Measurement of the Inclusive Z Cross Section via Decays to Tau Pairs in pp Collisions at sqrt(s)=7 TeV

EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN) CERN-PH-EP/2011-035 2011/04/11 CMS-EWK-10-013 Measurement of the Inclusive Z Cross Section via Decays to Tau Pairs in pp Collisions at √s=7 TeV The CMS Collaboration∗ Abstract A measurement of inclusive Z →τ+τ−production in pp collisions is presented, in the final states µ+hadrons, e+hadrons, e+µ, and µ+µ. The data sample corresponds to an integrated luminosity of 36 pb−1collected with the CMS detector at the LHC. The measured cross section is σ(pp →ZX)×B(Z→τ+τ−)=1.00 ±0.05 (stat.)± 0.08 (syst.)±0.04 (lumi.)nb, which is in good agreement with the next-to-next-toleading order QCD prediction and with previous measurements in the Z →e+e−and µ+µ−channels. The reconstruction efficiency for hadronic τdecays is determined with a precision of 7%. Submitted to the Journal of High Energy Physics ∗See Appendix A for the list of collaboration members arXiv:1104.1617v1 [hep-ex] 8 Apr 2011 1 1 Introduction The measurement of the production cross section for pp →ZXwith Z →τ+τ−constitutes an important physics benchmark at the Large Hadron Collider (LHC). The τlepton can decay either into purely leptonic final states (τ→eνeντdenoted as “τe” or τ→µνµντdenoted as “τµ”) or into hadronic final states denoted by “τhad” consisting of a hadronic system and a ντ. Constrained by the τmass, the hadronic system is characterized by a low particle multiplicity and a highly collimated jet which allows a τhad signal to be separated from the large QCD jet backgrounds. The validation of the τhad signal is essential in searches for new physics based on τleptons, such as Higgs boson decays to τ+τ−[1]. The Compact Muon Solenoid (CMS) Collaboration recently reported a search for the Higgs boson in this channel [2]. Tau leptons can also be important signatures for searches of supersymmetry, extra dimensions, and extra gauge bosons [3]. The Z →τ+τ−production cross section has been previously measured in proton-antiproton collisions by the CDF and D0 Collaborations [4, 5]. In this study, Z →τ+τ−events in the τµτhad, τeτhad,τeτµ, and τµτµfinal states are selected from a sample of √s=7 TeV proton-proton collision data recorded by the CMS experiment at the LHC. The data sample corresponds to an integrated luminosity of 36 ±1 pb−1. The results are compared to previous measurements made in the e+e−and µ+µ−final states [6], providing a validation of τhad reconstruction and identification [7–9] and a direct measurement of the tau selection efficiency. 2 CMS Detector The central feature of the CMS apparatus is a superconducting solenoid, of 6 m internal diameter, providing a magnetic field of 3.8 T. Within the field volume are the silicon pixel and strip tracker, the crystal electromagnetic calorimeter (ECAL) and the brass/scintillator hadron calorimeter (HCAL). Muons are measured in gas-ionization detectors embedded in the steel return yoke. CMS uses a right-handed coordinate system, with the origin at the nominal interaction point, the xaxis pointing to the centre of the LHC, the yaxis pointing up perpendicular to the LHC plane, and the zaxis along the counterclockwise-beam direction. The polar angle θis measured from the positive zaxis and the azimuthal angle φis measured in the xy plane. Variables used in this article are the pseudorapidity, η≡ −ln[tan(θ/2)], and the transverse momentum, pT=qp2 x+p2 y. The ECAL is designed to have both excellent energy resolution and high granularity, which are crucial for reconstructing electrons and photons produced in τdecays. The ECAL is constructed with projective lead tungstate crystals in two pseudorapidity regions: the barrel (|η|< 1.479) and the endcap (1.479 <|η|<3). The transition regions between the barrel and the endcaps, 1.444 <|η|<1.567, are not used for electron reconstruction. In the barrel region, the crystals are 25.8 X0long, where X0is the radiation length, and conform to a granularity of ∆η×∆φ=0.0174 ×0.0174. The endcap region is instrumented with a lead–silicon-strip preshower detector consisting of two orthogonal strip detectors with a strip pitch of 1.9 mm. One plane is at a depth of 2X0and the other at 3X0. The ECAL has an energy resolution of better than 0.5% for unconverted photons with transverse energies above 100 GeV. The energy resolution is 3% or better for the range of electron energies relevant for this analysis. The HCAL barrel and endcap regions cover the range |η|<3 and are subdivided into towers with a segmentation of ∆η×∆φ=0.087 ×0.087, corresponding to 5 ×5 ECAL crystals in the barrel 23 Lepton Reconstruction and Identification region. The HCAL forward region extends the calorimetry to |η|<5. The inner tracker measures charged particle tracks within the range |η|<2.5. It consists of 1 440 silicon pixel and 15 148 silicon strip detector modules and provides an impact parameter resolution of ∼15 µm and a transverse momentum resolution of about 1.5% for 100 GeV particles. The muon barrel region is covered by drift tubes and the endcap regions by cathode strip chambers. In both regions resistive plate chambers provide additional coordinate and timing information. Muons can be reconstructed in the range |η|<2.4, with a typical pTresolution of 1% for pT≈40 GeV. A more detailed description of CMS can be found in [10]. 