Probing the W tb vertex structure in t-channel single-top-quark production and decay in pp collisions at √s = 8 TeV with the ATLAS detector

JHEP04(2017)124 Published for SISSA by Springer Received:February 28, 2017 Revised:April 6, 2017 Accepted:April 7, 2017 Published:April 20, 2017 Probing the W tb vertex structure in t-channel single-top-quark production and decay in pp collisions at √s = 8 TeV with the ATLAS detector The ATLAS collaboration E-mail: [email protected] Abstract: To probe the Wtb vertex structure, top-quark and W-boson polarisation observables are measured from t-channel single-top-quark events produced in proton-proton collisions at a centre-of-mass energy of 8 TeV. The dataset corresponds to an integrated luminosity of 20.2 fb−1, recorded with the ATLAS detector at the LHC. Selected events contain one isolated electron or muon, large missing transverse momentum and exactly two jets, with one of them identified as likely to contain a b-hadron. Stringent selection requirements are applied to discriminate t-channel single-top-quark events from background. The polarisation observables are extracted from asymmetries in angular distributions measured with respect to spin quantisation axes appropriately chosen for the top quark and the Wboson. The asymmetry measurements are performed at parton level by correcting the observed angular distributions for detector effects and hadronisation after subtracting the background contributions. The measured top-quark and W-boson polarisation values are in agreement with the Standard Model predictions. Limits on the imaginary part of the anomalous coupling gRare also set from model-independent measurements. Keywords: Hadron-Hadron scattering (experiments) ArXiv ePrint: 1702.08309 Open Access, Copyright CERN, for the benefit of the ATLAS Collaboration. Article funded by SCOAP3. doi:10.1007/JHEP04(2017)124 JHEP04(2017)124 Contents 1 Introduction 1 2 Polarisation observables and asymmetries 3 3 The ATLAS detector 7 4 Data and simulation samples 7 5 Event reconstruction and selection 9 6 Background normalisation and modelling 11 7 Signal and background event yields 13 8 Angular distributions 16 9 Unfolding 17 10 Systematic uncertainties 20 11 Results 23 12 Conclusion 26 The ATLAS collaboration 33 1 Introduction At hadron colliders, top quarks are predominantly produced in pairs (t¯ t) via the flavourconserving strong interaction, but single top-quark production can occur via chargedcurrent electroweak processes involving a Wtb vertex. At leading order in QCD perturbation theory, three sub-processes contribute to single top-quark production: an exchange of a virtual Wboson either in the t-channel or in the s-channel, or the associated production of a top quark with an on-shell Wboson (Wt). The t-channel and s-channel processes do not interfere at next-to-leading-order in QCD and are thus well defined with that precision [1]. In proton-proton (pp) collisions, the t-channel exchange, depicted in figure 1, is the dominant production process of single top quarks. The exchange of a space-like Wboson due to the interaction of a light quark with a b-quark produces a top quark and a forward light-quark (called the spectator quark) in the final state. Furthermore, as a consequence of the vector minus axial-vector (V-A) form of the Wtb vertex in the Standard Model, the – 1 – JHEP04(2017)124 q q0 W g bt ¯ b Figure 1. Leading-order Feynman diagram for t-channel production of single top quarks in pp collisions. In the depicted four-flavour scheme (2 →3 process) the initial b-quark arises from a gluon splitting into a bb pair. produced top quarks are highly polarised, in particular along the direction of the spectatorquark momentum [2,3]. Within the Standard Model the top quark decays through the electroweak interaction into an on-shell Wboson and a b-quark, with a lifetime much shorter than the time scale necessary to depolarise the spin. The information on the top-quark spin can thus be obtained from its decay products. The produced real Wboson also possesses a polarisation (or helicity state), which can be extracted from angular distributions of its decay products through the measurement of spin-dependent observables [4]. Measuring the top-quark polarisation and the W-boson spin observables in t-channel single top-quark production provides a powerful probe for studying the Wtb vertex in both top-quark production and decay. New physics effects resulting in corrections to the Wtb vertex would affect the top-quark and W-boson polarisations. In the effective operator formalism the most general W tb Lagrangian can be written as [5]: LW tb =−g √2bγµ(VLPL+VRPR)tW− µ−g √2biσµνqν mW (gLPL+gRPR)tW− µ+ h.c. (1.1) In this expression gis the weak coupling constant, mWand qνare the mass and the fourmomentum of the Wboson, respectively, PL,R ≡(1 ∓γ5)/2 are the leftand right-handed projection operators, and σµν = [γµ, γν]/2. The constants VL,R and gL,R are the leftand right-handed vector and tensor couplings, respectively. In the Standard Model at tree level the coupling VLis the Vtb element of the quark-mixing Cabibbo-Kobayashi-Maskawa (CKM) matrix that is close to one, while the anomalous couplings VRand gL,R are all zero. Deviations from these values would provide hints of physics beyond the Standard Model, and complex values would imply that the top-quark decay has a CP-violating component [5]. The imaginary part of gR(Im gR) can be probed with the best precision in the t-channel production of single top quarks through the measurement of polarisation observables [5]. Limits on Im gRhave been set at the LHC by the ATLAS Collaboration at a centre-of-mass energy of 7 TeV from the analysis of the double-differential angular decay rates of the produced t-channel single-top-quark events [6]. Searches for anomalous – 2 – JHEP04(2017)124 Wtb couplings in single-top-quark production and decay at 7 and 8 TeV have also been published by the CMS Collaboration [7–9]. The top-quark polarisation and the W-boson spin observables can be extracted in an alternative way from the measurement of asymmetries in various angular distributions of the top-quark decay products [4,5]. Firstly, this article reports a determination of the topquark polarisation as well as the W-boson spin observables extracted from the measured angular asymmetries. Such measurements serve as a consistency check with the Standard Model predictions. Secondly, limits on Im gRare presented from the measurement of the socalled normal forward-backward asymmetry, which is the asymmetry predicted to have the highest sensitivity to Im gR[5], and the asymmetry related to the top-quark polarisation. Here Standard Model values are assumed for all other couplings. The measurements reported in this article use 20.2 fb−1of data collected at a centreof-mass energy of 8 TeV with the ATLAS detector at the LHC. Stringent selection requirements are applied in order to separate signal from background. The Wboson from the top-quark decay is identified through its decay modes leading to a final state with an electron or a muon, and missing transverse momentum for the neutrino. The measurement at parton level of the asymmetries is performed by unfolding the observed angular distributions from detector and physics effects after subtracting the background contributions. For all reported results the electron and muon channels are merged, and the analysis is carried out independently of the lepton charge, in order to measure the polarisation observables associated with the combined production and decay of top quarks and top antiquarks. 2 Polarisation observables and asymmetries The top-quark polarisation is determined from angular distributions of the decay products reconstructed in the top-quark rest frame, while the W-boson spin observables are determined from angular distributions of the charged lepton reconstructed in the W-boson rest frame. In the top-quark rest frame, the angular distribution of any decay product Xof the top quark is given by 1 Γ dΓ d(cos θX)=1 2(1 + αXPcos θX),(2.1) where θXis the angle between the top-quark spin axis and the direction of motion of the chosen decay product in the top-quark rest frame, Γ is the total decay width of the top quark, αXis the spin analysing power associated with X, and Pis the top-quark degree of polarisation. The charged lepton is the most sensitive spin analyser; at next-toleading-order (NLO) precision in QCD its spin analysing power is α`±=±0.998 [10]. In the t-channel, single top quarks are produced with a large degree of polarisation in the direction of motion of the spectator quark [3,11]. This direction is used to define the top-quark spin axis in this measurement. The corresponding degrees of polarisation calculated at NLO in QCD are 0.91 and −0.86 for top-quark and top-antiquark production, respectively [3]. In the framework of a general formalism developed in ref. [4], the spin-density matrix elements for the W-boson helicity components 0, ±1, resulting from the decay of polarised – 3 – JHEP04(2017)124 ~q (ˆz) ~ N(−ˆy) ~ T(ˆx) ˆst ~p` θ∗ ` θN ` φ∗ `(T) φ∗ N Figure 2. Coordinate system and angles used to define the W-boson spin observables and their related angular asymmetries in the decay of polarised top quarks. The W-boson momentum ~q in the top-quark rest frame defines the ˆz-axis; the top-quark spin direction ˆst, taken along the spectator-quark momentum in the top-quark rest frame, defines the ˆx–ˆzplane. The polar and azimuthal angles of the charged-lepton momentum ~p`in the W-boson rest frame are labelled θ∗ ` and φ∗ `, respectively. The normal and transverse axes are defined relatively to ~q and ˆstaccording to ~ N= ˆst×~q and ~ T=~q ×~ N; they are along the −ˆyand ˆxaxes of the coordinate system, respectively. The azimuthal angles φ∗ Nand φ∗ Tof the charged lepton in the W-boson rest frame are defined relatively to the ~ Nand ~ Taxes, respectively (φ∗ T≡φ∗ `), while θN `and θT `(not shown in the figure) are the relative angles between ~p`and the ~ Nand ~ Taxes, respectively. top-quarks, can be parameterised in terms of expectation values of six independent spin observables: hS1,2,3i,hT0iand hA1,2i. With (θ∗ `, φ∗ `) denoting the polar and azimuthal angles of the charged-lepton momentum in the W-boson rest frame, the fully differential decay width of a Wboson can be written as 1 Γ dΓ d(cos θ∗ `)dφ∗ ` =3 8π2 3+1 √6hT0i3 cos2θ∗ `−1+hS3icos θ∗ ` +hS1icos φ∗ `sin θ∗ `+hS2isin φ∗ `sin θ∗ ` −hA1icos φ∗ `sin 2θ∗ `−hA2isin φ∗ `sin 2θ∗ `.