Measurement of nuclear modification factors of gamma(1S), gamma(2S), and gamma(3S) mesons in PbPb collisions at √s(NN)=5.02 TeV

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Physics

Letters

B

www.elsevier.com/locate/physletb

Measurement

of

nuclear

modification

factors

of

ϒ(1S),

ϒ(2S),

and

ϒ(3S)

mesons

in

PbPb

collisions

at

√

s

=

5.02 TeV

.TheCMS Collaboration CERN,Switzerland

a r t i c l e i n f o a b s t ra c t

Articlehistory: Received23May2018

Receivedinrevisedform2January2019 Accepted7January2019

Availableonline17January2019 Editor:M.Doser Keywords: CMS Physics Bottomonium Quarkoniumsuppression Quarkgluonplasma Heavyioncollisions

The crosssectionsforϒ(1S),ϒ(2S),and ϒ(3S)productioninlead–lead(PbPb)and proton–proton(pp) collisions at√sNN=5.02 TeV have been measured usingthe CMS detector at the LHC. The nuclear

modification factors, RAA,derived from the PbPb-to-pp ratio ofyields for each state, are studied as

functionsofmesonrapidityandtransversemomentum,aswellasPbPbcollisioncentrality.Theyieldsof allthreestatesarefoundtobesignificantlysuppressed,andcompatiblewithasequentialorderingofthe suppression, RAA(ϒ(1S))>RAA(ϒ(2S))>RAA(ϒ(3S)).Thesuppressionofϒ(1S)islargerthanthatseen at√sNN=2.76 TeV,althoughthetwoarecompatiblewithinuncertainties.TheupperlimitontheRAAof ϒ(3S)integratedoverpT,rapidityandcentralityis0.096at95%confidencelevel,whichisthestrongest

suppressionobservedforaquarkoniumstateinheavyioncollisionstodate.

©2019TheAuthor(s).PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBYlicense (http://creativecommons.org/licenses/by/4.0/).FundedbySCOAP3_.

1. Introduction

Themeasurement ofquarkoniumproductioninheavy ion col-lisionsisone ofthemostpromisingwaystostudytheproperties ofstronglyinteractingmatterathighenergydensityand tempera-ture.Ithasbeenpredictedthatinsuchanenvironment,astrongly interactingmedium ofdeconfined quarksandgluons(the quark– gluonplasma,QGP)isformed [1,2].Bottomoniumstateshavebeen the subjectofstudies in heavy ion collisions forseveral reasons. Bottomoniaare produced during theearly stagesofcollisions via hard partonscattering.Their spectral functionsaremodified asa consequenceofDebyescreeningoftheheavy-quarkpotentialat fi-nitetemperatures [3,4],aswellasbythermalbroadeningoftheir widths due to interactions with gluons [5,6]. These in-medium effects have been studied in numerical simulations of quantum chromodynamics (QCD) on a space–time lattice, andcaptured as realand imaginarycomponents of theheavy-quark potential [7]. Oneofthemostremarkablesignaturesoftheseinteractions with themediumisthesequentialsuppressionofquarkoniumstatesin heavyioncollisionscomparedtotheproductioninproton–proton (pp) collisions, both in the charmonium (J/ψ, ψ(2S), χc, etc.) andthebottomonium (ϒ(1S), ϒ(2S),ϒ(3S), χb,etc.)families [8]. This scenario follows from the expectation that the suppression of quarkonia is stronger for states with smaller binding energy.

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

The quarkonium yield can also increase in the presence ofQGP, from the recombination of uncorrelatedquarks [9–12]. However, recombination-like processes for bottomonia are expected to be negligible compared to the charmonium family [13–15], because these processes are driven by the number of heavy-quark pairs presentina single event, whichismuch smallerforbeautythan for charm.The dissociation temperatures forthe ϒ states, above whichsuppressionoccurs,areexpectedtobecorrelatedwiththeir binding energies,andarepredictedto be Tdissoc≈2Tc,1.2Tc and 1Tc fortheϒ(1S),ϒ(2S),andϒ(3S)states,respectively,whereTc isthecriticaltemperaturefordeconfinement [16].Therefore, mea-surements ofthe yields of each ϒ state can provide information aboutthe thermalproperties ofthe medium during its hot early phase.

Modifications of particle production in nucleus–nucleus (AA) collisionsarequantifiedusingthenuclearmodificationfactor,RAA, whichis theratiooftheyieldmeasured inAA tothat inpp col-lisions, scaledbythemeannumberofbinary NNcollisions. Com-parisonsofthebottomoniumdatawithdynamicalmodels incorpo-ratingtheheavy-quarkpotentialeffectsfoundinhigh-temperature lattice QCD are thus expected to extend our understanding of the natureof colourdeconfinement inheavy ioncollisions. Mea-surements of both the charmonium (J/ψ and ψ(2S)) [17–20] andbottomonium(ϒ(1S),ϒ(2S),andϒ(3S)) [21,22] familieshave been carried out at a nucleon–nucleon (NN) center-of-mass en-ergyof√sNN=2.76 TeV and,mostrecently,at√sNN=0.2 TeV at RHIC [23–25].At√sNN=5.02 TeV,measurementsbytheCMS

Col-https://doi.org/10.1016/j.physletb.2019.01.006

0370-2693/©2019TheAuthor(s).PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBYlicense(http://creativecommons.org/licenses/by/4.0/).Fundedby SCOAP3_.

laborationshowstrongsuppressionofJ/ψandψ(2S)mesons [26, 27], as well as of both ϒ(2S) and ϒ(3S) relative to the ϒ(1S) groundstate [28]. The suppression of the excited ϒ(2S) relative totheϒ(1S) groundstate persistsatveryforwardrapidity,2.5<

y<4 [29].Thesemeasurementsprovidenewconstraintsfor theo-reticalmodelsofthemedium [9,11].

InthisLetter,wereportmeasurementsofthedifferentialcross sections and nuclear modification factors for ϒ(1S), ϒ(2S), and

ϒ(3S) mesons using their decay into two oppositely charged muonsinlead–lead (PbPb)andpp collisionsat√sNN=5.02 TeV. Resultsarepresentedasfunctionsoftheϒtransversemomentum (pT) andrapidity ( y),aswell asPbPbcollisioncentrality(i.e.,the degreeofoverlapofthetwoleadnuclei).Thedatawere collected withtheCMSdetectorattheCERNLHCin2015.

2. The CMS detector

The central feature of the CMS apparatus is a superconduct-ing solenoidof 6 m internal diameter,providing a magnetic field of3.8 T. Within thesolenoid volume are a silicontracker, a lead tungstatecrystalelectromagneticcalorimeter,andabrassand scin-tillator hadron calorimeter, each composed of a barrel and two endcap sections. Muons are detected in the pseudorapidity in-terval of |η|<2.4 using gas-ionization chambers made of three technologies: drift tubes, cathode strip chambers, and resistive-platechambers.Theseareembeddedinthesteelflux-returnyoke of the solenoid. The silicon tracker is composed of pixel detec-tors followedby microstrip detectors.The pT of muonsmatched to tracks reconstructed in the silicon detector is measured with a resolution between 1% and 2% fortypical muons used in this analysis [30]. In addition, CMS has extensive forward calorime-try, including two steel and quartz-fiber Cherenkov hadron for-ward (HF) calorimeters that cover the range of 2.9<|η|<5.2. TheHFcalorimetersaresegmentedintotowers andthe granular-ity is η× φ =0.175×0.175 radians. These are used in the presentanalysistoselectPbPbcollisioneventsandtodefinetheir centralityclass.Centrality, definedasthe fractionofthe total in-elastichadroniccrosssectionwith0% representingcollisions with the largest overlap of the two nuclei, is determined experimen-tallyusingthe totalenergyin bothHF calorimeters [31]. Amore detaileddescriptionoftheCMSdetector,togetherwithadefinition ofthecoordinatesystemandthekinematicvariables,canbefound inRef. [32].