3 Lepton Reconstruction and Identification Muons produced by τdecays in the Z →τ+τ−process are reconstructed in the tracker and muon chambers [11]. Quality cuts, based on the minimum number of hits in the silicon tracker, pixel detector, and muon chambers, are applied to suppress backgrounds from punch-throughs and decays in flight. Electrons are reconstructed by combining tracks produced by the Gaussian Sum Filter algorithm with ECAL clusters [12]. Requirements are imposed that distinguish prompt electrons from charged pions mimicking electron signatures, and from electrons produced by photon conversions. The CMS particle flow (PF) algorithm [8] is used to form a mutually exclusive collection of reconstructed particles (muons, electrons, photons, and charged and neutral hadrons) by combining tracks and calorimeter clusters. These reconstructed particles are used to build composite objects such as τ’s and jets, and to measure the missing transverse energy E/T. Electrons and muons from τdecays are expected to be isolated in the detector, while leptons from heavy-flavour (c and b) decays and decays in flight are expected to be found inside jets. A measure of isolation is used to discriminate the signal from the QCD multijet background, based on the charged hadrons, photons, and neutral hadrons falling within a cone ∆R=p∆η2+∆φ2=0.4 around the lepton momentum direction. In the τµτµfinal state, a cone of ∆R=0.3 is used. A sum of the pTfor each particle type is made for charged hadrons with pT>0.5 GeV and for photons and neutral hadrons with pT>1 GeV; photons and neutral hadrons are excluded from the sum if they fall within inner cones of ∆R=0.05 and ∆R=0.08, respectively. The relative isolation variable is IPF rel =Σpcharged T+pphoton T+pneutral T/p` T, where pcharged T,pphoton T, and pneutral Trefer to the charged hadrons, photons, and neutral hadrons in the sum, respectively, and p` Trefers to the pTof the lepton `=e, µ. For muons, it is required that IPF rel <0.1, while for electrons it is required that IPF rel <0.08 in the barrel and IPF rel <0.04 in the endcaps. A similar formula is used for the τeτµfinal state but with the isolation quantities based directly on tracker and calorimeter information, calculated in a cone of ∆R=0.3. In this case, it is required that Irel <0.15 for muons and Irel <0.1 for electrons. The τhad identification algorithm used in this measurement is known as the Hadrons Plus Strips algorithm [9], which starts from a high-pTcharged hadron and combines it with other nearby charged or neutral hadrons to reconstruct τdecay modes. The identification of π0mesons is enhanced by clustering electrons and photons in ”strips” along the bending plane to take into account possible broadening of calorimeter signatures by photon conversions. To reduce 3 the contamination from QCD jets, the τhad-candidate isolation is calculated in a cone of ∆R= 0.5 around the reconstructed τ-momentum direction. It is requested that there be no charged hadrons with pT>1.0 GeV and no photons with ET>1.5 GeV in the isolation cone, other than the τconstituents. 4 Event Selection The events preselected for this analysis in the τµτhad,τeτµ, and τµτµfinal states are required to pass the single-muon Level-1 (L1) trigger with a pTthreshold of 7 GeV and the single muon High Level Trigger (HLT) [13], with a threshold varying from 9 GeV to 15 GeV, depending on the instantaneous luminosity. Events in the τeτhad final state are selected using the singleelectron L1 trigger with a threshold of 8 GeV in the transverse energy, and a single-electron HLT trigger with a threshold of 12 GeV at higher instantaneous luminosity. At the end of the 2010 data taking period, a combined e+τtrigger was used in order to keep the rate low enough without a further increase of the electron threshold. The trigger has the same L1 requirements as the electron trigger, but the HLT requires the presence of an electron of transverse energy larger than 12 GeV and a hadronic tau decay with pTlarger than 15 GeV, tagged with a simplified version of the tau reconstruction algorithm with a less restrictive selection than the one used in the offline analysis. Offline event selection starts with the requirement of a well-defined primary vertex [14]. For the τµτhad and τeτhad final states, one isolated muon or electron is required with pT>15 GeV and |η|<2.1. The associated τhad must be oppositely charged, with pT>20 GeV and |η|<2.3. In order to reject events coming from the W+jets background, the transverse mass of the lepton and the E/T,MT(`,E/T) = q2p` TE/T·(1−cos ∆φ), is required to be less than 40 GeV, where ∆φ is the difference in azimuthal angle between the lepton and E/Tvectors. The MTdistribution and the selection requirement applied are illustrated in Fig. 1 (left) for the τµτhad final state. For the τeτµfinal state, one isolated muon with |η|<2.1 and one oppositely charged isolated electron with |η|<2.4 are required, both with pT>15 GeV. Further background suppression is achieved by requiring MT(µ,E/T)<50 GeV and MT(e, E/T)<50 GeV. For the τµτµfinal state, events with two oppositely charged isolated muons with |η|<2.1 are selected if one satisfies pT>19 GeV and the other pT>10 GeV. The requirement E/T<50 GeV suppresses tt and W+jets backgrounds, and a requirement on the azimuthal angle difference between the muons, ∆φµµ >2, rejects QCD background events, for muons originating from the same quarkonia decay or from a decay chain of heavy-flavour hadrons. Effective suppression of the Drell–Yan background is achieved with a multivariate likelihood ratio technique. For each event, the relative probabilities to belong to two event classes (Z →τ+τ−→τµτµand Z/γ∗→µ+µ−) are computed, exploiting the following set of discriminating variables: the ratio of the transverse momentum of the dimuon system to the scalar sum of the momenta of the two muons; the significance of the distance of closest approach (DCA) between the two muon helix tracks; the pseudorapidity of the dimuon system; and the azimuthal angle between the positive muon momentum and E/T. A normalized likelihood discriminant is computed and is shown in Fig. 1 (right). Events with a likelihood discriminant value larger than 0.87 are kept in the final sample. For the plots in Fig. 1, the QCD multijet, W and diboson backgrounds were simulated with PYTHIA [15], the Drell–Yan signal and background with the next-to-leading order (NLO) Monte Carlo generator POWHEG [16–18], and the top samples with Madgraph [19]. The tau decays were performed with Tauola [20]. The samples were normalized using the cross section 45 Background Estimation ) [GeV] T E, µ( T M 0 20 40 60 80 100 120 Events / (10 GeV) 0 50 100 150 200 250 300 data ττ → Z W+jets t EWK+t QCD CMS = 7 TeVs at -1 36 pb had τ µ τ → ττ →Z Normalized Likelihood 0 0.2 0.4 0.6 0.8 1 Events / 0.05 1 10 2 10 3 10 4 10 5 10 data µµ →* γ Z/ ττ → Z νµ → W t t QCD CMS = 7 TeVs at -1 36 pb µ τ µ τ → ττ →Z Figure 1: Muon+E/Ttransverse mass (left) for the τµτhad final state. Likelihood discriminant (right) for the τµτµfinal state. The arrows show the final selection criteria applied. at next-to-next-to-leading order (NNLO) for Drell–Yan and W, at leading order (LO) for QCD, and NLO for the tt sample. The EWK label in the figure refers to the Z →e+e−,µ+µ−, and diboson backgrounds. 