(2.2) In this formalism the W-boson spin axis is taken along the direction of the W-boson momentum in the top-quark rest frame, or equivalently along the direction opposite to the b-quark momentum in the W-boson rest frame. The coordinate system used and the various angles defined for the charged lepton in the W-boson rest frame are depicted in figure 2. The angular distribution expressed in equation (2.2) implies an integration over all the possible directions of the top-quark spin relative to the W-boson spin axis. The top-quark polarisation is propagated to the spin observables hS1,2iand hA1,2i, which depend in a – 4 – JHEP04(2017)124 proportional way on the value of P. The spin observables hS3iand hT0ido not depend on P, and are related to the W-boson helicity fractions FR,FLand F0[4]. From the values of the helicity fractions predicted by the Standard Model at nextto-next-to-leading order (NNLO) in QCD assuming a top-quark mass of 172.5 GeV and a b-quark mass of 4.8 GeV [12], one obtains hS3i=−0.31 and hT0i=−0.43. The uncertainties in these predictions due to the theoretical uncertainties in the helicity fractions are lower than 0.01 for both hS3iand hT0i. Combining the predicted degrees of polarisation Pt= 0.91 and P¯ t=−0.86 with the t-channel single-top cross-sections σt= 54.9 pb and σ¯ t= 29.7 pb calculated at NLO in QCD for top-quark and top-antiquark production [13], the Standard Model predictions for hS1,2iand hA1,2iare: hS1i= 0.46, hA1i= 0.23 and hS2i=hA2i= 0. These values are calculated at leading order (LO) in QCD from the expressions of the spin-density matrix elements given in refs. [4,5]. The uncertainties in these predictions resulting from the uncertainties in the top-quark, b-quark and W-boson masses, and from higher-order effects [14], are all smaller than 0.01. Measured values not equal to zero for the hS2iand hA2ispin observables would signal the presence of an imaginary coupling in the Wtb vertex, since hS2iand hA2iare only sensitive to Im gR[4].1However, hS2iis twice as sensitive as hA2ito Im gR, making this observable more suitable for determining this coupling. The other four W-boson spin observables are mainly sensitive to Re gR, with a poor sensitivity to Im gR[4,5]. The top-quark polarisation and the W-boson spin observables can be extracted from asymmetries derived by integrating the angular distributions expressed in equations (2.1) and (2.2). These asymmetries are based on single or combined angular observables. They are listed in table 1, together with their associated angular observables and their relation to the polarisation observables.2The asymmetry values predicted by the Standard Model are also reported in the table. Most of the polarisation observables are based on a forward-backward asymmetry, which is generically defined as a function of a given angular observable cos θaccording to AFB =N(cos θ > 0) −N(cos θ < 0) N(cos θ > 0) + N(cos θ < 0) ,(2.3) where Nis the number of events. One of the W-boson spin observables is determined from an asymmetry called edge-central and defined as follows AEC =N|cos θ|>1 2−N|cos θ|<1 2 N|cos θ|>1 2+N|cos θ|<1 2.(2.4) The product α`Pis extracted from the forward-backward asymmetry A` FB of the cos θ` angular distribution, where θ`is the angle between the lepton momentum in the top-quark rest frame and the top-quark spin axis. The measurement of Pcan also be performed from 1Including one-loop QCD and electroweak corrections the prediction for gRin the Standard Model is (−7.17 −1.23i) ×10−3[15], leading to values of the order of 10−3for the hS2iand hA2ispin observables. 2The asymmetries used in this article and in ref. [5] are related to the ones defined in refs. [4,16] through the equations AT FB =Ax FB,AN FB =−Ay FB,AT,φ FB =A1 FB,AN,φ FB =−A2 FB,AFB =Az FB. – 5 – JHEP04(2017)124 Asymmetry Angular observable Polarisation observable SM prediction A` FB cos θ`1 2α`P0.45 AtW FB cos θWcos θ∗ ` 3 8P(FR+FL) 0.10 AFB cos θ∗ ` 3 4hS3i=3 4(FR−FL)−0.23 AEC cos θ∗ ` 3 8q3 2hT0i=3 16 (1 −3F0)−0.20 AT FB cos θT ` 3 4hS1i0.34 AN FB cos θN `−3 4hS2i0 AT,φ FB cos θ∗ `cos φ∗ T−2 πhA1i −0.14 AN,φ FB cos θ∗ `cos φ∗ N 2 πhA2i0 Table 1. Asymmetries with their associated angular observables and their relation to the top-quark polarisation and W-boson spin observables. The values predicted by the Standard Model are also given. They are calculated using the predictions at NLO in QCD for Pand α`, the predictions at NNLO for the helicity fractions, and the predictions at LO for hS1,2iand hA1,2i. The uncertainties in these values are all lower than 0.01. They are estimated from the uncertainties in the top-quark, b-quark and W-boson masses, added in quadrature, including the uncertainty in αsand an estimate of the higher-order effects for the asymmetries related to the W-boson spin observables. the forward-backward asymmetry AtW FB defined with respect to the combined angular observable cos θWcos θ∗ `[17], where θWis the angle between the W-boson momentum in the top-quark rest frame and the top-quark spin axis. This asymmetry is proportional to the product of Pand the sum of two W-boson helicity fractions, as reported in table 1. The W-boson spin observables hS3iand hT0iare derived from the forward-backward asymmetry AFB and from the edge-central asymmetry AEC of the cos θ∗ `angular distribution, respectively. Using the definition [5] of the normal axis ~ N=~st×~q and transverse axis ~ T=~q ×~ N, as illustrated in figure 2,hS1iand hS2iare determined from the forward-backward asymmetries AT FB and AN FB in the angular observables cos θT `and cos θN `, respectively. The hA1i and hA2ispin observables are determined from the forward-backward asymmetries AT,φ FB and AN,φ FB based on the combination of cos θ∗ `with the cosine of the azimuthal angles φ∗ T and φ∗ Ndefined relatively to ~ Tand ~ N, respectively. Limits on Im gRcan be extracted from the measurement of the AN FB asymmetry, which has the highest sensitivity to this coupling. For small Im gRvalues, taking VL= 1 and VR=gL= 0, a linear dependence on Im gRis obtained for this asymmetry: AN FB = 0.64 PIm gR[5]. In this relation the weak dependence of Pon Im gR, which is of quadratic form, is not included. As AN FB depends on P, the measured value of the A` FB asymmetry is required to constrain Pfor the limit computation. The quadratic variation of Pand α`as a function of Im gR[5,18] is taken into account when setting the limits through the – 6 – JHEP04(2017)124 procedure explained in section 11. The A` FB asymmetry is chosen to constrain Pbecause its measurement is found to be independent of the value of Im gRassumed when unfolding the corresponding angular distribution; this is discussed in section 9. 3 The ATLAS detector The ATLAS detector [19] is a multi-purpose particle detector with a forward-backward symmetric, cylindrical geometry and a near 4πcoverage in solid angle around the collision point.3It consists of an inner tracking detector surrounded by a thin superconducting solenoid, electromagnetic and hadronic calorimeters, and a muon spectrometer. The inner detector is immersed in a 2 T axial magnetic field, and provides charged-particle tracking in the pseudorapidity range |η|<2.5. It contains a high-granularity silicon pixel detector, a silicon microstrip tracker, and a straw-tube transition radiation tracker. Lead/liquid-argon sampling calorimeters provide electromagnetic energy measurements with high granularity in the pseudorapidity ranges |η|<1.5 (barrel region) and 1.4<|η|<3.2 (endcap region). Hadronic energy measurements are provided by steel/scintillator-tile calorimeters in the central pseudorapidity range |η|<1.7 and by copper/liquid-argon calorimeters in the endcap region 1.5<|η|<3.2. The forward region is instrumented with liquid-argon calorimeters for electromagnetic and hadronic energy measurements, extending the coverage to |η|= 4.9. The muon spectrometer surrounds the calorimeters and incorporates three large air-core toroid superconducting magnets with eight coils each. It includes separate trigger detectors and high-precision tracking chambers, providing muon momentum measurement for |η|<2.7 and muon triggering up to |η|= 2.4. A three-level trigger system is used to select interesting events [20]. The first-level trigger is hardware-based and uses a subset of the detector information to reduce the accepted event rate to less than 75 kHz. The second and third levels are software-based and together reduce the event rate to about 400 Hz. 4 Data and simulation samples The analysis is performed using pp collision data collected in 2012 by the ATLAS detector at a centre-of-mass energy of 8 TeV. The events are required to pass single-electron or single-muon triggers [20,21], resulting, after detector and data-quality requirements, in a data sample corresponding to an integrated luminosity of 20.2 fb−1. The electron and muon triggers impose a threshold of 24 GeV on the transverse momentum (pT), along with isolation requirements. To recover efficiency for higher-pTleptons, the isolated lepton triggers are complemented by triggers without isolation requirements, but with a threshold raised to 60 GeV for electrons and to 36 GeV for muons. 