3. Data selection and simulation samples

Theϒmesonsareidentifiedusingtheirdimuondecaychannel. InbothppandPbPbcollisions,thedimuoneventsareselectedbya fasthardware-basedtriggersystem,whichrequirestwomuon can-didatesinagivenbunchcrossingwithnoexplicitrequirementon themuonmomentumbeyondtheintrinsicselectionduetothe ac-ceptancecoverageoftheCMSmuondetectors.Inppcollisions,this trigger registered an integral luminosity of 28.0 pb−1. The PbPb datawere takenwithtwo triggers basedon the same algorithm usedfor pp data.The firstmode, designedto enhance the event countformuonpairsfromperipheralevents,addedanadditional selection that the collision centrality be in the 30–100% range. This trigger sampled the full integrated luminosity of 464 μb−1. The second mode, usingjustthe pp trigger alone,was prescaled during part of the data taking and therefore sampled a smaller effectiveintegratedluminosity of368 μb−1. Datatakenwiththis latter trigger were used to analyze the yields in the 0–30% and 0–100%centralitybins.

In order to keep hadronic collisions and reject beam-related background processes (beam-gas collisions and beam scraping

events), an offline eventselection is applied. Events are required to have at least one reconstructed primary vertex. In pp colli-sions atleast25% ofthetracks haveto passa tighttrack-quality selection [33].Afilteronthecompatibilityofthesiliconpixel de-tector cluster width andthe vertex position isalso applied [34]. The PbPb collision events have an additional requirement ofthe presence ofat leastthree towers in theHF on both sidesofthe interaction point withan energyabove 3 GeV.The combined ef-ficiencyforthiseventselection,andtheremainingcontamination due to non-hadronic ultra-peripheral events which can raise the efficiency above 100%, is (99±2)% [35,36]. The minimum-bias trigger requirement removes a negligible fraction of the events withahardcollisionneededtoproduceϒmesons.Wealso stud-ied a possible contamination from photoproduction processes in the peripheral region and found it to be negligible. Multiple-collision events(pileup)have anegligible effecton the measure-ment,sincetheaveragenumberofadditionalcollisionsperbunch crossing is approximately 0.9 forpp and much smaller forPbPb data.

Muonsareselectedinthekinematicrangeof pμ_T >4 GeV and |ημ_{|<2.4, and are also required to be reconstructed using the}

combinedinformationofthetrackerandmuondetectors(so-called “globalmuons”definedinRef. [30]).Toremovecosmicraymuons, the distance of the muon track from the closest primary vertex mustbe lessthan20 cminthebeamdirectionand3 mm inthe transverse direction. Pairsofoppositely chargedmuonsare fitted withacommonvertexconstraintandkeptifthefit χ2_probability islarger than 1%.The studieddimuon kinematicrangeis limited to pμ_T+μ−<30 GeV and|yμ+μ−|<2.4.Dimuonsinthis pT range comprise 99% ofthose passing all of theanalysis selection crite-ria.

Simulated Monte Carlo (MC) ϒ events are used to calculate correctionfactorsforalloftheresultspresented,includingthe ge-ometrical acceptanceandreconstruction efficiency,aswell asthe triggerandoffline selectionefficiency.The samplesare generated using pythia 8.209[37] fortheppcollisionsand pythia 8.209 em-beddedin hydjet 1.9forthePbPbevents [38].ThePbPbsimulation is tuned to reproduce the observed charged-particle multiplicity andpT spectruminPbPbdata.TheCMSdetectorresponseis sim-ulatedusing Geant4 [39].SincethesimulatedpT spectrumofϒis notidenticaltothespectrumobservedindata,an event-by-event weightisappliedtothesimulationsinordertomatchthetwo dis-tributions.Theweightisgivenbyafunctionfittotheratioofdata overMC pTspectra.

4. Analysis procedure

4.1. Signalextraction

The yields of ϒ mesons are extracted using unbinned maximum-likelihood fits to the invariant mass spectra, following the same procedure forpp and PbPb data.The signal ofeach ϒ

state is modeled by a double Crystal-Ball (CB) function whichis thesumoftwo CBfunctions [40].Thischoice togetherwith leav-ing the width parameter forthe first CB free in the fit,is made in order to account forthe different mass resolution inthe bar-rel compared to the endcap region ofthe detector. A parameter relatesthewidthsofthe twoCB functions,the secondone being constrained to be narrower. The mass and the two radiative-tail

parameters of both CB functions for a given state are kept the same, as these are not affected by the detector resolution. The massparameterofthegroundstateisleftfreetoallowforpossible shiftsintheabsolutemomentum calibrationofthereconstructed tracks.Fortheexcitedstates(ϒ(2S)andϒ(3S)),theyieldscanvary whileallotherfitparametersarefixedtobeidenticaltothosefor thegroundstate except forthemean andwidthwhichare fixed tovaluesfoundbymultiplyingthoseforϒ(1S)bytheratioofthe published masses ofthe states [41]. In the pp datafits, the two radiative-tail parameters and the parameter for the ratio of the twowidthsareallowedtovarywithinaGaussianprobability den-sity function (PDF).The mean andthe width ofthe constraining Gaussian function represent the average and its uncertainty, re-spectively,fromthefitsinalltherapiditybinsoftheanalysiswith no fixed parameters. In the PbPb fits, in addition,the parameter forthefractionofthetwoCBfunctionsisalsoconstrained.Inthis case,themeanandthewidthoftheconstrainedparameters rep-resentthecorrespondingparametervaluesandtheiruncertainties fromthe pp fits for each kinematic region. The background PDF isan errorfunction multipliedby an exponential,withtheyield, the errorfunction’s two parameters, and thedecay parameter of theexponential all allowed to varyin the final fit.Forbins with

pT>6 GeV, an exponential without the error function provides thebestfit,andwasusedforthenominalresult.

Fig. 1 shows the dimuon invariant mass distributions in pp andPbPb collisionsalongwiththefitsusingthemodeldescribed above, for the kinematic range p_Tμ+μ−<30 GeV and |yμ+μ−|<

2.4.

4.2. Corrections

Inordertoobtainthenormalizedcrosssections,theyields ex-tractedfromthefitstothedimuoninvariantmassspectraare cor-rectedforacceptanceandefficiency,andscaled bythe integrated luminosity.Theacceptancecorrespondstothe fractionofdimuon eventsoriginatingfrom ϒ mesonswithin the kinematicrange of the analysis. The acceptance values forthe considered kinematic regionare22.5%(ϒ(1S)),27.8%(ϒ(2S)),and31.0%(ϒ(3S))forPbPb collisions anddiffer by<1% fromthecorresponding ppdata val-ues,withthesmalldifferencebeingduetoasmallresidual differ-enceinthekinematicspectraafterweightingtheMCtodata.

Thedimuonefficiencyisdefinedastheprobabilitythatamuon pair within the acceptance is reconstructed offline, satisfies the triggercondition,andpassestheanalysisqualitycriteriadescribed inSection3.ThedimuonefficiencyiscalculatedusingMC.The in-dividualcomponentsoftheefficiency(trackreconstruction,muon identificationandselection,andtriggering)are alsomeasured us-ing single muonsfrom J/ψ mesondecays inboth simulated and collisiondata, withthetag-and-probe (T&P) method [30].Forthe muonsusedinthisanalysis,data andMC efficienciesare seento differ only in the case of the trigger efficiency, and there only by 1%. For this case, scaling factors (SF), calculated as the ra-tioof dataover simulatedefficiencies asfunction of pμ_T and ημ,

areappliedtoeachdimuononanevent-by-eventbasis.Theother components of the T&P efficiency are used only for the estima-tionofsystematicuncertainties.Theaverageefficienciesintegrated overthefullkinematicrangeare73.5%(ϒ(1S)),74.4%(ϒ(2S)),and 75.0%(ϒ(3S))inPbPbcollisions, andthey are8–9%higherforpp collisions.

The integratedluminosity of28.0 pb−1 withan uncertainty of 2.3% [42] is used to normalize the yields for pp data. For PbPb collisions, thenumberof minimumbias collisionevents sampled by the trigger (NMB), together with the average nuclear overlap function (TAA), are usedforthe normalization. The overlap func-tion TAA is givenby thenumber ofbinary NNcollisions divided

Fig. 1. Invariantmass distributionofmuonpairsinpp (top) andPbPb(bottom) collisions, forthe kinematicrangepμT+μ−<30 GeV and|yμ

+_μ−

|<2.4.Inboth figures,theresultsofthefitstothedataareshownassolidbluelines.Theseparate yieldsforeachϒstateinppareshownasdashedredlinesinthetoppanel.The dashedredlinesinthebottompanelarederivedfromthefitstoPbPb(bluesolid line).Inordertoshowthesuppressionofallthreeϒstates,theamplitudesofthe correspondingpeaksareincreasedabovethosefoundinthefitbytheinverseof themeasuredRAAforthecorrespondingϒmeson.

by the inelastic NNcross section, andcan be interpreted as the NN-equivalent integrated luminosity per heavy ioncollision. Val-uesofTAAarecalculatedwithaGlaubermodelMCsimulation [43, 44], which is also used to obtain the average number of partic-ipating nucleons, Npart. This latter number is highly correlated with the impact parameter of the collision, and is used as the abscissawhenplottingresultsasafunctionofPbPbcollision cen-trality.