5 Background Estimation The Z →τ+τ−signal is established using the visible mass, which is the reconstructed mass of the `τhad system in the τ`τhad final states, and the dilepton invariant mass for the τeτµand τµτµfinal states. Due to the presence of neutrinos in the final state, the Z →τ+τ−visible mass peak extends across the range 30–100 GeV, which is considerably broader than the Z resonance itself. The backgrounds generally span the same mass range, so an accurate determination of the signal yield requires effective background estimation techniques. The main background sources are QCD multijet processes, W+jets, and Z →`+`−, with small contributions from top-quark decays and dibosons. All backgrounds are measured in control regions where their contributions are enhanced and extrapolated to the signal selection region using selection efficiencies determined either from data or the Monte Carlo simulation. In the τ`τhad final state, the QCD multijet background is estimated using samples of same-sign (SS) and opposite-sign (OS) events from data, for which the electron or muon isolation requirement is inverted; the QCD background estimate is based on the ratio of OS to SS yields. The visible mass distribution of the SS events is used to describe the background in the signal region. The W contribution is extracted from the region MT(`,E/T)>60 GeV, where it dominates the sample. In the τeτµfinal state, the background contributions are expected to be small and are estimated from the simulation. The large-transverse-mass region is used to check the estimated background contributions from W, diboson, and tt backgrounds. For the τµτµfinal state, the Drell–Yan muon-pair production events are selected with a reduced likelihood without including the muon DCA significance, and the resulting muon DCA significance distribution is fitted with signal and background shapes. The QCD multijet background estimate is obtained from a sample of SS dimuon events. The numbers of selected events and the expected background contributions are summarized in Table 1. The statistical and systematic uncertainties in the methods used are also given, where 5 the uncertainties are added in quadrature. Table 1: Numbers of expected background events and number of data events passing all the selection criteria in the four final states. The uncertainties shown include the statistical and systematic uncertainties added in quadrature. τµτhad τeτhad τeτµτµτµ (Mµµ <70 GeV) Z→`+`−, jet misidentified as τ6.4 ±2.4 15.0 ±6.2 - Z→`+`−, lepton misidentified as τ12.9 ±3.5 109 ±28 2.4 ±0.3 20.1 ±1.3 tt 6.0 ±3.0 2.6 ±1.3 7.1 ±1.3 0.15 ±0.03 W→`ν54.9 ±4.8 30.6 ±3.1 W→τν 14.7 ±1.3 7.0 ±0.7 1.5 ±0.5 2.5 ±2.5 QCD multijet 132 ±14 181 ±23 WW/WZ/ZZ 1.6 ±0.8 0.8 ±0.4 3.0 ±0.4 - Total background 228 ±16 346 ±37 14.0 ±1.8 22.8 ±2.8 Total data 517 540 101 58 6 Systematic Uncertainties The efficiencies for electron and muon reconstruction, identification, and isolation, as well as the trigger efficiencies are obtained from data. Correction factors for the values extracted from the simulation are determined using the method described in Ref. [6] (tag-and-probe method). The measured efficiencies have a small dependence on pTand cover the full range of pTused in the analysis. The uncertainties on the correction factors are in the range of 0.2–1.1%. A similar technique is used to estimate the hadronic tau identification efficiency. A data sample of taus is selected using Z →τ+τ−→τµτhad events. The events are preselected without applying the full tau identification but only kinematic cuts and a set of requirements to suppress the background from Z →µ+µ−, W, and QCD events. The efficiency is then calculated as a ratio of the number of events that pass the tau identification requirement to the number of all preselected events. The total uncertainty of the measurement arises from the statistical uncertainty of the sample and the systematic uncertainties related to the understanding of the backgrounds in the preselection sample and amounts to 23% [9]. To estimate the efficiency of the MTselection and the likelihood selection efficiency for the τµτµ final state, an embedded sample is used where the muons in a Z →µ+µ−data sample are replaced by simulated tau decays with the original muon momentum. The estimated uncertainties amount to 2%. To estimate the effect of the energy-scale uncertainties on the acceptance, the energy of all reconstructed objects (electrons, muons, taus, and jets) is varied within their respective uncertainty. After each independent shift, the missing transverse energy is recalculated and the event selection is repeated. The event yield is compared to the nominal value and the relative difference is quoted as the systematic uncertainty. The systematic uncertainties are in the range from 1% to 3.5%. To obtain the acceptance corrections, the D6T and Z2 PYTHIA tunes [21] were used in the simulation. The effect of the use of different tunes on the final extracted cross section is smaller than 1% and is not included in the systematic uncertainties. 