3ATLAS uses a right-handed coordinate system with its origin at the nominal interaction point in the centre of the detector and the z-axis along the beam pipe. The x-axis points from the interaction point to the centre of the LHC ring, and the y-axis points upwards. Cylindrical coordinates (r, φ) are used in the transverse plane, φbeing the azimuthal angle around the z-axis. The pseudorapidity is defined in terms of the polar angle θas η=−ln tan(θ/2). – 7 – JHEP04(2017)124 Samples of signal and background events are simulated using various Monte Carlo generators. The generated events are passed through a simulation of the ATLAS detector [22] based on the Geant4 framework [23]. For some samples a faster simulation (ATLFAST-II [24]), making use of a parameterised response of the electromagnetic and hadronic calorimeters, is performed instead. Minimum-bias events simulated with the Pythia (8.1) [25] generator are overlaid to model the pile-up effects from additional pp collisions in the same and nearby bunch crossings. All simulated events are then processed using the same reconstruction and analysis chain as for data events. Signal t-channel single-top-quark events are generated with the NLO Powheg-Box (r2556) [26–28] generator, which uses the four-flavour scheme (figure 1) for the matrixelement calculations [29]. Events are generated with the CT10f4 [30] parton distribution functions (PDFs), and the renormalisation and factorisation scales are set to µ2 R=µ2 F= 16 m2 b+p2 T,b, where mbis the mass of the b-quark and pT,b is the transverse momentum of the b-quark from the initial gluon splitting (called the spectator b-quark) [29]. Additional tchannel samples are produced with the LO Protos (2.2) [31] generator using the CTEQ6L1 PDFs [32]. Protos events are generated using the four-flavour scheme, as well, and anomalous couplings are enabled in both the production and the decay vertices, varying Re VLand Im gRsimultaneously to keep the top-quark width invariant. The factorisation scale is set to µ2 F=−p2 Wfor the light quark, where pWis the four-momentum of the exchanged Wboson, and to µ2 F=m2 b+p2 T,b for the gluon. Eight Protos samples generated with Im gRin the range [−0.144, 0.144] and Re VLin the range [0.982, 1] are used, including the Standard Model configuration Im gR= 0 and Re VL= 1. These Protos samples are used to compute the parton-level unfolding corrections and to check the reliability of the unfolding method, while the Powheg-Box sample is used to determine the expected event yields and template distributions. Samples of t¯ t[33], s-channel single-top-quark and Wt [34] background events are produced using the Powheg-Box (r2819, r3026) generator with the CT10 PDFs. To generate the t¯ tsample, the model parameter hdamp, which effectively regulates the high-pTgluon radiation, is set to the top-quark mass mt[35]. For the above samples, parton showering, hadronisation and the underlying event are simulated with Pythia (6.426) [36] using parameter values set to the Perugia 2011C tune [37], and the CTEQ6L1 PDFs. To study the modelling uncertainties of all processes involving top quarks, either alternative generators or parameter variations in the Powheg-Box and Pythia settings are used. For the estimation of the uncertainty in the t-channel matrix-element calculation, a sample is produced using the MadGraph5 aMC@NLO (2.0) [38] generator, interfaced to Herwig (6.52) [39,40] for parton showering and to Jimmy (4.31) [41] for the underlyingevent modelling with the ATLAS AUET2 tuned parameter settings [42] and the CT10f4 PDFs. The events are generated using the four-flavour scheme. For the t¯ t,s-channel and Wt processes, alternative samples are produced using the MC@NLO (4.03) [43–46] generator interfaced to Herwig (6.52) for parton showering and Jimmy (4.31) for the underlying-event modelling with the ATLAS AUET2 tune and the CT10 PDFs. To specif- – 8 – JHEP04(2017)124 Events / 0.2 0 20000 40000 Data 2012 tq bt,Wt tt +jetsW +jetsZ,VV Multijet Stat.+Multijet unc. ATLAS +jets control regionW -1 = 8 TeV, 20.2 fbs (j)|η| 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 Pred. Data 0.8 1 1.2 (a) Events / 0.3 0 20000 40000 60000 Data 2012 tq bt,Wt tt +jetsW +jetsZ,VV Multijet Stat.+Multijet unc. ATLAS +jets control regionW -1 = 8 TeV, 20.2 fbs (j,b)η∆ 0 1 2 3 4 5 6 Pred. Data 0.8 1 1.2 (b) Events / 10 GeV 0 20000 40000 Data 2012 tq bt,Wt tt +jetsW +jetsZ,VV Multijet Stat.+Multijet unc. ATLAS +jets control regionW -1 = 8 TeV, 20.2 fbs b) [GeV]νm(l 50 100 150 200 250 300 350 400 450 Pred. Data 0.8 1 1.2 (c) Events / 15 GeV 0 20000 40000 60000 Data 2012 tq bt,Wt tt +jetsW +jetsZ,VV Multijet Stat.+Multijet unc. ATLAS +jets control regionW -1 = 8 TeV, 20.2 fbs ) [GeV] miss T (l,j,E T H 100 200 300 400 500 600 Pred. Data 0.8 1 1.2 (d) Figure 5. Distributions of the selection variables in the W+jets control region: (a) |η|of the untagged jet, (b) separation in ηbetween the untagged and b-tagged jets, (c) reconstructed topquark mass, and (d) scalar sum of the pTof the lepton, the pTof the jets and Emiss T. The observed distributions are compared to the predicted signal and background distributions. The W+jets distributions are normalised to match the observed number of events. The labels tq and t¯ brefer to the t-channel and s-channel single-top-quark processes, respectively, and V V to diboson production. The uncertainty bands include the uncertainty due to the limited size of the simulation samples and the uncertainty in the normalisation of the multijet background, added in quadrature. The last bin of the histograms includes overflows. The lower panels show the ratio of data to prediction. expectation), are merged and fixed to the predictions. The multijet contribution is kept fixed to its data-driven estimate. The results of the maximum-likelihood fit together with the associated statistical uncertainties (referred to as statistical post-fit uncertainties) are shown in table 2. They are presented as scale factors to be applied to the predicted event yields. The results are found to be stable when the constraints imposed on the top-quark and W+jets backgrounds are significantly relaxed. Table 3provides the signal and background event yields in the signal region after scaling to the results of the fit to the data. The signal-to-background ratio is 1.2, the t-channel single top-quark production representing 54% of the total expectation. The two main background contributions come from W+jets (19%) and t¯ tproduction (18%). – 15 – JHEP04(2017)124 Process Scale factor t-channel 0.95 ±0.02 t¯ t,Wt,s-channel 1.01 ±0.01 W+jets 1.10 ±0.01 Table 2. Scale factors and uncertainties extracted for the signal and background processes from the simultaneous maximum-likelihood fit of the event yields in the signal, anti-signal and t¯ tregions. The quoted uncertainties are statistical only. Process Event yield t-channel 5700 ±110 Wt,s-channel 265 ±12 t¯ t1914 ±15 W+jets 2044 ±57 Z+jets, diboson 188 ±9 Multijet 420 ±290 Total expectation 10530 ±320 Data 10527 Table 3. Signal and background event yields in the signal region after scaling to the results of the maximum-likelihood fit. The quoted uncertainties add in quadrature the post-fit uncertainties and the uncertainties due to the limited size of the simulation samples, except for the data-driven multijet contribution to which the normalisation uncertainty of 70% is applied. The total expectation is compared to the observed number of events. 8 Angular distributions The distributions observed at reconstruction level for the angular observables used to measure the various asymmetries are shown in figures 6and 7. They are compared to the predicted signal and background distributions, normalised to the results of the maximumlikelihood fit. To minimise the unfolding corrections that are applied after background subtraction, two bins are chosen for the angular distributions from which forward-backward asymmetries are extracted, while four bins are used for the angular distribution from which the AEC asymmetry is determined. Depending on the angular observable, as described in section 2, the charged-lepton four-momentum is computed in the rest frame of the reconstructed top quark or in the rest frame of the reconstructed Wboson. The angular observables related to the top-quark polarisation are defined by taking the momentum of the untagged jet as the spectatorquark direction, whereas those related to the W-boson spin observables are defined by considering the reverse momentum of the b-tagged jet as the W-boson direction. – 16 – JHEP04(2017)124 Events 0 5000 10000 15000 Data 2012 tq bt,Wt tt +jetsW +jetsZ,VV Multijet Stat.+Multijet unc. ATLAS Signal region -1 = 8 TeV, 20.2 fbs l θcos -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 Pred. Data 0.95 1 1.05 (a) Events 0 5000 10000 Data 2012 tq bt,Wt tt +jetsW +jetsZ,VV Multijet Stat.+Multijet unc. ATLAS Signal region -1 = 8 TeV, 20.2 fbs * l θ cos W θcos -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 Pred. Data 0.95 1 1.05 (b) Events 0 5000 10000 Data 2012 tq bt,Wt tt +jetsW +jetsZ,VV Multijet Stat.+Multijet unc. ATLAS Signal region -1 = 8 TeV, 20.2 fbs * l θcos -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 Pred. Data 0.95 1 1.05 (c) Events / 0.5 0 2000 4000 6000 Data 2012 tq bt,Wt tt +jetsW +jetsZ,VV Multijet Stat.