4.3. Systematicuncertainties

Point-to-point systematic uncertainties arise from the choices ofsignal andbackgroundPDFsandofthecentral valuein thefit constraints,aswell asfromacceptanceandefficiencycorrections. Larger relative uncertainties are obtained when the background level is higher (at lower pT or moreforward y regions), and, in particularfortheϒ(3S),whentheabsoluteyieldissmall.

The uncertaintyfrom the choice of signal model isestimated byfittingthedatausingasingleCB functionincombinationwith a Gaussian function instead of a doubleCB function. The uncer-taintiesaredetermined bycalculatingthe differencebetweenthe yieldobtainedwiththealternativemodelcomparedtothe nomi-nalone.ForthePbPb (pp)yields,thedifferencesareintherange of1–7%(0.1–4.6%)for theϒ(1S), 2–19%(0.1–1.3%) forthe ϒ(2S), and5–78%(0.7–7%)fortheϒ(3S)mesons.

Thesystematicuncertaintyfromthechoiceofthecentralvalue inthefitconstraintsisestimatedby usinginsteadoftheaverage parametervaluesfromthepp fits,the valuesineach ppanalysis binwhenallparameters wereleft floating.Thedifferencesinthe PbPb(pp)signalyields,typicallybelow4%(4.5%)fortheϒ(1S), be-low8%(3%)fortheϒ(2S),and45%(2%)fortheϒ(3S),arequoted asasystematicuncertainty.

The systematic uncertainty due to the choice of background model is estimated using two alternative background functions. Oneisintheformofafourth-order polynomialfunctionandthe other is an exponential plus an additional linear function. The maximal deviations of the PbPb (pp) yield between these two models compared to the nominal are quoted as the uncertainty andaretypicallyintherangeof1–6%(1–5%)fortheϒ(1S),2–23% (2–4%)fortheϒ(2S),and5–200%(3–5%)fortheϒ(3S)mesons.

For the estimation of systematic uncertainties due to accep-tanceand efficiencycorrections, the source of uncertaintyis the imperfect knowledge of the simulated pT distribution shape. To take this source into account, the function used to weight the MC pT spectra event-by-event is modified within its fit uncer-tainty.Theacceptanceandefficiencyobtainedfromthesimulated

pTdistributionarecomparedwithandwithoutthevariationofthe function,withthedifferencebetweenthetwousedasanestimate of the systematic uncertainty. In addition, there is a systematic uncertainty forthe efficiencyin the T&P correction arising from theuncertaintyintheSFsofthesingle-muonefficiency. The sys-tematicuncertaintiesoftheSFsaretakenintoaccount fortrigger, tracking,andmuon identification. The uncertainties in the single muonefficiencies are propagated tothe dimuonefficiencyvalues toestimatethesystematicuncertaintyfromthissource.The statis-ticaluncertaintyinherentinthedatasetusedfortheT&Pstudies is alsoconsidered asan additional componentof the systematic uncertaintyinthecorrected yields.The PbPb(pp) systematic un-certaintiesareintherangeof3.5–6.4%(2.6–3.9%)inthecaseofthe totalefficiencycorrection andinthe rangeof0.1–3.0% (0.1–0.8%) fortheacceptancecorrection.

Finally, several sources of correlated uncertainties (i.e., global uncertainties common to all points) are considered: for the pp datasetfromtheppintegratedluminosity,andforthePbPbdataset fromtheTAAandthe NMBestimations.Theuncertaintyonthe in-tegratedluminosity measurementforthe pp datasetis2.3% [42]. Theuncertaintyfor NMB in PbPbcollisions is 2%,whichaccounts for the inefficiency of trigger and event selection. For the RAA calculation, TAA uncertainties (Table 2 in Appendix A) are es-timated by varying the Glauber model parameters within their uncertainties (Table 1 in Appendix A) [36]. The total combined uncertainty is calculated by adding the results from the various sources in quadrature. The globaluncertainty for the differential cross section results arises from the integratedluminosity in pp collisions and NMB in PbPb collisions. For the RAA results, the globaluncertaintycombinestheuncertainties fromTAA,pp lumi-nosity, andPbPb NMB for the binsintegrated over centrality. For the centrality dependent RAA results, the uncertainty from TAA is included bin-by-bin, while the total uncertainty from the pp measurementisincludedintheglobaluncertainty.Using the up-dateduncertainties oftheGlauber modelparametersinRef. [45], insteadofthose fromRef. [36],would reduce the TAA

uncertain-tiesby 0.1–1.1%andthetotalsystematicuncertainties for RAA by lessthan 0.7% (with thelargest change forthe 70–100% central-itybin). However, in order toallow direct comparisons to previ-ous results [27,36,46,47], theseupdated parameters are not used in this analysis. The binmigration effectdue to the momentum resolution is negligible for the kinematic range of this measure-ment.

5. Results

The ϒ crosssections andvalues of RAA are measured in sev-eralpTandybins.Therapiditystudiesareperformedintherange 0<|y|<2.4.Thisrapidityrangeisevenlydividedintosix, three, andtwobinsforϒ(1S),ϒ(2S),andϒ(3S),respectively.Forthe in-vestigation ofthebehavior ofthe RAA asa functionof centrality, the bin limitsof thecentrality classes are chosen as follows:[0, 5,10,20,30,40,50,60,70,100%] forthe ϒ(1S) andϒ(2S),and [0, 30, 100%] for the ϒ(3S). When plotted asa function of each variable (pT, y or centrality), values are integrated over the full kinematicrangeoftheothervariables.Theϒ(3S)mesonsshowa very strongsuppression inPbPb collisions, withyields whichare statisticallyconsistent with zero forall bins. The upperlimits at 68%and95%confidencelevel(CL)fortheϒ(3S)crosssectionand

RAA are foundusing theFeldman–Cousins method [48], withthe appropriate systematic uncertainties being includedin the upper limitcomputation.

5.1. DifferentialcrosssectionsinppandPbPbcollisions

Thedifferentialproductioncrosssectionofϒmesonsdecaying inthedimuonchannelinppcollisionsisgivenby

B dσ2 d ydpT =

N/(Aε)

LintypT

. (1)

Thebranchingfractionforthedecayϒ→μ+μ−isdenotedbyB. Thequantity N correspondstotheextractedyieldofϒmesonsin a given(pT, y) bin,(A ε) representsthe average acceptanceand efficiencyin the givenbin,Lint is theintegrated luminosity,and

pTandy arethewidthsofthegivenbin.ForPbPbdata,Lintis replacedby(NMBTAA),asexplainedinSection4.2,tocomparethe ppandPbPbdataunderthehypothesisofbinary-collisionscaling. Fig. 2 shows the differential production cross sections of ϒ

mesons as a function of pT in pp andPbPb collisions. The data pointsareplacedatthecenterofeachbin.Thecorresponding re-sultsasafunctionof|y|areshowninFig.3.

5.2. NuclearmodificationfactorRAA

The nuclear modification factor is derived from the pp cross sectionsandPbPbnormalizedyieldsas

RAA(pT,y)=

NAA(pT,y)

TAAσpp(pT,y)

, (2)

where TAA is the average value of TAA computedin each cen-trality bin. The quantities NAA _{and σ}pp _{refer to the normalized} yieldofϒmesonsinPbPbcollisions correctedbyacceptanceand efficiency, and the pp cross section for a given kinematic range, respectively.

