Measurement of the WZ production cross section in pp collisions at sqrt(s) = 13 TeV

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Measurement of the WZ production cross section in pp

collisions at sqrt(s) = 13 TeV

V. Khachatryan, M. Besançon, F. Couderc, M. Dejardin, D. Denegri, B.

Fabbro, J.L. Faure, C. Favaro, F. Ferri, S. Ganjour, et al.

To cite this version:

Contents lists available atScienceDirect

Physics

Letters

B

www.elsevier.com/locate/physletb

Measurement

of

the

WZ

production

cross

section

in

pp

collisions

at

√

s

=

13 TeV

Receivedinrevisedform10December2016 Accepted7January2017

Availableonline11January2017 Editor:M.Doser

Keywords:

CMS Physics Electroweak

TheWZproductioncrosssectioninproton–protoncollisionsat√s₌13 TeV ismeasuredwiththeCMS experiment at the LHC using a data sample corresponding to an integrated luminosity of 2.3 fb−1_.

The measurement is performed in the leptonic decay modes WZ→ ν, where ,=e,μ. The measuredcrosssectionfortherange60<m<120 GeV isσ(pp→WZ)=39.9±3.2(stat)₋+32..91(syst)±

0.4(theo)±1.3(lumi)pb,consistentwiththestandardmodelprediction.

©2017TheAuthor(s).PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBYlicense (http://creativecommons.org/licenses/by/4.0/).FundedbySCOAP3_.

1. Introduction

Measurements of the cross sections for massive gauge boson pair production in proton–proton collisions provide an essential test of the electroweak sector of the standard model (SM). The electroweak interaction in the SM is determined by the non-Abelian SU(2)L×U(1)Y gauge group. The non-Abelian nature of

theelectroweakgaugegroupleadstogaugebosonself-interactions via triple gauge couplings (TGCs) and quartic gauge couplings (QGCs). The weak gauge boson pair productionincludes TGC in-teractionsaswellasQGCinteractionsvia vectorbosonscattering. Thus, the studyof diboson productioncan directly test both the weak interaction and the non-Abelian nature ofthe electroweak gaugegroup.Thenext-to-leadingorder(NLO)and next-to-next-to-leading order(NNLO) perturbative QCD correctionsfortheboson pairproductionhavesubstantialimpactonthepredictedcross sec-tionsduetotheadditionofthegluon-initiatedprocessesthatare enhanced atenergies available atthe CERN LHC.The increase in thecrosssection issignificant comparedto theexperimental un-certainties, allowing LHC boson paircross section measurements todirectlyvalidatehigher-orderperturbativeQCDcalculations.

The observation ofWZ productionin proton–antiproton colli-sions atthe Tevatroncolliderwas reported by theCDF [1,2] and D0 [3]experiments. The WZ productioncross section in proton– protoncollisions hasbeen measured at theLHC by the CMS

ex- _{E-mailaddress:cms-publication-committee-chair@cern.ch.}

periment at √s=8 TeV [4]and the ATLAS experimentat √s= 7,8, and 13 TeV[5–7].All measurements are ingood agreement withSMpredictions.

This paper reportsthe CMSmeasurement of the WZ produc-tion cross section in proton–proton collisions at √s=13 TeV. The measurement is performed using the leptonic decay modes WZ→ ν,where,=e, μ.

2. TheCMSdetector

The CMS detector is described in detail elsewhere [8]. The key components forthis analysisare summarized here. The cen-tral feature of the CMS apparatus is a superconducting solenoid of 6 m internal diameter, providing a magnetic field of 3.8 T. Within the superconducting solenoid volume are a silicon pixel andstriptracker,aleadtungstatecrystalelectromagnetic calorime-ter(ECAL), andabrass andscintillatorhadron calorimeter,which providethepseudorapiditycoverage|η|<1.479 inabarrelsection and 1.479<|η|<3.0 in two endcapsections.Forward calorime-ters extend the coverage to |η|<5.0. Muons are measured in gas-ionization detectors embedded in the steel flux-return yoke outsidethesolenoid.

The firstleveloftheCMStriggersystem,composed ofcustom hardware processors, is designed to select the most interesting events in less than 4 μs using information from the calorime-ters and muon detectors. The high-level-trigger processor farm decreases the eventratefrom almost 100 kHz to around 1 kHz, beforedatastorage.

http://dx.doi.org/10.1016/j.physletb.2017.01.011

3. DataandMonteCarlosamples

This measurement uses a sample of proton–proton collisions collectedin2015at√s=13 TeV.Theintegratedluminosityofthe sampleis2.3 fb−1.SeveralMonteCarlo(MC)eventgeneratorsare usedtosimulatethesignalandbackgroundprocesses.

The WZ signal is generated at NLO in perturbative QCD with powheg2.0[9–12]. TheZZproduction via qq annihilationis gen-erated at NLO using powheg2.0, while the gg→ZZ process is simulatedatleading-order with mcfm 7.0[13].TheZγ,t¯tV (t¯tW, t¯tZ), tZ, and triboson events VVV (WWZ, WZZ, ZZZ) are gener-ated at NLO with MadGraph5_aMC@NLO [14]. The ZZ samples are scaled to the cross section calculated at NNLO for qq→ZZ

[15] (scaling k factor 1.1) and at NLO for gg→ZZ [16] (scaling k factor 1.7). The pythia 8.175 [17] program is used for parton showering, hadronization, and underlying eventsimulation using theCUETP8M1tune[18].TheNNPDF3.0[19] setofparton distri-butionfunctions(PDFs)isused,unlessotherwisespecified.

Forallprocesses,thedetectorresponseissimulatedusinga de-taileddescriptionoftheCMSdetector,basedonthe Geant4 pack-age[20],andtheeventreconstructionisperformedwiththesame algorithmsusedfordata.Thesimulatedsamplesincludeadditional interactionsperbunchcrossing(pileup)takenfromminimum-bias eventsgeneratedwith pythia.Thesimulatedeventsare weighted sothatthepileupdistributionmatchesthemeasuredone,withan averageofabout11pileupinteractionsperbunchcrossing.

4. Eventreconstruction

Using the information from all CMS subdetectors, a particle-flow (PF) technique is employed to identify and reconstruct the individualparticlesemergingfromeachcollisionevent[21,22].The particlesareclassifiedintomutuallyexclusivecategories:charged hadrons,neutralhadrons,photons,muons,andelectrons.

Electronsare reconstructed within the geometricalacceptance

|ηe_{|<2.5. The reconstruction combines the information from}

clusters of energy deposits in the ECAL and the trajectory in the tracker [23]. Electron identification relies on the electro-magnetic shower shape and other observables based on tracker and calorimeter information. The selection criteria depend on the transverse momentum, pT, and |η|, and on a

categoriza-tionaccordingto observablesthat aresensitive tothe amountof bremsstrahlung emitted along the trajectory in the tracker. Two workingpointsaredefined:tight andverytight.

Muons are reconstructed within |ημ_{|<2.4 [24]. The} recon-structioncombinestheinformationfromboththetrackerandthe muonspectrometer. The muons areselected fromamong the re-constructed muon track candidates by applying minimal quality requirements on the trackcomponents in the muon system and byensuringthatmuonsareassociatedtosmallenergydepositsin thecalorimeters.Asingletight workingpointisdefined.

Theelectronsandmuonsarerequiredtooriginatefromthe pri-mary vertex, which is chosen to be the vertex withthe highest sumof p2_T ofitsconstituenttracks[25].Foreach leptontrackthe distance ofclosest approach to the primary vertex in the trans-verse plane, dxy, is required to be less than 0.01(0.07)cm for

electrons in the barrel (endcap) region and 0.01 cm for muons withpT lessthan20 GeVand0.02 cmformuonswithpT greater

than 20 GeV. The distancealong the beamline, dz, must be less

than0.4(0.6)cm for electrons inthebarrel(endcap)and0.1 cm for muons. For the verytight electron working point, electrons mustpassdxy≤0.01(0.04)cm anddz≤0.05(0.4)cm inthe

bar-rel(endcap)region.

Jetsare reconstructedusingPFobjects.Theanti-kT jet

cluster-ingalgorithm[26]with R=0.4 isused.The standardmethodfor

jetenergycorrections[27]isapplied.Theseincludecorrectionsto thepileupcontributionthatkeepthejetenergycorrectionandthe corresponding uncertaintyalmost independent of the number of pileup interactions. Toexclude electrons andmuonsfrom thejet sample, the jetsare requiredto be separatedfrom theidentified leptons by R>0.3.In order to reject jetscoming from pileup collisions(pileupjets),amultivariate-basedjetidentification algo-rithm[28]isapplied.Thisalgorithmtakesadvantageofdifferences intheshapeofenergydepositsinajetconebetweenhard-scatter and pileup jets. The jets are required to have pT>20 GeV and

|η|<5.0. To identify the top quark background contribution in its decay to b quarks, the CSVv2 b tagging algorithm [29] with thetight workingpoint isused[30].Theefficiencyforselectingb quarkjetsis≈49% withamisidentificationprobability of≈4% for cquarkjetsand≈0.1% forlightquarkjets.

