pT>40 GeV and |η|<2.8), and are based on different selection criteria on the effective mass mincl eff , defined as the scalar sum of Emiss Tand the pTof the jets; the ratio of Emiss T/mNj eff , where mNj eff is meff constructed from only the leading Njjets; and the minimum azimuthal angle between jets and Emiss T. Two of the signal regions are designed to improve sensitivity to models with the cascade ˜qor ˜g decay via ˜χ± 1to Wand ˜χ0 1, in cases where the ˜χ± 1is nearly degenerate in mass with the ˜q or ˜g. These signal regions place additional requirements on the invariant masses m(Wcand) of the candidate Wbosons reconstructed from a single high-mass jet, or from a pair of jets. Following the same analysis strategy, two additional signal regions are included in this paper, which are optimized to increase the sensitivity of the 0L search for left-handed squarks within the pMSSM model described in section 2. These two signal regions target the two one-step decays of ˜qL, ˜qL→q˜χ±→qW ±˜χ0 1and ˜qL→q˜χ0 2→q(Z/h)˜χ0 1and are obtained by optimizing on two variables, Emiss T/mNj eff and mincl eff , in the channels with at least four or at least five jets. All other selection criteria are exactly the same as for the corresponding channels described in the original publication. The two new signal regions, named 4jt+ and 5jt following the naming convention from ref. [20], are summarized in table 8. A high jet multiplicity is expected from the decays of gluino pairs via a top squark, or via squarks involving the production of ˜χ±and ˜χ0 2in their decay chain, and is the main topology targeted by the 0-lepton + 7–10 jets + Emiss T(MULTJ) analysis [22]. The sensitivity of the search is enhanced by the subdivision into two categories. First, in the multi-jet+flavour stream, an event classification based on the number of jets (pT>50 GeV and |η|<2) and number of b-jets (pT>40 GeV and |η|<2.5) gives enhanced sensitivity to models which predict either more or fewer b-jets than the SM background. In the second category (multi-jet+MΣ Jstream), which targets models with large numbers of objects in the final state, the jets reconstructed with the jet radius parameter R= 0.4 are reclustered into large composite jets using the anti-ktalgorithm with R= 1.0. The event variable MΣ J is computed as the sum of the masses of the composite jets: MΣ J≡PjmR=1.0 j, where the composite jets satisfy pR=1.0 T>100 GeV and |ηR=1.0|<1.5. In total, nineteen signal regions – 23 – JHEP10(2015)054 additional signal regions for the 0L analysis. Table 12 displays the equivalent results for the two signal regions of the new 0LRaz analysis, and those for the additional region of the 1L(H) analysis are shown in table 13. All results are determined using the backgroundonly fit. The pre-fit background expectations are also shown in the tables, for comparison purposes. The prediction of the W/Z+jets background processes by the simulation prior to the fit is found to be overestimated in the phase space of interest and is consequently decreased by the fit. This is consistent with the behaviour observed in previous publications probing a similar phase space [20]. In all new signal regions presented in this paper the number of events observed is consistent with the post-fit SM expectations. The observed and expected upper limits at 95% CL on the number of BSM events (S95 obs and S95 exp), together with the upper limits on the visible cross-section of BSM physics (hσi95 obs) and the p-value for the background-only hypothesis, are also presented in the tables 11–13. The confidence levels are calculated with the CLSprescription [143]. For an observed number of events lower than expected, the p-value is truncated at 0.5. 10 Combination strategy Statistical combinations of the analyses, as listed in table 6, are performed in order to increase the exclusion reach in several SUSY models in which at least two analyses designed to be statistically independent in their signal and control region definitions provide comparable sensitivities. The conditions are satisfied for a combination of the 1L(S,H) and 0L searches. These analyses search for squarks and gluinos in final states containing jets and missing transverse momentum, either with at least one isolated electron or muon (1L(S,H)), or applying an explicit veto on events containing electrons or muons (0L). They are statistically independent due to a veto on any electron or muon with pT>10 GeV in the case of the 0L search, and requiring an electron or muon with pT(e/µ)>25 GeV (hard single-lepton) or pT(e/µ)>7/6 GeV (soft single-lepton) in the case of the 1L(S,H) search. It has been checked explicitly that the difference in lepton-pTthresholds in the 0L and soft single-lepton analyses does not result in events selected by both analyses. The control regions used to estimate contributions from W+jets and top backgrounds used by the 0L search have been slightly modified with respect to the original regions [20] such that events which are selected by the respective control regions in the 1L(S,H) analyses are vetoed. This modification ensures complete statistical independence of the three analyses, which can therefore be combined where relevant. The statistical combination is obtained from the individual likelihoods of the analyses involved. In the case of the 0L analysis the likelihood for the signal region that provides the best expected CLSvalue for the signal model considered, and its corresponding control regions, is chosen. The choice of this signal region can vary as a function of sparticle masses. For the 1L(S,H) analyses, all the available signal regions are statistically independent and hence a single likelihood that describes all of them serves as input for the combination procedure. Some of the systematic uncertainties can be correlated when building the combined likelihood. The correlated uncertainties in the combination procedure are the luminosity uncertainty, the uncertainty on the SUSY cross-sections, – 30 – JHEP10(2015)054 Signal region 0L 4jt+ 0L 5jt Expected background events before the fit t¯ t(+ V) + single top 0.37 2.9 W+jets 0.75 4.5 Z/γ∗+jets 2.1 4.8 Diboson −0.32 Fitted background events t¯ t(+ V) + single top 0.39 ±0.32 3.0±1.8 W+jets 0.55 ±0.33 2.0±1.5 Z/γ∗+jets 0.10+0.17 −0.10 1.7±0.9 Diboson −0.32 ±0.16 Multi-jet −0.58+0.73 −0.58 Total background 1.04 ±0.43 7.6±1.9 Observed events 0 8 hσi95 obs[fb] 0.17 0.40 S95 obs 3.4 8.2 S95 exp 3.5+1.3 −0.57.5+3.1 −2.0 p(s= 0) 0.50 0.35 Table 11. The background expectations before the fit and the background fit results for the new 0L signal regions. Negligible contributions are marked as ‘−’. The uncertainties shown combine the statistical uncertainties on the event samples with the systematic uncertainties. Also shown are the 95% CL upper limits on the visible cross-section (hσi95 obs) and on the number of signal events (S95 obs). The expected upper limit on the number of signal events (S95 exp) is calculated from the expected number of background events after fit, with uncertainties indicating the ±1σdeviations from the expectation. The p-value (p(s= 0)) is also presented in the table. b-tagging uncertainties, and the jet energy resolution and Emiss T-related uncertainties. Other systematic uncertainties, such as theoretical uncertainties, are not correlated, e.g. the uncertainties due to different Monte Carlo generators used in the analyses considered. The jet energy scale uncertainty, which is subdominant, is not correlated due to the use of different prescriptions in the analyses involved. The combination of the analyses was carefully validated by ensuring that the combined likelihood did not lead to artificial correlations between fit parameters or major changes in post-fit values of nuisance parameters with respect to the individual analysis fits discussed in refs. [20,23]. Figures 9and 10 show the result of the combination of the 1L(S,H) and 0L analyses for both squark-pair and gluino-pair production for the one-step decays of squarks and gluinos described in section 2.2.2. The limits obtained improve the results of the separate analyses, reaching higher ˜χ0 1mass and approximately 50 GeV higher squark or gluino mass – 31 – JHEP10(2015)054 Signal region 0LRaz SRloose 0LRaz SRtight Expected background events before the fit t¯ t138 1.8 Single top 23.9 1.6 t¯ t+V4.7 0.2 W+jets 794 49 Z+jets 762 58 Diboson 112 10 Fitted background events t¯ t117 ±22 1.7±0.5 Single top 24.9±2.6 1.8±0.3 t¯ t+V3.7±1.0 0.20 ±0.07 W+jets 454 ±40 27.0±3.0 Z+jets 618 ±76 45 ±6 Diboson 94 ±49 10 ±5 Multi-jet 14 ±13 2.4±2.4 Total background 1326 ±84 88 ±8 Observed events 1322 74 hσi95 obs[fb] 6.17 0.83 S95 obs 125.3 16.8 S95 exp 135.1+64.8 −42.224.3+9.9 −6.9 p(s= 0) 0.49 0.50 Table 12. The background expectations before the fit and the background fit results for the 0LRaz analysis. Negligible contributions are marked as ‘−’. The uncertainties shown combine the statistical uncertainties on the event samples with the systematic uncertainties. Also shown are the 95% CL upper limits on the visible cross-section (hσi95 obs) and on the number of signal events (S95 obs). The expected upper limit on the number of signal events (S95 exp) is calculated from the expected number of background events after fit, with uncertainties indicating the ±1σdeviations from the expectation. The p-value (p(s= 0)) is also presented in the table. for massless neutralinos. The combined limit also approaches the diagonal m(˜χ0 1) = m(˜q, ˜g) closer than the individual analyses. 11 Limits in SUSY models This section summarizes the exclusion limits placed in the various phenomenological and simplified models described in section 2(there is a one-to-one correspondence between the subsections of section 2and this section). The analyses and corresponding signal – 32 – JHEP10(2015)054 Signal region 1L(H) 7-jet Expected background events before the fit t¯ t81 Single top 3.4 t¯ t+V2.8 W+jets 11 Z+jets 0.59 Diboson 2.7 Fitted background events t¯ t56 ±27 Single top 3.4±2.2 t¯ t+V2.8±1.0 W+jets 8 ±4 Z+jets 0.59 ±0.17 Diboson 2.7±1.5 Multi-jet 2.4±2.3 Total background 76 ±27 Observed events 68 hσi95 obs[fb] 2.06 S95 obs 41.9 S95 exp 45+12 −10 p(s= 0) 0.5 Table 13. The background expectations before the fit and the background fit results for the new 1L(H) signal region. An overview of the selection criteria for the signal, validation and control regions used in this analysis is given in table 10. The uncertainties shown combine the statistical uncertainties on the event samples with the systematic uncertainties. Also shown are the 95% CL upper limits on the visible cross-section (hσi95 obs) and on the number of signal events (S95 obs). The expected upper limit on the number of signal events (S95 exp) is calculated from the expected number of background events after fit, with uncertainties indicating the ±1σdeviations from the expectation. The p-value (p(s= 0)) is also presented in the table. – 33 – JHEP10(2015)054 ) [GeV]q ~ m( 300 400 500 600 700 800 900 1000 ) [GeV] 1 0 χ ∼ m( 100 200 300 400 500 600 700 800 900 1000 , x=1/2 0 1 χ ∼ 0 1 χ ∼ qqWW→ q ~ -q ~ ATLAS -1 =8 TeV, 20 fbs 0L + 1L combination ) 1 0 χ ∼ ) < m( q ~ m( ) theory SUSY σ1 ±Observed limit ( ) exp σ1 ±Expected limit ( 1-lepton alone 0-lepton alone All limits at 95% CL Figure 9. Observed and expected exclusion limits for simplified models of squark-pair production with one-step decays via the ˜χ± 1into a Wboson and the ˜χ0 1. The mass of the ˜χ± 1is chosen to be between the m˜qand m˜χ0 1and is determined by x= (m˜χ± 1−m˜χ0 1)/(m˜q−m˜χ0 1) = 1/2. Squark and neutralino masses in the area below the observed limit are excluded at 95% CL. The yellow band includes all experimental uncertainties; the red dotted lines indicate the theory