Fig. 4 shows the nuclear modification factor for the ϒ(1S),

ϒ(2S), andϒ(3S) mesons asfunctionsof pT and|y|.Within the systematicuncertainties,theRAAvaluesshownocleardependence on pTor y.Theexcitedϒstatesarefoundtohavelarger suppres-sionthanthegroundstate,withRAA<0.2 overthefullkinematic

Fig. 2. Differentialcrosssectionsoftheϒ(1S),ϒ(2S),andϒ(3S)mesonsasa func-tionofpTforpp(top)andPbPb(bottom)collisions.Theerrorbarsrepresentthe

statisticaluncertaintiesandtheboxesthesystematicuncertainties.Fortheϒ(3S)

mesoninPbPbcollisions,theupperlimitsat68%(greenbox)and95%(green ar-row)CL areshown,andarecalculatedforthesamebinsasfortheppdataset.The globalintegratedluminosityuncertaintiesof2.3%inppcollisionsand+₋3.4%3.9%inPbPb

collisionsarenotshown.

range explored here. The kinematic dependence of RAA is use-fulto constrain models ofϒ meson suppression ina deconfined medium [9].

The dependenceof RAA on PbPb collision centrality, as quan-tified using the average Npart, is depicted in Fig. 5. The strong suppressionoftheϒ(3S)mesonisobservedinbothcentralitybins studied, 0–30% and30–100%. The RAA decreases with increasing centrality inthe case ofthe ϒ(1S) andϒ(2S) mesons. A hintof thiscentralitydependenceofRAA forϒ(2S)wasfirstseenindata at √sNN=2.76 TeV [21] and is now confirmedusing the larger datasampleat5.02 TeV.

Fig.6showsacomparisonbetweenthemeasuredRAAforϒ(1S) andϒ(2S)mesons and two models ofbottomonium suppression fromKrouppaandStrickland [9],andfromDu,He,andRapp [12]. Both models incorporatecolor-screening effects on the bottomo-niumfamilyandfeed-down contributionsfromdecaysof heavier quarkonia.No regeneration inQGPorcold nuclear mattereffects are considered by the first model, but are included in the

sec-Fig. 3. Differentialcrosssectionsoftheϒ(1S),ϒ(2S),andϒ(3S)mesonsasa func-tionofrapidityforpp (top)andPbPb(bottom)collisions.Theerrorbarsrepresent the statistical uncertainties and the boxes the systematicuncertainties. For the

ϒ(3S)mesoninPbPbcollisions,theupperlimitsat68%(greenbox)and95%(green arrow)CL areshown.Theglobalintegratedluminosityuncertaintiesof2.3%inpp collisionsand+₋3.4%3.9%inPbPbcollisionsarenotshown.

ond. Krouppa andStrickland treat the dynamical evolution using anisotropic hydrodynamics, where the relevant initial conditions are changed by varying the viscosity to entropy ratio, η/s, and theinitial momentum-spaceanisotropy.Theinitialtemperatureis determined by requiring agreement with charged particle multi-plicityandellipticflowmeasurements. ThemodelofDu,He,and Rappusesakinetic-rateequationtosimulatethetimeevolutionof bottomoniumabundances inultra-relativisticheavy ioncollisions. It considers medium effectswithtemperature-dependent binding energies,andalattice-QCD-basedequationofstateforthefireball evolution.Withinthecurrenttheoreticalandexperimental uncer-tainties,bothmodelsareinagreementwiththeresults.

Fig. 7 compares centrality-integrated RAA values at √sNN = 2.76 TeV to those at 5.02 TeV. The centrality-integrated RAA for

ϒ(1S) is measured to be 0.376±0.013(stat)±0.035(syst), to be compared with the result at 2.76 TeV, 0.453±0.014(stat)± 0.046(syst) [21]. The suppression at 5.02 TeV is larger by a fac-tor of ∼1.20±0.15 (in which only the TAA uncertainty was considered correlated and therefore removed), although the two

Fig. 4. Nuclearmodificationfactorsforϒ(1S),ϒ(2S),andϒ(3S)mesonsasfunctions ofpT(top)andrapidity(bottom).Theerrorbarsrepresentthestatistical

uncertain-tiesandthe boxesthesystematicuncertainties.Fortheϒ(3S)meson,theupper limitsat68%(greenbox)and95%(greenarrow)CL areshown.Thegrayboxnear thelineatunitydisplaystheglobaluncertainty,whichcombinestheuncertainties fromTAA,ppluminosity,andPbPb NMB.

Fig. 5. Nuclearmodificationfactorsfortheϒ(1S),ϒ(2S)and ϒ(3S)mesonsasa functionofNpart.Theboxesatthedashedlineatunityrepresentglobal

uncer-tainties:theopenboxfor theintegratedluminosityinppcollisionsand NMB in

PbPb collisions,whilethefullboxesshowtheuncertaintiesofppyieldsforϒ(1S) andϒ(2S)states(withthelargerboxcorrespondingtotheexcitedstate).Forthe

ϒ(3S)meson,theupperlimitsat68%(greenbox)and95%(greenarrow)CL are shown.

Fig. 6. Nuclearmodificationfactorsfortheϒ(1S)(top)andϒ(2S)(bottom)mesons asafunctionofNpartcomparedtocalculationsfromKrouppaandStrickland [9],

andDu,He,andRapp [12].Theboxatthedashedlineatunityrepresentstheglobal uncertaintyfromtheintegratedluminosityinppcollisions,NMBinPbPbcollisions,

andthetotaluncertaintyintheppyields.Thedatatotheoryratiosareshownin thebottompanels.ForRef. [9],thepointscorrespondtothe4π η/s=2 curve,while theerrorbarsshowthedifferencebetweenthisoneandtheothertwoη/s curves. ForRef. [12],thepointsanderrorbarscorrespondtothecenterandwidthofthe publishedtheoryband,respectively.

RAAvaluesarecompatiblewithintheuncertainties.The centrality-integratedresults fortheϒ(2S)andϒ(3S)statesat 5.02 TeV are

RAA(ϒ(2S))=0.117±0.022(stat)±0.019(syst) andRAA(ϒ(3S))= 0.022±0.038(stat)±0.016(syst) (<0.096at95%CL).Despite hav-ing a bigger binding energy than the already measured ψ(2S)

meson [18,19,27], no ϒ(3S) meson signal is found in the PbPb data,inanyofthestudiedkinematicregions.Thissuggestsa pT -and binding-energy-dependent interplay of different phenomena affectingquarkoniumstatesthatisyettobefullyunderstood [49]. Sincethe suppressionisexpectedtobe largerforhigher tem-peratures in the medium, the RAA results for the ϒ(1S) meson at the two different collision energies can provide information on the medium temperature. The temperatures reported in the model of Krouppa and Strickland shown in Fig. 6 are T =641, 631, and629 MeVcorrespondingto 4π η/s=1,2,and3, respec-tively.ForthemodelofDu,He,andRapp,thetemperaturesarein

Fig. 7. ComparisonofRAAvaluesfortheϒ(1S),ϒ(2S)andϒ(3S)mesonsat√sNN=

5.02 TeV and√sNN=2.76 TeV [21] forintegratedcentralityinthefullkinematic

range.Theerrorbarsrepresentthestatisticaluncertaintiesandtheboxesthe sys-tematicuncertainties,includingglobaluncertainties.

therangeT=550–800 MeV.Themodels,whicharealsoin agree-mentwiththeresultsat2.76 TeV [12,50],predictincreasesinthe medium temperature for PbPb collisions of ∼16% (Krouppa and Strickland)and∼7%(Du,He,andRapp)between√sNN=2.76 TeV and√sNN=5.02 TeV.

6. Summary

DatafromppandPbPbcollisionsat√sNN=5.02 TeV collected withthe CMS detector were analyzed to measure the cross sec-tionsofϒ(1S),ϒ(2S),andϒ(3S)mesonsandtheir nuclear modi-fication factorsasfunctionsofϒ transversemomentum(pT) and rapidity( y),aswellasPbPbcollisioncentrality.Agradualdecrease in RAA with Npart forthe ϒ(1S) and ϒ(2S) states is observed, whilenosignificantdependenceon pT or y isfoundinthe mea-suredregion.Thesuppressionofϒ(1S)islargerthanthat seenat √

sNN=2.76 TeV,although thetwo arecompatiblewithin uncer-tainties.TheRAA oftheϒ(3S)stateismeasuredtobebelow0.096 at95%confidencelevel,makingthisthestrongestsuppression ob-servedforaquarkoniumstateinheavyioncollisionstodate.

Acknowledgements

The authors would like to take this opportunity to acknowl-edgetheinvaluablecontributionsofRoyJ.Glauber tothefieldof heavyionnuclearphysics.Withouthiswork,ourunderstandingof themodificationsofparticleproductioninheavyioncollisions, of whichthispaperisonly oneofvery many,wouldnot havebeen possible.

