Study of Z boson production in pPb collisions at root S-NN=5.02 TeV

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Physics

Letters

B

www.elsevier.com/locate/physletb

Study

of

Z

boson

production

in

pPb

collisions

at

√

s

=

5

.

02

TeV

.CMSCollaboration CERN,Switzerland

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

Articlehistory:

Received21December2015

Receivedinrevisedform24March2016 Accepted16May2016

Availableonline18May2016 Editor:M.Doser

Keywords:

CMS Physics Heavyions

TheproductionofZbosonsinpPbcollisionsat√sNN=5.02 TeV isstudiedbytheCMSexperimentvia

theelectronandmuondecaychannels.Theinclusivecrosssectioniscomparedtoppcollisionpredictions, and foundto scale with the number ofelementarynucleon–nucleon collisions.The differential cross sectionsasafunctionoftheZ bosonrapidityandtransversemomentumaremeasured.Thoughtheyare found tobeconsistentwithinuncertainty withtheoretical predictionsbothwithand withoutnuclear effects, the forward–backwardasymmetry suggeststhe presence ofnuclear effects atlarge rapidities. Theseresultsprovidenewdataforconstrainingnuclearpartondistributionfunctions.

©2016TheAuthor.PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBYlicense (http://creativecommons.org/licenses/by/4.0/).FundedbySCOAP3_.

1. Introduction

Electroweakbosonproductionisanimportantbenchmark pro-cessin high-energy particle physics. The production of Zand W bosonshasbeenextensivelystudiedathadronande+e−colliders, atvariouscollisionenergies.Thelatestmeasurements inpp colli-sions attheLHC [1–8]are well described bythe standard model using higher-order perturbative quantum chromodynamics (QCD) andpartondistributionfunctions(PDFs).

Withits large center-of-massenergy andhighluminosity,the LHCenablesforthefirsttimethestudyofZandW boson produc-tion in heavy ion collisions. Electroweak bosons are unmodified by the hot and dense medium created in nucleus–nucleus col-lisions, and their leptonic decays are of particular interest since leptons pass through the medium withoutbeing affected by the stronginteraction.BoththeZandW bosonproductionwere mea-suredbytheATLAS[9,10]andtheCMS[11,12]experimentsusing PbPb collisions taken in 2010 and 2011 at a center-of-mass en-ergy per nucleon pair of √sNN=2.76 TeV, confirming that the production cross section scales with the number of elementary nucleon–nucleoncollisionswithaprecisionofabout10%.

However, in nuclear collisions, the production of electroweak bosonscanbeaffectedbytheinitialconditionsofthecollision.The free-proton PDFsare expected to be modified forprotons bound inthePbnucleus, which,together withthefact thatthe nucleus contains neutrons as well asprotons (isospin effect), can modify theobservedcross sectionsascompared topp collisions.Various groupshavestudiedthenuclearmodificationofPDFs,andseveral

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

results are available at next-to-leading-order (NLO) precision in QCD[13–15].Theseresultsareobtainedbyglobalfitstothe avail-abledeepinelasticscatteringandDrell–Yandata,whichconstrain thenuclearPDFs(nPDFs)intheregionofpartonlongitudinal mo-mentum fractionx>10−2 _{andfour-momentum transfer squared} Q2< (10 GeV)2.

The productionofelectroweakbosonsinproton–nucleus colli-sions atthe LHC provides an opportunity to studythe nPDFs at the high Q2_{≈ (100 GeV)}2 _{andlower x phasespace region [16].} The CMS experiment made the first measurement of W boson productioninpPbcollisions [17].Deviations fromthe current ex-pectationsforPDFswereobserved,showingtheneedforincluding W boson datainnPDFglobalfits. Furthermore,thedijet pseudo-rapidity distribution measured inpPbcollisions by CMS[18] and theZ bosonproductioninpPbcollisionsmeasured byATLAS[19] show better agreement with modified PDFs. Deviations frompp expectationswerealsoseenwithchargedhadrons[20].

Various models predict different nuclear modifications of the Z boson productioncross section (σ) asa function of transverse momentum (pT) and rapidity in the nucleon–nucleon center-of-massframe( ycm)[21–25].Processesmediatedbyavirtualphoton andinterferenceeffectsarealsoconsideredaspartoftheZ boson signal.TherapiditydistributionofZbosonsisparticularlysensitive to the parton content of the interacting nucleons. Consequently, thesymmetricrapidityspectrumoftheZbosonsinthe center-of-mass frameofpp collisions ismodified by nucleareffects inpPb collisions [24]. This can be quantified through measurements of theforward–backwardasymmetryinthecenter-of-massframe:

RFB(ycm)=

dσ(+ycm)/d ycm

dσ(−ycm)/d ycm

, (1)

http://dx.doi.org/10.1016/j.physletb.2016.05.044

0370-2693/©2016TheAuthor.PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBYlicense(http://creativecommons.org/licenses/by/4.0/).Fundedby SCOAP3_.

wherebyconventionpositiverapidityvaluescorrespondtothe di-rectionoftheincomingproton.

The aimof thispaper is to studythe Z→  process (where

represents eithermuonsorelectrons) andtomeasure the pro-ductioncross sectionasfunctionsof rapidity andtransverse mo-mentum.The typicalquark momentumfractionprobed inthePb nucleus is given by x=MZ/√sNNe−ycm, and thus with 0.002< x<0.3 in the measured rangeof −2.8<ycm<2.0. These mea-surementswillhelptoconstrainthepartoncontentofthe nucle-onsinthenucleus.

2. Experimental setup, data selection and reconstruction

Adetailed descriptionof the CMSdetector andits coordinate systemcan be found elsewhere [26]. Its central feature is a su-perconducting solenoid with internal diameter of 6 m, provid-ing a magnetic field of 3.8 T. Within the solenoid volume are a silicon pixel andstrip tracker,a lead tungstate crystal electro-magnetic calorimeter(ECAL), anda brass andscintillator hadron calorimeter (HCAL). Muons are detected in the pseudorapidity range|ηlab|<2.4 using gas-ionizationdetectorsembedded inthe steelreturnyokeoutsidethe solenoid. Electronsare measuredin theECALthatconsistsof75 848leadtungstatecrystalsprovidinga coverageinthebarrelregion of|ηlab|<1.48 andinthetwo end-capregions of1.48<|ηlab|<3.00.Extensive forwardcalorimetry complements the coverage provided by these barrel andendcap detectors.CMShasatwo-leveltriggersystem.Thefirstlevel, com-posedofcustom hardware processors, uses informationfromthe calorimeters and muon detectors to select the most interesting events.Thehigh-leveltriggerprocessorfarmfurtherdecreasesthe eventratebeforedatastorage.

TheanalysisisperformedusingthepPbcollisiondatatakenat the beginning of2013 andcorresponding to an integrated lumi-nosity of 34.6±1.2 nb−1 [27]. The beam energies were 4 TeV for protons and 1.58 TeV per nucleon for lead nuclei, resulting ina center-of-massenergy pernucleon pairof √sNN=5.02 TeV. As aconsequence ofthe energy differencebetween thecolliding beams, the nucleon–nucleon center-of-mass frame is not at rest withrespecttothelaboratoryframe.Masslessparticlesemittedat rapidityycm=0 inthenucleon–nucleoncenter-of-massframewill bedetected at ylab= −0.465 (clockwiseprotonbeam)or+0.465 (counterclockwise proton beam)in the laboratory frame. The re-sults presented here are expressed in the center-of-mass frame withtheproton-goingsidedefiningtheregionofpositiveycm val-ues,to respectthe usual convention ofthe protonfragmentation regionbeingprobedatpositiverapidity.Thedirectionofthehigher energyprotonbeamwasinitiallyclockwiseandwasthenreversed, producingtwocomparabledatasets.