The isolation ofindividual electronsormuonsis defined rela-tivetotheirtransversemomentump

T bysummingoverthe

trans-versemomentaofchargedhadronsandneutralparticleswithina conewithradius R=(η)2_{+ (φ)}2_{<0.4 aroundthelepton}

directionattheinteractionvertex:

I=   pcharged_T +max  0,pneutral_T +pγ_T −pPU_T  p_T. (1)

Here, pcharged_T is the scalar sum of the transverse momenta of charged hadrons originating from the primary vertex. The

pneutral_T and pγ_T are the scalar sums of the transverse mo-menta forneutral hadronsandphotons, respectively. The neutral contributiontotheisolationfrompileupevents, pPU_T ,isestimated differently for electrons and muons. For electrons, pPU

T ≡ρAeff,

where the average transverse momentum flow density ρ is cal-culated in each event using the “jet area” method [31], which defines ρ as the median of the ratio of the jet transverse mo-mentum tothe jetarea, pjet_T /Ajet,forall pileupjetsintheevent.

Theeffectivearea Aeff isthe geometricarea oftheisolation cone

times an η-dependent correction factor that accounts for the residual dependence of the isolation on the pileup. For muons, pPU

T ≡0.5

ip

PU,i

T ,where i runs over the chargedhadrons

origi-natingfrompileupverticesandthefactor0.5correctsfortheratio ofcharged toneutralparticle contributions inthe isolation cone. Electronsare consideredisolated if Ie_{<0.08(0.07) forthebarrel}

(endcap)region,whilemuonsareconsideredisolatedifIμ<0.15. Fortheverytight electron workingpoint, theelectronsmust pass Ie<0.04(0.06)forthebarrel(endcap)region.

The missing transverse momentum vector pmiss

T is definedas

the projection onto the plane perpendicular to thebeams ofthe negativevectorsumofthemomentaofallreconstructedPFobjects inanevent,correctedforthepileupcontribution.Itsmagnitudeis referredtoasEmiss

T .

Theoverallefficienciesofthereconstruction,identification,and isolation requirements for the prompt e or μ are measured in datain severalbinsof p_T and|η_{|using a“tag-and-probe”}

tech-nique [32] applied to an inclusive sample of Z events. The effi-ciency forselecting electrons inthe ECALbarrel (endcaps)varies from about 85% (77%) at pe_T≈10 GeV to about 95% (89%) for pe_T>20 GeV.Itisabout85%inthetransitionregionbetweenthe ECAL barrel and endcaps, 1.44<|η|<1.57, averaging over the whole pT range.Muonsare reconstructed andidentifiedwith

5. Eventselection

Collisioneventsare selectedby triggers that requirethe pres-enceofoneortwo electrons ormuons.The pT threshold forthe

singleleptonis23 (20) GeVfortheelectron(muon)trigger.Forthe dileptontriggers,withthesameordifferentflavors,theminimum pToftheleadingandsubleadingleptonsare17 (17)and12 (8) GeV

forelectrons(muons),respectively.Thetriggerefficiencyforevents withintheacceptanceofthisanalysisisgreaterthan99%.

A selected event is required to have three lepton candidates

.The pairhastwo leptonswithopposite charge andthe sameflavor,asexpectedforaZbosoncandidate.Oneofthe lep-tonsfromtheZbosoncandidateisrequiredtohave pT>20 GeV

andtheother pT>10 GeV.Ifmorethanonecombinationis

pos-sible, the one with invariant mass closest to the Z boson mass is selected. The lepton associated with the W boson must have pT>20 GeV. All leptons must pass the tight identification and

isolation requirements. To further reduce the contribution from Z+jets in eventswith an electron associated withthe W boson, thiselectronmustpasstherequirementsoftheverytight working point.

There mustbe no other isolated leptons with pT>10 GeV in

theevents.Toreducecontributionsfromt¯t events,thetwoleptons constitutingtheZ bosoncandidatearerequiredtohavean invari-antmasssatisfying76<m<106 GeV,andtheremustbenojets

withpT>20 GeV and|η|<2.4 thatpassabtaggingrequirement.

The WZ events are expected to have missing transverse energy consistentwiththepresenceofaneutrinointhefinalstate, there-foreEmiss

T >30 GeV isrequired.Theinvariantmassofanydilepton

pairmustbegreaterthan4 GeV.Thisrequirementprevents prob-lemswithcollinearemissionofsame-flavoropposite-signdilepton pairs in theoretical calculations. The selection is extended to all dileptonpairsatthedetectorleveltoreducebackgroundsfromlow massresonances witha negligibleeffecton signal efficiency.The trileptoninvariantmass,m3,isrequiredtobemorethan100 GeV

toexcludearegionwhereproductionofZbosonswithfinal-state radiationisexpectedtocontribute.

6. Backgroundestimation

The backgroundcontributionsin thisanalysisare dividedinto two categories: background processes with prompt isolated lep-tons,e.g., ZZ,Zγ,t¯tZ;andbackgroundprocessesfromnonprompt leptons from hadrons decaying to leptons inside jets or jets misidentified as isolated leptons, primarily Z+jets and t¯t. The background processes with prompt leptons are estimated from simulation.Theprocesseswithatleastonenonpromptleptonare estimatedfromdata.

The major background contributions with nonprompt leptons arise from the production of Z bosons in association with jets and from t¯t, whereas smaller contributions come from W bo-son production in association with jets and multijet processes. The nonprompt background contribution is evaluated using the “tight-to-loose”method.Themethodestimatestheprobabilitythat aloose candidateismisidentifiedasatight leptonandappliesthis probability to control regions with loose candidates to estimate theresultingcontribution tothesignal region.Theseloose candi-datesare selectedwithrelaxedleptonidentificationandisolation requirements.

Themisidentificationprobabilityismeasuredfromasample of dijeteventsenrichedinnonpromptleptons.Thesampleisselected withonejetpassingtherelaxedleptonidentificationrequirements matchedtoasingleleptontrigger,definedastheprobelepton.The probeleptonandthesecondjetmustbeseparatedbyR>1.The misidentificationratioforeach lepton flavoris definedinbinsof

lepton pT and ηastheratioofthe numberofprobeleptons that

passthefinalisolationandidentificationrequirementstothe num-ber ofprobeleptonsthat donotpassthe tight requirements.The contamination from W+jets is suppressed by requiring a trans-verse mass mT<20 GeV, where mT=

2Emiss_T p_T(1−cos(φ))

andφ istheazimuthalanglebetweenthevectors p_Tmiss andp_T. The contamination from Zboson events issuppressed by requir-ing the invariant mass of each pair of leptons composed of the probeleptonandofanyotherleptoncandidateintheeventtobe outsideofthewindow60–120 GeV.Contributionsfromlowmass resonancesdecayingintopairsofleptonsaresuppressedby requir-ing the dileptonmass to be greater than20 GeV. The transverse momentumspectrumoftheprobeleptonindijeteventsis differ-entfromthespectruminZandt¯t events.Wehaveverifiedindata that onecanmakethemsimilarwitharequirementonthe mini-mum transversemomentum ofthesecond jetof20(35) GeVfor thedijeteventswithoneprobemuon(electron).

A set of control regions with events containing three leptons isthenusedtoestimatethebackgroundfromnonpromptleptons. Zero, one, or two leptons are required to pass the signal region requirements, while the remaining leptons must pass the loose requirementsandfailthesignalregionrequirements.The misiden-tification ratio is applied to the loose leptons failing the tight identification requirements to estimate the corresponding contri-bution to the signal region. The total background is calculated as a sumof contributions fromdifferentregions. This method is validated in nonoverlapping data samples enriched in Drell–Yan and t¯t contributions. The Drell–Yan region is defined by invert-ingtheselectionrequirementinEmiss_T andthet¯t regionisdefined by requiring at least one b-tagged jet andrejecting events with 76<m<106 GeV whilekeepingallother requirementsforthe

signal region.The overallyield predictedwiththe“tight-to-loose” method agrees with that measured in the control region within 5%, witha maximumdeviationof30% ina singledecay channel. Theobserveddeviationsareusedassystematicuncertaintiesinthe predictedbackgroundyieldsinthesignalregion.

7. Systematicuncertainties

Systematic uncertainties are less than 1% for the trigger effi-ciencyand2–4%fortheleptonidentificationandisolation require-ments, depending on the lepton flavors. Other systematic uncer-tainties are related to the use of simulated samples: 1% for the effects of pileupand 1–2% forthe Emiss_T reconstruction, which is estimated by varying the energies ofthe PF objects within their uncertainties. The uncertainty in the b quark jet content in WZ events is 2% and accounts for differences in b-tagging efficien-cies between data and MC aswell as differencesin b quark jet content between Z+jetsand WZ+jetsevents.The uncertainty in theintegratedluminosityofthedatasampleis2.7%[33].This un-certainty affectsboth thesignalandthesimulatedportion ofthe backgroundestimationanddoesnotaffectthebackground estima-tion from data; the total effect of theluminosity uncertainty on thecrosssectionis3.2%.