+Multijet unc. ATLAS Signal region -1 = 8 TeV, 20.2 fbs * l θcos -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 Pred. Data 0.95 1 1.05 (d) Figure 6. Distributions in the signal region of the angular observables used to measure the various asymmetries: (a) cos θ`for A` FB, (b) cos θWcos θ∗ `for AtW FB , (c) cos θ∗ `with two bins for AFB, and (d) cos θ∗ `with four bins for AEC. The observed distributions are compared to the predicted signal and background distributions, normalised to the results of the maximum-likelihood fit. The template t-channel distributions are taken from the baseline Powheg-Box sample. The labels tq and t¯ b refer to the t-channel and s-channel single-top-quark processes, respectively, and V V to diboson production. The uncertainty bands include the statistical post-fit uncertainty, the uncertainty due to the limited size of the simulation samples and the uncertainty in the normalisation of the multijet background, added in quadrature. The lower panels show the ratio of data to prediction. 9 Unfolding The measured angular distributions are unfolded to the parton level,6so that the asymmetries extracted from the corrected angular distributions can be directly compared to theoretical calculations. The unfolding corrections account for distortions due to detector resolution, selection efficiencies, and reconstruction of the Wboson and top quark. They also include the effects due to hadronisation and parton showering. 6Partons are defined from the matrix-element hard process and immediate decays. – 17 – JHEP04(2017)124 Events 0 5000 10000 Data 2012 tq bt,Wt tt +jetsW +jetsZ,VV Multijet Stat.+Multijet unc. ATLAS Signal region -1 = 8 TeV, 20.2 fbs N l θcos -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 Pred. Data 0.95 1 1.05 (a) Events 0 5000 10000 Data 2012 tq bt,Wt tt +jetsW +jetsZ,VV Multijet Stat.+Multijet unc. ATLAS Signal region -1 = 8 TeV, 20.2 fbs T l θcos -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 Pred. Data 0.95 1 1.05 (b) Events 0 5000 10000 Data 2012 tq bt,Wt tt +jetsW +jetsZ,VV Multijet Stat.+Multijet unc. ATLAS Signal region -1 = 8 TeV, 20.2 fbs * N φ* cos l θcos -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 Pred. Data 0.95 1 1.05 (c) Events 0 5000 10000 Data 2012 tq bt,Wt tt +jetsW +jetsZ,VV Multijet Stat.+Multijet unc. ATLAS Signal region -1 = 8 TeV, 20.2 fbs * T φ* cos l θcos -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 Pred. Data 0.95 1 1.05 (d) Figure 7. Distributions in the signal region of the angular observables used to measure the various asymmetries: (a) cos θN `for AN FB, (b) cos θT `for AT FB, (c) cos θ∗ `cos φ∗ Nfor AN,φ FB , and (d) cos θ∗ `cos φ∗ T for AT,φ FB . The observed distributions are compared to the predicted signal and background distributions, normalised to the results of the maximum-likelihood fit. The template t-channel distributions are taken from the baseline Powheg-Box sample. The labels tq and t¯ brefer to the t-channel and s-channel single-top-quark processes, respectively, and V V to diboson production. The uncertainty bands include the statistical post-fit uncertainty, the uncertainty due to the limited size of the simulation samples and the uncertainty in the normalisation of the multijet background, added in quadrature. The lower panels show the ratio of data to prediction. The unfolding procedure is applied to the angular distributions after subtracting the background contributions, and is based on a matrix inversion combined with an efficiency correction. The number of unfolded signal events Nunfolded jin each bin jof the parton-level distribution is obtained from the background-subtracted yields Nmeasured imeasured in all bins iof the reconstructed distribution, according to Nunfolded j=PiM−1 ji Nmeasured i j ,(9.1) where Mji is the migration matrix which relates the parton-level and reconstructed values of the considered angular variable, and jis the event selection efficiency. Both the mi- – 18 – JHEP04(2017)124 gration matrix and the selection efficiency are computed using samples of t-channel events simulated with the Protos generator, as described below. For the chosen numbers of bins, the fractions of simulated events belonging to the diagonal elements of the migration matrices are found to be between 68% and 90%, depending on the angular observable. The selection efficiencies are between 0.6% and 1.6%, depending on the angular observable and on the bin range. The matrix inversion is performed by using the iterative Bayesian method [81] as implemented in the RooUnfold framework [82]. The number of iterations is chosen such that the absolute change in the extracted asymmetry between two successive steps becomes lower than 0.0005. The unfolding procedure has been validated through convergence and closure tests performed by using template distributions constructed from the t-channel Powheg-Box and Protos samples presented in section 4. The closure tests showed that the residual bias induced by the unfolding method is negligible, whatever the measured asymmetry. With the aim of testing their compatibility with the Standard Model predictions, all asymmetries described in section 2, except AN FB, are extracted using the Protos simulation generated with the Standard Model values of the W tb couplings to determine the migration matrix and the selection efficiency. For all the asymmetry measurements, the Standard Model Wtb couplings, as implemented in the Powheg-Box generator, are considered for the subtracted top-quark backgrounds. To constrain Im gRusing the method explained in section 2, the AN FB and A` FB asymmetries must be measured without any assumption about Im gR. It is observed that the presence of anomalous couplings in general modifies the kinematics in such a way that the efficiency corrections are dependent on the Wtb couplings. While the measurement of A` FB is found to be independent of the value of Im gRassumed in the unfolding corrections, the measurement of AN FB is found to depend on the unfolding corrections used. By applying an interpolation technique it is possible to unfold the cos θN `angular distribution independently of any assumption about Im gR, so that the extracted AN FB asymmetry, combined with A` FB, can be used to constrain this coupling. The interpolation method is based on determining the unfolding corrections using a linear combination of the migration and efficiency corrections provided by five Protos samples in which Im gRis varied (Im gR= 0,±0.094,±0.23). An iterative procedure is applied to determine the coefficients of the linear combination until convergence is reached in the extracted AN FB asymmetry. The method proceeds as follows. An initial value of AN FB is first extracted using the standard Protos unfolding corrections. This value is then used to determine, via a Lagrange interpolation, the weights to be applied to the five predicted corrections. A new value of AN FB is obtained after unfolding the cos θN `angular distribution with these corrections using the Bayesian method. The chosen convergence criterion for the interpolation procedure requires that the difference between the extracted AN FB from two successive steps is smaller than 0.0005. By using template distributions given by Protos samples not used in the linear combination of the unfolding corrections (Im gR=±0.043,±0.144), it has been checked that this method recovers the generated asymmetries at parton level. – 19 – JHEP04(2017)124 l θcos -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 Events 0 2000 4000 6000 Data 2012 = 0 R Im g = -0.23 R Im g = +0.23 R Im g Stat.+Multijet unc. ATLAS Signal region -1 = 8 TeV, 20.2 fbs (a) N l θcos -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 Events 0 2000 4000 6000 Data 2012 = 0 R Im g = -0.23 R Im g = +0.23 R Im g Stat.+Multijet unc. ATLAS Signal region-1 = 8 TeV, 20.2 fbs (b) Figure 8. Comparison of the distributions observed in the signal region with the distributions predicted as a function of Im gRfor the angular observables from which the asymmetries used to set limits on this coupling are measured: (a) cos θ`for A` FB and (b) cos θN `for AN FB. The predicted distributions are determined by adding the signal and background contributions normalised to the results of the maximum-likelihood fit. The template signal distributions are taken from the Protos samples generated with Im gR= 0 (Standard Model parameterisation) and Im gR=±0.23. The corresponding parton-level values for the AN FB asymmetry are 0 and ±0.10, respectively. For A` FB the predicted values are 0.45 for Im gR= 0 and 0.34 for Im gR=±0.23. The uncertainty bands include the statistical post-fit uncertainty, the uncertainty due to the limited size of the simulation samples and the uncertainty in the normalisation of the multijet background, added in quadrature. The sensitivity to Im gRof the cos θ`and cos θN `distributions, which are used to set limits on this coupling, is illustrated in figure 8. In this figure the observed distributions are compared to the signal-plus-background predictions built by adding the signal templates given by the Protos samples generated with Im gR= 0 (Standard Model parameterisation) and Im gR=±0.23, the latter corresponding to the maximum values considered in the interpolation method described above. 