WecongratulateourcolleaguesintheCERNaccelerator depart-ments for the excellent performance of the LHC and thank the technicalandadministrativestaffs atCERN andatother CMS in-stitutes for their contributions to the success of the CMS effort. Inaddition,wegratefullyacknowledgethecomputingcentresand personneloftheWorldwideLHCComputingGridfordeliveringso effectivelythe computinginfrastructureessential to ouranalyses. Finally, we acknowledge the enduring support for the construc-tionandoperation oftheLHCandthe CMSdetectorprovidedby thefollowingfundingagencies:BMWFWandFWF(Austria);FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIEN-CIAS(Colombia);MSESandCSF(Croatia);RPF(Cyprus);SENESCYT (Ecuador); MoER, ERC IUT, and ERDF (Estonia); Academy of Fin-land,MEC,andHIP(Finland);CEAandCNRS/IN2P3(France);BMBF,

Table 1

GlaubermodelparametersforPbPb colli-sionsat√sNN=5.02 TeV. Parameter Value Nuclear radius ( fm) 6.62±0.06 Skin depth ( fm) 0.546±0.010 dmin( fm) 0.4±0.4 σinel NN ( mb) 70±5 Table 2

Centrality classes, average number ofparticipating nucleons (Npart),numberofbinarycollisions(Ncoll),andthenuclear

overlap(TAA)forPbPbcollisionsat√sNN=5.02 TeV,obtained

usingtheGlaubermodelparametersofTable1.

Centrality class Npart Ncoll TAA (mb−1)

0–5% 384.3+₋1.82.0 1819+ 130 −137 25.98+ 0.47 −0.77 5–10% 333.3+₋3.33.2 1432+ 100 −106 20.46+ 0.38 −0.61 10–20% 264.2+3.6 −3.8 1005+ 69 −73 14.35+ 0.33 −0.46 20–30% 189.2+₋4.04.1 606+ 41 −44 8.66+ 0.29 −0.33 30–40% 131.4+₋4.04.0 349+ 25 −26 4.98+ 0.24 −0.24 40–50% 87.0+3.7 −3.7 186+ 15 −15 2.66+ 0.18 −0.17 50–60% 53.9+₋3.23.1 90.7+ 8.9 −8.7 1.30+ 0.12 −0.12 60–70% 30.6+₋2.62.4 40.1+ 5.0 −4.6 0.57+ 0.071 −0.064 70–100% 8.3+₋1.00.6 7.7+ 1.2 −0.7 0.11+ 0.018 −0.011 0–30% 270.7+3.2 −3.4 1079+ 74.3 −78.6 15.41+ 0.33 −0.47 30–100% 46.8+₋2.41.2 98.4+ 8.0 −6.4 1.41+ 0.094 −0.061 0–100% 114+₋2.62.6 393+ 27 −28 5.61+ 0.16 −0.19

DFG, andHGF (Germany); GSRT(Greece); NKFIA (Hungary); DAE andDST (India); IPM(Iran); SFI(Ireland); INFN (Italy); MSIPand NRF(RepublicofKorea);LAS(Lithuania);MOEandUM(Malaysia); BUAP, CINVESTAV, CONACYT, LNS, SEP, and UASLP-FAI (Mexico); MBIE (New Zealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT(Portugal);JINR(Dubna);MON,ROSATOM,RASandRFBR (Rus-sia);MESTD (Serbia);SEIDI,CPAN,PCTI andFEDER(Spain); Swiss Funding Agencies (Switzerland); MST (Taipei); ThEPCenter, IPST, STAR, andNSTDA (Thailand); TUBITAK andTAEK (Turkey); NASU andSFFR(Ukraine);STFC(UnitedKingdom);DOEandNSF(USA).

Individuals have received support from the Marie-Curie pro-gramme and the European Research Council and Horizon 2020 Grant, contractNo. 675440 (EuropeanUnion); theLeventis Foun-dation; the A.P. Sloan Foundation; the Alexander von Humboldt Foundation; the Belgian Federal Science Policy Office; the Fonds pourlaFormationàlaRecherchedansl’Industrieetdans l’Agricul-ture (FRIA-Belgium); the Agentschap voorInnovatie door Weten-schap en Technologie (IWT-Belgium); the Ministry of Education, YouthandSports(MEYS)oftheCzechRepublic;theCouncilof Sci-enceandIndustrialResearch,India;theHOMINGPLUSprogramme of the Foundation for Polish Science, cofinanced from European Union, RegionalDevelopmentFund, theMobilityPlusprogramme oftheMinistryofScienceandHigherEducation,theNational Sci-ence Center (Poland), contracts Harmonia 2014/14/M/ST2/00428, Opus 2014/13/B/ST2/02543, 2014/15/B/ST2/03998, and 2015/19/B/ST2/02861, Sonata-bis 2012/07/E/ST2/01406; the Na-tional Priorities Research Program by Qatar National Research Fund; the Programa Severo Ochoa del Principado de Asturias; the Thalis and Aristeia programmes cofinanced by EU-ESF and the Greek NSRF; the Rachadapisek Sompot Fund for Postdoctoral Fellowship, ChulalongkornUniversity andthe Chulalongkorn Aca-demic into Its 2nd Century Project Advancement Project (Thai-land); the Welch Foundation, contract C-1845; and the Weston HavensFoundation(USA).

Appendix A. Glauber model values

Centralityvariables computed usinga Glauber model [44] are summarizedin Tables 1 and2,where dmin is the minimum dis-tanceallowedbetweennucleonsand σinel

NN istheinelasticnucleon– nucleon(NN)crosssection [36].

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The CMS Collaboration

A.M. Sirunyan,A. Tumasyan

YerevanPhysicsInstitute,Yerevan,Armenia

W. Adam, F. Ambrogi, E. Asilar,T. Bergauer, J. Brandstetter, E. Brondolin,M. Dragicevic, J. Erö,

A. Escalante Del Valle,M. Flechl, M. Friedl,R. Frühwirth1, V.M. Ghete, J. Grossmann,J. Hrubec,

M. Jeitler1, A. König, N. Krammer,I. Krätschmer, D. Liko,T. Madlener, I. Mikulec,E. Pree, N. Rad,

H. Rohringer, J. Schieck1, R. Schöfbeck, M. Spanring, D. Spitzbart,A. Taurok, W. Waltenberger,

J. Wittmann, C.-E. Wulz1,M. Zarucki

InstitutfürHochenergiephysik,Wien,Austria

V. Chekhovsky, V. Mossolov,J. Suarez Gonzalez

InstituteforNuclearProblems,Minsk,Belarus

E.A. De Wolf,D. Di Croce, X. Janssen, J. Lauwers,M. Van De Klundert, H. Van Haevermaet,

P. Van Mechelen, N. Van Remortel

UniversiteitAntwerpen,Antwerpen,Belgium

S. Abu Zeid,F. Blekman, J. D’Hondt, I. De Bruyn, J. De Clercq, K. Deroover, G. Flouris, D. Lontkovskyi,

S. Lowette,I. Marchesini, S. Moortgat, L. Moreels,Q. Python, K. Skovpen, S. Tavernier, W. Van Doninck,

P. Van Mulders, I. Van Parijs

VrijeUniversiteitBrussel,Brussel,Belgium

D. Beghin,B. Bilin, H. Brun, B. Clerbaux, G. De Lentdecker, H. Delannoy, B. Dorney,G. Fasanella, L. Favart,

R. Goldouzian, A. Grebenyuk,A.K. Kalsi, T. Lenzi,J. Luetic, T. Maerschalk,T. Seva, E. Starling,

C. Vander Velde, P. Vanlaer, D. Vannerom,R. Yonamine, F. Zenoni

UniversitéLibredeBruxelles,Bruxelles,Belgium

T. Cornelis,D. Dobur, A. Fagot,M. Gul, I. Khvastunov2, D. Poyraz, C. Roskas, S. Salva,D. Trocino,

M. Tytgat, W. Verbeke,M. Vit, N. Zaganidis

GhentUniversity,Ghent,Belgium

H. Bakhshiansohi,O. Bondu, S. Brochet,G. Bruno, C. Caputo, A. Caudron, P. David, S. De Visscher,

C. Delaere, M. Delcourt, B. Francois,A. Giammanco, G. Krintiras,V. Lemaitre, A. Magitteri, A. Mertens,

M. Musich, K. Piotrzkowski,L. Quertenmont, A. Saggio, M. Vidal Marono, S. Wertz,J. Zobec

UniversitéCatholiquedeLouvain,Louvain-la-Neuve,Belgium

W.L. Aldá Júnior, F.L. Alves,G.A. Alves, L. Brito,G. Correia Silva, C. Hensel,A. Moraes,M.E. Pol,