Uncertaintiesinpromptbackgroundsourcesareestimatedfrom thetheoreticaluncertaintiesinthecrosssections.FortheZZ back-groundtheuncertaintyis4%[15,34],anditcontributestotheWZ cross section with an uncertainty of 0.4%. The uncertainties are 15%fort¯tV[14,35,36]and6%fortribosonandZγ [13];their con-tribution tothe uncertaintyintheWZ crosssection ismuchless than1%.

Table 1

Thecontributionsofeachsystematicuncertaintysourcetothecombined uncer-taintyinthecrosssectionmeasurement.Theintegratedluminosityaswellasthe PDFand scaleuncertaintiesarereported separatelyinEquations(2)and (3)as (lumi)and(theo),respectively,whiletheotheruncertaintiesarecombinedintoa singlesystematicuncertainty(syst).

Source of uncertainty Uncertainty in the cross section Background with nonpromptμ 5.4%

Background with nonprompt e 3.9% b tagging 2.1% Emiss T 2.0% Electron efficiency 1.9% Muon efficiency 1.5% Pileup 0.8% ZZ cross section 0.4% t¯tV cross section negligible Zγcross section negligible VVV cross section negligible Integrated luminosity 3.2% PDF and scales 1.0%

ofeventsinthecontrolregions.Thesystematicuncertaintyinthe misidentificationprobability is30%forboth electronsandmuons. It covers the largest difference observed between the estimated andmeasurednumbersofeventsindatacontrolsamplesenriched in t¯t and Drell–Yan contributions.The uncertainties are uncorre-latedbetweenelectronsandmuons.Thecontributiontothe uncer-taintyinthecrosssectionmeasurementis5.4% (3.9%)frommuons (electrons).

Theoretical uncertainties in the WZ→ ν acceptance are evaluatedusing powheg and mcfm byvaryingdynamic renormal-izationandfactorizationscales independently up anddown by a factoroftwo withrespect to thedefaultvalues μR=μF =mWZ

withtheconditionthat0.5≤μR/μF≤2,wheremWZisthemass

oftheWZsystematthegeneratorlevel.Theuncertaintyinthe ac-ceptanceduetothescalevariationscanbeneglected. Phenomeno-logicaluncertainties(PDF+αs) areestimatedusingtheCT14[37],

NNPDF3.0,andMMHT2014 [38] PDFsets accordingto their indi-vidualprescriptions. The largestvariation amongthesets defines anenvelopeofabout1%, whichistakenasthetheoretical uncer-taintyinthemeasuredcrosssection.

Asummaryofeachsystematicuncertaintyanditscontribution tothe final uncertaintyinthe crosssection measurement is pre-sentedinTable 1.

8. Results

Theobservedandexpectedeventyieldsforall decaychannels aresummarizedinTable 2.Theinvariantmassdistributionsforall channelscombinedare showninFig. 1 andcompared tothe SM

expectationsandtothebackgroundsestimatedfromdata.Thetwo upperplotsshowdistributionsforeventsafteralltheselection re-quirements are applied except the one displayed. The two lower plotsshow distributions withthefull WZselection requirements. KinematicdistributionsoftheselectedeventsareshowninFig. 2. Overall,thesimulatedsignal combinedwiththebackground con-tributionsareinagreementwiththedatawithinuncertainties.

The measured yields, corrected forthe efficiencyofthe event selectionsandtheacceptanceofthefiducialphasespace,areused toevaluatetheWZproductioncrosssection.

ThefiducialWZ→ νphasespaceisdefinedbythe require-mentoftwoleptons fromtheZbosondecaytohave pT>20 and

10 GeV, the charged lepton from W boson decay to have pT>

20 GeV, all leptons to bewithin |η|<2.5, 60<m<120 GeV,

and invariant mass of any same-flavor opposite-sign lepton pair is above 4 GeV. All the leptons are considered before final-state radiation(FSR). The difference betweenthecross section calcula-tionwithleptonsbeforeFSRandthecrosssectionwith“dressed” leptons, which are obtained by summing the lepton momentum andthemomentaofradiatedphotonswithin aconeofR<0.1 aroundthelepton,isfoundtobelessthan 1%.

Thecorrectionbetweenthefiducialdefinitionandtheselection requirements takes into account the effect of the Emiss_T require-ment,thereducedm masswindowintheselectionwithrespect

to the fiducial definition, and the requirements of exactly three isolatedleptonsandnob-taggedjetsintheevent.Asmall contri-butionfromWZeventswheretheWorZbosondecaysvia τ into an electronormuon isconsideredassignal atthedetectorlevel, butnotatthegeneratorlevel.Thusthecorrectionfor τ lepton de-caysisalsotakenintoaccountintheselectionefficiency.

Theefficiencyoftheselectionrequirementswithrespecttothe fiducialrequirementsvarieswiththechannel,from55%in μμμto 25%ineee.Itincludesa70%correctionfortheEmiss_T requirement at the reconstruction level, a 7% correction for the contribution from tau decays and the effects of the lepton identification re-quirements.ThedifferenceintheZbosonmasswindowdefinition attheselectionlevelandinthefiducialdefinitionhasa2%effect. Thetheoreticaluncertaintiesinthesecorrectionsareestimatedby checkingdifferencesbetweenthevarious powheg, MadGraph,and mcfm_{predictionsandarefoundtobe muchlessthan 1%sothey} areneglectedinthefiducialcrosssectionmeasurement.Themajor difference between the channels is the tighter identification and isolationrequirementsontheelectrons.

To includeall final statesin the crosssection calculation, the numberofexpectedsignalandbackgroundeventsisfittedtothe numberof observedevents simultaneouslyin all decaychannels. The likelihood is written as a combination of individual channel likelihoods forthe signal andbackground hypotheses.The statis-ticalandsystematicuncertaintiesareincludedasscalingnuisance parametersandthecorrelationbetweendifferentsourcesof uncer-taintiesacrosschannelsistakenintoaccount.

Table 2

TheexpectedyieldsofWZeventsandtheestimatedyieldsofbackgroundevents,consistingofthepromptleptonsestimatedfromsimulationandnonpromptbackground fromdata,comparedtothenumberofobservedeventsforeachdecaychannel.Thefirstuncertaintyisstatisticalandthesecondissystematic.

Fig. 1. (upperleft)Distributionofthereconstructedpairmasssummedforalldecaychannelswiththemselectionextendedto60–120 GeV.(upperright)Distribution

ofthereconstructedmasssummedforalldecaychannelswiththem3>100 GeV selectionrequirementremoved.(lowerleft)Thetransversemassoftheleptonfrom

theWbosonandthe Emiss

T system.(lowerright)Thetransversemassofthethreeleptonsandthe EmissT system.SolidsymbolsrepresentthedatawithPoissonstatistical

uncertainties,whilehistogramsrepresenttheexpectedWZsignalandbackgrounds.Theshadedbandrepresentstheuncertaintiesinthesignalandbackgroundestimated yieldsandincludessystematic,theoretical,andintegratedluminosityuncertaintiesinadditiontothestatisticaluncertainty.Thebackgroundshapesaretakenfromsimulation ordata,asdescribedinthetext.Aratiooftheobserved(Obs)andexpected(Exp)distributionsisalsoincluded.

The fiducial WZ→ ν cross section for p_T>20,10 GeV, p

T>20 GeV, all leptons within |η|<2.5, 60<m <120 GeV,

and invariant mass of any same-flavor opposite-sign lepton pair above4 GeVis

σfid(pp→WZ→ ν)=258±21 (stat)

+19

−20(syst)±8(lumi) fb, (2)

corresponding to a total crosssection for the range60<m<

120 GeV of

σ(pp→WZ)=39.9±3.2(stat)

+2.9

−3.1(syst)±0.4(theo)±1.3(lumi) pb. (3)

Theacceptanceofthefiducialphasespace,(45.0±0.4)%,is cal-culatedwith powheg.ThenominalZtodileptonbranchingfraction

B(Z→ )is(3.3658±0.0023)% foreachleptonflavor,whilefor theWbosontheaveragebranching fractiontoeach leptonflavor,

(10.67±0.16)%, isderived from(10.71±0.16)% fortheelectron channeland(10.63±0.15)% forthemuonchannel[39].

Themeasuredcrosssectionscanbecomparedtothetheoretical values of274+₋11₈ (scale)±4(PDF) fb for thefiducial crosssection and 42.3+₋1_1..₁4(scale)±0.6(PDF) pb for the total crosssection cal-culated with mcfm at NLO with NNPDF3.0 PDFs, with dynamic renormalization and factorization scales set to μR =μF =mWZ.

Theuncertaintyisobtainedbyvaryingthefactorizationand renor-malization scales independentlyup anddown by a factoroftwo withtheconditionthat 0.5≤μR/μF≤2.The mcfm and powheg

predicted cross sectionsagree within the statisticaluncertainties ofthegeneratedsamples.

The measuredtotal crosssection canalsobe comparedto the theoretical value of50.0+₋1_1..1₀(scale) pb, availableatNNLO via ma-trix [40] with fixed QCD scales set to μ_R =μ_F = 1

2(mZ+mW)

and NNPDF3.0 PDFs. Uncertainties in this calculation take into account only renormalization and factorization scale variations. The variations are done independently with the condition that 0.5≤μR/μF ≤2. The values from mcfm with this scale choice

Fig. 2. (upperleft)Distributionofthenumberofjetswith pT>30 GeV intheevent.(upperright)Transversemomentumoftheleptonassociatedwith theWboson.