Duringdatataking,muonandelectrontriggerswereemployed toselectandrecordalleventswithhigh-pT leptons.The measure-ments in the muon final state are based on a sample obtained by requiring at least one muon with pT greater than 12 GeV/c. The muon candidates are reconstructed with an algorithm that combinesinformationfromboththesilicontrackerandthemuon system[28].Backgroundmuonsfromcosmicraysandheavy-quark semileptonicdecaysarerejectedbyapplyingasetofquality crite-riatoeachmuon,basedonpreviousstudiesoftheperformanceof themuonreconstruction[28].Themuonsareselectedbyrequiring atleasttwomuonstationstobematchedtothemuontrack,a low

χ2_{/ndf oftheglobalfit,aminimumnumberoftrackerlayersand} pixelhits,andfinally,amaximumdistancefromtheprimary ver-texinthetransverseandlongitudinaldirection.

Theelectronmeasurementsarebasedonacandidatephotonor electronsamplecollectedbyrequiringatleastoneECALtransverse energy deposit of ET>15 GeV and online identification criteria

thatarelooserthantheelectronselectionappliedoffline.Electrons arereconstructedbymatchingECALclusterstotracksmeasuredin thesilicontracker.Thismatchingisusedtodifferentiateelectrons fromphotons[29].Theidentificationcriteriaarechosen tomatch thoseusedforppcollisions[30].Theelectronsareselectedby re-quiring a match between the η and φ coordinates of the track and the ECAL cluster, a narrow width of the ECAL cluster in η, a low HCAL energy measured in the ECAL cluster direction and byrejecting electronswithapartnertrackconsistentwitha pho-tonconversion.Inthismeasurement,noisolationrequirementsare imposedontheleptons.

3. Analysis procedure

The Z boson production cross section is calculated using the followingequation:

σ= S−B α Lint

, (2)

where S is thenumberofZcandidates, B is theestimated back-ground, α is theacceptance, is theefficiency,including correc-tionfactorsderivedfromdata,andLint istheintegrated luminos-ity. The phase spaceregion considered in the analysisis defined byrequiringtwoleptons withp_T>20 GeV/c andwith pseudora-pidity inthelaboratoryframe |η

lab|<2.4 in ordertoensurethat thetriggersaremaximallyefficientandarewithinthegeometrical coverage of themuon detectors. This fiducialregion ofthe mea-surementisextrapolatedtothefull phasespaceover p

T and ηlab by the acceptance correction. Each component of Eq. (2)is pre-sentedandsystematicuncertaintiessummarizedbelow.

3.1. Signalandbackground

The Z candidate events are selected by requiring a same-flavor,oppositely-chargedleptonpairwithaninvariantmassinthe 60–120 GeV/c2 _{range,where both leptons satisfy the acceptance} and quality requirements and at least one of them corresponds to the lepton that triggered the event. Fig. 1 shows the invari-ant massdistribution ofthe selected lepton pairs comparedto a combinationof pythia 6and hijing (pythia 6+hijing)MonteCarlo (MC) simulations. The pN→Z→  process is simulated using the pythia 6 [31] generator (version 6.424, tune Z2[32]) witha mixtureofppandpninteractionscorrespondingtopPbcollisions. Each pythia 6signal event isembedded in aminimum bias pPb backgroundeventwhichisproducedwiththe hijing event gener-ator version 1.383 [33].The detectorresponse foreach produced eventis simulated with Geant4[34].The signal and background events havethe same generated vertexlocation andare boosted to have the correctrapidity distribution in thelaboratory frame. Theembedding isdone atthelevelofdetectorhitsandthen the eventsareprocessedthroughthetriggeremulation andtheevent reconstructionchains.Thereconstructedlongitudinalprimary ver-texandoverallmultiplicity distributions arereweighted tomatch thoseobservedindata.

An electron energyscale correction is extractedby fitting the energy to momentum ratio of electrons in a very pure W→eν

controlsample[29].Afterfixingtheshapeofthedistributionfrom MC,theenergytomomentum ratioindataisfittedtoderivethe differenceoftheenergyscalebetweendataandMC,andthenthe data is corrected forthis difference. A correction of theelectron energyresolutionisappliedtoMC bycomparing themass distri-butionofelectronpairsbetweendataandMC.Suchcorrectionsare alsoestimatedfortheZ→μ+μ− channelandfoundtobe negli-gible.

Fig. 1. Invariantmassofselectedmuon(top)andelectron(bottom)pairscompared to pythia 6+hijing simulatedpN→Z→ eventswithN= (p, n)accordingtothe numberofnucleonsinthePbnucleus.TheMCsampleisnormalizedtothenumber ofeventsinthedata.

The rawyield, S, ofZ bosoncandidates in the pPbsample is determinedby countingthenumberofoppositely-chargedlepton pairs in the 60–120 GeV/c2 mass region that fulfill the accep-tanceandquality requirements.Thisnumberis foundtobe2183 inthe muon channel and 1571in the electron channel. The dif-ference betweenthetwo channelsis dueto thetighter selection criteria applied to the electrons in order to suppressthe higher background.Acharge misidentificationcorrectionof1%isapplied tothe dielectronyields;thiscorrection isnegligiblefordimuons. No eventsare found withmore than oneZ boson candidate.For the differential cross sections, the measurement is performedin thedileptontransversemomentumorrapiditybins,wherethe ra-pidityiscalculatedinthecenter-of-massframe.

Possible background contributions to the Z→  production are QCD multijetevents,tt pairs andelectroweakprocesses such as W+jets, diboson (WW, WZ, ZZ), and Z→τ τ production. Al-though theexpected backgroundcontamination is small, an esti-matebased ondata isused tosubtract its contributionfromthe dilepton raw yield. For tt, bb, WW, and Z→τ τ processes, two electron–muon events are expected for each dimuon or

dielec-tron event, because of lepton universality. In the Z boson mass range, the oppositely-charged electron–muon pairs are counted and translated into the expected number of muon or electron pairs, taking into account the differences inthe muon and elec-tron reconstruction and selection efficiencies. This background is subtracted fromthedileptonrawyieldandaccountsforthemain electroweak and tt backgrounds, as well as for the part of QCD multijetbackground(suchasbb decays)thatproduces oppositely-charged leptons. The background from random combinations of other leptons in the event is estimated by counting the same-charge pairs. Additional electroweak contributions from W+jets and diboson production are found to be negligible via MC sim-ulations. The fraction of background events subtracted from the raw yield is 2.4% (2.9%) in the muon (electron) channel, where thedominantbackgroundcontributioncomesfromQCDprocesses, sincenoisolationrequirementsareimposedontheleptons.