uncertainty on the cross-section. The individual limits from the 0L and the 1L(S,H) analyses are overlaid in green and magenta, respectively. ) [GeV]g ~ m( 400 600 800 1000 1200 1400 ) [GeV] 1 0 χ ∼ m( 100 200 300 400 500 600 700 800 900 1000 , x=1/2 0 1 χ ∼ 0 1 χ ∼ qqqqWW→ g ~ -g ~ ATLAS -1 =8 TeV, 20 fbs 0L + 1L combination ) 1 0 χ ∼ ) < m( g ~ m( ) theory SUSY σ1 ±Observed limit ( ) exp σ1 ±Expected limit ( 1-lepton alone 0-lepton alone All limits at 95% CL Figure 10. Observed and expected exclusion limits for simplified models of gluino-pair production with decays via the ˜χ± 1into a Wboson and the ˜χ0 1. The mass of the ˜χ± 1is chosen to be between the m˜gand m˜χ0 1and is determined by x= (m˜χ± 1−m˜χ0 1)/(m˜g−m˜χ0 1)=1/2. Gluino and neutralino masses in the area below the observed limit are excluded at 95% CL. The yellow band includes all experimental uncertainties; the red dotted lines indicate the theory uncertainty on the crosssection. The individual limits from the 0L and the 1L(S,H) analyses are overlaid in green and magenta, respectively. – 34 – JHEP10(2015)054 regions are referred to by their acronyms defined in table 5. An overview of all searches used to probe the phenomenological models described in section 2.1 and the simplified models described in section 2.2 is given in table 6. A limit obtained from the statistical combination of 1L(S,H) and 0L analyses is presented for models for which both analyses have comparable sensitivity and is used as a single contribution to the final combined limit. The final combined observed and expected 95% CL exclusion limits are obtained from the signal regions belonging to the contributing analyses that provide the best expected CLS value. Expected limits from the individual analyses which contribute to the final combined limits are also presented for comparison. The ±1σSUSY theory lines around the observed limits in the figures are obtained by changing the signal cross-section by one standard deviation (±1σ), as described in section 8. All mass limits on supersymmetric particles quoted later in this section are derived from the −1σSUSY theory line. 11.1 Limits in phenomenological models This section summarizes the exclusion limits placed on the phenomenological models described in section 2.1. 11.1.1 A phenomenological MSSM model The measurements are interpreted in a phenomenological MSSM model, which possesses three parameters: m˜qL,M1and M2, where M1and M2are the masses associated with the bino and wino fields. For the exclusion limits in figure 11 either M1is fixed to 60 GeV and M2is varied independently, or M1is varied and M2is set to M2= (M1+m˜qL)/2. The figures show limits in the (m˜q, m˜χ± 1,˜χ0 2) and (m˜q, m˜χ0 1) planes, for various gluino masses, as obtained from the 0L analysis with the additional 0L 4jt+ and 0L 5jt signal regions optimized specifically for this model. As expected, for the relatively light gluino mass of 1600 GeV, a large range of squark masses (up to 1500 GeV) and ˜χ± 1/˜χ0 2masses (up to 1150 GeV) can be excluded. The exclusion reach decreases with increasing gluino mass. 11.1.2 Minimal Supergravity/Constrained MSSM and bilinear R-parityviolation models The exclusion limits in the (m0,m1/2) mSUGRA/CMSSM plane with tan β= 30, A0=−2m0and µ > 0 are shown in figure 12. In the parameter space region with m0values smaller than about 1800 GeV the best sensitivity is obtained with the (0+1)- lepton combination, which slightly improves the individual limit obtained by the 0L 3jt signal region from the 0L search. For high m0values, final states with four top quarks dominate, and consequently the best sensitivity is provided by the 0/1L3B search. This search excludes gluino masses smaller than 1280 GeV. The exclusion limits for the RPV model, which uses the same parameters as the mSUGRA/CMSSM but allows for bilinear R-parity-violating terms in the superpotential resulting in an unstable LSP, are shown in the (m0,m1/2) plane in figure 13. The best sensitivity is provided by the TAU and the SS/3L searches. For m0values smaller than approximately 750 GeV the sensitivity is dominated by the TAU search which excludes m1/2 values up to 680 GeV using the combination of all final states considered in the search. At – 35 – JHEP10(2015)054 [GeV] q ~ m 600 800 1000 1200 1400 1600 1800 [GeV] , 2 0 χ ∼ , 1 ± χ ∼ m 200 400 600 800 1000 1200 1400 1600 Production L q ~ L q ~ Phenomenological MSSM: -1 = 8 TeV, L = 20.3 fbs miss T 0-lepton + 2-6 jets + E = 60 GeV 1 M = 1.6 TeV g ~ m ATLAS ) exp σ1 ±Expected limit ( ) theory SUSY σ1 ±Observed limit ( (a) [GeV] q ~ m 600 800 1000 1200 1400 1600 [GeV] 0 1 χ ∼ m 0 100 200 300 400 500 600 700 800 Production L q ~ L q ~ Phenomenological MSSM: -1 = 8 TeV, L = 20.3 fbs miss T 0-lepton + 2-6 jets + E )/2 L q ~ + m 1 = (M 2 M = 1.6 TeV g ~ m ATLAS ) exp σ1 ±Expected limit ( ) theory SUSY σ1 ±Observed limit ( (b) [GeV] q ~ m 600 800 1000 1200 1400 1600 1800 [GeV] , 2 0 χ ∼ , 1 ± χ ∼ m 200 400 600 800 1000 1200 1400 1600 Production L q ~ L q ~ Phenomenological MSSM: -1 = 8 TeV, L = 20.3 fbs miss T 0-lepton + 2-6 jets + E = 60 GeV 1 M = 2.2 TeV g ~ m ATLAS ) exp σ1 ±Expected limit ( ) theory SUSY σ1 ±Observed limit ( (c) [GeV] q ~ m 600 800 1000 1200 1400 1600 [GeV] 0 1 χ ∼ m 0 100 200 300 400 500 600 700 800 Production L q ~ L q ~ Phenomenological MSSM: -1 = 8 TeV, L = 20.3 fbs miss T 0-lepton + 2-6 jets + E )/2 L q ~ + m 1 = (M 2 M = 2.2 TeV g ~ m ATLAS ) exp σ1 ±Expected limit ( ) theory SUSY σ1 ±Observed limit ( (d) [GeV] q ~ m 600 800 1000 1200 1400 1600 1800 [GeV] , 2 0 χ ∼ , 1 ± χ ∼ m 200 400 600 800 1000 1200 1400 1600 Production L q ~ L q ~ Phenomenological MSSM: -1 = 8 TeV, L = 20.3 fbs miss T 0-lepton + 2-6 jets + E = 60 GeV 1 M = 3.0 TeV g ~ m ATLAS ) exp σ1 ±Expected limit ( ) theory SUSY σ1 ±Observed limit ( (e) [GeV] q ~ m 600 800 1000 1200 1400 1600 [GeV] 0 1 χ ∼ m 0 100 200 300 400 500 600 700 800 Production L q ~ L q ~ Phenomenological MSSM: -1 = 8 TeV, L = 20.3 fbs miss T 0-lepton + 2-6 jets + E )/2 L q ~ + m 1 = (M 2 M = 3.0 TeV g ~ m ATLAS ) exp σ1 ±Expected limit ( ) theory SUSY σ1 ±Observed limit ( (f) Figure 11. 95% CL exclusion limits in the pMSSM considered in the search for left-handed squarks, with mass parameters M1and M2, which are associated with the bino and wino masses, respectively. The limits are obtained from the 0L analysis with the additional 0L 4jt+ and 0L 5jt signal regions optimized specifically for this model. The parameter set considered here has either (a, c, e) M1= 60 GeV and M2varying or (b, d, f) M2= (M1+m˜qL)/2 and M1varying. For each M1,M2combination three gluino masses are considered, m˜g= 1600,2200,3000 GeV. Gluino pair production is not included. The solid red line and the dashed blue line show respectively the combined observed and expected 95% CL exclusion limits. – 36 – JHEP10(2015)054 [GeV] 0 m 0 1000 2000 3000 4000 5000 6000 [GeV] 1/2 m 300 400 500 600 700 800 900 1000 (2400 GeV) q ~ (1600 GeV) q ~ (1000 GeV) g ~ (1400 GeV) g ~ h (122 GeV) h (124 GeV) h (126 GeV) > 0µ, 0 = -2m 0 ) = 30, AβMSUGRA/CMSSM: tan( ATLAS -1 = 8 TeV, L = 20 fbs τ ∼ LSP All limits at 95% CL. ) exp σ1 ±Expected ( ) theory SUSY σ1 ±Observed ( Expected Expected (0+1)-lepton combination miss T 0/1-lepton + 3 b-jets + E Figure 12. Exclusion limits in the (m0,m1/2) plane for the mSUGRA/CMSSM model. The solid red line and the dashed red line show respectively the combined observed and expected 95% CL exclusion limits. Expected limits from the individual analyses which contribute to the final combined limits are also shown for comparison. [GeV] 0 m 400 600 800 1000 1200 1400 1600 1800 2000 2200 [GeV] 1/2 m 200 400 600 800 1000 1200 (2200 GeV) q ~ (1800 GeV) q ~ (1000 GeV) g ~ (1800 GeV) g ~ > 0µ, 0 = -2m 0 = 30, AβbRPV-MSUGRA: tan ATLAS -1 = 8 TeV, L = 20 fbs All limits at 95% CL. ) exp σ1 ±Expected ( ) theory SUSY σ1 ±Observed ( Expected Expected miss T Taus + jets + E miss T SS/3L + jets + E Figure 13. Exclusion limits in the (m0,m1/2) plane for the bRPV model. The solid red line and the dashed red line show respectively the combined observed and expected 95% CL exclusion limits. Expected limits from the individual analyses which contribute to the final combined limits are also shown for comparison. high m0values the best sensitivity is provided by the SS/3L SR3b signal region from the SS/3L search, which excludes values of m1/2between 200 GeV and 490 GeV. For m0values below 2200 GeV, signal models with m1/2<200 GeV are not considered because the lepton acceptance is significantly reduced due to the increased LSP lifetime in that region. – 37 – JHEP10(2015)054 [TeV]Λ 50 60 70 80 90 100 110 β tan 10 20 30 40 50 60 = 1 grav > 0, Cµ = 3, 5 = 250 TeV, N mess mGMSB: M ATLAS -1 = 8 TeV, L = 20 fbs (1200 GeV)g ~ (1400 GeV)g ~ (1600 GeV)g ~ (1800 GeV)g ~ (2000 GeV)g ~ (2200 GeV)g ~ (2400 GeV)g ~ Theory excl. All limits at 95% CL. ) exp σ1 ±Expected ( ) theory SUSY σ1 ±Observed ( miss T SS/3L + jets + E Figure 14. Exclusion limits in the (Λ, tan β) plane for the mGMSB model. The solid red line and the dashed red line show respectively the combined observed and expected 95% CL exclusion limits. The region of small Λ and large tan βjust above the exclusion limit is excluded theoretically since it leads to tachyonic states. 11.1.3 Minimal gauge-mediated supersymmetry breaking model The observed and expected limits for the mGMSB scenario are shown in figure 14, in the plane defined by the SUSY breaking scale Λ and the tan βvalue. The region of small Λ and large tan βjust above the exclusion limit is excluded theoretically since it leads to tachyonic states. The SS/3L search provides the best sensitivity for this model and excludes values of Λ up to about 75 TeV. 11.1.4 Natural gauge mediation model The limits obtained for the nGM scenario are shown in figure 15 in the (m˜τ,m˜g) plane. The best limits are obtained by the 1L(S,H) and TAU searches, resulting in an exclusion of gluino masses below approximately 1100 GeV independent of the ˜τmass. 11.1.5 Non-universal Higgs mass model with gaugino mediation The exclusion limits in the context of a NUHMG model with parameters m0= 0, tan β = 10, µ > 0 and m2 H2= 0 are shown in the (m2 H1,m1/2) plane in figure 16. They are provided by the (0+1)-lepton combination. A band in the (m2 H1,m1/2) plane can be excluded, extending up to the ranges 2000 ×103GeV2< m2 H1<5400 ×103GeV2and 450 GeV < m1/2<620 GeV. 11.1.6 Minimal Universal Extra Dimension model Finally, the limits obtained for the mUED scenario are shown in figure 17 in the (1/Rc, ΛRc) plane. The 2L(S), 2LRaz and SS/3L searches provide competitive sensitivities for this model in which the mass spectrum is naturally degenerate and the decay chain of the – 38 – JHEP10(2015)054 [GeV] τ ∼ m 120 140 160 180 200 220 240 260 280 300 320 [GeV] g ~ m 400 500 600 700 800 900 1000 1100 1200 1300 1400 = 400 GeVµ), g ~ ) >> m(q ~ is NLSP, m(τ ∼ Natural Gauge Mediation Model, ATLAS -1 = 8 TeV, L = 20 fbs All limits at 95% CL. ) exp σ1 ±Expected ( ) theory SUSY σ1 ±Observed ( Expected Expected miss T 1-lepton (soft+hard) + jets + E miss T Tau + jets + E Figure 15. Exclusion limits in the (m˜τ,m˜g) plane for the nGM model. The solid red line and the dashed red line show respectively the combined observed and expected 95% CL exclusion limits. Expected limits from the individual analyses which contribute to the final combined limits are also shown for comparison. ] 2 [GeV 2 1 H m 2000 2500 3000 3500 4000 4500 5000 5500 6000 6500 7000 3 10× [GeV] 1/2 m 450 500 550 600 650 700 750 800 850 900 <0 0 >0, Aµ=10, β=0, tan 2 2 H =0, m 0 NLSP, m τ ν ∼ NUHM model with gaugino mediation and (1000 GeV)q ~ (1200 GeV)q ~ (1400 GeV)q ~ (1600 GeV)q ~ (1200 GeV)g ~ (1400 GeV)g ~ (1600 GeV)g ~ (1800 GeV)g ~ ATLAS -1 = 8 TeV, L = 20 fbs tachyon 1 τ ∼ LSP 0 1 χ ∼ All limits at 95% CL. ) exp σ1 ±Expected ( ) theory SUSY σ1 ±Observed ( (0+1)-lepton combination Figure 16. Exclusion limits in the (m2 H1,m1/2) plane for the NUHMG model. The solid red line and the dashed red line show respectively the combined observed and expected 95% CL exclusion limits. – 39 – JHEP10(2015)054 The results of the searches for gluino-pair production with a one-step decay via an intermediate chargino into qqW ˜χ0 1are shown in figure 23. Figure 23(a) shows the limit for a chargino mass fixed at m˜χ± 1= (m˜g+m˜χ0 1)/2, where the (0+1)-lepton combination provides the best sensitivity. For a neutralino mass of 100 GeV, gluino masses below 1270 GeV are excluded. Neutralino masses are excluded below 480 GeV for gluino masses up to 1200 GeV. Fixing the neutralino mass at 60 GeV (figure 23(b)), one obtains limits on the variable x= ∆m(˜χ± 1,˜χ0 1)/∆m(˜g, ˜χ0 1). Nearly the whole range 0 <x<1 is excluded for gluino masses below 1100 GeV. 11.2.3 Two-step decays of squarks and gluinos This section presents the limits in simplified models with two-step decays of squarks and gluinos described in section 2.2.3. Exclusion limits for squark-pair production with a subsequent two-step squark decay via a chargino and neutralino to qWZ ˜χ0 1are shown in figure 24. Results are obtained with two searches, the 0L and the SS/3L searches. The 0L search is mainly sensitive in the low-mass region of 240 GeV < m˜q<300 GeV, whereas the SS/3L search is most sensitive for squark masses between 450 and 650 GeV, where ˜χ0 1masses below 250 GeV are excluded. Exclusion limits in a simplified model of gluino-pair production with a subsequent twostep gluino decay via a chargino and neutralino to qqWZ ˜χ0 1are shown in figure 25. The results are obtained with the (0+1)-lepton combination, MULTJ, and the SS/3L searches. The (0+1)-lepton combination provides the highest ˜χ0 1mass limits at low gluino masses. For the intermediate range around m˜g≈900 GeV the SS/3L search is most sensitive, while for high gluino masses the best limits are obtained by the MULTJ analysis. For gluino masses below 500 GeV, ˜χ0 1masses are excluded up to the kinematic limit indicated by the diagonal line, and in the range 500 GeV < m˜g<1000 GeV lower limits on ˜χ0 1masses are set around 400 GeV. For m˜χ0 1= 100 GeV, gluino masses are excluded below 1150 GeV. Another example of a simplified model with squark-pair production is considered in figure 26, where squarks decay through a two-step process via a chargino or neutralino and a slepton into final states with jets, leptons and missing transverse momentum. Figure 26 shows the exclusion limits in the (m˜q, m˜χ0 1) plane, for which the best results are obtained by the 2LRaz and the SS/3L searches. Masses for the lightest neutralino can be excluded nearly up to the kinematic limit (diagonal line) for squark masses below 630 GeV. For ˜χ0 1 masses below 100 GeV, squark masses can be excluded below 820 GeV. Similarly, a simplified model with gluino-pair production is considered in figure 27, where gluinos decay through a two-step process via a chargino or neutralino and sleptons into final states with jets, leptons and missing transverse momentum. Figure 27 shows the exclusion limits in the (m˜g, m˜χ0 1) plane. The combined 1L(S,H)+2LRaz searches based on the best expected CLSvalue and the SS/3L search provide the best sensitivities for this model. Masses for the lightest neutralino can be excluded nearly up to the kinematic limit (diagonal line) for gluino masses below 600 GeV. For ˜χ0 1masses below 100 GeV, gluino masses can be excluded below 1320 GeV. A further example of a simplified model of squark-pair production and decay through a two-step process is shown in figure 28, where squarks decay via charginos or neutralinos – 46 – JHEP10(2015)054 [GeV] g ~ m 400 600 800 1000 1200 1400 [GeV] 1 0 χ ∼ m 100 200 300 400 500 600 700 800 900 1000 1100 Decay forbidden ))/2 0 1 χ ∼ )+ m(g ~ ) = (m( ± 1 χ ∼ ; m( 0 1 χ ∼ qqW→g ~ production, g ~ g ~ ATLAS -1 = 8 TeV, L = 20 fbs All limits at 95% CL. ) exp σ1 ±Expected ( ) theory SUSY σ1 ±Observed ( (0+1)-lepton combination (a) [GeV] g ~ m 200 400 600 800 1000 1200 1400 1600 ) 0 1 χ ∼ ,g ~ m(∆)/ 0 1 χ ∼ , ± 1 χ ∼ m(∆x = 0 0.2 0.4 0.6 0.8 1 1.2 1.4 Decay forbidden ) = 60 GeV 0 1 χ ∼ ; m( 0 1 χ ∼ qqW→g ~ production, g ~ g ~ ATLAS -1 = 8 TeV, L = 20 fbs All limits at 95% CL. ) exp σ1 ±Expected ( ) theory SUSY σ1 ±Observed ( (0+1)-lepton combination (b) Figure 23. Exclusion limits for gluino-pair production with a one-step decay via an intermediate chargino into qqW ˜χ0 1. Figure (a) shows the limits in the (m˜g, m˜χ0 1) plane for a chargino mass fixed at m˜χ± 1= (m˜g+m˜χ0 1)/2. Alternatively (b), the neutralino mass is fixed at 60 GeV and exclusion limits are given for x= ∆m(˜χ± 1,˜χ0 1)/∆m(˜g, ˜χ0 1) as function of the gluino mass. The solid red line and the dashed red line show respectively the combined observed and expected 95% CL exclusion limits. – 47 – JHEP10(2015)054 [GeV] q ~ m 200 300 400 500 600 700 800 900 [GeV] 1 0 χ ∼ m 100 200 300 400 500 600 700 800 900 1000 Decay forbidden ))/2 1 0 χ ∼ ) + m( 1 ± χ ∼ ) = (m( 2 0 χ ∼ ))/2; m( 1 0 χ ∼ ) + m(q ~ ) = (m( 1 ± χ ∼ ; m( 1 0 χ ∼ qWZ→ q ~ production, q ~ q ~ ATLAS -1 = 8 TeV, L = 20 fbs All limits at 95% CL. ) exp σ1 ±Expected ( ) theory SUSY σ1 ±Observed ( Expected Expected miss T 0-lepton + 2-6 jets + E miss T SS/3L + jets + E Figure 24. Exclusion limits in the (m˜q, m˜χ0 1) plane for a simplified model of firstand secondgeneration squark-pair production with two-step decay into qqWWZZ ˜χ0 1˜χ0 1and missing transverse momentum. The solid red line and the dashed red line show respectively the combined observed and expected 95% CL exclusion limits. Expected limits from the individual analyses which contribute to the final combined limits are also shown for comparison. [GeV] g ~ m 400 600 800 1000 1200 1400 [GeV] 1 0 χ ∼ m 100 200 300 400 500 600 700 800 900 1000 Decay forbidden ))/2 1 0 χ ∼ ) + m( 1 ± χ ∼ ) = (m( 2 0 χ ∼ ))/2; m( 1 0 χ ∼ ) + m(g ~ ) = (m( 1 ± χ ∼ ; m( 1 0 χ ∼ qqWZ→ g ~ production, g ~ g ~ miss T (1/2)-lepton + jets + E = 7 TeVs -1 ATLAS, L = 4.7 fb ATLAS -1 = 8 TeV, L = 20 fbs All limits at 95% CL. ) exp σ1 ±Expected ( ) theory SUSY σ1 ±Observed ( Expected Expected Expected (0+1)-lepton combination miss T 0-lepton + 7-10 jets + E miss T SS/3L + jets + E Figure 25. Exclusion limits in the (m˜g, m˜χ0 1) plane for a simplified model of gluino-pair production with two-step decay into qqq0q0W W ZZ ˜χ0 1˜χ0 1and missing transverse momentum. The solid red line and the dashed red line show respectively the combined observed and expected 95% CL exclusion limits. Expected limits from the individual analyses which contribute to the final combined limits are also shown for comparison. A previous result from ATLAS [60] using 7 TeV proton-proton collisions is represented by the shaded (grey) area. – 48 – JHEP10(2015)054 [GeV] q ~ m 300 400 500 600 700 800 900 1000 1100 1200 [GeV] 1 0 χ ∼ m 100 200 300 400 500 600 700 800 Decay forbidden ))/2 1 0 χ ∼ ) + m( 2 0 χ ∼ , 1 ± χ ∼ ) = (m(ν ∼ ,l ~ )/2, m( 1 0 χ ∼ ) + m(q ~ ) = (m( 2 0 χ ∼ , 1 ± χ ∼ ; m( 1 0 χ ∼ /ll)ν q(l→ q ~ production, q ~ q ~ ATLAS -1 = 8 TeV, L = 20 fbs All limits at 95% CL. ) exp σ1 ±Expected ( ) theory SUSY σ1 ±Observed ( Expected Expected 2-lepton Razor miss T SS/3L + jets + E Figure 26. Exclusion limits in the (m˜q, m˜χ0 1) plane for a simplified model of squark-pair production with two-step decay into jets, leptons and missing transverse momentum via sleptons. The solid red line and the dashed red line show respectively the combined observed and expected 95% CL exclusion limits. Expected limits from the individual analyses which contribute to the final combined limits are also shown for comparison. [GeV] g ~ m 400 600 800 1000 1200 1400 1600 [GeV] 1 0 χ ∼ m 200 400 600 800 1000 1200 1400 1600 Decay forbidden ))/2 1 0 χ ∼ ) + m( 2 0 χ ∼ , 1 ± χ ∼ ) = (m(ν ∼ ,l ~ )/2, m( 1 0 χ ∼ ) + m(g ~ ) = (m( 2 0 χ ∼ , 1 ± χ ∼ ; m( 1 0 χ ∼ /ll)ν qq(l→ g ~ production, g ~ g ~ ATLAS -1 = 8 TeV, L = 20 fbs All limits at 95% CL. ) exp σ1 ±Expected ( ) theory SUSY σ1 ±Observed ( Expected Expected 1-lep. + 2-lep. Razor comb. miss T SS/3L + jets + E Figure 27. Exclusion limits in the (m˜g, m˜χ0 1) plane for a simplified model of gluino-pair production with two-step decay into jets, leptons and missing transverse momentum via sleptons. The solid red line and the dashed red line show respectively the combined observed and expected 95% CL exclusion limits. Expected limits from the individual analyses which contribute to the final combined limits are also shown for comparison. – 49 – JHEP10(2015)054 [GeV] q ~ m 300 400 500 600 700 800 900 1000 [GeV] 0 1 χ ∼ m 50 100 150 200 250 300 350 400 450 500 )/20 1 χ ∼ +m 0 2 χ ∼ = (m τ ν ∼ = m τ ∼ )/2, m0 1 χ ∼ +m q ~ = (m± 1 χ ∼ = m 0 2 χ ∼ , m 0 1 χ ∼ νν / q 0 1 χ ∼ ττ / q 0 1 χ ∼ ντ q→ q ~ production, q ~ q ~ 0 1 χ ∼ < m q ~ m ATLAS -1 = 8 TeV, L = 20.3 fbs miss T Taus + jets + E Combined Exclusion ) theory SUSY σ1 ±Observed limit ( ) exp σ1 ±Expected limit ( All Limits at 95% CL Figure 28. 95% CL exclusion limits in the (m˜q, m˜χ0 1) plane for a simplified model of squarkpair production with two-step decay via staus. The solid red line and the dashed black line show respectively the observed and expected 95% CL exclusion limits. and staus. The exclusion limits obtained by the TAU search are indicated in the (m˜q, m˜χ0 1) plane. For light ˜χ0 1masses around 50 GeV, squark masses below 850 GeV are excluded; and for light squark masses of 300 GeV, neutralino masses below 170 GeV are excluded. A simplified model of gluino-pair production and decay through a two-step process is shown in figure 29, where gluinos decay via charginos or neutralinos and staus. The exclusion limits obtained by the TAU search are indicated in the (m˜g, m˜χ0 1) plane. For light ˜χ0 1masses around 100 GeV, gluino masses below 1220 GeV are excluded; and for light gluino masses of 400 GeV, neutralino masses below 280 GeV are excluded. 11.2.4 Gluino decays via third-generation squarks This section summarizes the exclusion limits placed in the various simplified models with gluino decays via third-generation squarks described in section 2.2.4. The combined expected and observed exclusion limits for the gluino-off-shell-stop models are given in the (m˜g, m˜χ0 1) plane in figure 30, where a 100% branching ratio for the decay ˜g→t¯ t(∗)˜χ0 1via an off-shell stop is assumed. In the regions where m˜g<2mt+m˜χ0 1, the three-body decays (˜g→t¯ t˜χ0 1) are replaced by the more complex multi-body decays proceeding via off-shell top quarks and Wbosons, as discussed in appendix A. The best sensitivity for this model is provided by the 0/1L3B and the SS/3L searches. In the regions of parameter space where the mass difference between the gluino and the lightest neutralino is small, the most sensitive search is the SS/3L, and the sensitivity is dominated by the SS/3L SR3b signal region. In the regions with a large mass splitting between the gluino and the neutralino, where hard jets and large Emiss Tare expected, the sensitivity is dominated by the 0/1L3B SR-0l-7j signal regions from the 0/1L3B search. For these models, gluino masses below about 1310 GeV are excluded for m˜χ0 1<400 GeV. – 50 – JHEP10(2015)054 [GeV] g ~ m 400 500 600 700 800 900 1000 1100 1200 1300 1400 [GeV] 0 1 χ ∼ m 100 200 300 400 500 600 700 800 900 )/20 1 χ ∼ +m 0 2 χ ∼ = (m τ ν ∼ = m τ ∼ )/2, m0 1 χ ∼ +m g ~ = (m± 1 χ ∼ = m 0 2 χ ∼ , m 0 1 χ ∼ νν / qq 0 1 χ ∼ ττ / qq 0 1 χ ∼ ντ qq→ g ~ production, g ~ g ~ 0 1 χ ∼ < m g ~ m ATLAS -1 = 8 TeV, L = 20.3 fbs miss T Taus + jets + E Combined Exclusion ) theory SUSY σ1 ±Observed limit ( ) exp σ1 ±Expected limit ( All Limits at 95% CL Figure 29. 