(lowerleft)TransversemomentumofselectedZbosoncandidates.(lowerright)TransversemomentumofselectedWbosoncandidates.Solidsymbolsrepresentthedata withPoissonstatisticaluncertainties,whilehistogramsrepresenttheexpectedWZsignalandbackgrounds.Theshadedbandrepresentstheuncertaintiesinthesignaland backgroundestimatedyieldsandincludessystematic,theoretical,andintegratedluminosityuncertaintiesinadditiontothestatisticaluncertainty.Thebackgroundshapes aretakenfromsimulationordata,asdescribedinthetext.Aratiooftheobserved(Obs)andexpected(Exp)distributionsisalsoincluded.

9. Summary

The WZ production cross section in proton–proton collisions at √s=13 TeV has been measured with the CMS experiment at the LHC using a data sample corresponding to an integrated luminosity of 2.3 fb−1_{. The measurement is performed in the}

leptonic decaymodesWZ→ ν,where ,=e, μ.The mea-sured fiducial WZ→ ν cross section for two leptons from the Z boson decay with pT>20 and 10 GeV, the charged

lep-ton from the W boson decay with pT >20 GeV, all leptons

within |η|<2.5, and 60<m <120 GeV is σfid(pp→WZ→

ν)=258±21(stat)+₋19₂₀(syst)±8(lumi) fb.The corresponding total cross section is σ(pp→WZ)=39.9±3.2(stat)+₋2₃._.9₁(syst)± 0.4(theo)±1.3(lumi) pb forthedileptonmassrange60<m<

120 GeV. For both cross sections, the invariant mass of any same-flavor opposite-sign lepton pair is required to be above 4 GeV. This measurement is compared with the theoretical val-uesof274+₋11₈ (scale)±4(PDF) fb forthefiducialcrosssectionand 42.3+₋1₁._.4₁(scale)±0.6(PDF) pb forthetotalcrosssectioncalculated with mcfm atNLOwithNNPDF3.0PDFs,withdynamic renormal-izationandfactorization scales setto μR=μF =mWZ,and with

theNNLOpredictionfrom matrix.

Acknowledgements

CIN-VESTAV,CONACYT, LNS,SEP, andUASLP-FAI(Mexico); MBIE(New Zealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT (Portu-gal);JINR(Dubna);MON,RosAtom,RASandRFBR(Russia);MESTD (Serbia);SEIDIandCPAN(Spain);SwissFundingAgencies (Switzer-land); MST (Taipei); ThEPCenter, IPST, STAR and NSTDA (Thai-land);TUBITAKandTAEK(Turkey);NASUandSFFR(Ukraine);STFC (UnitedKingdom);DOEandNSF(USA).

Individuals have received support from the Marie-Curie pro-gramme and the European Research Council and EPLANET (Eu-ropean Union); the Leventis Foundation; the A.P. Sloan Foun-dation; the Alexander von Humboldt Foundation; the Belgian Federal Science Policy Office; the Fonds pour la Formation à la Recherche dans l’Industrie et dans l’Agriculture (FRIA-Belgium); the Agentschap voor Innovatie door Wetenschap en Technolo-gie (IWT-Belgium); the Ministry of Education, Youth and Sports (MEYS) of the Czech Republic; the Council of Science and In-dustrial Research, India; the HOMING PLUS programme of the Foundation for Polish Science, cofinanced from European Union, Regional Development Fund, the Mobility Plus programme of the Ministry of Science and Higher Education, the National Sci-ence Center (Poland), contracts Harmonia 2014/14/M/ST2/00428, Opus 2013/11/B/ST2/04202, 2014/13/B/ST2/02543 and 2014/15/B/ST2/03998,Sonata-bis2012/07/E/ST2/01406; the Thalis and Aristeia programmes cofinanced by EU-ESF and the Greek NSRF;theNationalPriorities ResearchProgramby Qatar National ResearchFund;theProgramaClarín-COFUNDdelPrincipadode As-turias;theRachadapisekSompotFundforPostdoctoralFellowship, Chulalongkorn University and the Chulalongkorn Academic into Its 2nd Century Project Advancement Project (Thailand); andthe WelchFoundation,contractC-1845.

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TheCMSCollaboration

V. Khachatryan,A.M. Sirunyan, A. Tumasyan YerevanPhysicsInstitute,Yerevan,Armenia

W. Adam, E. Asilar,T. Bergauer, J. Brandstetter, E. Brondolin, M. Dragicevic, J. Erö,M. Flechl, M. Friedl, R. Frühwirth1, V.M. Ghete, C. Hartl, N. Hörmann, J. Hrubec,M. Jeitler1,A. König, I. Krätschmer, D. Liko, T. Matsushita,I. Mikulec, D. Rabady, N. Rad, B. Rahbaran,H. Rohringer, J. Schieck1,J. Strauss,

W. Treberer-Treberspurg,W. Waltenberger, C.-E. Wulz1 InstitutfürHochenergiephysikderOeAW,Wien,Austria

V. Mossolov,N. Shumeiko,J. Suarez Gonzalez NationalCentreforParticleandHighEnergyPhysics,Minsk,Belarus

S. Alderweireldt, E.A. De Wolf,X. Janssen,J. Lauwers, M. Van De Klundert, H. Van Haevermaet, P. Van Mechelen,N. Van Remortel, A. Van Spilbeeck

UniversiteitAntwerpen,Antwerpen,Belgium

S. Abu Zeid,F. Blekman, J. D’Hondt, N. Daci,I. De Bruyn, K. Deroover, N. Heracleous,S. Lowette, S. Moortgat, L. Moreels,A. Olbrechts,Q. Python, S. Tavernier, W. Van Doninck, P. Van Mulders, I. Van Parijs

VrijeUniversiteitBrussel,Brussel,Belgium

H. Brun, C. Caillol, B. Clerbaux, G. De Lentdecker, H. Delannoy, G. Fasanella,L. Favart, R. Goldouzian, A. Grebenyuk,G. Karapostoli,T. Lenzi, A. Léonard,J. Luetic, T. Maerschalk,A. Marinov, A. Randle-conde, T. Seva,C. Vander Velde, P. Vanlaer,R. Yonamine, F. Zenoni, F. Zhang2

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A. Cimmino,T. Cornelis, D. Dobur, A. Fagot, G. Garcia, M. Gul, D. Poyraz,S. Salva, R. Schöfbeck, M. Tytgat, W. Van Driessche, E. Yazgan,N. Zaganidis

GhentUniversity,Ghent,Belgium

H. Bakhshiansohi,C. Beluffi3,O. Bondu, S. Brochet,G. Bruno, A. Caudron, S. De Visscher, C. Delaere, M. Delcourt,L. Forthomme, B. Francois,A. Giammanco, A. Jafari,P. Jez, M. Komm, V. Lemaitre, A. Magitteri,A. Mertens, M. Musich, C. Nuttens, K. Piotrzkowski,L. Quertenmont, M. Selvaggi, M. Vidal Marono, S. Wertz

UniversitéCatholiquedeLouvain,Louvain-la-Neuve,Belgium N. Beliy

UniversitédeMons,Mons,Belgium

W.L. Aldá Júnior, F.L. Alves,G.A. Alves,L. Brito, C. Hensel,A. Moraes, M.E. Pol,P. Rebello Teles CentroBrasileirodePesquisasFisicas,RiodeJaneiro,Brazil

D. Matos Figueiredo, C. Mora Herrera,L. Mundim, H. Nogima,W.L. Prado Da Silva, A. Santoro, A. Sznajder,E.J. Tonelli Manganote4, A. Vilela Pereira

UniversidadedoEstadodoRiodeJaneiro,RiodeJaneiro,Brazil

S. Ahujaa, C.A. Bernardesb, S. Dograa,T.R. Fernandez Perez Tomeia, E.M. Gregoresb, P.G. Mercadanteb, C.S. Moona, S.F. Novaesa, Sandra S. Padulaa, D. Romero Abadb,J.C. Ruiz Vargas

a_{UniversidadeEstadualPaulista,SãoPaulo,Brazil} b_{UniversidadeFederaldoABC,SãoPaulo,Brazil}

A. Aleksandrov, R. Hadjiiska, P. Iaydjiev,M. Rodozov, S. Stoykova, G. Sultanov, M. Vutova InstituteforNuclearResearchandNuclearEnergy,Sofia,Bulgaria

A. Dimitrov, I. Glushkov,L. Litov, B. Pavlov,P. Petkov UniversityofSofia,Sofia,Bulgaria

W. Fang5

BeihangUniversity,Beijing,China

M. Ahmad, J.G. Bian, G.M. Chen, H.S. Chen,M. Chen, Y. Chen6,T. Cheng, C.H. Jiang, D. Leggat, Z. Liu, F. Romeo,S.M. Shaheen, A. Spiezia, J. Tao, C. Wang,Z. Wang, H. Zhang, J. Zhao

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Y. Ban, G. Chen, Q. Li, S. Liu,Y. Mao, S.J. Qian, D. Wang,Z. Xu StateKeyLaboratoryofNuclearPhysicsandTechnology,PekingUniversity,Beijing,China