3.2. Efficiencyandacceptance

The efficiency, ,forZbosonsisdefinedasthenumberof re-constructedZcandidates,wherebothleptonsfulfilltheacceptance and quality requirements, divided by the number of generated Z bosons where bothleptons fulfill theacceptance requirements. Thiscombinedreconstruction,leptonidentification,andtrigger ef-ficiencyiscalculatedfromthe pythia 6+hijing simulationsamples sothattheeffectsofthepPbenvironmentaretakenintoaccount. FortherapidlyfallingdileptonpT spectrum,anunfolding tech-nique basedon theinversion ofa responsematrix similarto the oneusedinRef.[4]isfirstappliedtothedatabeforeapplyingthe efficiencycorrection.Theresponse matrixisconstructedfromthe pythia6+hijing simulationtotakeintoaccountthedetector reso-lution effects.Thedilepton pT resolution isabout0.5–1.5 GeV/c, which resultsina maximumbin-to-bin spill ofabout30% inthe lowest pTbinschosenforthisanalysis.Inthemeasurementofthe dileptonrapidity,theunfoldingisnotnecessaryastheshapeofthe ycm spectrumisalmost flatandtheresolutionisasmallfraction of theanalysisbin size.Instead,the resolutioneffects inrapidity aretakenintoaccountintheefficiencycorrections.

In order to correct for possible differences betweendata and simulation,amethodderivedfromdataisusedtodetermine cor-rection factors to the baseline efficiency from simulation. These correctionfactorsaredeterminedasafunctionoflepton ηandpT byapplyingthetag-and-probe methodtobothdataandsimulation tocalculatesingle leptonefficienciesforreconstruction, identifica-tion, andtriggering,similar tothe methoddescribed inRef. [28]. Theratioofeachefficiencyfromdataoverthecorresponding effi-ciencyinthesimulationisthenappliedtoreweightthesimulation on alepton-by-lepton basis.Theefficiencyforthe Z bosons,after correcting forthesmalldifferencesbetweendataandsimulation, isfoundto be0.878±0.015 inthedimuonand0.605±0.015 in thedielectrondecaychannel.Thesourcesofsystematic uncertain-tiesaredescribedinSection3.3.

Theacceptance, α,isdefinedasthenumberofgenerated dilep-ton eventswherebothleptons fulfilltheacceptancerequirements (p_T>20 GeV/c, |η

lab|<2.4) dividedby thenumberofall gener-ated dileptoneventsin the60–120 GeV/c2 _{massrange.It is} cal-culated using simulatedevents.The eventgeneration is provided by the powheg generator[35–38] withthe CT10freeprotonPDF set [39],interfacedwith pythia 6 partonshower, andthe events areboostedtothelaboratoryframe(powheg+pythia 6).Final-state photonradiationisalsosimulatedby pythia 6. Theintegrated ac-ceptanceisfoundtobe0.516±0.026 inbothdecaychannels.

3.3.Systematicuncertainties

The total systematic uncertainty in the Z boson production cross section is calculated by adding in quadrature the different contributionsfromthebackgroundsubtraction,acceptanceand ef-ficiencydetermination,andtheunfoldingtechnique.Theintegrated luminosity,calibratedby thevander Meerscans [27],hasa sys-tematicuncertaintyof 3.5%.It isthe dominantsystematic uncer-taintyofthemeasurementinthefiducialregion.

Thesignal yieldof Zcandidatesis affectedby theuncertainty inthebackgroundsubtractionmethod.The numberofsubtracted background events determined by the electron–muon method is variedconservativelyby±100%toassignanuncertaintyinthe sig-nalyield.Theuncertaintyinthesignalyieldfromthisbackground variationis1.7%(1.8%)inthemuon(electron)channel.

Theuncertaintyinthecorrectionfactorfortheelectronenergy scale ispropagated asa systematic uncertainty inthe dielectron yield.It is estimatedto be 0.5% inthe inclusive yieldand varies acrossthe analysis pT binsbetween4 and19%.The residual dif-ference in the mass resolution between data and simulation is taken asthe systematic uncertainty in the electron channel. Af-terpropagatingtotheinclusivecrosssection,itaccountsfora1.1% uncertainty.

The systematic uncertainty in the efficiency comes from two differentsources. Thefirst one isthe uncertaintyinthe underly-ingrapidityandtransversemomentumdistributionsreflectingthe poorlyknownPDFs.Thisisestimatedbyapplyingaweighttothe generatedeventsthatvarieslinearlybetween0.7and1.3overthe −3<ycm<3 range, and a weight that varies between 0.9 and 1.1overthe0<pT<150 GeV/c range. Thesevariations coverthe predictednucleareffectstotherapidityandpT spectrumfrom dif-ferentgroups[21,22,24] aswell asthestatisticaluncertainties in thepresentmeasurement andresultina 0.2%uncertainty inthe dilepton efficiency.Second, the statistical uncertaintyin the cor-rectionfactorscomingfromtheratioofdataandsimulationinthe tag-and-probemethodis propagatedto thedileptonefficiency.In addition,thetag-and-probe techniqueitselfcarriesanuncertainty ofabout1%,estimatedfromdifferencesobservedintheefficiencies byvaryingthefunctionalformortherangeofthefits.Finally,the uncertainties in the three different components of the efficiency arecombinedinquadrature,resultinginanoveralluncertaintyin thedimuon(dielectron)efficiencyof1.7%(2.5%).

All the uncertainties above are evaluated in bins of dilepton rapidityandtransversemomentumtogiveuncertaintiesinthe dif-ferentialcrosssections.Thesystematicuncertaintyoftheforward– backward asymmetry is calculated from the rapidity differential crosssection.Theuncertaintiesinthebackground,electronenergy scale,andefficiencyarepropagatedwithoutassumingany cancel-lation.Theuncertaintyoftheluminositycancelsintheratio.

There is an additional uncertainty in the dilepton pT spec-trum coming from the matrix inversion procedure used for the unfolding. This uncertainty is determined by varying the gener-ated dilepton pT distribution and the single lepton pT resolu-tion.The reconstructed pT distributionsfrom pythia 6+hijing and powheg+pythia6,aswellastheweighted p_T spectrumreflecting possiblenPDF differences, are all studied andtheir effecton the resultsis directly evaluated. These two sources give a combined uncertaintyintheunfoldedyieldofabout1–5%,dependingonthe pTbin.

Theuncertainty duetothe acceptancecorrection isestimated bychanging theshape ofthegeneratedrapidity and pT distribu-tions of the Z bosons with the same functionsas described for theefficiencyuncertaintyinordertocoverdifferencesinPDFsand possible nuclear effects. The resulting uncertainty in the accep-tanceisabout5%fromtheextrapolationtothemostforwardand

Table 1

Summaryofsystematicuncertaintiesinthetwodecaychannels.

Source Z→μμ Z→ee

Background 1.7% 1.8%

Electron energy scale – 0.5%

Electron resolution – 1.1%

Efficiency 1.7% 2.5%

Unfolding of pTspectrum 1–5%

Acceptance 5%

Luminosity 3.5%

Total (fiducial cross section) 4.2% 4.8% Total (total cross section) 6.6% 6.9%

backward rapidity regions andit onlyaffects the total cross sec-tion.Table 1 summarizes thesystematicuncertainties in thetwo decaychannels.

4. Results

The resultsare primarilycompared to theNLO pp predictions fromthe powheg+pythia 6generatorusingtheCT10[39]free pro-tonPDF set.ThepN→Z→ processisalsosimulatedwiththe mcfm[40]generator(version6.7)usingtheCT10free protonPDF set,aswellastheEPS09[14]andDSSZ[13]nuclearPDFsets.Since thesepredictionsincludetheoreticaluncertainties,their statistical compatibilitywiththemeasurementscanbetested.Allpredictions arescaledbythenumberofnucleonsinthePbnucleus( A=208) asisexpectedinthecaseofelementarynucleon–nucleoncollision scaling.