95% CL exclusion limits in the (m˜g, m˜χ0 1) plane for a simplified model of gluinopair production with two-step decay via staus. The solid red line and the dashed black line show respectively the observed and expected 95% CL exclusion limits. [GeV] g ~ m 500 600 700 800 900 1000 1100 1200 1300 1400 1500 [GeV] 1 0 χ ∼ m 200 400 600 800 1000 1200 Off-shell region On-shell region ), including up to five-body decaysg ~ ) >> m(t ~ ; m( 0 1 χ ∼ tt(*)→g ~ production, g ~ g ~ ATLAS -1 = 8 TeV, L = 20 fbs All limits at 95% CL. ) exp σ1 ±Expected ( ) theory SUSY σ1 ±Observed ( Expected Expected miss T SS/3L + jets + E miss T 0/1-lepton + 3 b-jets + E Figure 30. Exclusion limits in the (m˜g, m˜χ0 1) plane for the gluino-off-shell-stop simplified models in which the pair-produced gluinos decay via an off-shell stop, as ˜g→t¯ t˜χ0 1. In the region below the grey dashed line labelled “On-shell region”, m˜g>2mt+m˜χ0 1and thus gluinos decay to two real top quarks. In the “Off-shell region”, m˜g<2mt+m˜χ0 1and the decays of the gluino involve an off-shell top quark. Only four-body (˜g→tW b˜χ0 1) and five-body (˜g→WbW b˜χ0 1) decays are considered because for higher multiplicities the gluinos do not decay promptly. The solid red line and the dashed red line show respectively the combined observed and expected 95% CL exclusion limits. Expected limits from the individual analyses which contribute to the final combined limits are also shown for comparison. – 51 – JHEP10(2015)054 [GeV] g ~ m 700 800 900 1000 1100 1200 1300 1400 1500 [GeV] 1 t ~ m 400 600 800 1000 1200 1400 1600 Decay forbidden = 8 TeVs, -1 , L = 20 fb 1 t ~ 1 t ~ ATLAS ) = 60 GeV 1 0 χ ∼ ; m( 0 1 χ ∼ t→ 1 t ~ , 1 t ~ t→g ~ production, g ~ g ~ ATLAS -1 = 8 TeV, L = 20 fbs All limits at 95% CL. ) exp σ1 ±Expected ( ) theory SUSY σ1 ±Observed ( miss T 0/1-lepton + 3 b-jets + E Figure 31. Exclusion limits in the (m˜g, m˜ t1) plane for the gluino-stop simplified models in which the top squarks are produced in the decay of pair-produced gluinos and decay via ˜ t1→t˜χ0 1. The neutralino mass is set to 60 GeV. The solid red line and the dashed red line show respectively the combined observed and expected 95% CL exclusion limits. Also shown for reference is the limit from the ATLAS search for direct stop-pair production [18]. The exclusion limits for the gluino-stop simplified models are given in the (m˜g, m˜ t1) plane in figure 31. The ˜ t1is assumed to be the lightest squark while all other squarks are heavier than the gluino, and m˜g> m˜ t1+mtsuch that the branching ratio is 100% for ˜g→˜ t1tdecays, and the top squark decays as ˜ t1→t˜χ0 1. The 0/1L3B search provides the best sensitivity in these models, excluding gluino masses below 1220 GeV for stop masses up to 1000 GeV. Limits for the same class of simplified models, but assuming the ˜ t1→b˜χ± 1 decay of the top squark, are also given in the (m˜g, m˜ t1) plane, and summarized in figure 32. The mass of the lightest neutralino in these models is set to 60 GeV, and the mass of the chargino is assumed to be twice the mass of the neutralino. The chargino decays into a neutralino and a virtual Wboson. The strongest limits are provided by the 0/1L3B search. Compared to the models where the top squark decays via ˜ t1→t˜χ0 1, presented in figure 31, the sensitivity in these models is lower for most of the parameter space where soft Emiss Tand jets are expected from the chargino decay ˜χ± 1→W∗˜χ0 1. Gluino masses below 1180 GeV are excluded for stop masses up to 1000 GeV in these models. Another possible decay of the top squark, ˜ t1→c˜χ0 1, is considered within the same class of simplified models, with the mass difference between the ˜ t1and the lightest neutralino fixed to 20 GeV. The (0+1)-lepton combination provides the best sensitivity in these models. The 1L(S,H) search is complementary to the 0L search in that the expected limit for the single-lepton search is able to cover higher top squark masses at intermediate gluino masses (e.g. 80 GeV higher at m˜g= 900 GeV). The resulting exclusion limit is presented in the (m˜g, m˜ t1) plane in figure 33, and reaches gluino masses up to 1260 GeV. – 52 – JHEP10(2015)054 [GeV] g ~ m 700 800 900 1000 1100 1200 1300 1400 [GeV] 1 t ~ m 200 400 600 800 1000 1200 1400 1600 Decay forbidden = 8 TeVs, -1 , L= 20 fb 1 t ~ 1 t ~ ATLAS ) = 60 GeV 0 1 χ ∼ ), m( 0 1 χ ∼ ) = 2m( ± 1 χ ∼ ; m( 0 1 χ ∼ ± W*→ ± 1 χ ∼ , ± 1 χ ∼ b→ 1 t ~ , 1 t ~ t→ g ~ production, g ~ g ~ ATLAS -1 = 8 TeV, L = 20 fbs All limits at 95% CL. ) exp σ1 ±Expected ( ) theory SUSY σ1 ±Observed ( miss T 0/1-lepton + 3 b-jets + E Figure 32. Exclusion limits in the (m˜g, m˜ t1) plane for the gluino-stop simplified models in which the top squarks are produced in the decay of pair-produced gluinos and decay via ˜ t1→b˜χ± 1. The neutralino mass is set to 60 GeV and the mass of the chargino is assumed to be twice the mass of the neutralino. The solid red line and the dashed red line show respectively the combined observed and expected 95% CL exclusion limits. Also shown for reference is the limit from the ATLAS search for direct stop-pair production [18]. [GeV] g ~ m 400 600 800 1000 1200 1400 [GeV] 1 t ~ m 200 300 400 500 600 700 800 900 1000 Decay forbidden = 8 TeVs, -1 , L = 20 fb 1 t ~ 1 t ~ ATLAS ) - 20 GeV 1 t ~ ) = m( 0 1 χ ∼ ; m( 0 1 χ ∼ c→ 1 t ~ , 1 t ~ t→g ~ production, g ~ g ~ ATLAS -1 = 8 TeV, L = 20 fbs All limits at 95% CL. ) exp σ1 ±Expected ( ) theory SUSY σ1 ±Observed ( (0+1)-lepton combination Figure 33. Exclusion limits in the (m˜g, m˜ t1) plane for the gluino-stop simplified models in which the top squarks are produced in the decay of pair-produced gluinos and decay via ˜ t1→c+˜χ0 1. The mass difference between the ˜ t1and the lightest neutralino is fixed to 20 GeV. The solid red line and the dashed red line show respectively the combined observed and expected 95% CL exclusion limits. Also shown for reference is the limit from the ATLAS search for direct stop-pair production [18]. – 53 – JHEP10(2015)054 [GeV] g ~ m 500 600 700 800 900 1000 1100 1200 [GeV] 1 t ~ m 400 500 600 700 800 900 1000 bs→(RPV) 1 t ~ , t ~ t→ g ~ production, g ~ g ~ ATLAS -1 = 8 TeV, L = 20 fbs All limits at 95% CL. ) exp σ1 ±Expected ( ) theory SUSY σ1 ±Observed ( miss T 0-lepton + 7-10 jets + E Figure 34. Exclusion limits in the (m˜g, m˜ t1) plane for the gluino-stop simplified models in which the top squarks are produced in the decay of pair-produced gluinos and decay via R-parity and baryon number violation ˜ t1→sb. The solid red line and the dashed red line show respectively the combined observed and expected 95% CL exclusion limits. Expected limits from the individual analyses which contribute to the final combined limits are also shown for comparison. A simplified model is also considered, in which the top squark decay, ˜ t1→sb, involves R-parity and baryon number violation. The result is presented in the (m˜g, m˜ t1) plane in figure 34, where the best limit is obtained by the MULTJ search. Gluino masses below 880 GeV are excluded for top squark masses ranging from 400 GeV to 1000 GeV. The sensitivity in the gluino-sbottom simplified models in which the branching ratio for ˜g→˜ b1bdecays is 100% and the bottom squarks are assumed to decay exclusively via ˜ b1→b˜χ0 1is provided only by the 0/1L3B search [27] and the result is presented for completeness in figure 35. The search excludes gluino masses below 1200 GeV for sbottom masses up to about 1100 GeV. The limits for the gluino-off-shell-sbottom simplified models, which assume 100% branching ratio for the gluino three-body decay ˜g→b¯ b˜χ0 1via an off-shell sbottom, are given in the (m˜g, m˜χ0 1) plane in figure 36. The best sensitivities are provided by two searches, the 0/1L3B and the 0L search. The former is the most sensitive search in regions of the parameter space with a large mass splitting between the gluino and the lightest neutralino, and the latter in regions with a small mass splitting where softer jets and smaller Emiss Tare expected in the final state. In these models, gluino masses below 1250 GeV are excluded for m˜χ0 1<400 GeV while neutralino masses below 600 GeV are excluded in the gluino mass range between 700 and 1200 GeV. The sensitivity in the gluino-off-shell-stop/sbottom simplified models in which gluinos decay via virtual stops or sbottoms is provided only by the 0/1L3B search [27]. Here the mass difference between the particles is set such that the gluino decays result in an effectively three-body final state (bt˜χ0 1). The exclusion limit is presented in figure 37 for completeness. For neutralino masses of 500 GeV, gluino masses are excluded between 750 and 1250 GeV. – 54 – JHEP10(2015)054 ) [GeV]g ~ m( 400 600 800 1000 1200 1400 ) [GeV] 1 b ~ m( 400 600 800 1000 1200 1400 1600 =8 TeVs, -1 20.1 fb 1 b ~ 1 b ~ ATLAS 0 1 χ ∼ b+→ 1 b ~ production, g ~ -g ~ ) = 60 GeV 0 1 χ ∼ m( )g ~ ) >> m( 1,2 q ~ m( ) 1 b ~ ) < m(b) + m( g ~ m( =8 TeVs, -1 = 20.1 fb int L 0 lepton + 3 b-jets channel All limits at 95% CL ATLAS exp σ1 ±Expected limit theory SUSY σ 1 ±Observed limit Figure 35. Exclusion limits in the (m˜g, m˜ b1) plane for the gluino-sbottom simplified models, taken from ref. [27]. Also shown for reference is the limit from the ATLAS search for direct sbottom-pair production [18]. [GeV] g ~ m 400 600 800 1000 1200 1400 [GeV] 1 0 χ ∼ m 200 400 600 800 1000 1200 1400 Decay forbidden )g ~ ) >> m(b ~ ; m( 0 1 χ ∼ bb→ g ~ production, g ~ g ~ ATLAS -1 = 8 TeV, L = 20 fbs All limits at 95% CL. ) exp σ1 ±Expected ( ) theory SUSY σ1 ±Observed ( Expected Expected miss T 0-lepton + 2-6 jets + E miss T 0/1-lepton + 3 b-jets + E Figure 36. Exclusion limits in the (m˜g, m˜χ0 1) plane for the gluino-off-shell-sbottom simplified models in which the pair-produced gluinos decay via an off-shell sbottom as ˜g→b¯ b˜χ0 1. The solid red line and the dashed red line show respectively the combined observed and expected 95% CL exclusion limits. Expected limits from the individual analyses which contribute to the final combined limits are also shown for comparison. – 55 – JHEP10(2015)054 Requirement Signal regions in multi-jet + flavour stream 8j50 9j50 10j50 7j80 8j80 |η|jet <2.0 pjet T[GeV] >50 80 Njet = 8 = 9 ≥10 = 7 ≥8 Nb−jet 0 1 ≥2 0 1 ≥2 — 0 1 ≥2 0 1 ≥2 (pT>40 GeV,|η|<2.5) Emiss T/√HT[GeV1/2]>4 Requirement Signal regions in multi-jet + MΣ Jstream 8j50 9j50 10j50 |η|jet <2.8 pjet T[GeV] >50 Njet ≥8≥9≥10 MΣ J[GeV] >340 and >420 for each case Emiss T/√HT[GeV1/2]>4 Table 16. Selection criteria used to define the nineteen signal regions in the search with at least seven to at least ten jets, significant Emiss Tand the absence of isolated electrons or muons (0-lepton + 7–10 jets + Emiss T) [22]. The four-momenta of the R=0.4 jets satisfying pT>20 GeV and |η|<2.8 are used as inputs to a second iteration of the anti-ktjet algorithm, this time using the larger distance parameter R=1.0. The resulting larger objects are denoted as composite jets. The selection variable MΣ Jis then defined to be the sum of the masses of the composite jets: MΣ J≡PjmR=1.0 j, where the sum is over the composite jets that satisfy pR=1.0 T>100 GeV and |ηR=1.0|<1.5. The variable HTis defined as the scalar sum of pTof all jets with pT>40 GeV and |η|<2.8. constructed then Emiss T= 0 and MR Twould also be zero, while in the case where a jet is miscalibrated, the fake Emiss Ttends to align with one of the mega-jets (that are back-to-back), also creating small values of MR T. For SUSY-like events where the mega-jets tend not to be back-to-back, and their vector sum is opposite to the Emiss T, the quantity MR Tis large. The kinematic endpoint of MR Tis the mass difference between the heavy and the light sparticles. Finally, the razor variable is defined as: R=MR T M0 R .