C. Avila,A. Cabrera, L.F. Chaparro Sierra, C. Florez, J.P. Gomez, C.F. González Hernández,J.D. Ruiz Alvarez, J.C. Sanabria

UniversidaddeLosAndes,Bogota,Colombia

N. Godinovic, D. Lelas, I. Puljak,P.M. Ribeiro Cipriano

UniversityofSplit,FacultyofElectricalEngineering,MechanicalEngineeringandNavalArchitecture,Split,Croatia Z. Antunovic, M. Kovac

UniversityofSplit,FacultyofScience,Split,Croatia

V. Brigljevic,D. Ferencek, K. Kadija,S. Micanovic, L. Sudic, T. Susa InstituteRudjerBoskovic,Zagreb,Croatia

A. Attikis, G. Mavromanolakis, J. Mousa,C. Nicolaou, F. Ptochos, P.A. Razis,H. Rykaczewski UniversityofCyprus,Nicosia,Cyprus

M. Finger7, M. Finger Jr.7 CharlesUniversity,Prague,Czechia E. Carrera Jarrin

UniversidadSanFranciscodeQuito,Quito,Ecuador

A.A. Abdelalim8,9, Y. Mohammed10, E. Salama11,12

B. Calpas,M. Kadastik, M. Murumaa, L. Perrini, M. Raidal, A. Tiko, C. Veelken NationalInstituteofChemicalPhysicsandBiophysics,Tallinn,Estonia

P. Eerola,J. Pekkanen, M. Voutilainen DepartmentofPhysics,UniversityofHelsinki,Helsinki,Finland

J. Härkönen,V. Karimäki, R. Kinnunen, T. Lampén, K. Lassila-Perini,S. Lehti, T. Lindén,P. Luukka, T. Peltola,J. Tuominiemi,E. Tuovinen, L. Wendland

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LappeenrantaUniversityofTechnology,Lappeenranta,Finland

M. Besancon,F. Couderc, M. Dejardin, D. Denegri,B. Fabbro, J.L. Faure, C. Favaro, F. Ferri, S. Ganjour, S. Ghosh,A. Givernaud, P. Gras, G. Hamel de Monchenault, P. Jarry, I. Kucher, E. Locci,M. Machet, J. Malcles,J. Rander, A. Rosowsky, M. Titov, A. Zghiche

IRFU,CEA,UniversitéParis-Saclay,Gif-sur-Yvette,France

A. Abdulsalam,I. Antropov, S. Baffioni, F. Beaudette, P. Busson, L. Cadamuro, E. Chapon,C. Charlot, O. Davignon,R. Granier de Cassagnac, M. Jo, S. Lisniak,P. Miné, M. Nguyen, C. Ochando, G. Ortona, P. Paganini,P. Pigard, S. Regnard, R. Salerno,Y. Sirois, T. Strebler, Y. Yilmaz, A. Zabi

LaboratoireLeprince-Ringuet,EcolePolytechnique,IN2P3-CNRS,Palaiseau,France

J.-L. Agram13,J. Andrea, A. Aubin,D. Bloch, J.-M. Brom,M. Buttignol, E.C. Chabert,N. Chanon, C. Collard, E. Conte13,X. Coubez, J.-C. Fontaine13, D. Gelé, U. Goerlach,A.-C. Le Bihan, J.A. Merlin14, K. Skovpen, P. Van Hove

InstitutPluridisciplinaireHubertCurien,UniversitédeStrasbourg,UniversitédeHauteAlsaceMulhouse,CNRS/IN2P3,Strasbourg,France S. Gadrat

CentredeCalculdel’InstitutNationaldePhysiqueNucleaireetdePhysiquedesParticules,CNRS/IN2P3,Villeurbanne,France

S. Beauceron,C. Bernet, G. Boudoul,E. Bouvier, C.A. Carrillo Montoya, R. Chierici,D. Contardo, B. Courbon,P. Depasse, H. El Mamouni,J. Fan, J. Fay, S. Gascon,M. Gouzevitch, G. Grenier, B. Ille, F. Lagarde,I.B. Laktineh, M. Lethuillier,L. Mirabito, A.L. Pequegnot, S. Perries,A. Popov15,D. Sabes, V. Sordini,M. Vander Donckt, P. Verdier, S. Viret

UniversitédeLyon,UniversitéClaudeBernardLyon1,CNRS-IN2P3,InstitutdePhysiqueNucléairedeLyon,Villeurbanne,France T. Toriashvili16

GeorgianTechnicalUniversity,Tbilisi,Georgia Z. Tsamalaidze7

TbilisiStateUniversity,Tbilisi,Georgia

C. Autermann,S. Beranek, L. Feld, A. Heister, M.K. Kiesel, K. Klein, M. Lipinski, A. Ostapchuk, M. Preuten, F. Raupach, S. Schael, C. Schomakers,J.F. Schulte,J. Schulz, T. Verlage,H. Weber, V. Zhukov15

RWTHAachenUniversity,I.PhysikalischesInstitut,Aachen,Germany

P. Millet,S. Mukherjee, M. Olschewski, K. Padeken,T. Pook,M. Radziej, H. Reithler, M. Rieger,F. Scheuch, L. Sonnenschein, D. Teyssier,S. Thüer

RWTHAachenUniversity,III.PhysikalischesInstitutA,Aachen,Germany

V. Cherepanov, G. Flügge, W. Haj Ahmad, F. Hoehle, B. Kargoll, T. Kress, A. Künsken,J. Lingemann, A. Nehrkorn, A. Nowack,I.M. Nugent, C. Pistone, O. Pooth,A. Stahl14

RWTHAachenUniversity,III.PhysikalischesInstitutB,Aachen,Germany

M. Aldaya Martin,C. Asawatangtrakuldee, K. Beernaert, O. Behnke,U. Behrens, A.A. Bin Anuar, K. Borras17,A. Campbell, P. Connor, C. Contreras-Campana, F. Costanza, C. Diez Pardos,G. Dolinska, G. Eckerlin, D. Eckstein, E. Eren, E. Gallo18, J. Garay Garcia, A. Geiser, A. Gizhko, J.M. Grados Luyando, P. Gunnellini, A. Harb, J. Hauk, M. Hempel19,H. Jung,A. Kalogeropoulos,O. Karacheban19,M. Kasemann, J. Keaveney, J. Kieseler, C. Kleinwort,I. Korol, D. Krücker, W. Lange,A. Lelek, J. Leonard, K. Lipka,

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T. Schoerner-Sadenius,C. Seitz, S. Spannagel, N. Stefaniuk, K.D. Trippkewitz,G.P. Van Onsem, R. Walsh, C. Wissing

DeutschesElektronen-Synchrotron,Hamburg,Germany

V. Blobel, M. Centis Vignali, A.R. Draeger,T. Dreyer, E. Garutti, K. Goebel, D. Gonzalez, J. Haller,

M. Hoffmann, A. Junkes,R. Klanner,R. Kogler, N. Kovalchuk,T. Lapsien,T. Lenz,I. Marchesini, D. Marconi, M. Meyer, M. Niedziela,D. Nowatschin, J. Ott, F. Pantaleo14,T. Peiffer, A. Perieanu, J. Poehlsen, C. Sander, C. Scharf, P. Schleper, A. Schmidt, S. Schumann,J. Schwandt,H. Stadie, G. Steinbrück, F.M. Stober,

M. Stöver, H. Tholen, D. Troendle,E. Usai, L. Vanelderen,A. Vanhoefer, B. Vormwald UniversityofHamburg,Hamburg,Germany

C. Barth,C. Baus, J. Berger,E. Butz, T. Chwalek, F. Colombo, W. De Boer, A. Dierlamm,S. Fink, R. Friese, M. Giffels,A. Gilbert, P. Goldenzweig,D. Haitz, F. Hartmann14,S.M. Heindl, U. Husemann,I. Katkov15, P. Lobelle Pardo, B. Maier, H. Mildner, M.U. Mozer, T. Müller,Th. Müller, M. Plagge, G. Quast,

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G. Anagnostou, G. Daskalakis,T. Geralis,V.A. Giakoumopoulou, A. Kyriakis, D. Loukas, I. Topsis-Giotis InstituteofNuclearandParticlePhysics(INPP),NCSRDemokritos,AghiaParaskevi,Greece

A. Agapitos, S. Kesisoglou, A. Panagiotou, N. Saoulidou, E. Tziaferi NationalandKapodistrianUniversityofAthens,Athens,Greece

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N. Filipovic

MTA-ELTELendületCMSParticleandNuclearPhysicsGroup,EötvösLorándUniversity,Budapest,Hungary

G. Bencze,C. Hajdu, P. Hidas, D. Horvath20, F. Sikler,V. Veszpremi, G. Vesztergombi21,A.J. Zsigmond WignerResearchCentreforPhysics,Budapest,Hungary

M. Bartók21,P. Raics, Z.L. Trocsanyi, B. Ujvari UniversityofDebrecen,Debrecen,Hungary

S. Bahinipati, S. Choudhury23,P. Mal, K. Mandal, A. Nayak24,D.K. Sahoo, N. Sahoo,S.K. Swain NationalInstituteofScienceEducationandResearch,Bhubaneswar,India