The cross section of Z boson production is calculated using Eq.(2)forbothdecaychannels. Theanalysisofthemuonchannel results ina fiducialcross section (p

T>20 GeV/c,|ηlab|<2.4) of 70.1±1.5(stat)±1.7(syst)±2.5(lumi)nb andtheelectron chan-nelgives73.9±1.9(stat)±2.8(syst)±2.6(lumi)nb.

The muon and electron results, which agree within statistical andsystematicuncertainties,arecombined,separatingoutthe un-certainty relatedto theintegratedluminosity.Thebestlinear un-biasedestimate(BLUE)technique[41]isapplied,takingthemuon andelectronchannelcrosssectionsandtheiruncertaintiesineach bintobeuncorrelated.

ThemeasuredinclusiveZbosonproductioncrosssectioninthe fiducialregion, whereboth leptons fulfill the acceptance require-mentsis

σpPb→Z→(pT>20 GeV/c,|ηlab| <2.4)

=71.3±1.2(stat)±1.5(syst)±2.5(lumi)nb. (3)

The powheg+pythia 6 prediction gives a Z boson cross section in pp collisions at √s=5.02 TeV of 338±17 pb for Z→  production in the 60–120 GeV/c2 mass range after applying the acceptancerequirements on theleptons. The uncertainties in the theoretical prediction in pp collisions amount to about 5% and arise frommissing higher-order corrections andfrom the uncer-tainties inthePDF sets.Scaling thepp crosssection by A=208, resultsinthepredictionof70.4±3.5 nb forthepPbcrosssection, whichisconsistentwiththemeasuredvalue.

Fortheacceptance-correctedtotalcrosssection,thesystematic uncertainty inthe acceptance is correlated betweenthe two de-cay channels, which is taken into account in the BLUE method. The combined total Z boson production cross section in the 60–120 GeV/c2massregionis

Fig. 2. DifferentialcrosssectionoftheZbosonsinpPbcollisionsasafunctionof rapidityinthe fiducialregionforthe combinedleptonicdecay channel.Colored boxesarepredictionsfromthe mcfm generator,scaledby208(seetext),andusing nuclear(EPS09andDSSZ)orfree(CT10)PDFsets.Thebottompanelshowstheratio ofthedataandthenPDFpredictionstotheCT10PDFset.Theverticalbars(boxes) representthestatistical(systematic)uncertainties.

This measurement has an uncertainty of about 5% from the ex-trapolationofthedetectoracceptancetothefullphasespace.The powheg+pythia6 generatorafterscaling predicts 136.1±6.8 nb, whichisconsistentwiththemeasuredvalue.

Fig. 2showsthedifferentialcrosssectionoftheZbosonsinthe fiducialregioninpPbcollisionsasafunctionofrapidity.The lumi-nositynormalizationuncertaintyof3.5% isnotshown. The mcfm theoretical predictions, both withand without nuclear modifica-tion, are consistent with the measured differential cross section within uncertainties.The correspondingrapidity dependence pre-dictedby powheg+pythia 6forppcollisionsagreeswiththe mcfm calculation forpN collisions usingthe CT10PDF setwithout nu-clear modification, showing that any dependences on isospin or thePDFsetarewithinthetheoreticaluncertainties.

Nuclear effects are expected to modify the rapidity distribu-tion asymmetrically and thus they can be further quantified by theforward–backwardasymmetrydefinedinEq.(1).Thisquantity is expected to be more sensitive to nuclear effects [24] because normalizationuncertainties cancel both in theory and in experi-ment.Fig. 3showsthemeasuredforward–backwardasymmetryas a function of |ycm| compared to the mcfm predictionswith and withoutnuclearmodification.

While being consistent with the three theoretical predictions shown, the data tend to favor the presence ofnuclear effects in PDFs. The ATLAS collaboration reached similar conclusions from their Z boson measurement [19]. Together with the measured W bosonproduction in pPb collisions [17], theseresults can re-ducethenPDFuncertaintiesby addingnewdatatotheglobalfits inapreviouslyunexploredregionofthe(Q2,x)phasespace.

Inordertoquantifytheagreementbetweenthemeasurements andthepredictions withthedifferentPDF sets,a χ2 _{test is} per-formed for the rapidity-dependent differential cross section and theforward–backwardasymmetry.Thefewcorrelationsinthe ex-perimental uncertainties, only relevant for the cross section but notfortheasymmetry,aretakenintoaccount,aswellasthe cor-relations inthe theoreticaluncertainties. The resulting χ2 _values andprobabilities aregiveninTable 2.The theoretical calculations

Fig. 3. Forward–backwardasymmetryRFBdistributionoftheZbosonsinpPb colli-sionsasafunctionofrapidityinthefiducialregionforthecombinedleptonicdecay channelcomparedtothepredictionsfromthe mcfm generatorwithnuclear(EPS09 andDSSZ)orfree(CT10)PDFsets.Thebottompanelshowstheratioofthedata andthenPDFpredictionstotheCT10PDFset.Theverticalbars(boxes)represent thestatistical(systematic)uncertainties.

Fig. 4. DifferentialcrosssectionoftheZbosonsinpPbcollisionsasafunctionof transversemomentuminthefiducialregionforthecombinedleptonicdecay chan-nelcomparedtothepredictionfromthe powheg+pythia 6generatorscaledbythe numberofnucleonsinthePbnucleus.Theverticalbars(boxes)representthe sta-tistical(systematic)uncertainties.The3.5%luminosityuncertaintyisshowninthe ratioplotasahashedbandtogetherwiththeassumed5%theoreticaluncertainty, shownasayellowband.(Forinterpretationofthereferencestocolorinthisfigure legend,thereaderisreferredtothewebversionofthisarticle.)

includingnucleareffectsprovideasomewhatbetterdescriptionof themeasurements.

Fig. 4 showsthe differentialcross section asa function of pT inthefiducialregion.Theresultsarecomparedonlytotheoretical predictions from powheg+pythia 6,becausethe expectednuclear modification ofthe pT spectrumissmallcompared tothe uncer-tainties inthetheory [21,22].No largedeviationsare foundfrom the theoretical cross sections,apart from the lowest dilepton pT bins where thedifferences from powheg+pythia 6 are similar to theonesobservedintheppmeasurementsat7 TeV[2,4].

Table 2

Resultsoftheχ2_{testbetweenthemeasurementsandthetheoreticalpredictionswithandwithoutnuclearmodificationfromtheEPS09orDSSZnPDFsets.Thedifferential} crosssectionandtheforward–backwardasymmetryhavetwelveandfivenumbersofdegreesoffreedom(NDF),respectively.