(C.3) For SUSY-like events, when the mass splitting between the heavier and light sparticles is large, M0 Rpeaks near the mass of the heavier sparticle and MR Thas a kinematical endpoint at the mass of the heavier sparticle. For SM processes, Rtends to have a low value, while it tends to have a broad distribution centred around 0.5 for SUSY-like events. Thus Rcan be used as a discriminant between signal and background. – 62 – JHEP10(2015)054 Requirement Signal region Single-bin (binned) soft single-lepton Soft dimuon 3-jet 5-jet 3-jet inclusive 2-jet N`1 electron or muon 2 muons p` T[GeV] [7,25] for electron, [6,25] for muon [6,25] Lepton veto No additional electron or muon with pT>7 GeV or 6 GeV, respectively mµµ [GeV] − − − [15,60] Njet [3,4] ≥5≥3≥2 pTjet[GeV] >180, 25, 25 180, 25, 25, 25, 25 130, 100, 25 80, 25 Nb−jet − − 0 0 Emiss T[GeV] >400 300 180 mT[GeV] >100 120 40 Emiss T/mincl eff >0.3 (0.1) 0.1 0.3 ∆Rmin(jet, `)>1.0− − 1.0 (2nd muon) Binned variable (Emiss T/mincl eff in 4 bins) − Bin width (0.1, 4th is inclusive) − Requirement Signal region Single-bin (binned) hard single-lepton 3-jet 5-jet 6-jet N`1 electron or muon p` T[GeV] >25 Lepton veto pT2ndlepton <10 GeV Njet ≥3≥5≥6 pTjet[GeV] >80, 80, 30 80, 50, 40, 40, 40 80, 50, 40, 40, 40, 40 Jet veto (pT5thjet <40 GeV) (pT6thjet <40 GeV) − Emiss T[GeV] >500 (300) 300 350 (250) mT[GeV] >150 200 (150) 150 Emiss T/mexcl eff >0.3 − − mincl eff [GeV] >1400 (800) 600 Binned variable (mincl eff in 4 bins) (Emiss Tin 3 bins) Bin width (200 GeV, 4th is inclusive) (100 GeV, 3rd is inclusive) Table 17. Selection criteria used to define the signal regions in the search requiring at least one isolated lepton (1-lepton (soft+hard) + jets + Emiss T) and in the search requiring two soft muons (2-leptons + jets + Emiss T) [23]. For each jet multiplicity in the single-lepton channel, two sets of requirements are defined: one single-bin signal region optimized for discovery reach, which is also used to place limits on the visible cross-section, and one signal region which is binned in an appropriate variable in order to exploit the expected shape of the distribution of signal events when placing model-dependent limits. The requirements of the binned signal region are shown in parentheses when they differ from those of the single-bin signal region. The transverse mass (mT) of the lepton (`) and Emiss Tis defined as mT=q2p` TEmiss T(1 −cos[∆φ(~ `, Emiss T)]). The inclusive effective mass (minc eff ) is computed as the scalar sum of the pTof the lepton(s), the jets and Emiss T: minc eff =PN` i=1 p` T,i +PNjet j=1 pT,j +Emiss T, where the index iidentifies all the signal leptons and the index jall the signal jets in the event. The exclusive effective mass (mexcl eff ) is defined in a similar way to minc eff , with the exception that only the three leading signal jets are considered. The minimum angular separation ∆Rmin calculated between the signal lepton `and all preselected jets is used to reduce the background coming from misidentified or non-prompt leptons in the soft-lepton signal region with three jets and in the soft dimuon signal region. In the latter case, the subleading signal muon is used to compute ∆Rmin. – 63 – JHEP10(2015)054 Requirement Signal region Single-bin (binned) hard dilepton Low-multiplicity (≤2-jet) 3-jet ee/µµ eµ ee/µµ eµ N`2, 2 of opposite sign or ≥2 p` T[GeV] >14,10 N`` with 81< m`` <101 GeV 0 −0− Njet ≤2≥3 pTjet [GeV] >50,50 50, 50, 50 Nb−jet 0 R >0.5 >0.35 M0 R[GeV] >600 (400 in 8 bins) 800 (800 in 5 bins) M0 Rbin width [GeV] (100, the last is inclusive) Table 18. Selection criteria used to define the signal regions in the search requiring two hard leptons (2-leptons + jets + Emiss T) [23]. For each jet multiplicity two sets of requirements are defined: one single-bin signal region optimized for discovery reach, which is also used to place limits on the visible cross-section, and one signal region which is binned in an appropriate variable in order to exploit the expected shape of the distribution of signal events when placing model-dependent limits. The requirements of the binned signal region are shown in parentheses when they differ from those of the single-bin signal region. Details of the construction of Razor variables M0 Rand Rcan be found in the appendix C.1. In this case, mega-jets are constructed using the final-state jets and leptons. Requirement Signal region SR-2j-bveto SR-2j-btag SR-4j-bveto SR-4j-btag SR-loose Njet ≥ ≥ 2≥2≥4≥4 (2, ≥3) Nb−jet = 0 ≥1 = 0 ≥1 — Emiss T[GeV] >200 200 200 200 (150, 100) m`` [GeV] /∈[80, 110] [80, 110] [80, 110] [80, 110] [80, 110] Table 19. Selection criteria used to define the signal regions in the search requiring two sameflavour opposite-sign electrons or muons (2-leptons off-Z) [24]. If more than two leptons are present, the two with the largest values of pTare selected. The leading lepton in the event must have pT>25 GeV and the subleading lepton is required to have pT>20 GeV. These two leptons are used to define the dilepron invariant mass, m``. In addition, one SR with the same requirements as those used in the CMS search [148], which reported an excess of events above the SM background with a significance of 2.6 standard deviations, is defined (SR-loose) for comparison purposes. – 64 – JHEP10(2015)054 Requirement Signal region SR3b SR0b SR1b SR3Llow SR3Lhigh Leptons SS or 3L SS SS 3L 3L Nb−jet ≥3 =0 ≥1 - - Njet ≥5 3 3 4 4 Emiss T[GeV] >150 >150 50 < Emiss T<150 >150 mT[GeV] >- 100 - - - Veto - - SR3b Zboson, SR3b SR3b meff [GeV] >350 400 700 400 400 Table 20. Selection criteria used to define the signal regions in the search with multiple jets, and either two leptons of the same electric charge (same-sign leptons) or at least three leptons (SS/3L + jets + Emiss T) [25]. The effective mass (meff ) is computed from all selected leptons and selected jets in event, as meff =PN` i=1 p` T,i +PNjet j=1 pT,j +Emiss T. The transverse mass (mT) is computed from the highest-pTlepton (`1) and Emiss Tas mT=q2p`1 TEmiss T(1 −cos[∆φ(~ `1,Emiss T)]). C.2 Signal regions The SUSY models targeted by this search are expected to have final states characterized by the presence of jets, missing transverse momentum, and no leptons. In the simplest case of squark-pair production with direct decays to quarks and neutralinos, there are at least two jets visible in the detector, so the baseline inclusive signal regions require at least two jets. This is also the minimum number of visible objects in the final state necessary to construct the Razor variables. Figure 39 shows the values of Rand M0 Rfor two simplified model signal points, one with m˜q= 450 GeV and mLSP = 400 GeV, where the ∆m= 50 GeV is small (referred to as small-∆msignal) and the other with m˜q= 850 GeV and mLSP = 100 GeV, where the ∆m= 750 GeV is large (referred to as large-∆msignal), after requiring no leptons and at least two jets in the final state. Since the variable M0 Ris related to the mass difference between the squark and the neutralino, going from the small-∆msignal to the large-∆msignal, the events tend to populate higher M0 Rregions. Extending this to all points of the model with squark-pair production followed by the direct decay of squarks, the average value of M0 Ris approximately constant for a fixed mass splitting between the LSP and the squark, and increases with increasing ∆m, while the average R-value tends to be around 0.5. To select events for this search, the combination of two Emiss Ttriggers, which are fully efficient in events having offline reconstructed Emiss T>160 GeV is used. Two signal regions which target different regions of the (m˜q, m˜χ0 1) plane are defined: SRloose and SRtight. Signal region SRloose has a lower requirement on Rand targets regions of the (m˜q, m˜χ0 1) plane with small mass splitting, which typically have softer visible objects. Signal region SRtight was chosen to target high squark masses which typically contain harder visible objects. An overview of the selection criteria for these two signal regions is given in table 9. – 65 – JHEP10(2015)054 Requirement Signal region 1τLoose SR 1τTight SR Taus Nmedium τ= 1 pT>30 GeV ∆φ(jet1,2,Emiss T)>0.4 ∆φ(τ, Emiss T)>0.2 mτ T[GeV] >140 Emiss T[GeV] >200 300 HT[GeV] >800 1000 Requirement Signal region 2τInclusive SR 2τGMSB SR 2τnGM SR 2τbRPV SR Taus Nloose τ≥2 pT>20 GeV ∆φ(jet1,2,Emiss T)≥0.3 mτ1 T+mτ2 T[GeV] ≥150 250 250 150 H2j T[GeV] >1000 1000 600 1000 Njet ≥- 4 Requirement Signal region τ+`GMSB SR τ+`nGM SR τ+`bRPV SR τ+`mSUGRA SR Taus Nloose τ≥1 pT>20 GeV N`= 1 m` T[GeV] >100 meff [GeV] >1700 - 1300 - Emiss T[GeV] >- 350 - 300 Njet ≥- 3 4 3 Table 21. Selection criteria used to define the signal regions in the search requiring large missing transverse momentum, jets and at least one hadronically decaying tau lepton (taus + jets + Emiss T) [26]. The transverse mass mτ Tis formed from the Emiss Tand the pTof the tau lepton in the 1τchannel as: mτ T=p2pτ TEmiss T(1 −cos(∆φ(τ, Emiss T))). In addition, the variable mτ1 T+mτ2 Tis used as a discriminating variable in the 2τchannel. The transverse mass m` Tis similarly formed from the Emiss Tand the pTof the light leptons. The variable HTis defined as the scalar sum of the transverse momenta of the tau, light lepton and jets (pjet T>30 GeV): HT=PN` i=1 p` T+PNτ j=1 pτ T+PNjet k=1 pjet T. The variable H2j Tis defined as the scalar sum of the transverse momenta of the tau and light lepton candidates, and the two jets with the largest transverse momenta in the event: H2j T=PN` i=1 p` T+PNτ j=1 pτ T+Pk=1,2pjetk T. The effective mass (meff ) is defined as meff =H2j T+Emiss T. – 66 – JHEP10(2015)054 Requirement Signal region SR-0`-4j-A SR-0`-4j-B SR-0`-4j-C* SR-0`-7j-A SR-0`-7j-B SR-0`-7j-C Baseline 0-lepton selection lepton veto, pjet1 T>90 GeV, Emiss T>150 GeV Njets (pT[GeV]) ≥4 (50) 4 (50) 4 (30) 7 (30) 7 (30) 7 (30) Emiss T[GeV] >250 350 400 200 350 250 mincl eff [GeV] >- - - 1000 1000 1500 m4j eff [GeV] >1300 1100 1100 - - - Emiss T/qH4j T[√GeV] >- - 16 - - - Requirement Signal region SR-1`-6j-A SR-1`-6j-B SR-1`-6j-C Baseline 1-lepton selection ⩾1 signal lepton (e,µ), pjet1 T>90 GeV, Emiss T>150 GeV Njets (pT[GeV]) ≥6 (30) 6 (30) 6 (30) Emiss T[GeV] >175 225 275 mT[GeV] >140 140 160 mincl eff [GeV] >700 800 900 Table 22. Selection criteria used to define the signal regions in the search that requires at least three jets tagged as b-jets, no or at least one lepton, jets and large missing transverse momentum (0/1-lepton + 3b-jets + Emiss T) [27]. The jet pTthreshold requirements are also applied to b-jets. The notation SR-0`-4j-C* means that the leading jet is required to fail the b-tagging requirements, in order to target the region close to the kinematic boundary in the gluino-sbottom simplified models. In the 0-lepton selection, the inclusive effective mass mincl eff is defined as the scalar sum of the Emiss T and the pTof all jets with pT>30 GeV. In the 1-lepton selection the mincl eff is defined as for the 0lepton selection with the addition of the pTof all selected leptons with pT>20 GeV. The exclusive effective mass (m4j eff ) is defined as the scalar sum of the Emiss Tand the pTof the four leading jets. The transverse mass (mT) is computed from the leading lepton and the missing transverse momentum. The variable H4j Tis defined as the scalar sum of the transverse momenta of the four leading jets. C.3 Control and validation regions for SM background processes The dominant SM background processes which contribute to the event counts in the signal regions are: Z+jets, W+jets, top quark pairs, and multiple jets. For each of these processes a dedicated control region is defined. The production of boson (W/Z) pairs in which at least one boson decays to charged leptons and/or