S. Bansal,S.B. Beri, V. Bhatnagar, R. Chawla, U. Bhawandeep, A.K. Kalsi,A. Kaur, M. Kaur, R. Kumar, A. Mehta,M. Mittal, J.B. Singh, G. Walia

PanjabUniversity,Chandigarh,India

Ashok Kumar,A. Bhardwaj, B.C. Choudhary, R.B. Garg,S. Keshri, S. Malhotra,M. Naimuddin, N. Nishu, K. Ranjan,R. Sharma, V. Sharma

UniversityofDelhi,Delhi,India

R. Bhattacharya,S. Bhattacharya, K. Chatterjee, S. Dey,S. Dutt, S. Dutta, S. Ghosh, N. Majumdar, A. Modak, K. Mondal,S. Mukhopadhyay, S. Nandan,A. Purohit, A. Roy, D. Roy, S. Roy Chowdhury, S. Sarkar,M. Sharan, S. Thakur

SahaInstituteofNuclearPhysics,Kolkata,India P.K. Behera

IndianInstituteofTechnologyMadras,Madras,India

R. Chudasama,D. Dutta, V. Jha, V. Kumar, A.K. Mohanty14, P.K. Netrakanti,L.M. Pant, P. Shukla,A. Topkar BhabhaAtomicResearchCentre,Mumbai,India

T. Aziz,S. Dugad, G. Kole, B. Mahakud, S. Mitra, G.B. Mohanty, B. Parida,N. Sur, B. Sutar TataInstituteofFundamentalResearch-A,Mumbai,India

S. Banerjee, S. Bhowmik25,R.K. Dewanjee, S. Ganguly,M. Guchait, Sa. Jain, S. Kumar, M. Maity25, G. Majumder,K. Mazumdar, T. Sarkar25, N. Wickramage26

TataInstituteofFundamentalResearch-B,Mumbai,India

S. Chauhan,S. Dube, V. Hegde, A. Kapoor, K. Kothekar, A. Rane, S. Sharma IndianInstituteofScienceEducationandResearch(IISER),Pune,India

H. Behnamian,S. Chenarani27, E. Eskandari Tadavani,S.M. Etesami27,A. Fahim28,M. Khakzad,

M. Mohammadi Najafabadi,M. Naseri, S. Paktinat Mehdiabadi, F. Rezaei Hosseinabadi, B. Safarzadeh29, M. Zeinali

InstituteforResearchinFundamentalSciences(IPM),Tehran,Iran M. Felcini,M. Grunewald

UniversityCollegeDublin,Dublin,Ireland

M. Abbresciaa,b, C. Calabriaa,b, C. Caputoa,b, A. Colaleoa,D. Creanzaa,c, L. Cristellaa,b,N. De Filippisa,c, M. De Palmaa,b, L. Fiorea, G. Iasellia,c, G. Maggia,c, M. Maggia,G. Minielloa,b,S. Mya,b,S. Nuzzoa,b, A. Pompilia,b, G. Pugliesea,c,R. Radognaa,b,A. Ranieria, G. Selvaggia,b, L. Silvestrisa,14,R. Vendittia,b, P. Verwilligena

G. Abbiendia,C. Battilana, D. Bonacorsia,b, S. Braibant-Giacomellia,b, L. Brigliadoria,b, R. Campaninia,b, P. Capiluppia,b,A. Castroa,b,F.R. Cavalloa,S.S. Chhibraa,b, G. Codispotia,b, M. Cuffiania,b,

G.M. Dallavallea,F. Fabbria, A. Fanfania,b, D. Fasanellaa,b,P. Giacomellia,C. Grandia,L. Guiduccia,b, S. Marcellinia, G. Masettia, A. Montanaria, F.L. Navarriaa,b,A. Perrottaa, A.M. Rossia,b,T. Rovellia,b, G.P. Sirolia,b,N. Tosia,b,14

a_{INFNSezionediBologna,Bologna,Italy} b_{UniversitàdiBologna,Bologna,Italy}

S. Albergoa,b,M. Chiorbolia,b,S. Costaa,b,A. Di Mattiaa,F. Giordanoa,b,R. Potenzaa,b,A. Tricomia,b, C. Tuvea,b

a_{INFNSezionediCatania,Catania,Italy} b_{UniversitàdiCatania,Catania,Italy}

G. Barbaglia, V. Ciullia,b,C. Civininia, R. D’Alessandroa,b,E. Focardia,b,V. Goria,b, P. Lenzia,b, M. Meschinia, S. Paolettia,G. Sguazzonia,L. Viliania,b,14

a_{INFNSezionediFirenze,Firenze,Italy} b_{UniversitàdiFirenze,Firenze,Italy}

L. Benussi, S. Bianco, F. Fabbri,D. Piccolo, F. Primavera14 INFNLaboratoriNazionalidiFrascati,Frascati,Italy

V. Calvellia,b, F. Ferroa, M. Lo Veterea,b, M.R. Mongea,b,E. Robuttia,S. Tosia,b a_{INFNSezionediGenova,Genova,Italy}

b_{UniversitàdiGenova,Genova,Italy}

L. Brianza,M.E. Dinardoa,b, S. Fiorendia,b,S. Gennaia,A. Ghezzia,b, P. Govonia,b,S. Malvezzia,

R.A. Manzonia,b,14, B. Marzocchia,b,D. Menascea,L. Moronia, M. Paganonia,b,D. Pedrinia, S. Pigazzini, S. Ragazzia,b, T. Tabarelli de Fatisa,b

a_{INFNSezionediMilano-Bicocca,Milano,Italy} b_{UniversitàdiMilano-Bicocca,Milano,Italy}

S. Buontempoa, N. Cavalloa,c, G. De Nardo, S. Di Guidaa,d,14, M. Espositoa,b, F. Fabozzia,c, A.O.M. Iorioa,b, G. Lanzaa,L. Listaa, S. Meolaa,d,14,P. Paoluccia,14, C. Sciaccaa,b, F. Thyssen a_{INFNSezionediNapoli,Napoli,Italy}

b_{UniversitàdiNapoli‘FedericoII’,Napoli,Italy} c_{UniversitàdellaBasilicata,Potenza,Italy} d_{UniversitàG.Marconi,Roma,Italy}

P. Azzia,14, N. Bacchettaa, L. Benatoa,b,D. Biselloa,b, A. Bolettia,b,R. Carlina,b,

A. Carvalho Antunes De Oliveiraa,b, P. Checchiaa,M. Dall’Ossoa,b,P. De Castro Manzanoa,T. Dorigoa, U. Dossellia,F. Gasparinia,b,U. Gasparinia,b,A. Gozzelinoa,S. Lacapraraa, M. Margonia,b,

A.T. Meneguzzoa,b,J. Pazzinia,b,14, N. Pozzobona,b,P. Ronchesea,b, F. Simonettoa,b,E. Torassaa, M. Zanetti,P. Zottoa,b,A. Zucchettaa,b,G. Zumerlea,b

a_{INFNSezionediPadova,Padova,Italy} b_{UniversitàdiPadova,Padova,Italy} c_{UniversitàdiTrento,Trento,Italy}

A. Braghieria,A. Magnania,b, P. Montagnaa,b,S.P. Rattia,b, V. Rea, C. Riccardia,b,P. Salvinia,I. Vaia,b, P. Vituloa,b

a

INFNSezionediPavia,Pavia,Italy b_{UniversitàdiPavia,Pavia,Italy}

L. Alunni Solestizia,b,G.M. Bileia, D. Ciangottinia,b,L. Fanòa,b, P. Laricciaa,b,R. Leonardia,b, G. Mantovania,b,M. Menichellia, A. Sahaa, A. Santocchiaa,b

K. Androsova,30,P. Azzurria,14,G. Bagliesia,J. Bernardinia,T. Boccalia,R. Castaldia, M.A. Cioccia,30, R. Dell’Orsoa,S. Donatoa,c,G. Fedi, A. Giassia,M.T. Grippoa,30,F. Ligabuea,c, T. Lomtadzea, L. Martinia,b, A. Messineoa,b, F. Pallaa,A. Rizzia,b,A. Savoy-Navarroa,31, P. Spagnoloa,R. Tenchinia, G. Tonellia,b, A. Venturia,P.G. Verdinia

a_{INFNSezionediPisa,Pisa,Italy} b_{UniversitàdiPisa,Pisa,Italy}

c_{ScuolaNormaleSuperiorediPisa,Pisa,Italy}

L. Baronea,b, F. Cavallaria,M. Cipriania,b, G. D’imperioa,b,14,D. Del Rea,b,14,M. Diemoza, S. Gellia,b, C. Jordaa, E. Longoa,b, F. Margarolia,b,P. Meridiania,G. Organtinia,b, R. Paramattia,F. Preiatoa,b, S. Rahatloua,b,C. Rovellia, F. Santanastasioa,b

a_{INFNSezionediRoma,Roma,Italy} b_{UniversitàdiRoma,Roma,Italy}

N. Amapanea,b,R. Arcidiaconoa,c,14,S. Argiroa,b,M. Arneodoa,c,N. Bartosika,R. Bellana,b, C. Biinoa, N. Cartigliaa,F. Cennaa,b, M. Costaa,b,R. Covarellia,b,A. Deganoa,b,N. Demariaa, L. Fincoa,b, B. Kiania,b, C. Mariottia, S. Masellia,E. Migliorea,b, V. Monacoa,b, E. Monteila,b, M.M. Obertinoa,b,L. Pachera,b, N. Pastronea,M. Pelliccionia,G.L. Pinna Angionia,b, F. Raveraa,b,A. Romeroa,b, M. Ruspaa,c,R. Sacchia,b, K. Shchelinaa,b, V. Solaa,A. Solanoa,b,A. Staianoa,P. Traczyka,b

a_{INFNSezionediTorino,Torino,Italy} b_{UniversitàdiTorino,Torino,Italy}

c_{UniversitàdelPiemonteOrientale,Novara,Italy}

S. Belfortea,M. Casarsaa, F. Cossuttia,G. Della Riccaa,b, C. La Licataa,b, A. Schizzia,b, A. Zanettia a_{INFNSezionediTrieste,Trieste,Italy}

b_{UniversitàdiTrieste,Trieste,Italy}

D.H. Kim,G.N. Kim, M.S. Kim, S. Lee, S.W. Lee, Y.D. Oh,S. Sekmen, D.C. Son,Y.C. Yang KyungpookNationalUniversity,Daegu,RepublicofKorea