Observable CT10 CT10+EPS09 CT10+DSSZ χ2 /NDF Probability χ2 /NDF Probability χ2 /NDF Probability dσ/d ycm 10.8/12 54% 7.4/12 83% 6.6/12 88% RFB 7.3/5 20% 3.9/5 56% 3.4/5 64% 5. Summary

The cross section of Z boson production has been mea-suredinthe muon andelectrondecay channelsinpPb collisions at √sNN =5.02 TeV. The NLO pp inclusive cross section from powheg_{+pythia 6 scaled by the number ofelementary nucleon–} nucleon collisions is in agreement withthe measured pPb cross section. The pPb theoretical predictions for the differential cross sectionasafunctionoftheZbosonrapiditywithandwithout nu-cleareffects are compared to the measurement. Giventhe small differencesinthesepredictionsandtheirinherenttheoretical un-certainties as well as the sensitivity of the data,both scenarios, presence or not of nuclear effects, are consistent with the data. A more sensitive variable,the forward–backwardasymmetry, de-viatesfrompredictions assuming freeprotonPDFs byan amount whichiscompatiblewithboththeEPS09andtheDSSZnPDF mod-ifications, although the statistical precision of the measurement precludesmakingadefinitivestatement.Thedifferentialcross sec-tionasafunctionoftheZbosontransversemomentumhasbeen measured and is found to be in agreement with pp predictions from powheg+pythia 6,exceptatverylowtransversemomentum, where similar deviations as previously seen in pp are observed. The presented results provide new data for constraining nuclear PDFfits.

Acknowledgements

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,wegratefullyacknowledgethecomputingcentersand personneloftheWorldwideLHCComputingGridfordeliveringso effectivelythecomputinginfrastructure essential toour analyses. Finally, we acknowledge the enduring support for the construc-tionandoperationofthe LHCandtheCMSdetectorprovided by thefollowingfundingagencies:BMWFWandFWF(Austria);FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES(Bulgaria);CERN;CAS,MOST,andNSFC(China);COLCIENCIAS (Colombia);MSESandCSF(Croatia);RPF(Cyprus);MoER,ERCIUT andERDF(Estonia); AcademyofFinland,MEC, andHIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NIH (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); MSIP and NRF (Republic ofKorea); LAS (Lithuania);MOE andUM (Malaysia); CINVESTAV, CONACYT,SEP,andUASLP-FAI(Mexico);MBIE(NewZealand);PAEC (Pakistan);MSHEandNSC(Poland);FCT(Portugal);JINR(Dubna); MON,RosAtom,RASandRFBR(Russia);MESTD(Serbia);SEIDIand CPAN(Spain);SwissFundingAgencies(Switzerland);MST(Taipei); ThEPCenter,IPST,STARandNSTDA(Thailand);TUBITAKandTAEK (Turkey);NASUandSFFR(Ukraine);STFC (UnitedKingdom);DOE andNSF(USA).

Individuals have received support from the Marie-Curie pro-gramandtheEuropeanResearchCouncilandEPLANET(European Union); the Leventis Foundation; the Alfred P. Sloan Founda-tion; the Alexander von Humboldt Foundation; the Belgian Fed-eral Science Policy Office; the Fonds pour la Formation à la

Recherchedansl’Industrieetdansl’Agriculture(FRIA-Belgium);the AgentschapvoorInnovatiedoorWetenschapenTechnologie (IWT-Belgium); theMinistry ofEducation, YouthandSports (MEYS) of theCzechRepublic;theCouncilofScienceandIndustrialResearch, India; the HOMING PLUS program of the Foundation for Polish Science, cofinanced from European Union, Regional Development Fund;theOPUSprogram ofthe NationalScience Center(Poland); the CompagniadiSan Paolo(Torino); MIURproject 20108T4XTM (Italy);theThalisandAristeiaprogramscofinancedbyEU-ESFand theGreekNSRF;theNationalPrioritiesResearchProgrambyQatar NationalResearchFund;the RachadapisekSompot Fundfor Post-doctoralFellowship,ChulalongkornUniversity(Thailand);the Chu-lalongkorn Academic into Its 2nd Century Project Advancement Project(Thailand);andtheWelchFoundation,contractC-1845.

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CMS Collaboration

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, V. Knünz,A. König,

M. Krammer1,I. Krätschmer, D. Liko,T. Matsushita, I. Mikulec,D. Rabady2, N. Rad, B. Rahbaran,

H. Rohringer, J. Schieck1, R. Schöfbeck, 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, T. Cornelis,E.A. De Wolf, X. Janssen,A. Knutsson, J. Lauwers,S. Luyckx, 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,J. Keaveney, S. Lowette,L. Moreels, A. Olbrechts,Q. Python, D. Strom, S. Tavernier, W. Van Doninck, P. Van Mulders, G.P. Van Onsem,I. Van Parijs

P. Barria, H. Brun,C. Caillol, B. Clerbaux, G. De Lentdecker, W. Fang,G. Fasanella, L. Favart, R. Goldouzian, A. Grebenyuk,G. Karapostoli,T. Lenzi, A. Léonard,T. Maerschalk, A. Marinov,L. Perniè, A. Randle-conde, T. Seva,C. Vander Velde, P. Vanlaer,R. Yonamine, F. Zenoni, F. Zhang3

UniversitéLibredeBruxelles,Bruxelles,Belgium

K. Beernaert,L. Benucci, A. Cimmino, S. Crucy, D. Dobur, A. Fagot,G. Garcia,M. Gul, J. Mccartin, A.A. Ocampo Rios,D. Poyraz, D. Ryckbosch, S. Salva, M. Sigamani,M. Tytgat, W. Van Driessche, E. Yazgan,N. Zaganidis

GhentUniversity,Ghent,Belgium

S. Basegmez, C. Beluffi4, O. Bondu,S. Brochet,G. Bruno, A. Caudron, L. Ceard,C. Delaere, M. Delcourt, D. Favart,L. Forthomme, A. Giammanco,A. Jafari, P. Jez,M. Komm, V. Lemaitre, A. Mertens, M. Musich, C. Nuttens, L. Perrini, K. Piotrzkowski,A. Popov5, L. Quertenmont,M. Selvaggi, M. Vidal Marono

UniversitéCatholiquedeLouvain,Louvain-la-Neuve,Belgium

N. Beliy,G.H. Hammad

UniversitédeMons,Mons,Belgium

W.L. Aldá Júnior, F.L. Alves,G.A. Alves,L. Brito, M. Correa Martins Junior,M. Hamer, C. Hensel, A. Moraes,M.E. Pol, P. Rebello Teles

CentroBrasileirodePesquisasFisicas,RiodeJaneiro,Brazil

E. Belchior Batista Das Chagas, W. Carvalho,J. Chinellato6, A. Custódio, E.M. Da Costa,

D. De Jesus Damiao,C. De Oliveira Martins, S. Fonseca De Souza, L.M. Huertas Guativa, H. Malbouisson, D. Matos Figueiredo,C. Mora Herrera, L. Mundim,H. Nogima, W.L. Prado Da Silva, A. Santoro,

A. Sznajder,E.J. Tonelli Manganote6,A. Vilela Pereira

UniversidadedoEstadodoRiodeJaneiro,RiodeJaneiro,Brazil

S. Ahujaa,C.A. Bernardesb,A. De Souza Santosb, S. Dograa,T.R. Fernandez Perez Tomeia,

E.M. Gregoresb,P.G. Mercadanteb, C.S. Moona,7,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

M. Ahmad, J.G. Bian, G.M. Chen,H.S. Chen, M. Chen, T. Cheng,R. Du, C.H. Jiang, D. Leggat, R. Plestina8, F. Romeo,S.M. Shaheen, A. Spiezia,J. Tao, C. Wang, Z. Wang, H. Zhang