neutrinos (referred to as ‘dibosons’ below), the single-top production, and the t¯ t+W/Z boson production are small components of the total background and are estimated with MC simulated data. Figure 40 shows the values of Rand M0 Rfor the major SM backgrounds in this search. As previously discussed, the SM backgrounds tend to occupy regions with lower values of M0 Rand R, which is taken into account while defining control regions for the main background processes. A summary of the selection criteria used to define the control and validation regions in this search is shown in table 23. The largest potential background for a search with no leptons is expected to originate from the QCD-induced multi-jet event. However, the Razor variables were constructed – 67 – JHEP10(2015)054 Preselection Exactly two opposite-sign, Exactly one Exactly one No leptons No leptons same-flavour electrons electron or muon electron or muon or muons −No b-jets At least one b-jet − − 66< m(``)<116 GeV − − pjet1,2 T>150 GeV pjet1,2 T>200 GeV Emiss0 T=Emiss T+pT(``) Treat lepton as a jet Treat lepton as a jet − − 0LRaz CRZ 0LRaz CRW 0LRaz CRT 0LRaz CRQloose 0LRaz CRQtight − − − ∆φ(pjet2 T, Emiss T)<0.2 ∆φ(pjet2 T, Emiss T)<0.2 0.3< R < 0.55 0.3< R < 0.55 0.3< R < 0.55 0.35 < R < 0.45 0.5< R < 0.55 M0 R>800 GeV M0 R>800 GeV M0 R>800 GeV M0 R>1000 GeV M0 R>1000 GeV 0LRaz VRZ 0LRaz VRW 0LRaz VRT 0LRaz VRQloose 0LRaz VRQtight − − − ∆φ(pjet2 T, Emiss T)<0.4 ∆φ(pjet2 T, Emiss T)<1.4 0.55 < R < 1.0 0.55 < R < 1.0 0.55 < R < 1.0 0.45 < R < 0.5 0.55 < R < 0.6 400 < M0 R<1000 GeV 400 < M0 R<1000 GeV 400 < M0 R<1000 GeV M0 R>900 GeV M0 R>900 GeV Table 23. Overview of the selection criteria for the Z+jets, W+jets, semileptonic t¯ tand multi-jet control regions (0LRaz CRZ, 0LRaz CRW, 0LRaz CRT and 0LRaz CRQloose/tight respectively) and the corresponding validation regions (0LRaz VRZ, 0LRaz VRW, 0LRaz VRT, 0LRaz VRQloose/tight) used by the 0-lepton Razor analysis. Details of the construction of Razor variables M0 Rand Rcan be found in the appendix C.1. – 68 – JHEP10(2015)054 ' [GeV] R M 0 1000 2000 3000 R 0 0.2 0.4 0.6 0.8 1 1.2 1.4 Events / bin -3 10 -2 10 -1 10 ATLAS Simulation -1 = 8 TeV, L = 20 fbs )=(450, 400) GeV 0 1 χ ∼ , q ~ direct, m(q ~ q ~ (a) ' [GeV] R M 0 1000 2000 3000 R 0 0.2 0.4 0.6 0.8 1 1.2 1.4 Events / bin -5 10 -4 10 -3 10 ATLAS Simulation -1 = 8 TeV, L = 20 fbs )=(850, 100) GeV 0 1 χ ∼ , q ~ direct, m(q ~ q ~ (b) Figure 39. Distributions of the Razor variable Rversus the characteristic mass in the R-frame M0 Rfor two points of the simplified model with squark-pair production assuming the direct decay of squarks, after requiring no leptons and at least two jets. Figure (a) shows the case where m˜q = 450 GeV and mLSP = 400 GeV, and (b) where m˜q = 850 GeV and mLSP = 100 GeV. to be able to distinguish this background from a SUSY-like signal, which minimizes the contribution of the multi-jet events after the SR event selection has been applied. To estimate the contribution of multi-jet background events in the final signal region selection, a data-driven technique [156], which applies a resolution function to well-measured multijet events in order to estimate the impact of jet energy mis-measurement and heavy-flavour semileptonic decays on Emiss Tand other variables, is used. Two dedicated control regions, CRQloose and CRQtight, which use different selection criteria on Rand ∆φ(pj2 T, Emiss T), correspond to the loose and tight signal regions respectively, and select samples of events with similar kinematics to the SR but enriched in multi-jet background events. Since the QCD multi-jet background is significantly reduced by use of the Razor variables, the largest remaining backgrounds come from the production of W/Z bosons with additional jets and semileptonic t¯ tdecays, where the leptons can be mis-reconstructed as jets, non-prompt or be outside the lepton identification criteria. For each of these backgrounds a control region, rich in the respective process, is defined. The trigger requirements for these lepton-rich control regions follow those used by the corresponding control regions for the the 0L search [20]. The Razor variables are used to preselect a region which is dominated by the particular process. Following this preselection, to control the t¯ tbackground, the control region CRT requires at least one jet tagged as a b-jet and exactly one electron or muon, while the W+jets control region, CRW, applies a veto on the presence of b-jets and requires exactly one electron or muon. In both cases the lepton is treated as a jet in the reconstruction of the Razor variables. This treatment of leptons as jets is motivated by the observation that ∼75% of W(→`ν)+jets and semileptonic t¯ tevents appearing in the SRs possess leptons which have fake jets, either through the misidentification of electrons or by the production of tau leptons decaying hadronically (identification of hadronic tau decays is not used in this analysis). The Z+jets control region, CRZ, is required to have exactly two opposite-sign same-flavour leptons. The Z+jets contribution to the signal region largely originates from Zdecays to neutrinos. To mimic the behaviour of Z→νν in the – 69 – JHEP10(2015)054 ' [GeV] R M 0 1000 2000 3000 R 0 0.2 0.4 0.6 0.8 1 1.2 1.4 Events / bin 1 10 2 10 ATLAS Simulation -1 = 8 TeV, L = 20 fbs Z+jets (a) ' [GeV] R M 0 1000 2000 3000 R 0 0.2 0.4 0.6 0.8 1 1.2 1.4 Events / bin 1 10 2 10 ATLAS Simulation -1 = 8 TeV, L = 20 fbs W+jets (b) ' [GeV] R M 0 1000 2000 3000 R 0 0.2 0.4 0.6 0.8 1 1.2 1.4 Events / bin -1 10 1 10 ATLAS Simulation -1 = 8 TeV, L = 20 fbs Top (c) Figure 40. Distributions of the Razor variable Rversus the characteristic mass in the R-frame M0 R for the dominant Standard Model backgrounds: (a) Z+jets, (b) W+jets and (c) t¯ t, after requiring no-leptons and at least two jets in the final state. control region, the two leptons have been treated as invisible and are used to re-calculate Emiss Tas Emiss0 T=Emiss T+pT(``) with the invariant mass of the leptons falling within a Z-mass window, 66 < m(``)<116 GeV. The Razor variables are also calculated with this methodology where the leptons are treated as invisible objects. To validate the normalization parameters extracted in the background control regions, validation regions VRZ, VRW, VRT, VRQloose and VRQtight for Z+jets, W+jets, t¯ tand multi-jet backgrounds respectively, are defined (table 23). These validation regions are statistically independent from the signal and control regions previously defined, and are expected to have minimal contribution from any signal, if present. Following the definition of the control and validation regions, the backgrounds from Z+jets, W+jets, t¯ tand multi-jet processes are estimated by using the background-only fit, as described in section 6. Figures 41 and 42 show the M0 Rdistributions for these control and validation regions after the fit. Good agreement is seen between the fitted and observed yields in all regions. – 70 – JHEP10(2015)054 Events / 100 GeV 1 10 2 10 3 10 4 10 5 10 6 10 7 10 ATLAS -1 =8 TeV, L=20 fbs Razor Had CRZ Data Standard Model Others W+jets Z+jets Top Dibosons ' [GeV] R M 800 900 1000 1100 1200 1300 1400 1500 1600 Data / SM 0 1 2 (a) Events / 100 GeV 1 10 2 10 3 10 4 10 5 10 6 10 7 10 ATLAS -1 =8 TeV, L=20 fbs Razor Had CRW Data Standard Model Others W+jets Z+jets Top Dibosons ' [GeV] R M 800 900 1000 1100 1200 1300 1400 1500 1600 Data / SM 0 1 2 (b) Events / 100 GeV 1 10 2 10 3 10 4 10 5 10 6 10 7 10 ATLAS -1 =8 TeV, L=20 fbs Razor Had CRT Data Standard Model Others W+jets Z+jets Top Dibosons ' [GeV] R M 800 900 1000 1100 1200 1300 1400 1500 1600 Data / SM 0 1 2 (c) Events / 100 GeV 1 10 2 10 3 10 4 10 5 10 6 10 7 10 ATLAS -1 =8 TeV, L=20 fbs Razor Had CRQloose Data Standard Model Multijets Others W+jets Z+jets Top Dibosons ' [GeV] R M 1000 1100 1200 1300 1400 1500 1600 Data / SM 0 1 2 (d) Events / 100 GeV 1 10 2 10 3 10 4 10 5 10 ATLAS -1 =8 TeV, L=20 fbs Razor Had CRQtight Data Standard Model Multijets Others W+jets Z+jets Top Dibosons ' [GeV] R M 1000 1100 1200 1300 1400 1500 1600 Data / SM 0 1 2 (e) Figure 41. 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Gagnon61, C. Galea106, B. Galhardo126a,126c, E.J. Gallas120, B.J. Gallop131, P. Gallus128, G. Galster36, K.K. Gan111, J. Gao33b,85, Y. Gao46, Y.S. Gao143,e, F.M. Garay Walls46, F. Garberson176, C. Garc´ıa167, J.E. Garc´ıa Navarro167, M. Garcia-Sciveres15, R.W. Gardner31, N. Garelli143, V. Garonne119, C. Gatti47, A. Gaudiello50a,50b, G. Gaudio121a, B. Gaur141, L. Gauthier95, P. Gauzzi132a,132b, I.L. Gavrilenko96, C. Gay168, G. Gaycken21, E.N. Gazis10, P. Ge33d, Z. Gecse168, C.N.P. Gee131, Ch. Geich-Gimbel21, M.P. Geisler58a, C. Gemme50a, M.H. Genest55, S. Gentile132a,132b, M. George54, S. George77, D. Gerbaudo163, A. Gershon153, S. Ghasemi141, H. Ghazlane135b, B. Giacobbe20a, S. Giagu132a,132b, V. Giangiobbe12, P. Giannetti124a,124b, B. Gibbard25, S.M. Gibson77, M. Gilchriese15, T.P.S. Gillam28, D. Gillberg30, G. Gilles34, D.M. Gingrich3,d, N. Giokaris9, M.P. Giordani164a,164c, F.M. Giorgi20a, F.M. Giorgi16, P.F. Giraud136, P. Giromini47, D. Giugni91a, C. Giuliani48, M. Giulini58b, B.K. Gjelsten119, S. Gkaitatzis154, I. Gkialas154, E.L. Gkougkousis117, L.K. Gladilin99, C. Glasman82, J. Glatzer30, P.C.F. Glaysher46, A. Glazov42, M. Goblirsch-Kolb101, J.R. Goddard76, J. Godlewski39, S. Goldfarb89, T. Golling49, D. Golubkov130, A. Gomes126a,126b,126d, R. Gon¸calo126a, J. Goncalves Pinto Firmino Da Costa136, L. Gonella21, S. Gonz´alez de la Hoz167, G. Gonzalez Parra12, S. Gonzalez-Sevilla49, L. Goossens30, P.A. Gorbounov97, H.A. Gordon25, I. Gorelov105, B. Gorini30, E. Gorini73a,73b, A. Goriˇsek75, E. Gornicki39, A.T. Goshaw45, C. G¨ossling43, M.I. Gostkin65, D. Goujdami135c, A.G. Goussiou138, N. Govender145b, E. Gozani152, H.M.X. Grabas137, L. Graber54, I. Grabowska-Bold38a, P.O.J. Gradin166, P. Grafstr¨om20a,20b, K-J. Grahn42, J. Gramling49, E. Gramstad119, S. Grancagnolo16, V. Gratchev123, H.M. Gray30, E. Graziani134a, Z.D. Greenwood79,n, K. Gregersen78, I.M. Gregor42, P. Grenier143, J. Griffiths8, A.A. Grillo137, K. Grimm72, S. Grinstein12,o, Ph. Gris34, J.-F. Grivaz117, J.P. Grohs44, A. Grohsjean42, E. Gross172, J. Grosse-Knetter54, G.C. Grossi79, Z.J. Grout149, L. Guan89, J. Guenther128, F. Guescini49, D. Guest176, O. Gueta153, E. Guido50a,50b, T. Guillemin117, S. Guindon2, U. Gul53, C. Gumpert44, J. Guo33e, Y. Guo33b, S. Gupta120, G. Gustavino132a,132b, P. Gutierrez113, N.G. Gutierrez Ortiz78, C. Gutschow44, C. Guyot136, C. Gwenlan120, C.B. Gwilliam74, A. Haas110, C. Haber15, H.K. Hadavand8, N. Haddad135e, P. Haefner21, S. Hageb¨ock21, Z. Hajduk39, H. Hakobyan177, M. Haleem42, J. Haley114, D. Hall120, G. Halladjian90, G.D. Hallewell85, K. Hamacher175, P. Hamal115, K. Hamano169, A. Hamilton145a, G.N. Hamity139, P.G. Hamnett42, L. Han33b, K. Hanagaki66,p, K. Hanawa155, M. Hance15, P. Hanke58a, R. Hanna136, J.B. Hansen36, J.D. Hansen36, M.C. Hansen21, P.H. Hansen36, K. Hara160, A.S. Hard173, T. Harenberg175, F. Hariri117, S. Harkusha92, R.D. Harrington46, P.F. Harrison170, F. Hartjes107, M. Hasegawa67, S. Hasegawa103, Y. Hasegawa140, A. Hasib113, S. Hassani136, S. Haug17, R. Hauser90, L. Hauswald44, M. Havranek127, C.M. Hawkes18, R.J. Hawkings30, A.D. Hawkins81, T. Hayashi160, D. Hayden90, C.P. Hays120, J.M. Hays76, H.S. Hayward74, S.J. Haywood131, S.J. Head18, T. Heck83, V. Hedberg81, L. Heelan8, S. Heim122, T. Heim175, B. Heinemann15, L. Heinrich110, J. Hejbal127, L. Helary22, S. Hellman146a,146b, D. Hellmich21, C. Helsens12, J. Henderson120, R.C.W. Henderson72, Y. Heng173, C. Hengler42, A. Henrichs176, A.M. Henriques Correia30, S. Henrot-Versille117, G.H. Herbert16, Y. Hern´andez Jim´enez167, R. Herrberg-Schubert16, G. Herten48, R. Hertenberger100, L. Hervas30, G.G. Hesketh78, N.P. Hessey107, J.W. Hetherly40, R. Hickling76, E. Hig´on-Rodriguez167, E. Hill169, J.C. Hill28, K.H. Hiller42, S.J. Hillier18, I. Hinchliffe15, E. Hines122, R.R. Hinman15, M. Hirose157, D. Hirschbuehl175, J. Hobbs148, N. Hod107, M.C. Hodgkinson139, P. Hodgson139, A. Hoecker30, M.R. Hoeferkamp105, F. Hoenig100, M. Hohlfeld83, D. Hohn21, T.R. Holmes15, M. Homann43, T.M. Hong125, L. Hooft van Huysduynen110, W.H. Hopkins116, Y. Horii103, A.J. Horton142, – 86 – JHEP10(2015)054 J-Y. Hostachy55, S. Hou151, A. Hoummada135a, J. Howard120, J. Howarth42, M. Hrabovsky115, I. Hristova16, J. Hrivnac117, T. Hryn’ova5, A. Hrynevich93, C. Hsu145c, P.J. Hsu151,q, S.