67 Cross Section Measurement The main source of theoretical uncertainty in the calculation of the experimental acceptance comes from the parton distribution functions (PDFs). The central acceptance value is obtained with the CT10 PDF [22]. The uncertainty is estimated using the error sets of the PDFs: CT10, MSTW2008NLO [23], and NNPDF2.0 [24], and amounts to 2%. The experimental and theoretical uncertainties are summarized in Table 2. Table 2: Summary of the sources of systematic uncertainties and their estimated effect on the measured Z →τ+τ−cross section. Source τµτhad τeτhad τeτµτµτµ Trigger 0.2% 3% 0.2% 0.3% Lepton identification and isolation 1.0% 1.1% 1% 1% τhad identification 23% - Efficiency of MTselection 2% - Likelihood selection efficiency - 2% Acceptance due to τhad energy scale, 3% 3.5% - Acceptance due to e energy scale, 2% - 1.6% 1.6% - Acceptance due to µmomentum scale, 1% 1% - 1% 2% Luminosity 4% Parton distribution functions 2% 7 Cross Section Measurement The cross section is obtained for each final state with the following formula: σ(pp →ZX)×B(Z→τ+τ−) = N AeB0L, (1) where Nis the number of extracted signal events, Ais the acceptance of signal events, eis the signal selection efficiency, B0is the branching fraction of the τ-decay mode considered [25], and Lis the integrated luminosity [26]. The visible mass distributions of the τµτhad,τeτhad,τeτµand τµτµfinal states are shown in Fig. 2. To extract the signal, a fit is performed using the visible mass shapes from the simulation, except for the QCD multijet and Z →`+`−backgrounds, which are obtained from data. For the simulation shapes, a variation of the electron and tau energy scales within their uncertainties is considered. The effect of the muon energy scale is negligible. The background normalizations correspond to the numbers listed in Table 1 and are allowed to vary within the estimated uncertainties. The background yields and signal shapes shown in Fig. 2 are those obtained from the fitting procedure. Table 3: Acceptance, selection efficiency and fraction of selected events outside the generatorlevel mass window for the four final states considered. τµτhad τeτhad τeτµτµτµ Acceptance A0.13 0.12 0.074 0.16 Selection efficiency e0.37 0.23 0.55 0.17 Mass window correction fout 0.03 0.03 0.02 0.01 7 Visible Mass [GeV] 0 50 100 150 200 Events / (10 GeV) 0 50 100 150 data ττ → Z t EWK+t QCD yields from fit CMS = 7 TeVs at -1 36 pb had τ µ τ → ττ →Z Visible Mass [GeV] 0 50 100 150 200 Events / (10 GeV) 0 50 100 150 data ττ → Z t EWK+t QCD yields from fit CMS = 7 TeVs at -1 36 pb had τ e τ → ττ →Z Invariant Mass [GeV]µe0 50 100 150 200 Events / (10 GeV) 0 10 20 30 40 50 data ττ → Z t EWK+t QCD yields from fit CMS = 7 TeVs at -1 36 pb µ τ e τ → ττ →Z Invariant Mass [GeV]µ-µ 0 50 100 150 200 Events / (10 GeV) 1 10 2 10 3 10 data ττ → Z µµ →* γ Z/ QCD yields from fit CMS = 7 TeVs at -1 36 pb µ τ µ τ → ττ →Z Figure 2: Visible mass distributions of the τµτhad (top left), τeτhad (top right), τeτµ(bottom left), and τµτµ(bottom right) final states. The acceptances were obtained with the NLO QCD program POWHEG in the Z →τ+τ−mass region 60 <Mτ+τ−<120 GeV. Table 3 shows the acceptances and the selection efficiencies for the different final states considered. The number of extracted events from the fit, Nfit, is corrected for the fraction of signal events outside the generator-level mass window, fout, where N=Nfit ·(1−fout)in Eq. 1. The correction factors used are also shown in Table 3. The measured values of the cross section from the four final states considered are shown in Table 4, where the uncertainties shown are due to statistical, systematic, integrated luminosity and τidentification uncertainties. The measured values are compatible with each other and with the NNLO theoretical prediction, 0.972 ±0.042 nb [27]. They are also consistent with the CMS measurement based on Z→e+e−,µ+µ−events [6]. The dominant uncertainty on the Z →τ+τ−cross section measurement comes from the τhad reconstruction and identification efficiency. A simultaneous fit to all four final states is performed to obtain the cross section and a scale factor for the τhad efficiency, which is the ratio of the efficiency in the data to that in the simulation. The result of the global fit is shown in 14 A The CMS Collaboration University of Sofia, Sofia, Bulgaria A. Dimitrov, R. Hadjiiska, A. Karadzhinova, V. Kozhuharov, L. Litov, M. Mateev, B. Pavlov, P. Petkov Institute of High Energy Physics, Beijing, China J.G. Bian, G.M. Chen, H.S. Chen, C.H. Jiang, D. Liang, S. Liang, X. Meng, J. Tao, J. Wang, J. Wang, X. Wang, Z. Wang, H. Xiao, M. Xu, J. Zang, Z. Zhang State Key Lab. of Nucl. Phys. and Tech., Peking University, Beijing, China Y. Ban, S. Guo, Y. Guo, W. Li, Y. Mao, S.J. Qian, H. Teng, L. Zhang, B. Zhu, W. Zou Universidad de Los Andes, Bogota, Colombia A. Cabrera, B. Gomez Moreno, A.A. Ocampo Rios, A.F. Osorio Oliveros, J.C. Sanabria Technical University of Split, Split, Croatia N. Godinovic, D. Lelas, K. Lelas, R. Plestina3, D. Polic, I. Puljak University of Split, Split, Croatia Z. Antunovic, M. Dzelalija Institute Rudjer Boskovic, Zagreb, Croatia V. Brigljevic, S. Duric, K. Kadija, S. Morovic University of Cyprus, Nicosia, Cyprus A. Attikis, M. Galanti, J. Mousa, C. Nicolaou, F. Ptochos, P.A. Razis Charles University, Prague, Czech Republic M. Finger, M. Finger Jr. Academy of Scientific Research and Technology of the Arab Republic of Egypt, Egyptian Network of High Energy Physics, Cairo, Egypt Y. Assran4, S. Khalil5, M.A. Mahmoud6 National Institute of Chemical Physics and Biophysics, Tallinn, Estonia A. Hektor, M. Kadastik, M. M¨ untel, M. Raidal, L. Rebane Department of Physics, University of Helsinki, Helsinki, Finland V. Azzolini, P. Eerola, G. Fedi Helsinki Institute of Physics, Helsinki, Finland S. Czellar, J. H¨ ark¨ onen, A. Heikkinen, V. Karim¨ aki, R. Kinnunen, M.J. Kortelainen, T. Lamp´ en, K. Lassila-Perini, S. Lehti, T. Lind´ en, P. Luukka, T. M¨ aenp¨ a¨ a, E. Tuominen, J. Tuominiemi, E. Tuovinen, D. Ungaro, L. Wendland Lappeenranta University of Technology, Lappeenranta, Finland K. Banzuzi, A. Korpela, T. Tuuva Laboratoire d’Annecy-le-Vieux de Physique des Particules, IN2P3-CNRS, Annecy-le-Vieux, France D. Sillou DSM/IRFU, CEA/Saclay, Gif-sur-Yvette, France M. Besancon, S. Choudhury, M. Dejardin, D. Denegri, B. Fabbro, J.L. Faure, F. Ferri, S. Ganjour, F.X. Gentit, A. Givernaud, P. Gras, G. Hamel de Monchenault, P. Jarry, E. Locci, J. Malcles, M. Marionneau, L. Millischer, J. Rander, A. Rosowsky, I. Shreyber, M. Titov, P. Verrecchia 15 Laboratoire Leprince-Ringuet, Ecole Polytechnique, IN2P3-CNRS, Palaiseau, France S. Baffioni, F. Beaudette, L. Benhabib, L. Bianchini, M. Bluj7, C. Broutin, P. Busson, C. Charlot, T. Dahms, L. Dobrzynski, S. Elgammal, R. Granier de Cassagnac, M. Haguenauer, P. Min´ e, C. Mironov, C. Ochando, P. Paganini, D. Sabes, R. Salerno, Y. Sirois, C. Thiebaux, B. Wyslouch8, A. Zabi Institut Pluridisciplinaire Hubert Curien, Universit´e de Strasbourg, Universit´e de Haute Alsace Mulhouse, CNRS/IN2P3, Strasbourg, France J.