InstituteofHighEnergyPhysics,Beijing,China

C. Asawatangtrakuldee, Y. Ban,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, B. Gomez Moreno, J.C. Sanabria

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,K. Kadija, J. Luetic, S. Micanovic,L. Sudic

InstituteRudjerBoskovic,Zagreb,Croatia

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

UniversityofCyprus,Nicosia,Cyprus

M. Bodlak,M. Finger9,M. Finger Jr.9

CharlesUniversity,Prague,CzechRepublic

E. El-khateeb10, T. Elkafrawy10,A. Mohamed11, E. Salama12,10

AcademyofScientificResearchandTechnologyoftheArabRepublicofEgypt,EgyptianNetworkofHighEnergyPhysics,Cairo,Egypt

B. Calpas, M. Kadastik, M. Murumaa, 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

HelsinkiInstituteofPhysics,Helsinki,Finland

J. Talvitie, T. Tuuva

LappeenrantaUniversityofTechnology,Lappeenranta,Finland

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

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A. Abdulsalam, I. Antropov, S. Baffioni, F. Beaudette, P. Busson, L. Cadamuro, E. Chapon, C. Charlot, O. Davignon,N. Filipovic, R. Granier de Cassagnac, M. Jo, S. Lisniak,L. Mastrolorenzo, P. Miné,

I.N. Naranjo, M. Nguyen,C. Ochando, G. Ortona, P. Paganini, P. Pigard,S. Regnard, R. Salerno, J.B. Sauvan, 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,C. Goetzmann, A.-C. Le Bihan, J.A. Merlin2, K. Skovpen, P. Van Hove

InstitutPluridisciplinaireHubertCurien,UniversitédeStrasbourg,UniversitédeHauteAlsaceMulhouse,CNRS/IN2P3,Strasbourg,France

S. Gadrat

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, B. Ille, F. Lagarde,

I.B. Laktineh,M. Lethuillier, L. Mirabito,A.L. Pequegnot, S. Perries, J.D. Ruiz Alvarez,D. Sabes, V. Sordini, M. Vander Donckt, P. Verdier,S. Viret

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

T. Toriashvili14

GeorgianTechnicalUniversity,Tbilisi,Georgia

Z. Tsamalaidze9

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, J.F. Schulte,T. Verlage, H. Weber, V. Zhukov5

RWTHAachenUniversity,I.PhysikalischesInstitut,Aachen,Germany

M. Ata, M. Brodski,E. Dietz-Laursonn, D. Duchardt, M. Endres,M. Erdmann, S. Erdweg, T. Esch, R. Fischer,A. Güth, T. Hebbeker,C. Heidemann, K. Hoepfner, S. Knutzen,P. Kreuzer, M. Merschmeyer, A. Meyer,P. Millet, S. Mukherjee,M. Olschewski, K. Padeken, P. Papacz,T. Pook, M. Radziej, H. Reithler, M. Rieger,F. Scheuch, L. Sonnenschein, D. Teyssier,S. Thüer

RWTHAachenUniversity,III.PhysikalischesInstitutA,Aachen,Germany

V. Cherepanov, Y. Erdogan,G. Flügge, H. Geenen, M. Geisler, F. Hoehle, B. Kargoll, T. Kress, A. Künsken, J. Lingemann, A. Nehrkorn, A. Nowack,I.M. Nugent, C. Pistone,O. Pooth, A. Stahl

RWTHAachenUniversity,III.PhysikalischesInstitutB,Aachen,Germany

M. Aldaya Martin,I. Asin, N. Bartosik, O. Behnke,U. Behrens, K. Borras15,A. Burgmeier, A. Campbell, C. Contreras-Campana, F. Costanza, C. Diez Pardos,G. Dolinska, S. Dooling,T. Dorland,G. Eckerlin,

D. Eckstein, T. Eichhorn, G. Flucke,E. Gallo16, J. Garay Garcia, A. Geiser, A. Gizhko,P. Gunnellini, J. Hauk, M. Hempel17,H. Jung, A. Kalogeropoulos,O. Karacheban17,M. Kasemann, P. Katsas, J. Kieseler,

C. Kleinwort,I. Korol, W. Lange,J. Leonard, K. Lipka,A. Lobanov, W. Lohmann17,R. Mankel,

I.-A. Melzer-Pellmann,A.B. Meyer, G. Mittag, J. Mnich, A. Mussgiller, S. Naumann-Emme, A. Nayak, E. Ntomari,H. Perrey, D. Pitzl,R. Placakyte, A. Raspereza,B. Roland, M.Ö. Sahin, P. Saxena,

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

DeutschesElektronen-Synchrotron,Hamburg,Germany

V. Blobel, M. Centis Vignali, A.R. Draeger,J. Erfle, E. Garutti,K. Goebel, D. Gonzalez, M. Görner,J. Haller, M. Hoffmann,R.S. Höing,A. Junkes, R. Klanner, R. Kogler, N. Kovalchuk,T. Lapsien, T. Lenz,I. Marchesini, D. Marconi,M. Meyer, D. Nowatschin, J. Ott, F. Pantaleo2,T. Peiffer, A. Perieanu, N. Pietsch, J. Poehlsen, D. Rathjens,C. Sander, C. Scharf, P. Schleper, E. Schlieckau, A. Schmidt, S. Schumann,J. Schwandt,

V. Sola,H. Stadie, G. Steinbrück, F.M. Stober,H. Tholen, D. Troendle,E. Usai, L. Vanelderen, A. Vanhoefer, B. Vormwald

UniversityofHamburg,Hamburg,Germany

C. Barth,C. Baus, J. Berger,C. Böser, E. Butz, T. Chwalek, F. Colombo, W. De Boer,A. Descroix,

A. Dierlamm,S. Fink, F. Frensch, R. Friese,M. Giffels, A. Gilbert,D. Haitz, F. Hartmann2,S.M. Heindl, U. Husemann,I. Katkov5, A. Kornmayer2, P. Lobelle Pardo, B. Maier, H. Mildner, M.U. Mozer, T. Müller, Th. Müller, M. Plagge, G. Quast, K. Rabbertz,S. Röcker, F. Roscher,M. Schröder, G. Sieber, H.J. Simonis, R. Ulrich, J. Wagner-Kuhr,S. Wayand, M. Weber, T. Weiler, S. Williamson,C. Wöhrmann, R. Wolf

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

InstituteofNuclearandParticlePhysics(INPP),NCSRDemokritos,AghiaParaskevi,Greece

A. Agapitos, S. Kesisoglou, A. Panagiotou, N. Saoulidou, E. Tziaferi

NationalandKapodistrianUniversityofAthens,Athens,Greece

I. Evangelou, G. Flouris,C. Foudas, P. Kokkas, N. Loukas, N. Manthos, I. Papadopoulos,E. Paradas, J. Strologas

UniversityofIoánnina,Ioánnina,Greece

G. Bencze,C. Hajdu, A. Hazi,P. Hidas, D. Horvath18,F. Sikler, V. Veszpremi, G. Vesztergombi19, A.J. Zsigmond

WignerResearchCentreforPhysics,Budapest,Hungary

N. Beni, S. Czellar, J. Karancsi20,J. Molnar, Z. Szillasi2

InstituteofNuclearResearchATOMKI,Debrecen,Hungary

M. Bartók21,A. Makovec, P. Raics, Z.L. Trocsanyi,B. Ujvari

UniversityofDebrecen,Debrecen,Hungary

S. Choudhury22,P. Mal, K. Mandal, D.K. Sahoo,N. Sahoo, S.K. Swain

NationalInstituteofScienceEducationandResearch,Bhubaneswar,India

S. Bansal, S.B. Beri,V. Bhatnagar, R. Chawla, R. Gupta,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. Malhotra, M. Naimuddin, N. Nishu, K. Ranjan, R. Sharma,V. Sharma