-C. Hsu138, D. Hu35, Q. Hu33b, X. Hu89, Y. Huang42, Z. Hubacek128, F. Hubaut85, F. Huegging21, T.B. Huffman120, E.W. Hughes35, G. Hughes72, M. Huhtinen30, T.A. H¨ulsing83, N. Huseynov65,b, J. Huston90, J. Huth57, G. Iacobucci49, G. Iakovidis25, I. Ibragimov141, L. Iconomidou-Fayard117, E. Ideal176, Z. Idrissi135e, P. Iengo30, O. Igonkina107, T. Iizawa171, Y. Ikegami66, K. Ikematsu141, M. Ikeno66, Y. Ilchenko31,r, D. Iliadis154, N. Ilic143, T. Ince101, G. Introzzi121a,121b, P. Ioannou9, M. Iodice134a, K. Iordanidou35, V. Ippolito57, A. Irles Quiles167, C. Isaksson166, M. Ishino68, M. Ishitsuka157, R. Ishmukhametov111, C. Issever120, S. Istin19a, J.M. Iturbe Ponce84, R. Iuppa133a,133b, J. Ivarsson81, W. Iwanski39, H. Iwasaki66, J.M. Izen41, V. Izzo104a, S. Jabbar3, B. Jackson122, M. Jackson74, P. Jackson1, M.R. Jaekel30, V. Jain2, K. Jakobs48, S. Jakobsen30, T. Jakoubek127, J. Jakubek128, D.O. Jamin114, D.K. Jana79, E. Jansen78, R. Jansky62, J. Janssen21, M. Janus54, G. Jarlskog81, N. Javadov65,b, T. Jav˚urek48, L. Jeanty15, J. Jejelava51a,s, G.-Y. Jeng150, D. Jennens88, P. Jenni48,t, J. Jentzsch43, C. Jeske170, S. J´ez´equel5, H. Ji173, J. Jia148, Y. Jiang33b, S. Jiggins78, J. Jimenez Pena167, S. Jin33a, A. Jinaru26a, O. Jinnouchi157, M.D. Joergensen36, P. Johansson139, K.A. Johns7, K. Jon-And146a,146b, G. Jones170, R.W.L. Jones72, T.J. Jones74, J. Jongmanns58a, P.M. Jorge126a,126b, K.D. Joshi84, J. Jovicevic159a, X. Ju173, C.A. Jung43, P. Jussel62, A. Juste Rozas12,o, M. Kaci167, A. Kaczmarska39, M. Kado117, H. Kagan111, M. Kagan143, S.J. Kahn85, E. Kajomovitz45, C.W. Kalderon120, S. Kama40, A. Kamenshchikov130, N. Kanaya155, S. Kaneti28, V.A. Kantserov98, J. Kanzaki66, B. Kaplan110, L.S. Kaplan173, A. Kapliy31, D. Kar145c, K. Karakostas10, A. Karamaoun3, N. Karastathis10,107, M.J. Kareem54, E. Karentzos10, M. Karnevskiy83, S.N. Karpov65, Z.M. Karpova65, K. Karthik110, V. Kartvelishvili72, A.N. Karyukhin130, L. Kashif173, R.D. Kass111, A. Kastanas14, Y. Kataoka155, C. Kato155, A. Katre49, J. Katzy42, K. Kawagoe70, T. Kawamoto155, G. Kawamura54, S. Kazama155, V.F. Kazanin109,c, R. Keeler169, R. Kehoe40, J.S. Keller42, J.J. Kempster77, H. Keoshkerian84, O. Kepka127, B.P. Kerˇsevan75, S. Kersten175, R.A. Keyes87, F. Khalil-zada11, H. Khandanyan146a,146b, A. Khanov114, A.G. Kharlamov109,c, T.J. Khoo28, V. Khovanskiy97, E. Khramov65, J. Khubua51b,u, S. Kido67, H.Y. Kim8, S.H. Kim160, Y.K. Kim31, N. Kimura154, O.M. Kind16, B.T. King74, M. King167, S.B. King168, J. Kirk131, A.E. Kiryunin101, T. Kishimoto67, D. Kisielewska38a, F. Kiss48, K. Kiuchi160, O. Kivernyk136, E. Kladiva144b, M.H. Klein35, M. Klein74, U. Klein74, K. Kleinknecht83, P. Klimek146a,146b, A. Klimentov25, R. Klingenberg43, J.A. Klinger139, T. Klioutchnikova30, E.-E. Kluge58a, P. Kluit107, S. Kluth101, J. Knapik39, E. Kneringer62, E.B.F.G. Knoops85, A. Knue53, A. Kobayashi155, D. Kobayashi157, T. Kobayashi155, M. Kobel44, M. Kocian143, P. Kodys129, T. Koffas29, E. Koffeman107, L.A. Kogan120, S. Kohlmann175, Z. Kohout128, T. Kohriki66, T. Koi143, H. Kolanoski16, I. Koletsou5, A.A. Komar96,∗, Y. Komori155, T. Kondo66, N. Kondrashova42, K. K¨oneke48, A.C. K¨onig106, T. Kono66, R. Konoplich110,v, N. Konstantinidis78, R. Kopeliansky152, S. Koperny38a, L. K¨opke83, A.K. Kopp48, K. Korcyl39, K. Kordas154, A. Korn78, A.A. Korol109,c, I. Korolkov12, E.V. Korolkova139, O. Kortner101, S. Kortner101, T. Kosek129, V.V. Kostyukhin21, V.M. Kotov65, A. Kotwal45, A. Kourkoumeli-Charalampidi154, C. Kourkoumelis9, V. Kouskoura25, A. Koutsman159a, R. Kowalewski169, T.Z. Kowalski38a, W. Kozanecki136, A.S. Kozhin130, V.A. Kramarenko99, G. Kramberger75, D. Krasnopevtsev98, M.W. Krasny80, A. Krasznahorkay30, J.K. Kraus21, A. Kravchenko25, S. Kreiss110, M. Kretz58c, J. Kretzschmar74, K. Kreutzfeldt52, P. Krieger158, K. Krizka31, K. Kroeninger43, H. Kroha101, J. Kroll122, J. Kroseberg21, J. Krstic13, U. Kruchonak65, H. Kr¨uger21, N. Krumnack64, A. Kruse173, M.C. Kruse45, M. Kruskal22, T. Kubota88, H. Kucuk78, S. Kuday4b, S. Kuehn48, A. Kugel58c, F. Kuger174, A. Kuhl137, T. Kuhl42, V. Kukhtin65, Y. Kulchitsky92, S. Kuleshov32b, M. Kuna132a,132b, T. Kunigo68, A. Kupco127, H. Kurashige67, Y.A. Kurochkin92, V. Kus127, – 87 – JHEP10(2015)054 Joao del Rei (UFSJ), Sao Joao del Rei; (d)Instituto de Fisica, Universidade de Sao Paulo, Sao Paulo, Brazil 25 Physics Department, Brookhaven National Laboratory, Upton NY, United States of America 26 (a)National Institute of Physics and Nuclear Engineering, Bucharest; (b)National Institute for Research and Development of Isotopic and Molecular Technologies, Physics Department, Cluj Napoca; (c)University Politehnica Bucharest, Bucharest; (d)West University in Timisoara, Timisoara, Romania 27 Departamento de F´ısica, Universidad de Buenos Aires, Buenos Aires, Argentina 28 Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom 29 Department of Physics, Carleton University, Ottawa ON, Canada 30 CERN, Geneva, Switzerland 31 Enrico Fermi Institute, University of Chicago, Chicago IL, United States of America 32 (a)Departamento de F´ısica, Pontificia Universidad Cat´olica de Chile, Santiago; (b)Departamento de F´ısica, Universidad T´ecnica Federico Santa Mar´ıa, Valpara´ıso, Chile 33 (a)Institute of High Energy Physics, Chinese Academy of Sciences, Beijing; (b)Department of Modern Physics, University of Science and Technology of China, Anhui; (c)Department of Physics, Nanjing University, Jiangsu; (d)School of Physics, Shandong University, Shandong; (e)Department of Physics and Astronomy, Shanghai Key Laboratory for Particle Physics and Cosmology, Shanghai Jiao Tong University, Shanghai; (f)Physics Department, Tsinghua University, Beijing 100084, China 34 Laboratoire de Physique Corpusculaire, Clermont Universit´e and Universit´e Blaise Pascal and CNRS/IN2P3, Clermont-Ferrand, France 35 Nevis Laboratory, Columbia University, Irvington NY, United States of America 36 Niels Bohr Institute, University of Copenhagen, Kobenhavn, Denmark 37 (a)INFN Gruppo Collegato di Cosenza, Laboratori Nazionali di Frascati; (b)Dipartimento di Fisica, Universit`a della Calabria, Rende, Italy 38 (a)AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, Krakow; (b)Marian Smoluchowski Institute of Physics, Jagiellonian University, Krakow, Poland 39 Institute of Nuclear Physics Polish Academy of Sciences, Krakow, Poland 40 Physics Department, Southern Methodist University, Dallas TX, United States of America 41 Physics Department, University of Texas at Dallas, Richardson TX, United States of America 42 DESY, Hamburg and Zeuthen, Germany 43 Institut f¨ur Experimentelle Physik IV, Technische Universit¨at Dortmund, Dortmund, Germany 44 Institut f¨ur Kernund Teilchenphysik, Technische Universit¨at Dresden, Dresden, Germany 45 Department of Physics, Duke University, Durham NC, United States of America 46 SUPA - School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom 47 INFN Laboratori Nazionali di Frascati, Frascati, Italy 48 Fakult¨at f¨ur Mathematik und Physik, Albert-Ludwigs-Universit¨at, Freiburg, Germany 49 Section de Physique, Universit´e de Gen`eve, Geneva, Switzerland 50 (a)INFN Sezione di Genova; (b)Dipartimento di Fisica, Universit`a di Genova, Genova, Italy 51 (a)E. Andronikashvili Institute of Physics, Iv. Javakhishvili Tbilisi State University, Tbilisi; (b) High Energy Physics Institute, Tbilisi State University, Tbilisi, Georgia 52 II Physikalisches Institut, Justus-Liebig-Universit¨at Giessen, Giessen, Germany 53 SUPA - School of Physics and Astronomy, University of Glasgow, Glasgow, United Kingdom 54 II Physikalisches Institut, Georg-August-Universit¨at, G¨ottingen, Germany 55 Laboratoire de Physique Subatomique et de Cosmologie, Universit´e Grenoble-Alpes, CNRS/IN2P3, Grenoble, France 56 Department of Physics, Hampton University, Hampton VA, United States of America 57 Laboratory for Particle Physics and Cosmology, Harvard University, Cambridge MA, United States of America 58 (a)Kirchhoff-Institut f¨ur Physik, Ruprecht-Karls-Universit¨at Heidelberg, Heidelberg; (b) Physikalisches Institut, Ruprecht-Karls-Universit¨at Heidelberg, Heidelberg; (c)ZITI Institut f¨ur – 94 – JHEP10(2015)054 technische Informatik, Ruprecht-Karls-Universit¨at Heidelberg, Mannheim, Germany 59 Faculty of Applied Information Science, Hiroshima Institute of Technology, Hiroshima, Japan 60 (a)Department of Physics, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong; (b) Department of Physics, The University of Hong Kong, Hong Kong; (c)Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China 61 Department of Physics, Indiana University, Bloomington IN, United States of America 62 Institut f¨ur Astround Teilchenphysik, Leopold-Franzens-Universit¨at, Innsbruck, Austria 63 University of Iowa, Iowa City IA, United States of America 64 Department of Physics and Astronomy, Iowa State University, Ames IA, United States of America 65 Joint Institute for Nuclear Research, JINR Dubna, Dubna, Russia 66 KEK, High Energy Accelerator Research Organization, Tsukuba, Japan 67 Graduate School of Science, Kobe University, Kobe, Japan 68 Faculty of Science, Kyoto University, Kyoto, Japan 69 Kyoto University of Education, Kyoto, Japan 70 Department of Physics, Kyushu University, Fukuoka, Japan 71 Instituto de F´ısica La Plata, Universidad Nacional de La Plata and CONICET, La Plata, Argentina 72 Physics Department, Lancaster University, Lancaster, United Kingdom 73 (a)INFN Sezione di Lecce; (b)Dipartimento di Matematica e Fisica, Universit`a del Salento, Lecce, Italy 74 Oliver Lodge Laboratory, University of Liverpool, Liverpool, United Kingdom 75 Department of Physics, Joˇzef Stefan Institute and University of Ljubljana, Ljubljana, Slovenia 76 School of Physics and Astronomy, Queen Mary University of London, London, United Kingdom 77 Department of Physics, Royal Holloway University of London, Surrey, United Kingdom 78 Department of Physics and Astronomy, University College London, London, United Kingdom 79 Louisiana Tech University, Ruston LA, United States of America 80 Laboratoire de Physique Nucl´eaire et de Hautes Energies, UPMC and Universit´e Paris-Diderot and CNRS/IN2P3, Paris, France 81 Fysiska institutionen, Lunds universitet, Lund, Sweden 82 Departamento de Fisica Teorica C-15, Universidad Autonoma de Madrid, Madrid, Spain 83 Institut f¨ur Physik, Universit¨at Mainz, Mainz, Germany 84 School of Physics and Astronomy, University of Manchester, Manchester, United Kingdom 85 CPPM, Aix-Marseille Universit´e and CNRS/IN2P3, Marseille, France 86 Department of Physics, University of Massachusetts, Amherst MA, United States of America 87 Department of Physics, McGill University, Montreal QC, Canada 88 School of Physics, University of Melbourne, Victoria, Australia 89 Department of Physics, The University of Michigan, Ann Arbor MI, United States of America 90 Department of Physics and Astronomy, Michigan State University, East Lansing MI, United States of America 91 (a)INFN Sezione di Milano; (b)Dipartimento di Fisica, Universit`a di Milano, Milano, Italy 92 