P. Rebello Teles

CentroBrasileirodePesquisasFisicas,RiodeJaneiro,Brazil

E. Belchior Batista Das Chagas, W. Carvalho,J. Chinellato3,E. Coelho, E.M. Da Costa, G.G. Da Silveira4,

D. De Jesus Damiao,S. Fonseca De Souza, L.M. Huertas Guativa, H. Malbouisson,M. Melo De Almeida,

C. Mora Herrera,L. Mundim, H. Nogima,L.J. Sanchez Rosas, A. Santoro,A. Sznajder, M. Thiel,

E.J. Tonelli Manganote3,F. Torres Da Silva De Araujo, A. Vilela Pereira

UniversidadedoEstadodoRiodeJaneiro,RiodeJaneiro,Brazil

S. Ahujaa, C.A. Bernardesa, T.R. Fernandez Perez Tomeia, E.M. Gregoresb,P.G. Mercadanteb,

S.F. Novaesa, Sandra S. Padulaa, Romero Abadb,J.C. Ruiz Vargasb

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

A. Aleksandrov, R. Hadjiiska,P. Iaydjiev, A. Marinov, M. Misheva, M. Rodozov,M. Shopova, G. Sultanov

InstituteforNuclearResearchandNuclearEnergy,BulgarianAcademyofSciences,Sofia,Bulgaria

A. Dimitrov,L. Litov, B. Pavlov,P. Petkov

UniversityofSofia,Sofia,Bulgaria

W. Fang5, X. Gao5,L. Yuan

BeihangUniversity,Beijing,China

M. Ahmad, J.G. Bian, G.M. Chen,H.S. Chen, M. Chen, Y. Chen, C.H. Jiang, D. Leggat,H. Liao, Z. Liu,

F. Romeo,S.M. Shaheen, A. Spiezia,J. Tao, C. Wang, Z. Wang, E. Yazgan, H. Zhang,J. Zhao

InstituteofHighEnergyPhysics,Beijing,China

Y. Ban, G. Chen, J. Li,Q. Li, S. Liu, Y. Mao,S.J. Qian, D. Wang,Z. Xu, F. Zhang5

StateKeyLaboratoryofNuclearPhysicsandTechnology,PekingUniversity,Beijing,China

Y. Wang

TsinghuaUniversity,Beijing,China

C. Avila,A. Cabrera, C.A. Carrillo Montoya, L.F. Chaparro Sierra, C. Florez,C.F. González Hernández,

J.D. Ruiz Alvarez,M.A. Segura Delgado

UniversidaddeLosAndes,Bogota,Colombia

B. Courbon,N. Godinovic, D. Lelas,I. Puljak, P.M. Ribeiro Cipriano, T. Sculac

UniversityofSplit,FacultyofElectricalEngineering,MechanicalEngineeringandNavalArchitecture,Split,Croatia

Z. Antunovic,M. Kovac

UniversityofSplit,FacultyofScience,Split,Croatia

V. Brigljevic,D. Ferencek, K. Kadija,B. Mesic, A. Starodumov6, T. Susa

InstituteRudjerBoskovic,Zagreb,Croatia

M.W. Ather,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,CzechRepublic

E. Carrera Jarrin

UniversidadSanFranciscodeQuito,Quito,Ecuador

M.A. Mahmoud8,9,Y. Mohammed8,E. Salama9,10

AcademyofScientificResearchandTechnologyoftheArabRepublicofEgypt,EgyptianNetworkofHighEnergyPhysics,Cairo,Egypt

S. Bhowmik, R.K. Dewanjee,M. Kadastik, L. Perrini, M. Raidal, C. Veelken

NationalInstituteofChemicalPhysicsandBiophysics,Tallinn,Estonia

P. Eerola,H. Kirschenmann, J. Pekkanen,M. Voutilainen

J. Havukainen, J.K. Heikkilä, T. Järvinen,V. Karimäki, R. Kinnunen, T. Lampén, K. Lassila-Perini,S. Laurila,

S. Lehti, T. Lindén,P. Luukka, T. Mäenpää, H. Siikonen,E. Tuominen, J. Tuominiemi

HelsinkiInstituteofPhysics,Helsinki,Finland

T. Tuuva

LappeenrantaUniversityofTechnology,Lappeenranta,Finland

M. Besancon, F. Couderc,M. Dejardin, D. Denegri, J.L. Faure, F. Ferri, S. Ganjour, S. Ghosh, A. Givernaud,

P. Gras, G. Hamel de Monchenault, P. Jarry,C. Leloup,E. Locci, M. Machet, J. Malcles,G. Negro, J. Rander,

A. Rosowsky, M.Ö. Sahin,M. Titov

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

A. Abdulsalam11,C. Amendola, I. Antropov, S. Baffioni, F. Beaudette, P. Busson, L. Cadamuro,C. Charlot,

R. Granier de Cassagnac, M. Jo,I. Kucher, S. Lisniak, A. Lobanov, J. Martin Blanco, M. Nguyen,

C. Ochando, G. Ortona,P. Paganini, P. Pigard, R. Salerno,J.B. Sauvan, Y. Sirois, A.G. Stahl Leiton,

T. Strebler, Y. Yilmaz, A. Zabi,A. Zghiche

LaboratoireLeprince-Ringuet,Ecolepolytechnique,CNRS/IN2P3,UniversitéParis-Saclay,Palaiseau,France

J.-L. Agram12, J. Andrea, D. Bloch,J.-M. Brom, M. Buttignol,E.C. Chabert, C. Collard,E. Conte12,

X. Coubez, F. Drouhin12, J.-C. Fontaine12,D. Gelé, U. Goerlach,M. Jansová, P. Juillot,A.-C. Le Bihan,

N. Tonon, P. Van Hove

UniversitédeStrasbourg,CNRS,IPHCUMR7178,F-67000Strasbourg,France

S. Gadrat

CentredeCalculdel’InstitutNationaldePhysiqueNucleaireetdePhysiquedesParticules,CNRS/IN2P3,Villeurbanne,France

S. Beauceron,C. Bernet, G. Boudoul, N. Chanon, R. Chierici,D. Contardo, P. Depasse, H. El Mamouni,

J. Fay, L. Finco, S. Gascon,M. Gouzevitch, G. Grenier, B. Ille, F. Lagarde, I.B. Laktineh, M. Lethuillier,

L. Mirabito,A.L. Pequegnot, S. Perries, A. Popov13, V. Sordini,M. Vander Donckt, S. Viret,S. Zhang

UniversitédeLyon,UniversitéClaudeBernardLyon1,CNRS-IN2P3,InstitutdePhysiqueNucléairedeLyon,Villeurbanne,France