10 Systematic uncertainties Several sources of systematic uncertainty affect the asymmetry measurements, modifying the signal and background event yields and angular distributions. To evaluate the impact of each source the asymmetries are extracted by unfolding the template distributions after varying them to reflect that source of uncertainty. In each case a new background estimation is performed before subtraction, using the fitting procedure described in section 7. For all sources of systematic uncertainty other than those associated with the limited size of the simulation samples, the nominal unfolding corrections are considered. The systematic uncertainty is evaluated as the difference between the nominal asymmetry value and the one measured using the varied normalisations and shapes. The sources of systematic uncertainty are split into the following categories: – 20 – JHEP04(2017)124 Background normalisation. The uncertainties in the normalisation of the top-quark and W+jets background processes are determined from the maximum-likelihood fit. For the merged Z+jets and diboson processes the normalisation uncertainty of 20% introduced in section 6is applied to the predictions. For the data-driven normalisation of the multijet background the uncertainty of 70% estimated from the comparison of the matrix-method estimates with those given by the jet-electron and anti-muon methods is used. The uncertainty in the integrated luminosity is 1.9% [83]. It is propagated to the asymmetry measurements through the normalisation of the simulated backgrounds. Detector modelling. Systematic uncertainties in the reconstruction and energy calibration of jets, electrons and muons are propagated in the analysis through variations in the modelling of the detector response. For the jets, the main source of uncertainty is the energy scale, evaluated using a combination of in situ techniques [54]. Other jet-related uncertainty sources are the modelling of the energy resolution [84] and reconstruction efficiency [54] (both referred to as jet reconstruction uncertainties), and the modelling of the tagging efficiencies of b-quark jets, c-quark jets and light-flavour jets [57,58]. Uncertainties related to leptons come from trigger, identification and isolation efficiencies, as well as from the energy scale and resolution [49,50] (all referred to as lepton reconstruction uncertainties). The uncertainties in the energy scale and resolution corrections applied to leptons and jets are propagated to the computation of the missing transverse momentum. The scale and resolution uncertainties due to soft jets and to contributions of calorimeter energy deposits not associated with any reconstructed objects are also considered and evaluated independently (they are labelled Emiss Treconstruction uncertainties). For all detector modelling uncertainties, positive and negative uncertainties are estimated separately from the corresponding shifts. Signal and background modelling. Systematic uncertainties associated with the signal and background modelling are estimated by comparing event samples from different generators and by varying parameters in the event generation. The uncertainty in the matrix-element calculation in the simulation of the t-channel single-top-quark process is estimated by comparing MadGraph5 aMC@NLO+Herwig with Powheg-Box+Herwig. For the t¯ tand Wt processes, MC@NLO is compared with Powheg-Box, both generators interfaced to Herwig. The uncertainty in the parton shower is estimated by comparing Powheg-Box interfaced with Pythia and Herwig for the t-channel, t¯ tand Wt processes. For the s-channel single-top-quark contribution the uncertainty due to the choice of generator and parton shower is estimated in a combined way by comparing MC@NLO+Herwig with Powheg-Box+Pythia. An additional modelling uncertainty is considered for the signal process by comparing the NLO Powheg-Box sample to the LO Protos sample implementing the Standard Model parameterisation of the W tb couplings. To estimate this uncertainty, only the shapes of the distributions are varied in order to assess the impact of using a LO generator to determine the unfolding corrections. The uncertainty in the amount of QCD radiation is evaluated for all top-quark processes by comparing the Powheg-Box samples generated with the varied hard-process and – 21 – JHEP04(2017)124 parton-shower scales presented in section 4. The largest shift in the measured asymmetries is taken as uncertainty. The dependence of the measured asymmetries on the top-quark mass is estimated using Powheg-Box samples generated with different top-quark masses. Variations lower than 0.01 per GeV are found for the measured asymmetry values. Therefore, these variations are not included in the total systematic uncertainty. The impact of the flavour composition on the modelling of the W+jets distributions is determined by propagating an uncertainty of 50% in the ratio of W+b¯ bto W+c¯cevents. As reported in section 7,W+light-flavour jets events give a small contribution in the signal region and no associated modelling uncertainty is taken into account. An additional shapemodelling uncertainty is considered for the W+jets distributions. Indeed, in the W+jets control region a few kinematic variables are slightly mismodelled, and the impact of this mismodelling is evaluated by reweighting the W+jets angular distributions in the signal region. The applied event weights are derived from matching to data (after subtraction of all processes other than W+jets) the mismodelled kinematic variables in the W+jets control region. This procedure leads to a conservative estimate since it also accounts for mismodelling of the W+light-flavour jets events, which have a much more important contribution in the W+jets control region than in the signal region. The systematic uncertainty associated with the data-driven shape modelling of the multijet events is estimated by comparing the shapes provided by the baseline matrix method and the alternative modelling given by the jet-electron and anti-muon methods. All the signal and background modelling uncertainties, except that associated with the W+jets flavour composition, are symmetrised by taking the difference between the nominal and varied measurements as positive and negative uncertainties. Systematic uncertainties related to the parton distribution functions are estimated for all processes, except for the multijet contribution. The uncertainty is estimated, following the PDF4LHC prescription [67], by calculating the envelope of the uncertainties at 68% confidence level of the CT10 [30], MSTW2008NLO [68] and NNPDF2.3 [71] sets. Limited size of simulation samples. The uncertainty due to the limited size of the Monte Carlo samples is evaluated by varying the background normalisation and shape, as well as the unfolding corrections, through Gaussian fluctuations. The standard deviation of the distribution of the measured asymmetry provided by an ensemble test of pseudoexperiments built from these variations is taken as a systematic uncertainty. Tables 4and 5show the contribution of each source of systematic uncertainty to the asymmetry measurements. The total uncertainties are obtained from the sum in quadrature of all contributions. Tables 4and 5also include the statistical uncertainty from the data sample. It is evaluated using a procedure similar to that used for the uncertainty associated with the size of the simulation samples, but varying the observed numbers of events and the shape of the angular distributions through Poisson fluctuations. The asymmetry measurements are dominated by the systematic uncertainties. The largest contributions are from the uncertainties in the modelling of the t-channel and t¯ t processes, and in the jet reconstruction and energy scale. Significant contributions also – 22 – JHEP04(2017)124 come from the uncertainty in the modelling of the multijet or W+jets events, depending on the measured asymmetry, and from the limited size of the simulation samples. The statistical uncertainty of the data sample, although lower than the systematic uncertainty, also has a sizeable impact on the measurement precision. 11 Results The values of the asymmetries related to the top-quark polarisation and to the W-boson spin observables, measured using the Standard Model Wtb couplings for the signal unfolding corrections and for the top-quark background modelling, are A` FB = 0.49 ±0.03(stat.) ±0.05(syst.) = 0.49 ±0.06 , AtW FB = 0.10 ±0.03(stat.) ±0.05(syst.) = 0.10 ±0.06 , AFB =−0.26 ±0.02(stat.) ±0.07(syst.) = −0.26 ±0.08 , AEC =−0.25 ±0.03(stat.) ±0.05(syst.) = −0.25 ±0.06 , AT FB = 0.39 ±0.03(stat.) ±0.09(syst.) = 0.39 ±0.09 , AN,φ FB =−0.03 ±0.03(stat.) ±0.05(syst.) = −0.03 ±0.06 , AT,φ FB =−0.17 ±0.05(stat.)+0.11 −0.10(syst.) = −0.17+0.12 −0.11 . The values for the top-quark polarisation combined with the charged-lepton spin analysing power and with the sum of the W-boson helicity fractions, derived from the measured A` FB and AtW FB asymmetries using the relations given in table 1, are α`P= 0.97 ±0.05(stat.) ±0.11(syst.) = 0.97 ±0.12 , P(FR+FL)=0.25 ±0.08(stat.) ±0.14(syst.) = 0.25 ±0.16 . The values of the W-boson spin observables derived from the measured AFB,AEC, AT FB,AN,φ FB and AT,φ FB asymmetries through the relations given in table 1are hS3i=−0.35 ±0.03(stat.) ±0.10(syst.) = −0.35 ±0.10 , hT0i=−0.55 ±0.06(stat.) ±0.12(syst.) = −0.55 ±0.13 , hS1i= 0.52 ±0.04(stat.) ±0.12(syst.) = 0.52 ±0.12 , hA2i=−0.05 ±0.05(stat.) ±0.09(syst.) = −0.05 ±0.10 , hA1i= 0.27 ±0.07(stat.)+0.16 −0.17(syst.) = 0.27+0.17 −0.19 . The results for the AN FB asymmetry, which has the highest sensitivity to the anomalous Wtb coupling Im gR, and for its associated W-boson spin observable are AN FB =−0.04 ±0.02(stat.) ±0.03(syst.) = −0.04 ±0.04 , hS2i= 0.06 ±0.03(stat.) ±0.04(syst.) = 0.06 ±0.05 . These observables are measured using the signal corrections interpolated with respect to Im gRas explained in section 9, and using the Standard Model couplings for the top-quark background modelling. – 23 – JHEP04(2017)124 Uncertainty source ∆A` FB ×102∆AtW FB ×102∆AFB ×102∆AEC ×102 Statistical uncertainty ±2.6 ±3.1 ±2.3 ±2.8 Simulation statistics ±1.7 ±1.9 ±1.4 ±1.7 Luminosity <0.1 <0.1 <0.1 <0.1 Background normalisation ±0.5 ±0.5 ±0.9 ±0.7 Emiss Treconstruction +0.9 −0.1 +0.4 −0.7 +1.1 −0.7 +0.8 −0.2 Lepton reconstruction +1.0 −0.4 +0.1 −1.3±1.4 +0.6 −0.3 Jet reconstruction ±2.1 ±2.5 ±1.2 ±1.8 Jet energy scale +1.3 −1.2 +2.0 −1.6 +3.4 −2.7 +2.0 −0.7 Jet flavour tagging ±0.9 ±0.3 ±0.6 ±0.4 PDF ±0.2 <0.1 <0.1 ±0.2 t¯ tgenerator ±2.3 ±1.0 ±0.2 ±1.2 t¯ tparton shower ±0.6 ±0.5 ±2.7 ±0.3 t¯ tscales ±0.2 ±0.4 ±1.2 ±0.3 Wt,s-channel generator ±1.0 ±1.1 ±0.4 ±0.3 Wt,s-channel scales ±0.9 ±0.3 ±0.3 ±0.3 t-channel NLO generator ±1.4 ±0.6 ±0.6 ±2.7 t-channel LO-NLO generator ±1.5 ±2.0 ±2.6 ±1.8 t-channel parton shower ±0.5 ±1.0 ±3.5 ±0.2 t-channel scales ±1.1 ±2.0 ±0.6 ±1.6 W+jets, multijet modelling +1.9 −2.4 +0.9 −1.0 +2.2 −2.1 +1.3 −1.2 Total systematic uncertainty +5.4 −5.4 +5.2 −5.3 +7.3 −6.9 +5.3 −4.8 Table 4. Uncertainties contributing to the measurements of the A` FB,AtW FB ,AFB and AEC asymmetries. For better readability the uncertainties are multiplied by 102. Figure 9shows the measured and predicted values of all asymmetries, while figure 10 compares the derived values for the six W-boson spin observables. Compatibility between the measurements and Standard Model predictions is observed. The overall compatibility of the measurements with the Standard Model predictions is evaluated through the construction of a χ2test statistic taking into account all measured quantities with their correlations. The theoretical uncertainties, which are negligible compared to the measurement uncertainties, are not taken into account in the χ2calculation. The overall covariance matrix is computed from the sum of the covariance matrices associated with the various sources of statistical and systematic uncertainty. 