UniversityofDelhi,Delhi,India

S. Bhattacharya, K. Chatterjee,S. Dey, S. Dutta, N. Majumdar, A. Modak, K. Mondal, S. Mukhopadhyay, A. Roy,D. Roy, S. Roy Chowdhury, S. Sarkar,M. Sharan

SahaInstituteofNuclearPhysics,Kolkata,India

R. Chudasama, D. Dutta, V. Jha, V. Kumar, A.K. Mohanty2, L.M. Pant,P. Shukla, A. Topkar

BhabhaAtomicResearchCentre,Mumbai,India

T. Aziz, S. Banerjee, S. Bhowmik23,R.M. Chatterjee, R.K. Dewanjee, S. Dugad, S. Ganguly,S. Ghosh, M. Guchait,A. Gurtu24,Sa. Jain, G. Kole, S. Kumar, B. Mahakud, M. Maity23,G. Majumder, K. Mazumdar, S. Mitra, G.B. Mohanty, B. Parida, T. Sarkar23,N. Sur, B. Sutar, N. Wickramage25

TataInstituteofFundamentalResearch,Mumbai,India

S. Chauhan,S. Dube, A. Kapoor, K. Kothekar, S. Sharma

IndianInstituteofScienceEducationandResearch(IISER),Pune,India

H. Bakhshiansohi,H. Behnamian, S.M. Etesami26, A. Fahim27, M. Khakzad, M. Mohammadi Najafabadi, M. Naseri, S. Paktinat Mehdiabadi, F. Rezaei Hosseinabadi, B. Safarzadeh28, M. Zeinali

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,c,S. Nuzzoa,b, A. Pompilia,b, G. Pugliesea,c,R. Radognaa,b,A. Ranieria, G. Selvaggia,b, L. Silvestrisa,2,R. Vendittia,b

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

G. Abbiendia,C. Battilana2,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,2

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

G. Cappellob, 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,2

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

L. Benussi,S. Bianco, F. Fabbri, D. Piccolo,F. Primavera2

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, R. Gerosaa,b,A. Ghezzia,b, P. Govonia,b,

S. Malvezzia, R.A. Manzonia,b,2,B. Marzocchia,b,D. Menascea,L. Moronia,M. Paganonia,b, D. Pedrinia, S. Ragazzia,b,N. Redaellia,T. Tabarelli de Fatisa,b

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

S. Buontempoa, N. Cavalloa,c,S. Di Guidaa,d,2, M. Espositoa,b, F. Fabozzia,c,A.O.M. Iorioa,b, G. Lanzaa, L. Listaa,S. Meolaa,d,2,M. Merolaa,P. Paoluccia,2,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,2,N. Bacchettaa,L. Benatoa,b, D. Biselloa,b, A. Bolettia,b, R. Carlina,b, P. Checchiaa,

M. Dall’Ossoa,b,2,T. Dorigoa, U. Dossellia,F. Gasparinia,b,U. Gasparinia,b,A. Gozzelinoa,S. Lacapraraa, M. Margonia,b, A.T. Meneguzzoa,b,M. Passaseoa, J. Pazzinia,b,2,M. Pegoraroa, N. Pozzobona,b,

A. Zucchettaa,b,2,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,2, L. Fanòa,b,P. Laricciaa,b, G. Mantovania,b, M. Menichellia, A. Sahaa, A. Santocchiaa,b

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

K. Androsova,29,P. Azzurria,2, G. Bagliesia, J. Bernardinia, T. Boccalia, R. Castaldia,M.A. Cioccia,29, R. Dell’Orsoa,S. Donatoa,c,2, G. Fedi,L. Foàa,c,†, A. Giassia,M.T. Grippoa,29,F. Ligabuea,c, T. Lomtadzea, L. Martinia,b, A. Messineoa,b, F. Pallaa,A. Rizzia,b,A. Savoy-Navarroa,30, A.T. Serbana,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, G. D’imperioa,b,2, D. Del Rea,b,2, 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,P. Traczyka,b,2

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

N. Amapanea,b, R. Arcidiaconoa,c,2, S. Argiroa,b, M. Arneodoa,c, R. Bellana,b, C. Biinoa,N. Cartigliaa, M. Costaa,b,R. Covarellia,b,A. Deganoa,b,N. Demariaa,L. Fincoa,b,2,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,A. Solanoa,b, A. Staianoa

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

c_{UniversitàdelPiemonteOrientale,Novara,Italy}

S. Belfortea,V. Candelisea,b,M. Casarsaa, F. Cossuttia,G. Della Riccaa,b, B. Gobboa, C. La Licataa,b, M. Maronea,b,A. Schizzia,b, A. Zanettia

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

A. Kropivnitskaya,S.K. Nam

KangwonNationalUniversity,Chunchon,RepublicofKorea

D.H. Kim,G.N. Kim, M.S. Kim,D.J. Kong, S. Lee, Y.D. Oh,A. Sakharov, D.C. Son

KyungpookNationalUniversity,Daegu,RepublicofKorea

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

ChonbukNationalUniversity,Jeonju,RepublicofKorea

S. Song

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

KoreaUniversity,Seoul,RepublicofKorea

H.D. Yoo

SeoulNationalUniversity,Seoul,RepublicofKorea

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

UniversityofSeoul,Seoul,RepublicofKorea

Y. Choi,J. Goh, D. Kim, E. Kwon, J. Lee,I. Yu

SungkyunkwanUniversity,Suwon,RepublicofKorea

V. Dudenas, A. Juodagalvis,J. Vaitkus

VilniusUniversity,Vilnius,Lithuania

I. Ahmed,Z.A. Ibrahim, J.R. Komaragiri, M.A.B. Md Ali31,F. Mohamad Idris32,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 Cruz33, A. Hernandez-Almada,R. Lopez-Fernandez, J. Mejia Guisao, A. Sanchez-Hernandez

CentrodeInvestigacionydeEstudiosAvanzadosdelIPN,MexicoCity,Mexico

S. Carrillo Moreno, F. Vazquez Valencia

UniversidadIberoamericana,MexicoCity,Mexico

I. Pedraza, H.A. Salazar Ibarguen

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,T. Khurshid, 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

G. Brona,K. Bunkowski, A. Byszuk34,K. Doroba, A. Kalinowski, M. Konecki, J. Krolikowski, M. Misiura, M. Olszewski,M. Walczak

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, F. Nguyen, 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. Matveev35,36,P. Moisenz, V. Palichik,V. Perelygin, S. Shmatov, S. Shulha, N. Skatchkov, V. Smirnov, A. Zarubin

JointInstituteforNuclearResearch,Dubna,Russia

V. Golovtsov, Y. Ivanov, V. Kim37,E. Kuznetsova, P. Levchenko, V. Murzin, V. Oreshkin, I. Smirnov, 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