B.I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, Minsk, Republic of Belarus 93 National Scientific and Educational Centre for Particle and High Energy Physics, Minsk, Republic of Belarus 94 Department of Physics, Massachusetts Institute of Technology, Cambridge MA, United States of America 95 Group of Particle Physics, University of Montreal, Montreal QC, Canada 96 P.N. Lebedev Institute of Physics, Academy of Sciences, Moscow, Russia 97 Institute for Theoretical and Experimental Physics (ITEP), Moscow, Russia 98 National Research Nuclear University MEPhI, Moscow, Russia 99 D.V. Skobeltsyn Institute of Nuclear Physics, M.V. Lomonosov Moscow State University, Moscow, Russia 100 Fakult¨at f¨ur Physik, Ludwig-Maximilians-Universit¨at M¨unchen, M¨unchen, Germany – 95 – JHEP10(2015)054 101 Max-Planck-Institut f¨ur Physik (Werner-Heisenberg-Institut), M¨unchen, Germany 102 Nagasaki Institute of Applied Science, Nagasaki, Japan 103 Graduate School of Science and Kobayashi-Maskawa Institute, Nagoya University, Nagoya, Japan 104 (a)INFN Sezione di Napoli; (b)Dipartimento di Fisica, Universit`a di Napoli, Napoli, Italy 105 Department of Physics and Astronomy, University of New Mexico, Albuquerque NM, United States of America 106 Institute for Mathematics, Astrophysics and Particle Physics, Radboud University Nijmegen/Nikhef, Nijmegen, Netherlands 107 Nikhef National Institute for Subatomic Physics and University of Amsterdam, Amsterdam, Netherlands 108 Department of Physics, Northern Illinois University, DeKalb IL, United States of America 109 Budker Institute of Nuclear Physics, SB RAS, Novosibirsk, Russia 110 Department of Physics, New York University, New York NY, United States of America 111 Ohio State University, Columbus OH, United States of America 112 Faculty of Science, Okayama University, Okayama, Japan 113 Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, Norman OK, United States of America 114 Department of Physics, Oklahoma State University, Stillwater OK, United States of America 115 Palack´y University, RCPTM, Olomouc, Czech Republic 116 Center for High Energy Physics, University of Oregon, Eugene OR, United States of America 117 LAL, Universit´e Paris-Sud and CNRS/IN2P3, Orsay, France 118 Graduate School of Science, Osaka University, Osaka, Japan 119 Department of Physics, University of Oslo, Oslo, Norway 120 Department of Physics, Oxford University, Oxford, United Kingdom 121 (a)INFN Sezione di Pavia; (b)Dipartimento di Fisica, Universit`a di Pavia, Pavia, Italy 122 Department of Physics, University of Pennsylvania, Philadelphia PA, United States of America 123 National Research Centre “Kurchatov Institute” B.P.Konstantinov Petersburg Nuclear Physics Institute, St. Petersburg, Russia 124 (a)INFN Sezione di Pisa; (b)Dipartimento di Fisica E. Fermi, Universit`a di Pisa, Pisa, Italy 125 Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh PA, United States of America 126 (a)Laborat´orio de Instrumenta¸c˜ao e F´ısica Experimental de Part´ıculas - LIP, Lisboa; (b)Faculdade de Ciˆencias, Universidade de Lisboa, Lisboa; (c)Department of Physics, University of Coimbra, Coimbra; (d)Centro de F´ısica Nuclear da Universidade de Lisboa, Lisboa; (e)Departamento de Fisica, Universidade do Minho, Braga; (f)Departamento de Fisica Teorica y del Cosmos and CAFPE, Universidad de Granada, Granada (Spain); (g)Dep Fisica and CEFITEC of Faculdade de Ciencias e Tecnologia, Universidade Nova de Lisboa, Caparica, Portugal 127 Institute of Physics, Academy of Sciences of the Czech Republic, Praha, Czech Republic 128 Czech Technical University in Prague, Praha, Czech Republic 129 Faculty of Mathematics and Physics, Charles University in Prague, Praha, Czech Republic 130 State Research Center Institute for High Energy Physics, Protvino, Russia 131 Particle Physics Department, Rutherford Appleton Laboratory, Didcot, United Kingdom 132 (a)INFN Sezione di Roma; (b)Dipartimento di Fisica, Sapienza Universit`a di Roma, Roma, Italy 133 (a)INFN Sezione di Roma Tor Vergata; (b)Dipartimento di Fisica, Universit`a di Roma Tor Vergata, Roma, Italy 134 (a)INFN Sezione di Roma Tre; (b)Dipartimento di Matematica e Fisica, Universit`a Roma Tre, Roma, Italy 135 (a)Facult´e des Sciences Ain Chock, R´eseau Universitaire de Physique des Hautes Energies - Universit´e Hassan II, Casablanca; (b)Centre National de l’Energie des Sciences Techniques Nucleaires, Rabat; (c)Facult´e des Sciences Semlalia, Universit´e Cadi Ayyad, LPHEA-Marrakech; (d)Facult´e des Sciences, Universit´e Mohamed Premier and LPTPM, Oujda; (e)Facult´e des sciences, Universit´e Mohammed V-Agdal, Rabat, Morocco – 96 – JHEP10(2015)054 136 DSM/IRFU (Institut de Recherches sur les Lois Fondamentales de l’Univers), CEA Saclay (Commissariat `a l’Energie Atomique et aux Energies Alternatives), Gif-sur-Yvette, France 137 Santa Cruz Institute for Particle Physics, University of California Santa Cruz, Santa Cruz CA, United States of America 138 Department of Physics, University of Washington, Seattle WA, United States of America 139 Department of Physics and Astronomy, University of Sheffield, Sheffield, United Kingdom 140 Department of Physics, Shinshu University, Nagano, Japan 141 Fachbereich Physik, Universit¨at Siegen, Siegen, Germany 142 Department of Physics, Simon Fraser University, Burnaby BC, Canada 143 SLAC National Accelerator Laboratory, Stanford CA, United States of America 144 (a)Faculty of Mathematics, Physics & Informatics, Comenius University, Bratislava; (b) Department of Subnuclear Physics, Institute of Experimental Physics of the Slovak Academy of Sciences, Kosice, Slovak Republic 145 (a)Department of Physics, University of Cape Town, Cape Town; (b)Department of Physics, University of Johannesburg, Johannesburg; (c)School of Physics, University of the Witwatersrand, Johannesburg, South Africa 146 (a)Department of Physics, Stockholm University; (b)The Oskar Klein Centre, Stockholm, Sweden 147 Physics Department, Royal Institute of Technology, Stockholm, Sweden 148 Departments of Physics & Astronomy and Chemistry, Stony Brook University, Stony Brook NY, United States of America 149 Department of Physics and Astronomy, University of Sussex, Brighton, United Kingdom 150 School of Physics, University of Sydney, Sydney, Australia 151 Institute of Physics, Academia Sinica, Taipei, Taiwan 152 Department of Physics, Technion: Israel Institute of Technology, Haifa, Israel 153 Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, Tel Aviv, Israel 154 Department of Physics, Aristotle University of Thessaloniki, Thessaloniki, Greece 155 International Center for Elementary Particle Physics and Department of Physics, The University of Tokyo, Tokyo, Japan 156 Graduate School of Science and Technology, Tokyo Metropolitan University, Tokyo, Japan 157 Department of Physics, Tokyo Institute of Technology, Tokyo, Japan 158 Department of Physics, University of Toronto, Toronto ON, Canada 159 (a)TRIUMF, Vancouver BC; (b)Department of Physics and Astronomy, York University, Toronto ON, Canada 160 Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Japan 161 Department of Physics and Astronomy, Tufts University, Medford MA, United States of America 162 Centro de Investigaciones, Universidad Antonio Narino, Bogota, Colombia 163 Department of Physics and Astronomy, University of California Irvine, Irvine CA, United States of America 164 (a)INFN Gruppo Collegato di Udine, Sezione di Trieste, Udine; (b)ICTP, Trieste; (c) Dipartimento di Chimica, Fisica e Ambiente, Universit`a di Udine, Udine, Italy 165 Department of Physics, University of Illinois, Urbana IL, United States of America 166 Department of Physics and Astronomy, University of Uppsala, Uppsala, Sweden 167 Instituto de F´ısica Corpuscular (IFIC) and Departamento de F´ısica At´omica, Molecular y Nuclear and Departamento de Ingenier´ıa Electr´onica and Instituto de Microelectr´onica de Barcelona (IMB-CNM), University of Valencia and CSIC, Valencia, Spain 168 Department of Physics, University of British Columbia, Vancouver BC, Canada 169 Department of Physics and Astronomy, University of Victoria, Victoria BC, Canada 170 Department of Physics, University of Warwick, Coventry, United Kingdom 171 Waseda University, Tokyo, Japan 172 Department of Particle Physics, The Weizmann Institute of Science, Rehovot, Israel 173 Department of Physics, University of Wisconsin, Madison WI, United States of America – 97 – JHEP10(2015)054 174 Fakult¨at f¨ur Physik und Astronomie, Julius-Maximilians-Universit¨at, W¨urzburg, Germany 175 Fachbereich C Physik, Bergische Universit¨at Wuppertal, Wuppertal, Germany 176 Department of Physics, Yale University, New Haven CT, United States of America 177 Yerevan Physics Institute, Yerevan, Armenia 178 Centre de Calcul de l’Institut National de Physique Nucl´eaire et de Physique des Particules (IN2P3), Villeurbanne, France aAlso at Department of Physics, King’s College London, London, United Kingdom bAlso at Institute of Physics, Azerbaijan Academy of Sciences, Baku, Azerbaijan cAlso at Novosibirsk State University, Novosibirsk, Russia dAlso at TRIUMF, Vancouver BC, Canada eAlso at Department of Physics, California State University, Fresno CA, United States of America fAlso at Department of Physics, University of Fribourg, Fribourg, Switzerland gAlso at Departamento de Fisica e Astronomia, Faculdade de Ciencias, Universidade do Porto, Portugal hAlso at Tomsk State University, Tomsk, Russia iAlso at CPPM, Aix-Marseille Universit´e and CNRS/IN2P3, Marseille, France jAlso at Universita di Napoli Parthenope, Napoli, Italy kAlso at Institute of Particle Physics (IPP), Canada lAlso at Particle Physics Department, Rutherford Appleton Laboratory, Didcot, United Kingdom mAlso at Department of Physics, St. Petersburg State Polytechnical University, St. Petersburg, Russia nAlso at Louisiana Tech University, Ruston LA, United States of America oAlso at Institucio Catalana de Recerca i Estudis Avancats, ICREA, Barcelona, Spain pAlso at Graduate School of Science, Osaka University, Osaka, Japan qAlso at Department of Physics, National Tsing Hua University, Taiwan rAlso at Department of Physics, The University of Texas at Austin, Austin TX, United States of America sAlso at Institute of Theoretical Physics, Ilia State University, Tbilisi, Georgia tAlso at CERN, Geneva, Switzerland uAlso at Georgian Technical University (GTU),Tbilisi, Georgia vAlso at Manhattan College, New York NY, United States of America wAlso at Hellenic Open University, Patras, Greece xAlso at Institute of Physics, Academia Sinica, Taipei, Taiwan yAlso at LAL, Universit´e Paris-Sud and CNRS/IN2P3, Orsay, France zAlso at Academia Sinica Grid Computing, Institute of Physics, Academia Sinica, Taipei, Taiwan aa Also at School of Physics, Shandong University, Shandong, China ab Also at Moscow Institute of Physics and Technology State University, Dolgoprudny, Russia ac Also at section de Physique, Universit´e de Gen`eve, Geneva, Switzerland ad Also at International School for Advanced Studies (SISSA), Trieste, Italy ae Also at Department of Physics and Astronomy, University of South Carolina, Columbia SC, United States of America af Also at School of Physics and Engineering, Sun Yat-sen University, Guangzhou, China ag Also at Faculty of Physics, M.V.Lomonosov Moscow State University, Moscow, Russia ah Also at National Research Nuclear University MEPhI, Moscow, Russia ai Also at Department of Physics, Stanford University, Stanford CA, United States of America aj Also at Institute for Particle and Nuclear Physics, Wigner Research Centre for Physics, Budapest, Hungary ak Also at Department of Physics, The University of Michigan, Ann Arbor MI, United States of America al Also at University of Malaya, Department of Physics, Kuala Lumpur, Malaysia ∗Deceased – 98 –