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Galea108, B. Galhardo128a,128c, E.J. Gallas122, B.J. Gallop133, P. Gallus130, G. Galster39, K.K. Gan113, S. Ganguly37, J. Gao36a, Y. Gao49, Y.S. Gao145,g, F.M. Garay Walls49, C. Garc´ıa170, J.E. Garc´ıa Navarro170, M. Garcia-Sciveres16, R.W. Gardner33, N. Garelli145, V. Garonne121, A. Gascon Bravo45, K. Gasnikova45, C. Gatti50, A. Gaudiello53a,53b, G. Gaudio123a, L. Gauthier97, I.L. Gavrilenko98, C. Gay171, G. Gaycken23, E.N. Gazis10, Z. Gecse171, C.N.P. Gee133, Ch. Geich-Gimbel23, M. Geisen86, M.P. Geisler60a, K. Gellerstedt148a,148b, C. Gemme53a, M.H. Genest58, C. Geng36a,r, S. Gentile134a,134b, C. Gentsos156, S. George80, D. Gerbaudo13, A. Gershon155, S. Ghasemi143, M. Ghneimat23, B. Giacobbe22a, S. Giagu134a,134b, P. Giannetti126a,126b, S.M. Gibson80, M. Gignac171, M. Gilchriese16, T.P.S. Gillam30, D. Gillberg31, G. Gilles178, D.M. Gingrich3,d, N. Giokaris9,∗, M.P. Giordani167a,167c, F.M. Giorgi22a, P.F. Giraud138, P. Giromini59, D. Giugni94a, F. Giuli122, C. Giuliani103, M. Giulini60b, B.K. Gjelsten121, S. Gkaitatzis156, I. Gkialas9, E.L. Gkougkousis139, L.K. Gladilin101, C. Glasman85, J. Glatzer13, P.C.F. Glaysher49, A. Glazov45, M. Goblirsch-Kolb25, J. Godlewski42, S. Goldfarb91, T. Golling52, D. Golubkov132, A. Gomes128a,128b,128d, R. Gon¸calo128a, R. Goncalves Gama26a, J. Goncalves Pinto Firmino Da Costa138, G. Gonella51, L. Gonella19, A. Gongadze68, S. Gonz´alez de la Hoz170, S. Gonzalez-Sevilla52, L. Goossens32, P.A. Gorbounov99, H.A. Gordon27, I. Gorelov107, B. Gorini32, E. Gorini76a,76b, A. Goriˇsek78, A.T. Goshaw48, C. G¨ossling46, M.I. Gostkin68, C.R. Goudet119, D. Goujdami137c, A.G. Goussiou140, N. Govender147b,s, E. Gozani154, L. Graber57, I. Grabowska-Bold41a, P.O.J. Gradin58, P. Grafstr¨om22a,22b, J. Gramling52, E. Gramstad121, S. Grancagnolo17, V. Gratchev125, P.M. Gravila28e, H.M. Gray32, E. Graziani136a, Z.D. Greenwood82,t, C. Grefe23, K. Gregersen81, I.M. Gregor45, P. Grenier145, K. Grevtsov5, J. Griffiths8, A.A. Grillo139, K. Grimm75, S. Grinstein13,u, Ph. Gris37, J.-F. Grivaz119, S. Groh86, E. Gross175, J. Grosse-Knetter57, G.C. Grossi82, Z.J. Grout81, L. Guan92, W. Guan176, J. Guenther65, F. Guescini52, D. Guest166, O. Gueta155, B. Gui113, E. Guido53a,53b, T. Guillemin5, S. Guindon2, U. Gul56, C. Gumpert32, J. Guo36c, W. Guo92, Y. Guo36a,r, R. Gupta43, S. Gupta122, G. Gustavino134a,134b, P. Gutierrez115, N.G. Gutierrez Ortiz81, C. Gutschow81, C. Guyot138, C. Gwenlan122, C.B. Gwilliam77, A. Haas112, C. Haber16, H.K. Hadavand8, A. Hadef88, S. Hageb¨ock23, M. Hagihara164, H. Hakobyan180,∗, M. Haleem45, J. Haley116, G. Halladjian93, G.D. Hallewell88, K. Hamacher178, P. Hamal117, K. Hamano172, A. Hamilton147a, G.N. Hamity141, P.G. Hamnett45, L. Han36a, S. Han35a, K. Hanagaki69,v, K. Hanawa157, M. Hance139, B. Haney124, P. Hanke60a, R. Hanna138, J.B. Hansen39, J.D. Hansen39, M.C. Hansen23, P.H. Hansen39, K. Hara164, A.S. Hard176, T. Harenberg178, F. Hariri119, S. Harkusha95, R.D. Harrington49, P.F. Harrison173, F. Hartjes109, N.M. Hartmann102, M. Hasegawa70, Y. Hasegawa142, A. Hasib115, S. Hassani138, S. Haug18, R. Hauser93, L. Hauswald47, M. Havranek129, C.M. Hawkes19, R.J. Hawkings32, D. Hayakawa159, D. Hayden93, C.P. Hays122, J.M. Hays79, H.S. Hayward77, S.J. Haywood133, S.J. Head19, T. Heck86, V. Hedberg84, L. Heelan8, K.K. Heidegger51, S. Heim124, T. Heim16, B. Heinemann45,w, J.J. Heinrich102, L. Heinrich112, C. Heinz55, J. Hejbal129, L. Helary32, S. Hellman148a,148b, C. Helsens32, J. Henderson122, R.C.W. Henderson75, Y. Heng176, – 36 – JHEP04(2017)124 S. Henkelmann171, A.M. Henriques Correia32, S. Henrot-Versille119, G.H. Herbert17, H. Herde25, V. Herget177, Y. Hern´andez Jim´enez147c, G. Herten51, R. Hertenberger102, L. Hervas32, G.G. Hesketh81, N.P. Hessey163a, J.W. Hetherly43, E. Hig´on-Rodriguez170, E. Hill172, J.C. Hill30, K.H. Hiller45, S.J. Hillier19, I. Hinchliffe16, E. Hines124, M. Hirose51, D. Hirschbuehl178, O. Hladik129, X. Hoad49, J. Hobbs150, N. Hod163a, M.C. Hodgkinson141, P. Hodgson141, A. Hoecker32, M.R. Hoeferkamp107, F. Hoenig102, D. Hohn23, T.R. Holmes16, M. Homann46, S. Honda164, T. Honda69, T.M. Hong127, B.H. Hooberman169, W.H. Hopkins118, Y. Horii105, A.J. Horton144, J-Y. Hostachy58, S. Hou153, A. Hoummada137a, J. Howarth45, J. Hoya74, M. Hrabovsky117, I. Hristova17, J. Hrivnac119, T. Hryn’ova5, A. Hrynevich96, P.J. Hsu63, S.-C. Hsu140, Q. Hu36a, S. Hu36c, Y. Huang45, Z. Hubacek130, F. Hubaut88, F. Huegging23, T.B. Huffman122, E.W. Hughes38, G. Hughes75, M. Huhtinen32, P. Huo150, N. Huseynov68,b, J. Huston93, J. Huth59, G. Iacobucci52, G. Iakovidis27, I. Ibragimov143, L. Iconomidou-Fayard119, E. Ideal179, P. Iengo32, O. Igonkina109,x, T. Iizawa174, Y. Ikegami69, M. Ikeno69, Y. Ilchenko11,y, D. Iliadis156, N. Ilic145, G. Introzzi123a,123b, P. Ioannou9,∗, M. Iodice136a, K. Iordanidou38, V. Ippolito59, N. Ishijima120, M. Ishino157, M. Ishitsuka159, C. Issever122, S. Istin20a, F. Ito164, J.M. Iturbe Ponce87, R. Iuppa162a,162b, H. Iwasaki69, J.M. Izen44, V. Izzo106a, S. Jabbar3, B. Jackson124, P. Jackson1, V. Jain2, K.B. Jakobi86, K. Jakobs51, S. Jakobsen32, T. Jakoubek129, D.O. Jamin116, D.K. Jana82, R. Jansky65, J. Janssen23, M. Janus57, P.A. Janus41a, G. Jarlskog84, N. Javadov68,b, T. Jav˚urek51, M. Javurkova51, F. Jeanneau138, L. Jeanty16, J. Jejelava54a,z, G.-Y. Jeng152, P. Jenni51,aa, C. Jeske173, S. J´ez´equel5, H. Ji176, J. Jia150, H. Jiang67, Y. Jiang36a, Z. Jiang145, S. Jiggins81, J. Jimenez Pena170, S. Jin35a, A. Jinaru28b, O. Jinnouchi159, H. Jivan147c, P. Johansson141, K.A. Johns7, C.A. Johnson64, W.J. Johnson140, K. Jon-And148a,148b, G. Jones173, R.W.L. Jones75, S. Jones7, T.J. Jones77, J. Jongmanns60a, P.M. Jorge128a,128b, J. Jovicevic163a, X. Ju176, A. Juste Rozas13,u, M.K. K¨ohler175, A. Kaczmarska42, M. Kado119, H. Kagan113, M. Kagan145, S.J. Kahn88, T. Kaji174, E. Kajomovitz48, C.W. Kalderon122, A. Kaluza86, S. Kama43, A. Kamenshchikov132, N. Kanaya157, S. Kaneti30, L. Kanjir78, V.A. Kantserov100, J. Kanzaki69, B. Kaplan112, L.S. Kaplan176, A. Kapliy33, D. Kar147c, K. Karakostas10, A. Karamaoun3, N. Karastathis10, M.J. Kareem57, E. Karentzos10, S.N. Karpov68, Z.M. Karpova68, K. Karthik112, V. Kartvelishvili75, A.N. Karyukhin132, K. Kasahara164, L. Kashif176, R.D. Kass113, A. Kastanas149, Y. Kataoka157, C. Kato157, A. Katre52, J. Katzy45, K. Kawade105, K. Kawagoe73, T. Kawamoto157, G. Kawamura57, V.F. Kazanin111,c, R. Keeler172, R. Kehoe43, J.S. Keller45, J.J. Kempster80, H. Keoshkerian161, O. Kepka129, B.P. Kerˇsevan78, S. Kersten178, R.A. Keyes90, M. Khader169, F. Khalil-zada12, A. Khanov116, A.G. Kharlamov111,c, T. Kharlamova111,c, T.J. Khoo52, V. Khovanskiy99,∗, E. Khramov68, J. Khubua54b,ab, S. Kido70, C.R. Kilby80, H.Y. Kim8, S.H. Kim164, Y.K. Kim33, N. Kimura156, O.M. Kind17, B.T. King77, M. King170, D. Kirchmeier47, J. Kirk133, A.E. Kiryunin103, T. Kishimoto157, D. Kisielewska41a, F. Kiss51, K. Kiuchi164, O. Kivernyk138, E. Kladiva146b, T. Klapdor-Kleingrothaus51, M.H. Klein38, M. Klein77, U. Klein77, K. Kleinknecht86, P. Klimek110, A. Klimentov27, R. Klingenberg46, T. Klioutchnikova32, E.-E. Kluge60a, P. Kluit109, S. Kluth103, J. Knapik42, E. Kneringer65, E.B.F.G. Knoops88, A. Knue103, A. Kobayashi157, D. Kobayashi159, T. Kobayashi157, M. Kobel47, M. Kocian145, P. Kodys131, T. Koffas31, E. Koffeman109, N.M. K¨ohler103, T. Koi145, H. Kolanoski17, M. Kolb60b, I. Koletsou5, A.A. Komar98,∗, Y. Komori157, T. Kondo69, N. Kondrashova36c, K. K¨oneke51, A.C. K¨onig108, T. Kono69,ac, R. Konoplich112,ad, N. Konstantinidis81, R. Kopeliansky64, S. Koperny41a, A.K. Kopp51, K. Korcyl42, K. Kordas156, A. Korn81, A.A. Korol111,c, I. Korolkov13, E.V. Korolkova141, O. Kortner103, S. Kortner103, T. Kosek131, V.V. Kostyukhin23, A. Kotwal48, A. Koulouris10, A. Kourkoumeli-Charalampidi123a,123b, C. Kourkoumelis9, V. Kouskoura27, A.B. Kowalewska42, – 37 – JHEP04(2017)124 R. Kowalewski172, T.Z. Kowalski41a, C. Kozakai157, W. Kozanecki138, A.S. Kozhin132, V.A. Kramarenko101, G. Kramberger78, D. Krasnopevtsev100, M.W. Krasny83, A. Krasznahorkay32, A. Kravchenko27, M. Kretz60c, J. Kretzschmar77, K. Kreutzfeldt55, P. Krieger161, K. Krizka33, K. Kroeninger46, H. Kroha103, J. Kroll124, J. Kroseberg23, J. Krstic14, U. Kruchonak68, H. Kr¨uger23, N. Krumnack67, M.C. Kruse48, M. Kruskal24, T. Kubota91, H. Kucuk81, S. Kuday4b, J.T. Kuechler178, S. Kuehn51, A. Kugel60c, F. Kuger177, T. Kuhl45, V. Kukhtin68, R. Kukla138, Y. Kulchitsky95, S. Kuleshov34b, M. Kuna134a,134b, T. Kunigo71, A. Kupco129, O. Kuprash155, H. Kurashige70, L.L. Kurchaninov163a, Y.A. Kurochkin95, M.G. Kurth44, V. Kus129, E.S. Kuwertz172, M. Kuze159, J. Kvita117, T. Kwan172, D. Kyriazopoulos141, A. La Rosa103, J.L. La Rosa Navarro26d, L. La