InstituteforNuclearResearch,Moscow,Russia

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

InstituteforTheoreticalandExperimentalPhysics,Moscow,Russia

M. Chadeeva,R. Chistov, M. Danilov, V. Rusinov, E. Tarkovskii

NationalResearchNuclearUniversity‘MoscowEngineeringPhysicsInstitute’(MEPhI),Moscow,Russia

V. Andreev,M. Azarkin36, I. Dremin36,M. Kirakosyan, A. Leonidov36, G. Mesyats,S.V. Rusakov

P.N.LebedevPhysicalInstitute,Moscow,Russia

A. Baskakov,A. Belyaev, E. Boos,A. Ershov, A. Gribushin, A. Kaminskiy38,O. Kodolova, V. Korotkikh, I. Lokhtin,I. Miagkov, S. Obraztsov, S. Petrushanko,V. Savrin, A. Snigirev, I. Vardanyan

SkobeltsynInstituteofNuclearPhysics,LomonosovMoscowStateUniversity,Moscow,Russia

I. Azhgirey,I. Bayshev,S. Bitioukov, V. Kachanov, A. Kalinin, D. Konstantinov, V. Krychkine, V. Petrov, R. Ryutin, A. Sobol, L. Tourtchanovitch,S. Troshin, N. Tyurin, A. Uzunian,A. Volkov

StateResearchCenterofRussianFederation,InstituteforHighEnergyPhysics,Protvino,Russia

P. Adzic39, P. Cirkovic, D. Devetak,J. Milosevic, V. Rekovic

UniversityofBelgrade,FacultyofPhysicsandVincaInstituteofNuclearSciences,Belgrade,Serbia

J. Alcaraz Maestre, 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

C. Albajar, J.F. de Trocóniz, M. Missiroli, D. Moran

UniversidadAutónomadeMadrid,Madrid,Spain

J. Cuevas, J. Fernandez Menendez,S. Folgueras, I. Gonzalez Caballero, E. Palencia Cortezon, J.M. Vizan Garcia

I.J. Cabrillo, A. Calderon, J.R. Castiñeiras De Saa, E. Curras, P. De Castro Manzano,M. Fernandez, J. Garcia-Ferrero,G. Gomez, A. Lopez Virto, J. Marco,R. Marco, C. Martinez Rivero,F. Matorras,

J. Piedra Gomez,T. Rodrigo, A.Y. Rodríguez-Marrero,A. Ruiz-Jimeno, L. Scodellaro, N. Trevisani,I. Vila, R. Vilar Cortabitarte

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

D. Abbaneo, E. Auffray, G. Auzinger, M. Bachtis,P. Baillon, A.H. Ball, D. Barney, A. Benaglia,J. Bendavid, L. Benhabib,G.M. Berruti, P. Bloch,A. Bocci, A. Bonato, C. Botta, H. Breuker, T. Camporesi, R. Castello, M. Cepeda, G. Cerminara, M. D’Alfonso, D. d’Enterria, A. Dabrowski,V. Daponte, A. David,

M. De Gruttola,F. De Guio, A. De Roeck, S. De Visscher, E. Di Marco40, M. Dobson,M. Dordevic, B. Dorney,T. du Pree, D. Duggan, M. Dünser,N. Dupont,A. Elliott-Peisert, G. Franzoni, J. Fulcher,

W. Funk, D. Gigi,K. Gill,D. Giordano, M. Girone, F. Glege,R. Guida, S. Gundacker, M. Guthoff,J. Hammer, P. Harris,J. Hegeman, V. Innocente, P. Janot, H. Kirschenmann,M.J. Kortelainen, K. Kousouris, K. Krajczar, P. Lecoq,C. Lourenço,M.T. Lucchini, N. Magini, L. Malgeri, M. Mannelli,A. Martelli, L. Masetti,F. Meijers, S. Mersi,E. Meschi, F. Moortgat, S. Morovic, M. Mulders, M.V. Nemallapudi,H. Neugebauer,

S. Orfanelli41, L. Orsini, L. Pape,E. Perez, M. Peruzzi,A. Petrilli, G. Petrucciani, A. Pfeiffer,M. Pierini, D. Piparo, A. Racz, T. Reis,G. Rolandi42, M. Rovere, M. Ruan, H. Sakulin,C. Schäfer, C. Schwick,M. Seidel, A. Sharma,P. Silva,M. Simon, P. Sphicas43,J. Steggemann, B. Stieger,M. Stoye, Y. Takahashi, D. Treille, A. Triossi,A. Tsirou,G.I. Veres19,N. Wardle,H.K. Wöhri, A. Zagozdzinska34,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. Starodumov44,M. Takahashi, V.R. Tavolaro, K. Theofilatos, R. Wallny

InstituteforParticlePhysics,ETHZurich,Zurich,Switzerland

T.K. Aarrestad, C. Amsler45, 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

K.H. Chen,T.H. Doan, Sh. Jain,R. Khurana, M. Konyushikhin, C.M. Kuo, W. Lin, Y.J. Lu,A. Pozdnyakov, S.Y. Tseng,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,

U. Grundler,W.-S. Hou,Y. Hsiung, Y.F. Liu, R.-S. Lu, M. Miñano Moya,E. Petrakou, J.f. Tsai,Y.M. Tzeng

NationalTaiwanUniversity(NTU),Taipei,Taiwan

B. Asavapibhop,K. Kovitanggoon, G. Singh, N. Srimanobhas, N. Suwonjandee

ChulalongkornUniversity,FacultyofScience,DepartmentofPhysics,Bangkok,Thailand

A. Adiguzel, S. Cerci46,S. Damarseckin, Z.S. Demiroglu, C. Dozen, I. Dumanoglu, S. Girgis, G. Gokbulut, Y. Guler,E. Gurpinar, I. Hos, E.E. Kangal47,A. Kayis Topaksu, G. Onengut48,K. Ozdemir49,S. Ozturk50, B. Tali46,H. Topakli50, C. Zorbilmez

B. Bilin, S. Bilmis, B. Isildak51, G. Karapinar52, M. Yalvac, M. Zeyrek

MiddleEastTechnicalUniversity,PhysicsDepartment,Ankara,Turkey

E. Gülmez,M. Kaya53,O. Kaya54, E.A. Yetkin55, T. Yetkin56

BogaziciUniversity,Istanbul,Turkey

A. Cakir,K. Cankocak, S. Sen57,F.I. Vardarlı

IstanbulTechnicalUniversity,Istanbul,Turkey

B. Grynyov

InstituteforScintillationMaterialsofNationalAcademyofScienceofUkraine,Kharkov,Ukraine

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, Z. Meng, D.M. Newbold58, S. Paramesvaran,A. Poll, T. Sakuma, S. Seif El Nasr-storey,S. Senkin, D. Smith, V.J. Smith

UniversityofBristol,Bristol,UnitedKingdom

A. Belyaev59, 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,S.D. Worm

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, P. Dunne, A. Elwood, D. Futyan, G. Hall,G. Iles, R. Lane, R. Lucas58,L. Lyons, A.-M. Magnan,S. Malik, J. Nash, A. Nikitenko44, J. Pela, M. Pesaresi,D.M. Raymond, A. Richards,A. Rose, C. Seez,A. Tapper, K. Uchida, M. Vazquez Acosta60, T. Virdee,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

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

BrownUniversity,Providence,USA

R. Breedon,G. Breto, M. Calderon De La Barca Sanchez, S. Chauhan,M. Chertok, J. Conway,R. Conway, P.T. Cox, R. Erbacher,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