T. Toriashvili14

GeorgianTechnicalUniversity,Tbilisi,Georgia

Z. Tsamalaidze7

TbilisiStateUniversity,Tbilisi,Georgia

C. Autermann, L. Feld, M.K. Kiesel, K. Klein, M. Lipinski, M. Preuten,C. Schomakers, J. Schulz,

M. Teroerde,B. Wittmer, V. Zhukov13

RWTHAachenUniversity,I.PhysikalischesInstitut,Aachen,Germany

A. Albert, D. Duchardt, M. Endres,M. Erdmann, S. Erdweg, T. Esch, R. Fischer,A. Güth, T. Hebbeker,

C. Heidemann,K. Hoepfner, S. Knutzen,M. Merschmeyer,A. Meyer, P. Millet, S. Mukherjee,T. Pook,

M. Radziej, H. Reithler,M. Rieger, F. Scheuch,D. Teyssier, S. Thüer

RWTHAachenUniversity,III.PhysikalischesInstitutA,Aachen,Germany

G. Flügge, B. Kargoll, T. Kress, A. Künsken, T. Müller,A. Nehrkorn, A. Nowack, C. Pistone,O. Pooth,

A. Stahl15

M. Aldaya Martin,T. Arndt, C. Asawatangtrakuldee, K. Beernaert,O. Behnke, U. Behrens,

A. Bermúdez Martínez, A.A. Bin Anuar, K. Borras16,V. Botta, A. Campbell,P. Connor,

C. Contreras-Campana, F. Costanza, C. Diez Pardos,G. Eckerlin, D. Eckstein, T. Eichhorn, E. Eren,

E. Gallo17, J. Garay Garcia, A. Geiser, J.M. Grados Luyando, A. Grohsjean, P. Gunnellini, M. Guthoff,

A. Harb,J. Hauk, M. Hempel18, H. Jung,M. Kasemann, J. Keaveney, C. Kleinwort,I. Korol, D. Krücker,

W. Lange,A. Lelek, T. Lenz, K. Lipka,W. Lohmann18, R. Mankel, I.-A. Melzer-Pellmann, A.B. Meyer,

M. Missiroli, G. Mittag, J. Mnich, A. Mussgiller, D. Pitzl,A. Raspereza, M. Savitskyi,P. Saxena,

R. Shevchenko,N. Stefaniuk, G.P. Van Onsem,R. Walsh, Y. Wen,K. Wichmann, C. Wissing, O. Zenaiev

DeutschesElektronen-Synchrotron,Hamburg,Germany

R. Aggleton,S. Bein, V. Blobel, M. Centis Vignali, T. Dreyer,E. Garutti, D. Gonzalez, J. Haller,

A. Hinzmann, M. Hoffmann,A. Karavdina, G. Kasieczka, R. Klanner, R. Kogler,N. Kovalchuk, S. Kurz,

D. Marconi,M. Meyer, M. Niedziela, D. Nowatschin, F. Pantaleo15,T. Peiffer, A. Perieanu, C. Scharf,

P. Schleper, A. Schmidt, S. Schumann,J. Schwandt,J. Sonneveld, H. Stadie,G. Steinbrück, F.M. Stober,

M. Stöver,H. Tholen, D. Troendle, E. Usai, A. Vanhoefer, B. Vormwald

UniversityofHamburg,Hamburg,Germany

M. Akbiyik, C. Barth,M. Baselga,S. Baur, E. Butz, R. Caspart, T. Chwalek, F. Colombo, W. De Boer,

A. Dierlamm,N. Faltermann, B. Freund,R. Friese, M. Giffels,M.A. Harrendorf,F. Hartmann15,

S.M. Heindl,U. Husemann, F. Kassel15, S. Kudella, H. Mildner, M.U. Mozer,Th. Müller, M. Plagge,

G. Quast, K. Rabbertz,M. Schröder, I. Shvetsov,G. Sieber, H.J. Simonis, R. Ulrich, S. Wayand,M. Weber,

T. Weiler, S. Williamson,C. Wöhrmann, R. Wolf

KarlsruherInstitutfuerTechnologieGermany

G. Anagnostou,G. Daskalakis, T. Geralis,A. Kyriakis, D. Loukas,I. Topsis-Giotis

InstituteofNuclearandParticlePhysics(INPP),NCSRDemokritos,AghiaParaskevi,Greece

G. Karathanasis,S. Kesisoglou, A. Panagiotou, N. Saoulidou, E. Tziaferi

NationalandKapodistrianUniversityofAthens,Athens,Greece

K. Kousouris

NationalTechnicalUniversityofAthens,Athens,Greece

I. Evangelou,C. Foudas, P. Gianneios, P. Katsoulis, P. Kokkas, S. Mallios,N. Manthos, I. Papadopoulos,

E. Paradas, J. Strologas,F.A. Triantis, D. Tsitsonis

UniversityofIoánnina,Ioánnina,Greece

M. Csanad,N. Filipovic, G. Pasztor,O. Surányi, G.I. Veres19

MTA-ELTELendületCMSParticleandNuclearPhysicsGroup,EötvösLorándUniversity,Budapest,Hungary

G. Bencze,C. Hajdu, D. Horvath20, Á. Hunyadi, F. Sikler,V. Veszpremi, G. Vesztergombi19

WignerResearchCentreforPhysics,Budapest,Hungary

N. Beni,S. Czellar, J. Karancsi21,A. Makovec,J. Molnar, Z. Szillasi

InstituteofNuclearResearchATOMKI,Debrecen,Hungary

M. Bartók19,P. Raics, Z.L. Trocsanyi, B. Ujvari

InstituteofPhysics,UniversityofDebrecen,Debrecen,Hungary

S. Choudhury,J.R. Komaragiri

S. Bahinipati22, P. Mal, K. Mandal, A. Nayak23, D.K. Sahoo22, N. Sahoo, S.K. Swain

NationalInstituteofScienceEducationandResearch,HBNI,Bhubaneswar,India

S. Bansal, S.B. Beri,V. Bhatnagar, R. Chawla, N. Dhingra, A. Kaur, M. Kaur, S. Kaur,R. Kumar, P. Kumari,

A. Mehta,J.B. Singh, G. Walia

PanjabUniversity,Chandigarh,India

A. Bhardwaj,S. Chauhan, B.C. Choudhary, R.B. Garg,S. Keshri,A. Kumar, Ashok Kumar, S. Malhotra,

M. Naimuddin,K. Ranjan, Aashaq Shah, R. Sharma

UniversityofDelhi,Delhi,India

R. Bhardwaj24,R. Bhattacharya,S. Bhattacharya, U. Bhawandeep24,D. Bhowmik, S. Dey, S. Dutt24,

S. Dutta, S. Ghosh, N. Majumdar, A. Modak, K. Mondal, S. Mukhopadhyay, S. Nandan, A. Purohit,

P.K. Rout,A. Roy, S. Roy Chowdhury, S. Sarkar,M. Sharan, B. Singh, S. Thakur24

SahaInstituteofNuclearPhysics,HBNI,Kolkata,India

P.K. Behera

IndianInstituteofTechnologyMadras,Madras,India

R. Chudasama, D. Dutta, V. Jha,V. Kumar, A.K. Mohanty15,P.K. Netrakanti,L.M. Pant, P. Shukla,A. Topkar

BhabhaAtomicResearchCentre,Mumbai,India

T. Aziz, S. Dugad,B. Mahakud, S. Mitra, G.B. Mohanty, N. Sur, B. Sutar

TataInstituteofFundamentalResearch-A,Mumbai,India

S. Banerjee, S. Bhattacharya, S. Chatterjee,P. Das, 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, S. Pandey, A. Rane, S. Sharma

IndianInstituteofScienceEducationandResearch(IISER),Pune,India

S. Chenarani27, E. Eskandari Tadavani,S.M. Etesami27,M. Khakzad, M. Mohammadi Najafabadi,

M. Naseri, S. Paktinat Mehdiabadi28,F. Rezaei Hosseinabadi, B. Safarzadeh29,M. Zeinali

InstituteforResearchinFundamentalSciences(IPM),Tehran,Iran

M. Felcini,M. Grunewald

UniversityCollegeDublin,Dublin,Ireland

M. Abbresciaa,b_{, C. Calabria}a,b_{,A. Colaleo}a_{,D. Creanza}a,c_{, L. Cristella}a,b_{,N. De Filippis}a,c_,

M. De Palmaa,b, F. Erricoa,b, L. Fiorea, G. Iasellia,c, S. Lezkia,b, G. Maggia,c,M. Maggia, B. Marangellia,b, G. Minielloa,b,S. Mya,b,S. Nuzzoa,b,A. Pompilia,b,G. Pugliesea,c, R. Radognaa,A. Ranieria,

G. Selvaggia,b, A. Sharmaa,L. Silvestrisa,15, R. Vendittia,P. Verwilligena,G. Zitoa

a_{INFNSezionediBari,Bari,Italy} b_{UniversitàdiBari,Bari,Italy} c_{PolitecnicodiBari,Bari,Italy}

G. Abbiendia,C. Battilanaa,b,D. Bonacorsia,b,L. Borgonovia,b,S. Braibant-Giacomellia,b, R. Campaninia,b, P. Capiluppia,b,A. Castroa,b,F.R. Cavalloa, S.S. Chhibraa,b, G. Codispotia,b,

L. Guiduccia,b,F. Iemmi,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

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

S. Albergoa,b_{, S. Costa}a,b_{, A. Di Mattia}a_{,F. Giordano}a,b_{, R. Potenza}a,b_{,A. Tricomi}a,b_{, C. Tuve}a,b

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

G. Barbaglia,K. Chatterjeea,b,V. Ciullia,b,C. Civininia,R. D’Alessandroa,b, E. Focardia,b, G. Latino, P. Lenzia,b, M. Meschinia, S. Paolettia,L. Russoa,30, G. Sguazzonia,D. Stroma,L. Viliania