A. Lee

ChonbukNationalUniversity,Jeonju,RepublicofKorea J.A. Brochero Cifuentes,T.J. Kim HanyangUniversity,Seoul,RepublicofKorea

S. Cho,S. Choi, Y. Go, D. Gyun,S. Ha,B. Hong, Y. Jo,Y. Kim, B. Lee, K. Lee,K.S. Lee, S. Lee, J. Lim, S.K. Park,Y. Roh

KoreaUniversity,Seoul,RepublicofKorea

J. Almond,J. Kim, S.B. Oh,S.h. Seo, U.K. Yang,H.D. Yoo, G.B. Yu SeoulNationalUniversity,Seoul,RepublicofKorea

M. Choi,H. Kim, H. Kim,J.H. Kim, J.S.H. Lee, I.C. Park, G. Ryu, M.S. Ryu UniversityofSeoul,Seoul,RepublicofKorea

Y. Choi,J. Goh, C. Hwang, J. Lee,I. Yu SungkyunkwanUniversity,Suwon,RepublicofKorea

I. Ahmed,Z.A. Ibrahim, J.R. Komaragiri, M.A.B. Md Ali32,F. Mohamad Idris33,W.A.T. Wan Abdullah, M.N. Yusli,Z. Zolkapli

NationalCentreforParticlePhysics,UniversitiMalaya,KualaLumpur,Malaysia

E. Casimiro Linares, H. Castilla-Valdez, E. De La Cruz-Burelo,I. Heredia-De La Cruz34,

A. Hernandez-Almada,R. Lopez-Fernandez, R. Magaña Villalba, J. Mejia Guisao,A. Sanchez-Hernandez CentrodeInvestigacionydeEstudiosAvanzadosdelIPN,MexicoCity,Mexico

S. Carrillo Moreno, C. Oropeza Barrera, F. Vazquez Valencia UniversidadIberoamericana,MexicoCity,Mexico

S. Carpinteyro, I. Pedraza, H.A. Salazar Ibarguen, C. Uribe Estrada BenemeritaUniversidadAutonomadePuebla,Puebla,Mexico

A. Morelos Pineda

UniversidadAutónomadeSanLuisPotosí,SanLuisPotosí,Mexico D. Krofcheck

UniversityofAuckland,Auckland,NewZealand P.H. Butler

UniversityofCanterbury,Christchurch,NewZealand

A. Ahmad, M. Ahmad, Q. Hassan,H.R. Hoorani, W.A. Khan, M.A. Shah, M. Shoaib, M. Waqas NationalCentreforPhysics,Quaid-I-AzamUniversity,Islamabad,Pakistan

H. Bialkowska, M. Bluj,B. Boimska, T. Frueboes,M. Górski, M. Kazana, K. Nawrocki, K. Romanowska-Rybinska, M. Szleper,P. Zalewski

NationalCentreforNuclearResearch,Swierk,Poland

K. Bunkowski,A. Byszuk35, K. Doroba,A. Kalinowski, M. Konecki,J. Krolikowski, M. Misiura, M. Olszewski, M. Walczak

InstituteofExperimentalPhysics,FacultyofPhysics,UniversityofWarsaw,Warsaw,Poland

P. Bargassa,C. Beirão Da Cruz E Silva, A. Di Francesco, P. Faccioli, P.G. Ferreira Parracho,M. Gallinaro, J. Hollar, N. Leonardo,L. Lloret Iglesias, M.V. Nemallapudi, J. Rodrigues Antunes, J. Seixas,O. Toldaiev, D. Vadruccio,J. Varela, P. Vischia

LaboratóriodeInstrumentaçãoeFísicaExperimentaldePartículas,Lisboa,Portugal

S. Afanasiev,P. Bunin, M. Gavrilenko, I. Golutvin, I. Gorbunov, A. Kamenev,V. Karjavin, A. Lanev,

A. Malakhov,V. Matveev36,37,P. Moisenz, V. Palichik,V. Perelygin, S. Shmatov, S. Shulha, N. Skatchkov, V. Smirnov, N. Voytishin, A. Zarubin

JointInstituteforNuclearResearch,Dubna,Russia

L. Chtchipounov,V. Golovtsov, Y. Ivanov, V. Kim38, E. Kuznetsova39,V. Murzin, V. Oreshkin, V. Sulimov, A. Vorobyev

PetersburgNuclearPhysicsInstitute,Gatchina(St.Petersburg),Russia

Yu. Andreev,A. Dermenev, S. Gninenko, N. Golubev, A. Karneyeu,M. Kirsanov, N. Krasnikov, A. Pashenkov,D. Tlisov, A. Toropin

V. Epshteyn,V. Gavrilov, N. Lychkovskaya,V. Popov, I. Pozdnyakov,G. Safronov, A. Spiridonov, M. Toms, E. Vlasov,A. Zhokin

InstituteforTheoreticalandExperimentalPhysics,Moscow,Russia A. Bylinkin37

MoscowInstituteofPhysicsandTechnology,Russia

M. Chadeeva40, M. Danilov40, O. Markin

NationalResearchNuclearUniversity‘MoscowEngineeringPhysicsInstitute’(MEPhI),Moscow,Russia

V. Andreev,M. Azarkin37,I. Dremin37, M. Kirakosyan, A. Leonidov37,S.V. Rusakov, A. Terkulov P.N.LebedevPhysicalInstitute,Moscow,Russia

A. Baskakov,A. Belyaev, E. Boos,M. Dubinin41,L. Dudko, A. Ershov, A. Gribushin, V. Klyukhin, O. Kodolova,I. Lokhtin,I. Miagkov, S. Obraztsov, S. Petrushanko,V. Savrin, A. Snigirev

SkobeltsynInstituteofNuclearPhysics,LomonosovMoscowStateUniversity,Moscow,Russia V. Blinov42, Y. Skovpen42

NovosibirskStateUniversity(NSU),Novosibirsk,Russia

I. Azhgirey,I. Bayshev,S. Bitioukov, D. Elumakhov, V. Kachanov, A. Kalinin, D. Konstantinov, V. Krychkine, V. Petrov, R. Ryutin, A. Sobol,S. Troshin, N. Tyurin,A. Uzunian, A. Volkov StateResearchCenterofRussianFederation,InstituteforHighEnergyPhysics,Protvino,Russia

P. Adzic43,P. Cirkovic, D. Devetak,M. Dordevic, J. Milosevic,V. Rekovic UniversityofBelgrade,FacultyofPhysicsandVincaInstituteofNuclearSciences,Belgrade,Serbia

J. Alcaraz Maestre,M. Barrio Luna, E. Calvo,M. Cerrada,M. Chamizo Llatas, N. Colino, B. De La Cruz, A. Delgado Peris,A. Escalante Del Valle, C. Fernandez Bedoya,J.P. Fernández Ramos, J. Flix, M.C. Fouz, P. Garcia-Abia,O. Gonzalez Lopez, S. Goy Lopez, J.M. Hernandez, M.I. Josa,E. Navarro De Martino, A. Pérez-Calero Yzquierdo,J. Puerta Pelayo, A. Quintario Olmeda,I. Redondo, L. Romero,M.S. Soares CentrodeInvestigacionesEnergéticasMedioambientalesyTecnológicas(CIEMAT),Madrid,Spain

J.F. de Trocóniz,M. Missiroli, D. Moran UniversidadAutónomadeMadrid,Madrid,Spain

J. Cuevas,J. Fernandez Menendez, I. Gonzalez Caballero, J.R. González Fernández,E. Palencia Cortezon, S. Sanchez Cruz,I. Suárez Andrés, J.M. Vizan Garcia