-L. Agram9, J. Andrea, D. Bloch, D. Bodin, J.-M. Brom, M. Cardaci, E.C. Chabert, C. Collard, E. Conte9, F. Drouhin9, C. Ferro, J.-C. Fontaine9, D. Gel´ e, U. Goerlach, S. Greder, P. Juillot, M. Karim9, A.-C. Le Bihan, Y. Mikami, P. Van Hove Centre de Calcul de l’Institut National de Physique Nucleaire et de Physique des Particules (IN2P3), Villeurbanne, France F. Fassi, D. Mercier Universit´e de Lyon, Universit´e Claude Bernard Lyon 1, CNRS-IN2P3, Institut de Physique Nucl´eaire de Lyon, Villeurbanne, France C. Baty, S. Beauceron, N. Beaupere, M. Bedjidian, O. Bondu, G. Boudoul, D. Boumediene, H. Brun, R. Chierici, D. Contardo, P. Depasse, H. El Mamouni, J. Fay, S. Gascon, B. Ille, T. Kurca, T. Le Grand, M. Lethuillier, L. Mirabito, S. Perries, V. Sordini, S. Tosi, Y. Tschudi, P. Verdier Institute of High Energy Physics and Informatization, Tbilisi State University, Tbilisi, Georgia D. Lomidze RWTH Aachen University, I. Physikalisches Institut, Aachen, Germany G. Anagnostou, M. Edelhoff, L. Feld, N. Heracleous, O. Hindrichs, R. Jussen, K. Klein, J. Merz, N. Mohr, A. Ostapchuk, A. Perieanu, F. Raupach, J. Sammet, S. Schael, D. Sprenger, H. Weber, M. Weber, B. Wittmer RWTH Aachen University, III. Physikalisches Institut A, Aachen, Germany M. Ata, W. Bender, E. Dietz-Laursonn, M. Erdmann, J. Frangenheim, T. Hebbeker, A. Hinzmann, K. Hoepfner, T. Klimkovich, D. Klingebiel, P. Kreuzer, D. Lanske†, C. Magass, M. Merschmeyer, A. Meyer, P. Papacz, H. Pieta, H. Reithler, S.A. Schmitz, L. Sonnenschein, J. Steggemann, D. Teyssier, M. Tonutti RWTH Aachen University, III. Physikalisches Institut B, Aachen, Germany M. Bontenackels, M. Davids, M. Duda, G. Fl¨ ugge, H. Geenen, M. Giffels, W. Haj Ahmad, D. Heydhausen, T. Kress, Y. Kuessel, A. Linn, A. Nowack, L. Perchalla, O. Pooth, J. Rennefeld, P. Sauerland, A. Stahl, M. Thomas, D. Tornier, M.H. Zoeller Deutsches Elektronen-Synchrotron, Hamburg, Germany M. Aldaya Martin, W. Behrenhoff, U. Behrens, M. Bergholz10, A. Bethani, K. Borras, A. Cakir, A. Campbell, E. Castro, D. Dammann, G. Eckerlin, D. Eckstein, A. Flossdorf, G. Flucke, A. Geiser, J. Hauk, H. Jung1, M. Kasemann, I. Katkov11, P. Katsas, C. Kleinwort, H. Kluge, A. Knutsson, M. Kr¨ amer, D. Kr¨ ucker, E. Kuznetsova, W. Lange, W. Lohmann10, R. Mankel, M. Marienfeld, I.-A. Melzer-Pellmann, A.B. Meyer, J. Mnich, A. Mussgiller, J. Olzem, D. Pitzl, A. Raspereza, A. Raval, M. Rosin, R. Schmidt10, T. Schoerner-Sadenius, N. Sen, A. Spiridonov, M. Stein, J. Tomaszewska, R. Walsh, C. Wissing University of Hamburg, Hamburg, Germany C. Autermann, V. Blobel, S. Bobrovskyi, J. Draeger, H. Enderle, U. Gebbert, K. Kaschube, G. Kaussen, R. Klanner, J. Lange, B. Mura, S. Naumann-Emme, F. Nowak, N. Pietsch, C. Sander, 16 A The CMS Collaboration H. Schettler, P. Schleper, M. Schr¨ oder, T. Schum, J. Schwandt, H. Stadie, G. Steinbr¨ uck, J. Thomsen Institut f¨ur Experimentelle Kernphysik, Karlsruhe, Germany C. Barth, J. Bauer, V. Buege, T. Chwalek, W. De Boer, A. Dierlamm, G. Dirkes, M. Feindt, J. Gruschke, C. Hackstein, F. Hartmann, M. Heinrich, H. Held, K.H. Hoffmann, S. Honc, J.R. Komaragiri, T. Kuhr, D. Martschei, S. Mueller, Th. M¨ uller, M. Niegel, O. Oberst, A. Oehler, J. Ott, T. Peiffer, D. Piparo, G. Quast, K. Rabbertz, F. Ratnikov, N. Ratnikova, M. Renz, C. Saout, A. Scheurer, P. Schieferdecker, F.-P. Schilling, M. Schmanau, G. Schott, H.J. Simonis, F.M. Stober, D. Troendle, J. Wagner-Kuhr, T. Weiler, M. Zeise, V. Zhukov11, E.B. Ziebarth Institute of Nuclear Physics ”Demokritos”, Aghia Paraskevi, Greece G. Daskalakis, T. Geralis, K. Karafasoulis, S. Kesisoglou, A. Kyriakis, D. Loukas, I. Manolakos, A. Markou, C. Markou, C. Mavrommatis, E. Ntomari, E. Petrakou University of Athens, Athens, Greece L. Gouskos, T.J. Mertzimekis, A. Panagiotou, E. Stiliaris University of Io´annina, Io´annina, Greece I. Evangelou, C. Foudas, P. Kokkas, N. Manthos, I. Papadopoulos, V. Patras, F.A. Triantis KFKI Research Institute for Particle and Nuclear Physics, Budapest, Hungary A. Aranyi, G. Bencze, L. Boldizsar, C. Hajdu1, P. Hidas, D. Horvath12, A. Kapusi, K. Krajczar13, F. Sikler1, G.I. Veres13, G. Vesztergombi13 Institute of Nuclear Research ATOMKI, Debrecen, Hungary N. Beni, J. Molnar, J. Palinkas, Z. Szillasi, V. Veszpremi University of Debrecen, Debrecen, Hungary P. Raics, Z.L. Trocsanyi, B. Ujvari Panjab University, Chandigarh, India S. Bansal, S.B. Beri, V. Bhatnagar, N. Dhingra, R. Gupta, M. Jindal, M. Kaur, J.M. Kohli, M.Z. Mehta, N. Nishu, L.K. Saini, A. Sharma, A.P. Singh, J.B. Singh, S.P. Singh University of Delhi, Delhi, India S. Ahuja, S. Bhattacharya, B.C. Choudhary, P. Gupta, S. Jain, S. Jain, A. Kumar, K. Ranjan, R.K. Shivpuri Bhabha Atomic Research Centre, Mumbai, India R.K. Choudhury, D. Dutta, S. Kailas, V. Kumar, A.K. Mohanty1, L.M. Pant, P. Shukla Tata Institute of Fundamental Research - EHEP, Mumbai, India T. Aziz, M. Guchait14, A. Gurtu, M. Maity15, D. Majumder, G. Majumder, K. Mazumdar, G.B. Mohanty, A. Saha, K. Sudhakar, N. Wickramage Tata Institute of Fundamental Research - HECR, Mumbai, India S. Banerjee, S. Dugad, N.K. Mondal Institute for Research and Fundamental Sciences (IPM), Tehran, Iran H. Arfaei, H. Bakhshiansohi16, S.M. Etesami, A. Fahim16, M. Hashemi, A. Jafari16, M. Khakzad, A. Mohammadi17, M. Mohammadi