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

L. Benussi,S. Bianco, F. Fabbri, D. Piccolo,F. Primavera15

INFNLaboratoriNazionalidiFrascati,Frascati,Italy

V. Calvellia,b, F. Ferroa, F. Raveraa,b, E. Robuttia,S. Tosia,b

a_{INFNSezionediGenova,Genova,Italy} b_{UniversitàdiGenova,Genova,Italy}

A. Benagliaa,A. Beschib,L. Brianzaa,b,F. Brivioa,b,V. Cirioloa,b,15, M.E. Dinardoa,b,S. Fiorendia,b, S. Gennaia,A. Ghezzia,b,P. Govonia,b,M. Malbertia,b,S. Malvezzia,R.A. Manzonia,b,D. Menascea, L. Moronia, M. Paganonia,b,K. Pauwelsa,b, D. Pedrinia,S. Pigazzinia,b,31,S. Ragazzia,b,

T. Tabarelli de Fatisa,b

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

S. Buontempoa, N. Cavalloa,c,S. Di Guidaa,d,15, F. Fabozzia,c,F. Fiengaa,b, A.O.M. Iorioa,b,W.A. Khana, L. Listaa,S. Meolaa,d,15,P. Paoluccia,15,C. Sciaccaa,b,F. Thyssena

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

P. Azzia, N. Bacchettaa, L. Benatoa,b,D. Biselloa,b,A. Bolettia,b,A. Carvalho Antunes De Oliveiraa,b, M. Dall’Ossoa,b, P. De Castro Manzanoa,T. Dorigoa,U. Dossellia, F. Gasparinia,b, U. Gasparinia,b,

A. Gozzelinoa,S. Lacapraraa, P. Lujan,M. Margonia,b, A.T. Meneguzzoa,b,N. Pozzobona,b,P. Ronchesea,b, R. Rossina,b, F. Simonettoa,b,A. Tiko, E. Torassaa,S. Venturaa, M. Zanettia,b,P. Zottoa,b,G. Zumerlea,b

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

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

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

L. Alunni Solestizia,b, M. Biasinia,b, G.M. Bileia,C. Cecchia,b,D. Ciangottinia,b, L. Fanòa,b,P. Laricciaa,b, R. Leonardia,b,E. Manonia, G. Mantovania,b,V. Mariania,b, M. Menichellia,A. Rossia,b, A. Santocchiaa,b,

D. Spigaa

a_{INFNSezionediPerugia,Perugia,Italy} b_{UniversitàdiPerugia,Perugia,Italy}

K. Androsova,P. Azzurria,15,G. Bagliesia,L. Bianchinia,T. Boccalia, L. Borrello, R. Castaldia, M.A. Cioccia,b, R. Dell’Orsoa,G. Fedia, L. Gianninia,c, A. Giassia, M.T. Grippoa,30,F. Ligabuea,c, T. Lomtadzea, E. Mancaa,c,G. Mandorlia,c,A. Messineoa,b,F. Pallaa, A. Rizzia,b, 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. Cavallari}a_{, M. Cipriani}a,b_{,N. Daci}a_{, D. Del Re}a,b_{,E. Di Marco}a,b_{,M. Diemoz}a_{, S. Gelli}a,b_,

E. Longoa,b, F. Margarolia,b,B. Marzocchia,b, P. Meridiania,G. Organtinia,b,R. Paramattia,b,F. Preiatoa,b, S. Rahatloua,b,C. Rovellia,F. Santanastasioa,b

a_{INFNSezionediRoma,Rome,Italy} b_{SapienzaUniversitàdiRoma,Rome,Italy}

N. Amapanea,b, R. Arcidiaconoa,c,S. Argiroa,b,M. Arneodoa,c,N. Bartosika,R. Bellana,b, C. Biinoa, N. Cartigliaa, R. Castelloa,b, F. Cennaa,b,M. Costaa,b,R. Covarellia,b, A. Deganoa,b,N. Demariaa, B. Kiania,b,C. Mariottia,S. Masellia,E. Migliorea,b,V. Monacoa,b,E. Monteila,b,M. Montenoa, M.M. Obertinoa,b,L. Pachera,b,N. Pastronea, M. Pelliccionia, G.L. Pinna Angionia,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,A. Zanettia

a_{INFNSezionediTrieste,Trieste,Italy} b_{UniversitàdiTrieste,Trieste,Italy}

D.H. Kim,G.N. Kim, M.S. Kim,J. Lee, S. Lee,S.W. Lee, C.S. Moon, Y.D. Oh, S. Sekmen,D.C. Son, Y.C. Yang

KyungpookNationalUniversity,SouthKorea

H. Kim,D.H. Moon, G. Oh

ChonnamNationalUniversity,InstituteforUniverseandElementaryParticles,Kwangju,RepublicofKorea

J.A. Brochero Cifuentes, J. Goh,T.J. Kim

HanyangUniversity,Seoul,RepublicofKorea

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

S.K. Park,Y. Roh

KoreaUniversity,Seoul,RepublicofKorea

J. Almond, J. Kim,J.S. Kim, H. Lee,K. Lee, K. Nam,S.B. Oh, B.C. Radburn-Smith, S.h. Seo, U.K. Yang,

H.D. Yoo,G.B. Yu

SeoulNationalUniversity,Seoul,RepublicofKorea

H. Kim,J.H. Kim, J.S.H. Lee, I.C. Park

UniversityofSeoul,Seoul,RepublicofKorea

Y. Choi,C. Hwang, J. Lee, I. Yu

SungkyunkwanUniversity,Suwon,RepublicofKorea

V. Dudenas, A. Juodagalvis,J. Vaitkus

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

NationalCentreforParticlePhysics,UniversitiMalaya,KualaLumpur,Malaysia

M.C. Duran-Osuna, H. Castilla-Valdez,E. De La Cruz-Burelo, G. Ramirez-Sanchez, I. Heredia-De La Cruz34,

R.I. Rabadan-Trejo,R. Lopez-Fernandez, J. Mejia Guisao, R. Reyes-Almanza,A. Sanchez-Hernandez

CentrodeInvestigacionydeEstudiosAvanzadosdelIPN,MexicoCity,Mexico

S. Carrillo Moreno, C. Oropeza Barrera, F. Vazquez Valencia

UniversidadIberoamericana,MexicoCity,Mexico

J. Eysermans,I. Pedraza, H.A. Salazar Ibarguen, C. Uribe Estrada

BenemeritaUniversidadAutonomadePuebla,Puebla,Mexico

A. Morelos Pineda

UniversidadAutónomadeSanLuisPotosí,SanLuisPotosí,Mexico

D. Krofcheck

UniversityofAuckland,Auckland,NewZealand

S. Bheesette,P.H. Butler

UniversityofCanterbury,Christchurch,NewZealand

A. Ahmad, M. Ahmad, Q. Hassan,H.R. Hoorani, A. Saddique, 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, M. Szleper,

P. Zalewski

NationalCentreforNuclearResearch,Swierk,Poland

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

M. Olszewski,A. Pyskir, M. Walczak

InstituteofExperimentalPhysics,FacultyofPhysics,UniversityofWarsaw,Warsaw,Poland

P. Bargassa,C. Beirão Da Cruz E Silva, A. Di Francesco, P. Faccioli,B. Galinhas, M. Gallinaro, J. Hollar,

N. Leonardo,L. Lloret Iglesias, M.V. Nemallapudi, J. Seixas,G. Strong,O. Toldaiev, D. Vadruccio, J. Varela

LaboratóriodeInstrumentaçãoeFísicaExperimentaldePartículas,Lisboa,Portugal

A. Baginyan, A. Golunov, I. Golutvin, V. Karjavin, I. Kashunin,V. Korenkov, G. Kozlov,A. Lanev,

A. Malakhov,V. Matveev36,37_{,P. Moisenz, V. Palichik,V. Perelygin, S. Shmatov, N. Skatchkov, V. Smirnov,}

V. Trofimov, B.S. Yuldashev38,A. Zarubin

JointInstituteforNuclearResearch,Dubna,Russia

Y. Ivanov,V. Kim39,E. Kuznetsova40, P. Levchenko,V. Murzin, V. Oreshkin, I. Smirnov, D. Sosnov,

V. Sulimov,L. Uvarov, S. Vavilov, 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