UniversidaddeOviedo,Oviedo,Spain

I.J. Cabrillo, A. Calderon, J.R. Castiñeiras De Saa, E. Curras, M. Fernandez,J. Garcia-Ferrero,G. Gomez, A. Lopez Virto,J. Marco, C. Martinez Rivero,F. Matorras, J. Piedra Gomez, T. Rodrigo, A. Ruiz-Jimeno, L. Scodellaro,N. Trevisani, I. Vila, R. Vilar Cortabitarte

InstitutodeFísicadeCantabria(IFCA),CSIC-UniversidaddeCantabria,Santander,Spain

M.J. Kortelainen, K. Kousouris,M. Krammer1, P. Lecoq,C. Lourenço,M.T. Lucchini, L. Malgeri, M. Mannelli,A. Martelli, F. Meijers, S. Mersi, E. Meschi, F. Moortgat,S. Morovic, M. Mulders,

H. Neugebauer,S. Orfanelli, L. Orsini, L. Pape,E. Perez, M. Peruzzi,A. Petrilli, G. Petrucciani, A. Pfeiffer, M. Pierini,A. Racz, T. Reis,G. Rolandi45, M. Rovere,M. Ruan, H. Sakulin,J.B. Sauvan, C. Schäfer,

C. Schwick,M. Seidel, A. Sharma,P. Silva, M. Simon, P. Sphicas46, J. Steggemann,M. Stoye, Y. Takahashi, M. Tosi,D. Treille, A. Triossi, A. Tsirou,V. Veckalns47, G.I. Veres21,N. Wardle, A. Zagozdzinska35, W.D. Zeuner

CERN,EuropeanOrganizationforNuclearResearch,Geneva,Switzerland

W. Bertl,K. Deiters, W. Erdmann, R. Horisberger, Q. Ingram, H.C. Kaestli, D. Kotlinski,U. Langenegger, T. Rohe

PaulScherrerInstitut,Villigen,Switzerland

F. Bachmair, L. Bäni, L. Bianchini, B. Casal, G. Dissertori, M. Dittmar, M. Donegà, P. Eller, C. Grab, C. Heidegger, D. Hits, J. Hoss,G. Kasieczka, P. Lecomte†, W. Lustermann,B. Mangano, M. Marionneau, P. Martinez Ruiz del Arbol, M. Masciovecchio, M.T. Meinhard,D. Meister,F. Micheli, P. Musella, F. Nessi-Tedaldi, F. Pandolfi, J. Pata, F. Pauss,G. Perrin, L. Perrozzi,M. Quittnat, M. Rossini, M. Schönenberger, A. Starodumov48,V.R. Tavolaro, K. Theofilatos,R. Wallny

InstituteforParticlePhysics,ETHZurich,Zurich,Switzerland

T.K. Aarrestad, C. Amsler49, L. Caminada,M.F. Canelli, V. Chiochia,A. De Cosa, C. Galloni, A. Hinzmann, T. Hreus, B. Kilminster,C. Lange, J. Ngadiuba, D. Pinna,G. Rauco, P. Robmann, D. Salerno, Y. Yang UniversitätZürich,Zurich,Switzerland

V. Candelise,T.H. Doan, Sh. Jain,R. Khurana, M. Konyushikhin, C.M. Kuo, W. Lin, Y.J. Lu,A. Pozdnyakov, S.S. Yu

NationalCentralUniversity,Chung-Li,Taiwan

Arun Kumar, P. Chang, Y.H. Chang,Y.W. Chang, Y. Chao, K.F. Chen, P.H. Chen, C. Dietz,F. Fiori, W.-S. Hou, Y. Hsiung, Y.F. Liu,R.-S. Lu, M. Miñano Moya, E. Paganis, A. Psallidas,J.f. Tsai, Y.M. Tzeng

NationalTaiwanUniversity(NTU),Taipei,Taiwan

B. Asavapibhop, G. Singh, N. Srimanobhas,N. Suwonjandee ChulalongkornUniversity,FacultyofScience,DepartmentofPhysics,Bangkok,Thailand

A. Adiguzel, S. Damarseckin, Z.S. Demiroglu, C. Dozen, E. Eskut, S. Girgis, G. Gokbulut, Y. Guler, E. Gurpinar,I. Hos, E.E. Kangal50, O. Kara, A. Kayis Topaksu,U. Kiminsu, M. Oglakci,G. Onengut51, K. Ozdemir52, S. Ozturk53,A. Polatoz, B. Tali54,S. Turkcapar,I.S. Zorbakir, C. Zorbilmez

CukurovaUniversity,Adana,Turkey

B. Bilin, S. Bilmis, B. Isildak55, G. Karapinar56, M. Yalvac, M. Zeyrek MiddleEastTechnicalUniversity,PhysicsDepartment,Ankara,Turkey

E. Gülmez,M. Kaya57,O. Kaya58, E.A. Yetkin59, T. Yetkin60 BogaziciUniversity,Istanbul,Turkey

A. Cakir,K. Cankocak, S. Sen61 IstanbulTechnicalUniversity,Istanbul,Turkey B. Grynyov

L. Levchuk,P. Sorokin

NationalScientificCenter,KharkovInstituteofPhysicsandTechnology,Kharkov,Ukraine

R. Aggleton,F. Ball, L. Beck, J.J. Brooke, D. Burns,E. Clement, D. Cussans, H. Flacher,J. Goldstein, M. Grimes, G.P. Heath, H.F. Heath,J. Jacob, L. Kreczko, C. Lucas, D.M. Newbold62, S. Paramesvaran, A. Poll, T. Sakuma,S. Seif El Nasr-storey, D. Smith,V.J. Smith

UniversityofBristol,Bristol,UnitedKingdom

K.W. Bell,A. Belyaev63,C. Brew, R.M. Brown, L. Calligaris,D. Cieri, D.J.A. Cockerill, J.A. Coughlan,

K. Harder,S. Harper, E. Olaiya, D. Petyt, C.H. Shepherd-Themistocleous, A. Thea,I.R. Tomalin, T. Williams RutherfordAppletonLaboratory,Didcot,UnitedKingdom

M. Baber,R. Bainbridge, O. Buchmuller, A. Bundock,D. Burton, S. Casasso,M. Citron, D. Colling, L. Corpe, P. Dauncey,G. Davies, A. De Wit, M. Della Negra, R. Di Maria, P. Dunne, A. Elwood, D. Futyan,Y. Haddad, G. Hall,G. Iles, T. James, R. Lane, C. Laner, R. Lucas62,L. Lyons, A.-M. Magnan,S. Malik, L. Mastrolorenzo, J. Nash, A. Nikitenko48,J. Pela, B. Penning, M. Pesaresi, D.M. Raymond, A. Richards,A. Rose,C. Seez, S. Summers,A. Tapper, K. Uchida, M. Vazquez Acosta64, T. Virdee14, J. Wright,S.C. Zenz

ImperialCollege,London,UnitedKingdom

J.E. Cole, P.R. Hobson,A. Khan, P. Kyberd,D. Leslie, I.D. Reid, P. Symonds, L. Teodorescu, M. Turner BrunelUniversity,Uxbridge,UnitedKingdom

A. Borzou,K. Call,J. Dittmann, K. Hatakeyama, H. Liu, N. Pastika BaylorUniversity,Waco,USA

O. Charaf,S.I. Cooper, C. Henderson, P. Rumerio TheUniversityofAlabama,Tuscaloosa,USA

D. Arcaro, A. Avetisyan, T. Bose,D. Gastler, D. Rankin, C. Richardson,J. Rohlf, L. Sulak,D. Zou BostonUniversity,Boston,USA

G. Benelli, E. Berry,D. Cutts, A. Garabedian,J. Hakala, U. Heintz, J.M. Hogan,O. Jesus, E. Laird, G. Landsberg, Z. Mao,M. Narain, S. Piperov,S. Sagir, E. Spencer, R. Syarif

BrownUniversity,Providence,USA

R. Breedon,G. Breto, D. Burns,M. Calderon De La Barca Sanchez, S. Chauhan, M. Chertok, J. Conway, R. Conway, P.T. Cox, R. Erbacher,C. Flores, G. Funk, M. Gardner,W. Ko, R. Lander, C. Mclean,

M. Mulhearn, D. Pellett,J. Pilot, F. Ricci-Tam, S. Shalhout, J. Smith, M. Squires, D. Stolp, M. Tripathi, S. Wilbur,R. Yohay

UniversityofCalifornia,Davis,Davis,USA

R. Cousins,P. Everaerts, A. Florent, J. Hauser,M. Ignatenko, D. Saltzberg, E. Takasugi,V. Valuev, M. Weber UniversityofCalifornia,LosAngeles,USA

K. Burt,R. Clare, J. Ellison, J.W. Gary, G. Hanson,J. Heilman, P. Jandir, E. Kennedy, F. Lacroix,O.R. Long, M. Malberti,M. Olmedo Negrete, M.I. Paneva, A. Shrinivas,H. Wei, S. Wimpenny,B.R. Yates

UniversityofCalifornia,Riverside,Riverside,USA

J.G. Branson, G.B. Cerati,S. Cittolin, M. Derdzinski, R. Gerosa, A. Holzner, D. Klein, V. Krutelyov, J. Letts, I. Macneill,D. Olivito, S. Padhi, M. Pieri, M. Sani, V. Sharma, S. Simon,M. Tadel, A. Vartak,