Najafabadi, S. Paktinat Mehdiabadi, B. Safarzadeh, M. Zeinali18 INFN Sezione di Bari a, Universit`a di Bari b, Politecnico di Bari c, Bari, Italy M. Abbresciaa,b, L. Barbonea,b, C. Calabriaa,b, A. Colaleoa, D. Creanzaa,c, N. De Filippisa,c,1, 17 M. De Palmaa,b, L. Fiorea, G. Iasellia,c, L. Lusitoa,b, G. Maggia,c, M. Maggia, N. Mannaa,b, B. Marangellia,b, S. Mya,c, S. Nuzzoa,b, N. Pacificoa,b, G.A. Pierroa, A. Pompilia,b, G. Pugliesea,c, F. Romanoa,c, G. Rosellia,b, G. Selvaggia,b, L. Silvestrisa, R. Trentaduea, S. Tupputia,b, G. Zitoa INFN Sezione di Bologna a, Universit`a di Bologna b, Bologna, Italy G. Abbiendia, A.C. Benvenutia, D. Bonacorsia, S. Braibant-Giacomellia,b, L. Brigliadoria, P. Capiluppia,b, A. Castroa,b, F.R. Cavalloa, M. Cuffiania,b, G.M. Dallavallea, F. Fabbria, A. Fanfania,b, D. Fasanellaa, P. Giacomellia, M. Giuntaa, C. Grandia, S. Marcellinia, G. Masetti, M. Meneghellia,b, A. Montanaria, F.L. Navarriaa,b, F. Odoricia, A. Perrottaa, F. Primaveraa, A.M. Rossia,b, T. Rovellia,b, G. Sirolia,b INFN Sezione di Catania a, Universit`a di Catania b, Catania, Italy S. Albergoa,b, G. Cappelloa,b, M. Chiorbolia,b,1, S. Costaa,b, A. Tricomia,b, C. Tuvea INFN Sezione di Firenze a, Universit`a di Firenze b, Firenze, Italy G. Barbaglia, V. Ciullia,b, C. Civininia, R. D’Alessandroa,b, E. Focardia,b, S. Frosalia,b, E. Galloa, S. Gonzia,b, P. Lenzia,b, M. Meschinia, S. Paolettia, G. Sguazzonia, A. Tropianoa,1 INFN Laboratori Nazionali di Frascati, Frascati, Italy L. Benussi, S. Bianco, S. Colafranceschi19, F. Fabbri, D. Piccolo INFN Sezione di Genova, Genova, Italy P. Fabbricatore, R. Musenich INFN Sezione di Milano-Biccoca a, Universit`a di Milano-Bicocca b, Milano, Italy A. Benagliaa,b, F. De Guioa,b,1, L. Di Matteoa,b, A. Ghezzia,b, S. Malvezzia, A. Martellia,b, A. Massironia,b, D. Menascea, L. Moronia, M. Paganonia,b, D. Pedrinia, S. Ragazzia,b, N. Redaellia, S. Salaa, T. Tabarelli de Fatisa,b, V. Tancinia,b INFN Sezione di Napoli a, Universit`a di Napoli ”Federico II” b, Napoli, Italy S. Buontempoa, C.A. Carrillo Montoyaa,1, N. Cavalloa,20, A. De Cosaa,b, F. Fabozzia,20, A.O.M. Iorioa,1, L. Listaa, M. Merolaa,b, P. Paoluccia INFN Sezione di Padova a, Universit`a di Padova b, Universit`a di Trento (Trento) c, Padova, Italy P. Azzia, N. Bacchettaa, P. Bellana,b, A. Brancaa, R. Carlina,b, P. Checchiaa, M. De Mattiaa,b, T. Dorigoa, U. Dossellia, F. Gasparinia,b, U. Gasparinia,b, A. Kaminskiya,b,11, S. Lacapraraa,21, I. Lazzizzeraa,c, M. Margonia,b, M. Mazzucatoa, A.T. Meneguzzoa,b, M. Nespoloa,1, M. Passaseoa, L. Perrozzia,1, N. Pozzobona,b, P. Ronchesea,b, F. Simonettoa,b, E. Torassaa, M. Tosia,b, S. Vaninia,b, S. Venturaa, P. Zottoa,b INFN Sezione di Pavia a, Universit`a di Pavia b, Pavia, Italy P. Baessoa,b, U. Berzanoa, S.P. Rattia,b, C. Riccardia,b, P. Torrea,b, P. Vituloa,b, C. Viviania,b INFN Sezione di Perugia a, Universit`a di Perugia b, Perugia, Italy M. Biasinia,b, G.M. Bileia, B. Caponeria,b, L. Fan` oa,b, P. Laricciaa,b, A. Lucaronia,b,1, G. Mantovania,b, M. Menichellia, A. Nappia,b, F. Romeoa,b, A. Santocchiaa,b, S. Taronia,b,1, M. Valdataa,b INFN Sezione di Pisa a, Universit`a di Pisa b, Scuola Normale Superiore di Pisa c, Pisa, Italy P. Azzurria,c, G. Bagliesia, J. Bernardinia,b, T. Boccalia,1, G. Broccoloa,c, R. Castaldia, R.T. D’Agnoloa,c, R. Dell’Orsoa, F. Fioria,b, L. Fo` aa,c, A. Giassia, A. Kraana, F. Ligabuea,c, T. Lomtadzea, L. Martinia,22, A. Messineoa,b, F. Pallaa, G. Segneria, A.T. Serbana, P. Spagnoloa, R. Tenchinia, G. Tonellia,b,1, A. Venturia,1, P.G. Verdinia 18 A The CMS Collaboration INFN Sezione di Roma a, Universit`a di Roma ”La Sapienza” b, Roma, Italy L. Baronea,b, F. Cavallaria, D. Del Rea,b, E. Di Marcoa,b, M. Diemoza, D. Francia,b, M. Grassia,1, E. Longoa,b, S. Nourbakhsha, G. Organtinia,b, F. Pandolfia,b,1, R. Paramattia, S. Rahatloua,b INFN Sezione di Torino a, Universit`a di Torino b, Universit`a del Piemonte Orientale (Novara) c, Torino, Italy N. Amapanea,b, R. Arcidiaconoa,c, S. Argiroa,b, M. Arneodoa,c, C. Biinoa, C. Bottaa,b,1, N. Cartigliaa, R. Castelloa,b, M. Costaa,b, N. Demariaa, A. Grazianoa,b,1, C. Mariottia, M. Maronea,b, S. Masellia, E. Migliorea,b, G. Milaa,b, V. Monacoa,b, M. Musicha,b, M.M. Obertinoa,c, N. Pastronea, M. Pelliccionia,b, A. Romeroa,b, M. Ruspaa,c, R. Sacchia,b, V. Solaa,b, A. Solanoa,b, A. Staianoa, A. Vilela Pereiraa,b INFN Sezione di Trieste a, Universit`a di Trieste b, Trieste, Italy S. Belfortea, F. Cossuttia, G. Della Riccaa,b, B. Gobboa, D. Montaninoa,b, A. Penzoa Kangwon National University, Chunchon, Korea S.G. Heo, S.K. Nam Kyungpook National University, Daegu, Korea S. Chang, J. Chung, D.H. Kim, G.N. Kim, J.E. Kim, D.J. Kong, H. Park, S.R. Ro, D. Son, D.C. Son, T. Son Chonnam National University, Institute for Universe and Elementary Particles, Kwangju, Korea Zero Kim, J.Y. Kim, S. Song Korea University, Seoul, Korea S. Choi, B. Hong, M.S. Jeong, M. Jo, H. Kim, J.H. Kim, T.J. Kim, K.S. Lee, D.H. Moon, S.K. Park, H.B. Rhee, E. Seo, S. Shin, K.S. Sim University of Seoul, Seoul, Korea M. Choi, S. Kang, H. Kim, C. Park, I.C. Park, S. Park, G. Ryu Sungkyunkwan University, Suwon, Korea Y. Choi, Y.K. Choi, J. Goh, M.S. Kim, E. Kwon, J. Lee, S. Lee, H. Seo, I. Yu Vilnius University, Vilnius, Lithuania M.J. Bilinskas, I. Grigelionis, M. Janulis, D. Martisiute, P. Petrov, T. Sabonis Centro de Investigacion y de Estudios Avanzados del IPN, Mexico City, Mexico H. Castilla-Valdez, E. De La Cruz-Burelo, R. Lopez-Fernandez, R. Maga˜ na Villalba, A. S´ anchezHern´ andez, L.M. Villasenor-Cendejas Universidad Iberoamericana, Mexico City, Mexico S. Carrillo Moreno, F. Vazquez Valencia Benemerita Universidad Autonoma de Puebla, Puebla, Mexico H.A. Salazar Ibarguen Universidad Aut´onoma de San Luis Potos´ı, San Luis Potos´ı, Mexico E. Casimiro Linares, A. Morelos Pineda, M.A. Reyes-Santos University of Auckland, Auckland, New Zealand D. Krofcheck, J. Tam University of Canterbury, Christchurch, New Zealand P.H. Butler, R. Doesburg, H. Silverwood 19 National Centre for