Rotonda40a,40b, C. Lacasta170, F. Lacava134a,134b, J. Lacey31, H. Lacker17, D. Lacour83, E. Ladygin68, R. Lafaye5, B. Laforge83, T. Lagouri179, S. Lai57, S. Lammers64, W. Lampl7, E. Lan¸con138, U. Landgraf51, M.P.J. Landon79, M.C. Lanfermann52, V.S. Lang60a, J.C. Lange13, A.J. Lankford166, F. Lanni27, K. Lantzsch23, A. Lanza123a, A. Lapertosa53a,53b, S. Laplace83, C. Lapoire32, J.F. Laporte138, T. Lari94a, F. Lasagni Manghi22a,22b, M. Lassnig32, P. Laurelli50, W. Lavrijsen16, A.T. Law139, P. Laycock77, T. Lazovich59, M. Lazzaroni94a,94b, B. Le91, O. Le Dortz83, E. Le Guirriec88, E.P. Le Quilleuc138, M. LeBlanc172, T. LeCompte6, F. Ledroit-Guillon58, C.A. Lee27, S.C. Lee153, L. Lee1, B. Lefebvre90, G. Lefebvre83, M. Lefebvre172, F. Legger102, C. Leggett16, A. Lehan77, G. Lehmann Miotto32, X. Lei7, W.A. Leight31, A.G. Leister179, M.A.L. Leite26d, R. Leitner131, D. Lellouch175, B. Lemmer57, K.J.C. Leney81, T. Lenz23, B. Lenzi32, R. Leone7, S. Leone126a,126b, C. Leonidopoulos49, S. Leontsinis10, G. Lerner151, C. Leroy97, A.A.J. Lesage138, C.G. Lester30, M. Levchenko125, J. Levˆeque5, D. Levin92, L.J. Levinson175, M. Levy19, D. Lewis79, M. Leyton44, B. Li36a,r, C. Li36a, H. Li150, L. Li48, L. Li36c, Q. Li35a, S. Li48, X. Li87, Y. Li143, Z. Liang35a, B. Liberti135a, A. Liblong161, P. Lichard32, K. Lie169, J. Liebal23, W. Liebig15, A. Limosani152, S.C. Lin153,ae, T.H. Lin86, B.E. Lindquist150, A.E. Lionti52, E. Lipeles124, A. Lipniacka15, M. Lisovyi60b, T.M. Liss169, A. Lister171, A.M. Litke139, B. Liu153,af , D. Liu153, H. Liu92, H. Liu27, J. Liu36b, J.B. Liu36a, K. Liu88, L. Liu169, M. Liu36a, Y.L. Liu36a, Y. Liu36a, M. Livan123a,123b, A. Lleres58, J. Llorente Merino35a, S.L. Lloyd79, F. Lo Sterzo153, E.M. Lobodzinska45, P. Loch7, F.K. Loebinger87, K.M. Loew25, A. Loginov179,∗, T. Lohse17, K. Lohwasser45, M. Lokajicek129, B.A. Long24, J.D. Long169, R.E. Long75, L. Longo76a,76b, K.A. Looper113, J.A. Lopez34b, D. Lopez Mateos59, B. Lopez Paredes141, I. Lopez Paz13, A. Lopez Solis83, J. Lorenz102, N. Lorenzo Martinez64, M. Losada21, P.J. L¨osel102, X. Lou35a, A. Lounis119, J. Love6, P.A. Love75, H. Lu62a, N. Lu92, H.J. Lubatti140, C. Luci134a,134b, A. Lucotte58, C. Luedtke51, F. Luehring64, W. Lukas65, L. Luminari134a, O. Lundberg148a,148b, B. Lund-Jensen149, P.M. Luzi83, D. Lynn27, R. Lysak129, E. Lytken84, V. Lyubushkin68, H. Ma27, L.L. Ma36b, Y. Ma36b, G. Maccarrone50, A. Macchiolo103, C.M. Macdonald141, B. Maˇcek78, J. Machado Miguens124,128b, D. Madaffari88, R. Madar37, H.J. Maddocks168, W.F. Mader47, A. Madsen45, J. Maeda70, S. Maeland15, T. Maeno27, A. Maevskiy101, E. Magradze57, J. Mahlstedt109, C. Maiani119, C. Maidantchik26a, A.A. Maier103, T. Maier102, A. Maio128a,128b,128d, S. Majewski118, Y. Makida69, N. Makovec119, B. Malaescu83, Pa. Malecki42, V.P. Maleev125, F. Malek58, U. Mallik66, D. Malon6, C. Malone30, S. Maltezos10, S. Malyukov32, J. Mamuzic170, G. Mancini50, L. Mandelli94a, I. Mandi´c78, J. Maneira128a,128b, L. Manhaes de Andrade Filho26b, J. Manjarres Ramos163b, A. Mann102, A. Manousos32, B. Mansoulie138, J.D. Mansour35a, R. Mantifel90, M. Mantoani57, S. Manzoni94a,94b, L. Mapelli32, G. Marceca29, L. March52, G. Marchiori83, M. Marcisovsky129, M. Marjanovic14, D.E. Marley92, F. Marroquim26a, S.P. Marsden87, Z. Marshall16, S. Marti-Garcia170, B. Martin93, T.A. Martin173, V.J. Martin49, B. Martin dit Latour15, M. Martinez13,u, – 38 – JHEP04(2017)124 V.I. Martinez Outschoorn169, S. Martin-Haugh133, V.S. Martoiu28b, A.C. Martyniuk81, A. Marzin32, L. Masetti86, T. Mashimo157, R. Mashinistov98, J. Masik87, A.L. Maslennikov111,c, I. Massa22a,22b, L. Massa22a,22b, P. Mastrandrea5, A. Mastroberardino40a,40b, T. Masubuchi157, P. M¨attig178, J. Mattmann86, J. Maurer28b, S.J. Maxfield77, D.A. Maximov111,c, R. Mazini153, I. Maznas156, S.M. Mazza94a,94b, N.C. Mc Fadden107, G. Mc Goldrick161, S.P. Mc Kee92, A. McCarn92, R.L. McCarthy150, T.G. McCarthy103, L.I. McClymont81, E.F. McDonald91, J.A. Mcfayden81, G. Mchedlidze57, S.J. McMahon133, R.A. McPherson172,n, M. Medinnis45, S. Meehan140, S. Mehlhase102, A. Mehta77, K. Meier60a, C. Meineck102, B. Meirose44, D. Melini170,ag, B.R. Mellado Garcia147c, M. Melo146a, F. Meloni18, S.B. Menary87, L. Meng77, X.T. Meng92, A. Mengarelli22a,22b, S. Menke103, E. Meoni165, S. Mergelmeyer17, P. Mermod52, L. Merola106a,106b, C. Meroni94a, F.S. Merritt33, A. Messina134a,134b, J. Metcalfe6, A.S. Mete166, C. Meyer86, C. Meyer124, J-P. Meyer138, J. Meyer109, H. Meyer Zu Theenhausen60a, F. Miano151, R.P. Middleton133, S. Miglioranzi53a,53b, L. Mijovi´c49, G. Mikenberg175, M. Mikestikova129, M. Mikuˇz78, M. Milesi91, A. Milic27, D.W. Miller33, C. Mills49, A. Milov175, D.A. Milstead148a,148b, A.A. Minaenko132, Y. Minami157, I.A. Minashvili68, A.I. Mincer112, B. Mindur41a, M. Mineev68, Y. Minegishi157, Y. Ming176, L.M. Mir13, K.P. Mistry124, T. Mitani174, J. Mitrevski102, V.A. Mitsou170, A. Miucci18, P.S. Miyagawa141, A. Mizukami69, J.U. Mj¨ornmark84, M. Mlynarikova131, T. Moa148a,148b, K. Mochizuki97, P. Mogg51, S. Mohapatra38, S. Molander148a,148b, R. Moles-Valls23, R. Monden71, M.C. Mondragon93, K. M¨onig45, J. Monk39, E. Monnier88, A. Montalbano150, J. Montejo Berlingen32, F. Monticelli74, S. Monzani94a,94b, R.W. Moore3, N. Morange119, D. Moreno21, M. Moreno Ll´acer57, P. Morettini53a, S. Morgenstern32, D. Mori144, T. Mori157, M. Morii59, M. Morinaga157, V. Morisbak121, S. Moritz86, A.K. Morley152, G. Mornacchi32, J.D. Morris79, L. Morvaj150, P. Moschovakos10, M. Mosidze54b, H.J. Moss141, J. Moss145,ah, K. Motohashi159, R. Mount145, E. Mountricha27, E.J.W. Moyse89, S. Muanza88, R.D. Mudd19, F. Mueller103, J. Mueller127, R.S.P. Mueller102, T. Mueller30, D. Muenstermann75, P. Mullen56, G.A. Mullier18, F.J. Munoz Sanchez87, J.A. Murillo Quijada19, W.J. Murray173,133, H. Musheghyan57, M. Muˇskinja78, A.G. Myagkov132,ai, M. Myska130, B.P. Nachman16, O. Nackenhorst52, K. Nagai122, R. Nagai69,ac, K. Nagano69, Y. Nagasaka61, K. Nagata164, M. Nagel51, E. Nagy88, A.M. Nairz32, Y. Nakahama105, K. Nakamura69, T. Nakamura157, I. Nakano114, R.F. Naranjo Garcia45, R. Narayan11, D.I. Narrias Villar60a, I. Naryshkin125, T. Naumann45, G. Navarro21, R. Nayyar7, H.A. Neal92, P.Yu. Nechaeva98, T.J. Neep87, A. Negri123a,123b, M. Negrini22a, S. Nektarijevic108, C. Nellist119, A. Nelson166, S. Nemecek129, P. Nemethy112, A.A. Nepomuceno26a, M. Nessi32,aj , M.S. Neubauer169, M. Neumann178, R.M. Neves112, P. Nevski27, P.R. Newman19, T. Nguyen Manh97, R.B. Nickerson122, R. Nicolaidou138, J. Nielsen139, V. Nikolaenko132,ai, I. Nikolic-Audit83, K. Nikolopoulos19, J.K. Nilsen121, P. Nilsson27, Y. Ninomiya157, A. Nisati134a, R. Nisius103, T. Nobe157, M. Nomachi120, I. Nomidis31, T. Nooney79, S. Norberg115, M. Nordberg32, N. Norjoharuddeen122, O. Novgorodova47, S. Nowak103, M. Nozaki69, L. Nozka117, K. Ntekas166, E. Nurse81, F. Nuti91, D.C. O’Neil144, A.A. O’Rourke45, V. O’Shea56, F.G. Oakham31,d, H. Oberlack103, T. Obermann23, J. Ocariz83, A. Ochi70, I. Ochoa38, J.P. Ochoa-Ricoux34a, S. Oda73, S. Odaka69, H. Ogren64, A. Oh87, S.H. Oh48, C.C. Ohm16, H. Ohman168, H. Oide53a,53b, H. Okawa164, Y. Okumura157, T. Okuyama69, A. Olariu28b, L.F. Oleiro Seabra128a, S.A. Olivares Pino49, D. Oliveira Damazio27, A. Olszewski42, J. Olszowska42, A. Onofre128a,128e, K. Onogi105, P.U.E. Onyisi11,y, M.J. Oreglia33, Y. Oren155, D. Orestano136a,136b, N. Orlando62b, R.S. Orr161, B. Osculati53a,53b,∗, R. Ospanov87, G. Otero y Garzon29, H. Otono73, M. Ouchrif137d, F. Ould-Saada121, A. Ouraou138, K.P. Oussoren109, Q. Ouyang35a, M. Owen56, R.E. Owen19, V.E. Ozcan20a, N. Ozturk8, K. Pachal144, A. Pacheco Pages13, L. Pacheco Rodriguez138, – 39 – JHEP04(2017)124 C. Padilla Aranda13, S. Pagan Griso16, M. Paganini179, F. Paige27, P. Pais89, K. Pajchel121, G. Palacino64, S. Palazzo40a,40b, S. Palestini32, M. Palka41b, D. Pallin37, E.St. Panagiotopoulou10, I. Panagoulias10, C.E. Pandini83, J.G. Panduro Vazquez80, P. Pani148a,148b, S. Panitkin27, D. Pantea28b, L. Paolozzi52, Th.D. Papadopoulou10, K. Papageorgiou9, A. Paramonov6, D. Paredes Hernandez179, A.J. Parker75, M.A. Parker30, K.A. Parker141, F. Parodi53a,53b, J.A. Parsons38, U. Parzefall51, V.R. Pascuzzi161, E. Pasqualucci134a, S. Passaggio53a, Fr. Pastore80, G. P´asztor31,ak, S. Pataraia178, J.R. Pater87, T. Pauly32, J. Pearce172, B. Pearson115, L.E. Pedersen39, S. Pedraza Lopez170, R. Pedro128a,128b, S.V. Peleganchuk111,c, O. Penc129, C. Peng35a, H. Peng36a, J. Penwell64, B.S. Peralva26b, M.M. Perego138, D.V. Perepelitsa27, E. Perez Codina163a, L. Perini94a,94b, H. Pernegger32, S. Perrella106a,106b, R. Peschke45, V.D. Peshekhonov68, K. Peters45, R.F.Y. Peters87, B.A. Petersen32, T.C. Petersen39, E. Petit58, A. Petridis1, C. Petridou156, P. Petroff119, E. Petrolo134a, M. Petrov122, F. Petrucci136a,136b, N.E. Pettersson89, A. Peyaud138, R. Pezoa34b, P.W. Phillips133, G. Piacquadio150, E. Pianori173, A. Picazio89, E. Piccaro79, M. Piccinini22a,22b, M.A. Pickering122, R. Piegaia29, J.E. Pilcher33, A.D. Pilkington87, A.W.J. Pin87, M. Pinamonti167a,167c,al, J.L. Pinfold3, A. Pingel39, S. Pires83, H. Pirumov45, M. Pitt175, L. Plazak146a, M.