Physics, Quaid-I-Azam University, Islamabad, Pakistan M. Ahmad, I. Ahmed, M.I. Asghar, H.R. Hoorani, W.A. Khan, T. Khurshid, S. Qazi Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Warsaw, Poland G. Brona, M. Cwiok, W. Dominik, K. Doroba, A. Kalinowski, M. Konecki, J. Krolikowski Soltan Institute for Nuclear Studies, Warsaw, Poland T. Frueboes, R. Gokieli, M. G´ orski, M. Kazana, K. Nawrocki, K. Romanowska-Rybinska, M. Szleper, G. Wrochna, P. Zalewski Laborat´orio de Instrumenta¸c˜ao e F´ısica Experimental de Part´ıculas, Lisboa, Portugal N. Almeida, P. Bargassa, A. David, P. Faccioli, P.G. Ferreira Parracho, M. Gallinaro, P. Musella, A. Nayak, P.Q. Ribeiro, J. Seixas, J. Varela Joint Institute for Nuclear Research, Dubna, Russia S. Afanasiev, I. Belotelov, P. Bunin, I. Golutvin, A. Kamenev, V. Karjavin, G. Kozlov, A. Lanev, P. Moisenz, V. Palichik, V. Perelygin, S. Shmatov, V. Smirnov, A. Volodko, A. Zarubin Petersburg Nuclear Physics Institute, Gatchina (St Petersburg), Russia V. Golovtsov, Y. Ivanov, V. Kim, P. Levchenko, V. Murzin, V. Oreshkin, I. Smirnov, V. Sulimov, L. Uvarov, S. Vavilov, A. Vorobyev, A. Vorobyev Institute for Nuclear Research, Moscow, Russia Yu. Andreev, A. Dermenev, S. Gninenko, N. Golubev, M. Kirsanov, N. Krasnikov, V. Matveev, A. Pashenkov, A. Toropin, S. Troitsky Institute for Theoretical and Experimental Physics, Moscow, Russia V. Epshteyn, V. Gavrilov, V. Kaftanov†, M. Kossov1, A. Krokhotin, N. Lychkovskaya, V. Popov, G. Safronov, S. Semenov, V. Stolin, E. Vlasov, A. Zhokin Moscow State University, Moscow, Russia E. Boos, M. Dubinin23, L. Dudko, A. Ershov, A. Gribushin, O. Kodolova, I. Lokhtin, A. Markina, S. Obraztsov, M. Perfilov, S. Petrushanko, L. Sarycheva, V. Savrin, A. Snigirev P.N. Lebedev Physical Institute, Moscow, Russia V. Andreev, M. Azarkin, I. Dremin, M. Kirakosyan, A. Leonidov, S.V. Rusakov, A. Vinogradov State Research Center of Russian Federation, Institute for High Energy Physics, Protvino, Russia I. Azhgirey, S. Bitioukov, V. Grishin1, V. Kachanov, D. Konstantinov, A. Korablev, V. Krychkine, V. Petrov, R. Ryutin, S. Slabospitsky, A. Sobol, L. Tourtchanovitch, S. Troshin, N. Tyurin, A. Uzunian, A. Volkov University of Belgrade, Faculty of Physics and Vinca Institute of Nuclear Sciences, Belgrade, Serbia P. Adzic24, M. Djordjevic, D. Krpic24, J. Milosevic Centro de Investigaciones Energ´eticas Medioambientales y Tecnol´ogicas (CIEMAT), Madrid, Spain M. Aguilar-Benitez, J. Alcaraz Maestre, P. Arce, C. Battilana, E. Calvo, M. Cepeda, M. Cerrada, M. Chamizo Llatas, N. Colino, B. De La Cruz, A. Delgado Peris, C. Diez Pardos, D. Dom´ ınguez V´ azquez, C. Fernandez Bedoya, J.P. Fern´ andez Ramos, A. Ferrando, J. Flix, M.C. Fouz, P. Garcia-Abia, O. Gonzalez Lopez, S. Goy Lopez, J.M. Hernandez, M.I. Josa, G. Merino, J. Puerta Pelayo, I. Redondo, L. Romero, J. Santaolalla, M.S. Soares, C. Willmott 20 A The CMS Collaboration Universidad Aut´onoma de Madrid, Madrid, Spain C. Albajar, G. Codispoti, J.F. de Troc´ oniz Universidad de Oviedo, Oviedo, Spain J. Cuevas, J. Fernandez Menendez, S. Folgueras, I. Gonzalez Caballero, L. Lloret Iglesias, J.M. Vizan Garcia Instituto de F´ısica de Cantabria (IFCA), CSIC-Universidad de Cantabria, Santander, Spain J.A. Brochero Cifuentes, I.J. Cabrillo, A. Calderon, S.H. Chuang, J. Duarte Campderros, M. Felcini25, M. Fernandez, G. Gomez, J. Gonzalez Sanchez, C. Jorda, P. Lobelle Pardo, A. Lopez Virto, J. Marco, R. Marco, C. Martinez Rivero, F. Matorras, F.J. Munoz Sanchez, J. Piedra Gomez26, T. Rodrigo, A.Y. Rodr´ ıguez-Marrero, A. Ruiz-Jimeno, L. Scodellaro, M. Sobron Sanudo, I. Vila, R. Vilar Cortabitarte CERN, European Organization for Nuclear Research, Geneva, Switzerland D. Abbaneo, E. Auffray, G. Auzinger, P. Baillon, A.H. Ball, D. Barney, A.J. Bell27, D. Benedetti, C. Bernet3, W. Bialas, P. Bloch, A. Bocci, S. Bolognesi, M. Bona, H. Breuker, K. Bunkowski, T. Camporesi, G. Cerminara, J.A. Coarasa Perez, B. Cur´ e, D. D’Enterria, A. De Roeck, S. Di Guida, A. Elliott-Peisert, B. Frisch, W. Funk, A. Gaddi, S. Gennai, G. Georgiou, H. Gerwig, D. Gigi, K. Gill, D. Giordano, F. Glege, R. Gomez-Reino Garrido, M. Gouzevitch, P. Govoni, S. Gowdy, L. Guiducci, M. Hansen, C. Hartl, J. Harvey, J. Hegeman, B. Hegner, H.F. Hoffmann, A. Honma, V. Innocente, P. Janot, K. Kaadze, E. Karavakis, P. Lecoq, C. Lourenc¸o, T. M¨ aki, M. Malberti, L. Malgeri, M. Mannelli, L. Masetti, A. Maurisset, F. Meijers, S. Mersi, E. Meschi, R. Moser, M.U. Mozer, M. Mulders, E. Nesvold1, M. Nguyen, T. Orimoto, L. Orsini, E. Perez, A. Petrilli, A. Pfeiffer, M. Pierini, M. Pimi¨ a, G. Polese, A. Racz, J. Rodrigues Antunes, G. Rolandi28, T. Rommerskirchen, C. Rovelli, M. Rovere, H. Sakulin, C. Sch¨ afer, C. Schwick, I. Segoni, A. Sharma, P. Siegrist, M. Simon, P. Sphicas29, M. Spiropulu23, M. Stoye, P. Tropea, A. Tsirou, P. Vichoudis, M. Voutilainen, W.D. Zeuner Paul Scherrer Institut, Villigen, Switzerland W. Bertl, K. Deiters, W. Erdmann, K. Gabathuler, R. Horisberger, Q. Ingram, H.C. Kaestli, S. K¨ onig, D. Kotlinski, U. Langenegger, F. Meier, D. Renker, T. Rohe, J. Sibille30, A. Starodumov31 Institute for Particle Physics, ETH Zurich, Zurich, Switzerland P. Bortignon, L. Caminada32, N. Chanon, Z. Chen, S. Cittolin, G. Dissertori, M. Dittmar, J. Eugster, K. Freudenreich, C. Grab, A. Herv´ e, W. Hintz, P. Lecomte, W. Lustermann, C. Marchica32, P. Martinez Ruiz del Arbol, P. Meridiani, P. Milenovic33, F. Moortgat, C. N¨ ageli32, P. Nef, F. Nessi-Tedaldi, L. Pape, F. Pauss, T. Punz, A. Rizzi, F.J. Ronga, M. Rossini, L. Sala, A.K. Sanchez, M.-C. Sawley, B. Stieger, L. Tauscher†, A. Thea, K. Theofilatos, D. Treille, C. Urscheler, R. Wallny, M. Weber, L. Wehrli, J. Weng Universit¨at Z¨urich, Zurich, Switzerland E. Aguil´ o, C. Amsler, V. Chiochia, S. De Visscher, C. Favaro, M. Ivova Rikova, B. Millan Mejias, P. Otiougova, C. Regenfus, P. Robmann, A. Schmidt, H. Snoek National Central University, Chung-Li, Taiwan Y.H. Chang, K.H. Chen, C.M. Kuo, S.W. Li, W. Lin, Z.K. Liu, Y.J. Lu, D. Mekterovic, R. Volpe, J.H. Wu, S.S. Yu National Taiwan University (NTU), Taipei, Taiwan P. Bartalini, P. Chang, Y.H. Chang, Y.W. Chang, Y. Chao, K.F. Chen, W.-S. Hou, Y. Hsiung, K.Y. Kao, Y.J. Lei, R.-S. Lu, J.G. Shiu, Y.M. Tzeng, M. Wang 21 Cukurova University, Adana, Turkey A. Adiguzel, M.N. Bakirci34, S. Cerci35, C. Dozen, I. Dumanoglu, E. Eskut, S. Girgis, G. Gokbulut, Y. Guler, E. Gurpinar, I. Hos, E.E. Kangal, T. Karaman, A. Kayis Topaksu, A. Nart, G. Onengut, K. Ozdemir, S. Ozturk, A. Polatoz, K. Sogut36, D. Sunar Cerci35, B. Tali, H. Topakli34, D. Uzun, L.N. Vergili, M. Vergili, C. Zorbilmez Middle East Technical University, Physics Department, Ankara, Turkey I.V. Akin, T. Aliev, S. Bilmis, M. Deniz, H. Gamsizkan, A.M. Guler, K. Ocalan, A. Ozpineci, M. Serin, R. Sever, U.E. Surat, E. Yildirim, M. Zeyrek Bogazici University, Istanbul, Turkey M. Deliomeroglu, D. Demir37, E. G¨ ulmez, B. Isildak, M. Kaya38, O. Kaya38, S. Ozkorucuklu39, N. Sonmez40 National Scientific Center, Kharkov Institute of Physics and Technology, Kharkov, Ukraine L. Levchuk University of Bristol, Bristol, United Kingdom F. Bostock, J.J. Brooke, T.L. Cheng, E. Clement, D. Cussans, R. Frazier, J. Goldstein, M. Grimes, M. Hansen, D. Hartley, G.P. Heath, H.F. Heath, J. Jackson, L. Kreczko, S. Metson, D.M. Newbold41, K. Nirunpong, A. Poll, S. Senkin, V.J. Smith, S. Ward Rutherford Appleton Laboratory, Didcot, United Kingdom L. Basso42, K.W. Bell, A. Belyaev42, C. Brew, R.M. Brown, B. Camanzi, D.J.A. Cockerill, J.A. Coughlan, K. Harder, S. Harper, B.W. Kennedy, E. Olaiya, D. Petyt, B.C. Radburn-Smith, C.H. Shepherd-Themistocleous, I.R. Tomalin, W.J. Womersley, S.D. Worm Imperial College, London, United Kingdom R. Bainbridge, G. Ball, J. Ballin, R. Beuselinck, O. Buchmuller, D. Colling, N. Cripps, M. Cutajar, G. Davies, M. Della Negra, W. Ferguson, J. Fulcher, D. Futyan, A. Gilbert, A. Guneratne Bryer, G. Hall, Z. Hatherell, J. Hays, G. Iles, M. 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Breedon, M. Calderon De La Barca Sanchez, S. Chauhan, M. Chertok, J. Conway, P.T. Cox, J. Dolen, R. Erbacher, E. Friis, W. Ko, A. Kopecky, R. Lander, H. Liu, S. Maruyama, T. Miceli, 22 A The CMS Collaboration M. Nikolic, D. Pellett, J. Robles, S. Salur, T. Schwarz, M. Searle, J. Smith, M. Squires, M. Tripathi, R. Vasquez Sierra, C. Veelken University of California, Los Angeles, Los Angeles, USA V. Andreev, K. Arisaka, D. Cline, R. Cousins, A. Deisher, J. Duris, S. Erhan, C. Farrell, J. Hauser, M. Ignatenko, C. Jarvis, C. Plager, G. Rakness, P. Schlein†, J. Tucker, V. Valuev University of California, Riverside, Riverside, USA J. Babb, A. Chandra, R. Clare, J. Ellison, J.W. Gary, F. Giordano, G. Hanson, G.Y. Jeng, S.C. Kao, F. Liu, H. Liu, O.R. Long, A. Luthra, H. Nguyen, B.C. Shen†, R. Stringer, J. Sturdy, S. Sumowidagdo, R. Wilken, S. Wimpenny University of California, San Diego, La Jolla, USA W. Andrews, J.G. Branson, G.B. Cerati, E. Dusinberre, D. Evans, F. Golf, A. Holzner, R. Kelley, M. Lebourgeois, J. Letts, B. Mangano, S. Padhi, C. Palmer, G. Petrucciani, H. Pi, M. Pieri, R. Ranieri, M. Sani, V. Sharma, S. Simon, Y. Tu, A. Vartak, S. Wasserbaech44, F. W¨ urthwein, A. Yagil, J. Yoo University of California, Santa Barbara, Santa Barbara, USA D. Barge, R. Bellan, C. Campagnari, M. D’Alfonso, T. Danielson, K. Flowers, P. Geffert, J. Incandela, C. Justus, P. Kalavase, S.A. Koay, D. Kovalskyi, V. Krutelyov, S. Lowette, N. Mccoll, V. Pavlunin, F. Rebassoo, J. Ribnik, J. Richman, R. Rossin, D. Stuart, W. To, J.R. Vlimant California Institute of Technology, Pasadena, USA A. Apresyan, A. Bornheim, J. Bunn, Y. Chen, M. Gataullin, Y. Ma, A. Mott, H.B. Newman, C. Rogan, K. Shin, V. Timciuc, P. Traczyk, J. Veverka, R. Wilkinson, Y. Yang, R.Y. Zhu Carnegie Mellon University, Pittsburgh, USA B. Akgun, R. Carroll, T. Ferguson, Y. Iiyama, D.W. Jang, S.Y. Jun, Y.F. Liu, M. Paulini, J. Russ, H. Vogel, I. Vorobiev University of Colorado at Boulder, Boulder, USA J.P. 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Zakaria Florida International University, Miami, USA C. Ceron, V. Gaultney, L. Kramer, L.M. Lebolo, S. Linn, P. Markowitz, G. Martinez, D. Mesa, J.L. Rodriguez Florida State University, Tallahassee, USA T. Adams, A. Askew, D. Bandurin, J. Bochenek, J. Chen, B. Diamond, S.V. Gleyzer, J. Haas, S. Hagopian, V. Hagopian, M. Jenkins, K.F. Johnson, H. Prosper, L. Quertenmont, S. Sekmen, V. Veeraraghavan Florida Institute of Technology, Melbourne, USA M.M. Baarmand, B. Dorney, S. Guragain, M. Hohlmann, H. Kalakhety, R. Ralich, I. Vodopiyanov University of Illinois at Chicago (UIC), Chicago, USA M.R. Adams, I.M. Anghel, L. Apanasevich, Y. Bai, V.E. Bazterra, R.R. Betts, J. Callner, R. Cavanaugh, C. Dragoiu, L. Gauthier, C.E. Gerber, D.J. Hofman, S. Khalatyan, G.J. Kunde46, F. Lacroix, M. Malek, C. O’Brien, C. Silvestre, A. Smoron, D. Strom, N. Varelas The University of Iowa, Iowa City, USA U. Akgun, E.A. Albayrak, B. Bilki, W. Clarida, F. Duru, C.K. Lae, E. McCliment, J.-P. Merlo, H. Mermerkaya47, A. Mestvirishvili, A. Moeller, J. Nachtman, C.R. Newsom, E. Norbeck, J. Olson, Y. Onel, F. Ozok, S. Sen, J. Wetzel, T. Yetkin, K. Yi Johns Hopkins University, Baltimore, USA B.A. Barnett, B. Blumenfeld, A. Bonato, C. Eskew, D. Fehling, G. Giurgiu, A.V. Gritsan, Z.J. Guo, G. Hu, P. Maksimovic, S. Rappoccio, M. Swartz, N.V. Tran, A. Whitbeck The University of Kansas, Lawrence, USA P. Baringer, A. Bean, G. Benelli, O. Grachov, R.P. Kenny Iii, M. Murray, D. Noonan, S. Sanders, J.S. Wood, V. Zhukova Kansas State University, Manhattan, USA A.f. Barfuss, T. Bolton, I. Chakaberia, A. Ivanov, S. Khalil, M. Makouski, Y. Maravin, S. Shrestha, I. Svintradze, Z. Wan Lawrence Livermore National Laboratory, Livermore, USA J. Gronberg, D. Lange, D. Wright University of Maryland, College Park, USA A. Baden, M. Boutemeur, S.C. Eno, D. Ferencek, J.A. Gomez, N.J. Hadley, R.G. Kellogg, M. Kirn, Y. Lu, A.C. Mignerey, K. Rossato, P. Rumerio, F. Santanastasio, A. Skuja, J. Temple, M.B. 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