-A. Pleier27, V. Pleskot86, E. Plotnikova68, D. Pluth67, R. Poettgen148a,148b, L. Poggioli119, D. Pohl23, G. Polesello123a, A. Poley45, A. Policicchio40a,40b, R. Polifka161, A. Polini22a, C.S. Pollard56, V. Polychronakos27, K. Pomm`es32, L. Pontecorvo134a, B.G. Pope93, G.A. Popeneciu28c, A. Poppleton32, S. Pospisil130, K. Potamianos16, I.N. Potrap68, C.J. Potter30, C.T. Potter118, G. Poulard32, J. Poveda32, V. Pozdnyakov68, M.E. Pozo Astigarraga32, P. Pralavorio88, A. Pranko16, S. Prell67, D. Price87, L.E. Price6, M. Primavera76a, S. Prince90, K. Prokofiev62c, F. Prokoshin34b, S. Protopopescu27, J. Proudfoot6, M. Przybycien41a, D. Puddu136a,136b, M. Purohit27,am, P. Puzo119, J. Qian92, G. Qin56, Y. Qin87, A. Quadt57, W.B. Quayle167a,167b, M. Queitsch-Maitland45, D. Quilty56, S. Raddum121, V. Radeka27, V. Radescu122, S.K. Radhakrishnan150, P. Radloff118, P. Rados91, F. Ragusa94a,94b, G. Rahal181, J.A. Raine87, S. Rajagopalan27, M. Rammensee32, C. Rangel-Smith168, M.G. Ratti94a,94b, D.M. Rauch45, F. Rauscher102, S. Rave86, T. Ravenscroft56, I. Ravinovich175, M. Raymond32, A.L. Read121, N.P. Readioff77, M. Reale76a,76b, D.M. Rebuzzi123a,123b, A. Redelbach177, G. Redlinger27, R. Reece139, R.G. Reed147c, K. Reeves44, L. Rehnisch17, J. Reichert124, A. Reiss86, C. Rembser32, H. Ren35a, M. Rescigno134a, S. Resconi94a, E.D. Resseguie124, O.L. Rezanova111,c, P. Reznicek131, R. Rezvani97, R. Richter103, S. Richter81, E. Richter-Was41b, O. Ricken23, M. Ridel83, P. Rieck103, C.J. Riegel178, J. Rieger57, O. Rifki115, M. Rijssenbeek150, A. Rimoldi123a,123b, M. Rimoldi18, L. Rinaldi22a, B. Risti´c52, E. Ritsch32, I. Riu13, F. Rizatdinova116, E. Rizvi79, C. Rizzi13, R.T. Roberts87, S.H. Robertson90,n, A. Robichaud-Veronneau90, D. Robinson30, J.E.M. Robinson45, A. Robson56, C. Roda126a,126b, Y. Rodina88,an, A. Rodriguez Perez13, D. Rodriguez Rodriguez170, S. Roe32, C.S. Rogan59, O. Røhne121, J. Roloff59, A. Romaniouk100, M. Romano22a,22b, S.M. Romano Saez37, E. Romero Adam170, N. Rompotis140, M. Ronzani51, L. Roos83, E. Ros170, S. Rosati134a, K. Rosbach51, P. Rose139, N.-A. Rosien57, V. Rossetti148a,148b, E. Rossi106a,106b, L.P. Rossi53a, J.H.N. Rosten30, R. Rosten140, M. Rotaru28b, I. Roth175, J. Rothberg140, D. Rousseau119, A. Rozanov88, Y. Rozen154, X. Ruan147c, F. Rubbo145, M.S. Rudolph161, F. R¨uhr51, A. Ruiz-Martinez31, Z. Rurikova51, N.A. Rusakovich68, A. Ruschke102, H.L. Russell140, J.P. Rutherfoord7, N. Ruthmann32, Y.F. Ryabov125, M. Rybar169, G. Rybkin119, S. Ryu6, A. Ryzhov132, G.F. Rzehorz57, A.F. Saavedra152, G. Sabato109, S. Sacerdoti29, H.F-W. Sadrozinski139, R. Sadykov68, F. Safai Tehrani134a, P. Saha110, M. Sahinsoy60a, M. Saimpert138, T. Saito157, H. Sakamoto157, Y. Sakurai174, G. Salamanna136a,136b, A. Salamon135a,135b, J.E. Salazar Loyola34b, D. Salek109, P.H. Sales De Bruin140, D. Salihagic103, – 40 – JHEP04(2017)124 135 (a)INFN Sezione di Roma Tor Vergata; (b)Dipartimento di Fisica, Universit`a di Roma Tor Vergata, Roma, Italy 136 (a)INFN Sezione di Roma Tre; (b)Dipartimento di Matematica e Fisica, Universit`a Roma Tre, Roma, Italy 137 (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, Rabat, Morocco 138 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 139 Santa Cruz Institute for Particle Physics, University of California Santa Cruz, Santa Cruz CA, U.S.A. 140 Department of Physics, University of Washington, Seattle WA, U.S.A. 141 Department of Physics and Astronomy, University of Sheffield, Sheffield, U.K. 142 Department of Physics, Shinshu University, Nagano, Japan 143 Department Physik, Universit¨at Siegen, Siegen, Germany 144 Department of Physics, Simon Fraser University, Burnaby BC, Canada 145 SLAC National Accelerator Laboratory, Stanford CA, U.S.A. 146 (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 147 (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 148 (a)Department of Physics, Stockholm University; (b)The Oskar Klein Centre, Stockholm, Sweden 149 Physics Department, Royal Institute of Technology, Stockholm, Sweden 150 Departments of Physics & Astronomy and Chemistry, Stony Brook University, Stony Brook NY, U.S.A. 151 Department of Physics and Astronomy, University of Sussex, Brighton, U.K. 152 School of Physics, University of Sydney, Sydney, Australia 153 Institute of Physics, Academia Sinica, Taipei, Taiwan 154 Department of Physics, Technion: Israel Institute of Technology, Haifa, Israel 155 Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, Tel Aviv, Israel 156 Department of Physics, Aristotle University of Thessaloniki, Thessaloniki, Greece 157 International Center for Elementary Particle Physics and Department of Physics, The University of Tokyo, Tokyo, Japan 158 Graduate School of Science and Technology, Tokyo Metropolitan University, Tokyo, Japan 159 Department of Physics, Tokyo Institute of Technology, Tokyo, Japan 160 Tomsk State University, Tomsk, Russia 161 Department of Physics, University of Toronto, Toronto ON, Canada 162 (a)INFN-TIFPA; (b)University of Trento, Trento, Italy 163 (a)TRIUMF, Vancouver BC; (b)Department of Physics and Astronomy, York University, Toronto ON, Canada 164 Faculty of Pure and Applied Sciences, and Center for Integrated Research in Fundamental Science and Engineering, University of Tsukuba, Tsukuba, Japan 165 Department of Physics and Astronomy, Tufts University, Medford MA, U.S.A. 166 Department of Physics and Astronomy, University of California Irvine, Irvine CA, U.S.A. 167 (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 168 Department of Physics and Astronomy, University of Uppsala, Uppsala, Sweden – 47 – JHEP04(2017)124 169 Department of Physics, University of Illinois, Urbana IL, U.S.A. 170 Instituto de Fisica Corpuscular (IFIC) and Departamento de Fisica Atomica, 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 171 Department of Physics, University of British Columbia, Vancouver BC, Canada 172 Department of Physics and Astronomy, University of Victoria, Victoria BC, Canada 173 Department of Physics, University of Warwick, Coventry, U.K. 174 Waseda University, Tokyo, Japan 175 Department of Particle Physics, The Weizmann Institute of Science, Rehovot, Israel 176 Department of Physics, University of Wisconsin, Madison WI, U.S.A. 177 Fakult¨at f¨ur Physik und Astronomie, Julius-Maximilians-Universit¨at, W¨urzburg, Germany 178 Fakult¨at f¨ur Mathematik und Naturwissenschaften, Fachgruppe Physik, Bergische Universit¨at Wuppertal, Wuppertal, Germany 179 Department of Physics, Yale University, New Haven CT, U.S.A. 180 Yerevan Physics Institute, Yerevan, Armenia 181 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, U.K. 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 & Astronomy, University of Louisville, Louisville, KY, U.S.A. fAlso at Physics Department, An-Najah National University, Nablus, Palestine gAlso at Department of Physics, California State University, Fresno CA, U.S.A. hAlso at Department of Physics, University of Fribourg, Fribourg, Switzerland iAlso at Departament de Fisica de la Universitat Autonoma de Barcelona, Barcelona, Spain jAlso at Departamento de Fisica e Astronomia, Faculdade de Ciencias, Universidade do Porto, Portugal kAlso at Tomsk State University, Tomsk, Russia, Russia lAlso at The Collaborative Innovation Center of Quantum Matter (CICQM), Beijing, China mAlso at Universita di Napoli Parthenope, Napoli, Italy nAlso at Institute of Particle Physics (IPP), Canada oAlso at Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest, Romania pAlso at Department of Physics, St. Petersburg State Polytechnical University, St. Petersburg, Russia qAlso at Borough of Manhattan Community College, City University of New York, New York City, U.S.A. rAlso at Department of Physics, The University of Michigan, Ann Arbor MI, U.S.A. sAlso at Centre for High Performance Computing, CSIR Campus, Rosebank, Cape Town, South Africa tAlso at Louisiana Tech University, Ruston LA, U.S.A. uAlso at Institucio Catalana de Recerca i Estudis Avancats, ICREA, Barcelona, Spain vAlso at Graduate School of Science, Osaka University, Osaka, Japan wAlso at Fakult¨at f¨ur Mathematik und Physik, Albert-Ludwigs-Universit¨at, Freiburg, Germany xAlso at Institute for Mathematics, Astrophysics and Particle Physics, Radboud University Nijmegen/Nikhef, Nijmegen, Netherlands yAlso at Department of Physics, The University of Texas at Austin, Austin TX, U.S.A. zAlso at Institute of Theoretical Physics, Ilia State University, Tbilisi, Georgia aa Also at CERN, Geneva, Switzerland ab Also at Georgian Technical University (GTU),Tbilisi, Georgia ac Also at Ochadai Academic Production, Ochanomizu University, Tokyo, Japan – 48 – JHEP04(2017)124 ad Also at Manhattan College, New York NY, U.S.A. ae Also at Academia Sinica Grid Computing, Institute of Physics, Academia Sinica, Taipei, Taiwan af Also at School of Physics, Shandong University, Shandong, China ag Also at Departamento de Fisica Teorica y del Cosmos and CAFPE, Universidad de Granada, Granada (Spain), Portugal ah Also at Department of Physics, California State University, Sacramento CA, U.S.A. ai Also at Moscow Institute of Physics and Technology State University, Dolgoprudny, Russia aj Also at Departement de Physique Nucleaire et Corpusculaire, Universit´e de Gen`eve, Geneva, Switzerland ak Also at Eotvos Lorand University, Budapest, Hungary al Also at International School for Advanced Studies (SISSA), Trieste, Italy am Also at Department of Physics and Astronomy, University of South Carolina, Columbia SC, U.S.A. an Also at Institut de F´ısica d’Altes Energies (IFAE), The Barcelona Institute of Science and Technology, Barcelona, Spain ao Also at School of Physics, Sun Yat-sen University, Guangzhou, China ap Also at Institute for Nuclear Research and Nuclear Energy (INRNE) of the Bulgarian Academy of Sciences, Sofia, Bulgaria aq Also at Faculty of Physics, M.V.Lomonosov Moscow State University, Moscow, Russia ar Also at Institute of Physics, Academia Sinica, Taipei, Taiwan as Also at National Research Nuclear University MEPhI, Moscow, Russia at Also at Department of Physics, Stanford University, Stanford CA, U.S.A. au Also at Institute for Particle and Nuclear Physics, Wigner Research Centre for Physics, Budapest, Hungary av Also at Giresun University, Faculty of Engineering, Turkey aw Also at Flensburg University of Applied Sciences, Flensburg, Germany ax Also at CPPM, Aix-Marseille Universit´e and CNRS/IN2P3, Marseille, France ay Also at University of Malaya, Department of Physics, Kuala Lumpur, Malaysia az Also at LAL, Univ. Paris-Sud, CNRS/IN2P3, Universit´e Paris-Saclay, Orsay, France ∗Deceased – 49 –