Centrality and transverse momentum dependence of inclusive J/ψ production at midrapidity in Pb–Pb collisions at sNN=5.02 TeV

.

ALICE

Collaboration



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Articlehistory:

Received 16 November 2019

Received in revised form 8 February 2020 Accepted 15 April 2020

Available online 21 April 2020 Editor: W.-D. Schlatter

TheinclusiveJ/ψmesonproductioninPb–Pb collisionsatacenter-of-massenergypernucleon–nucleon collision of √sNN=5.02 TeV atmidrapidity (|y|<0.9) is reported by the ALICE Collaboration. The

measurementsareperformedinthedielectrondecaychannel,asafunctionofeventcentralityandJ/ψ

transverse momentum pT,downto pT=0. TheJ/ψ mean transversemomentum pT andrAA ratio,

defined as p2

TPbPb/p2Tpp, are evaluated. Bothobservables show acentrality dependence decreasing

towards central (head-on) collisions. The J/ψ nuclear modification factor RAA exhibits a strong pT

dependence with a large suppression at high pT and an increase to unity for decreasing pT. When

integratingoverthemeasuredmomentumrange pT<10 GeV/c,theJ/ψ RAA showsaweakcentrality

dependence. Each measurementis comparedwith results atlower center-of-mass energiesand with ALICEmeasurements atforwardrapidity,as wellastotheorycalculations.Allreportedfeaturesofthe J/ψproductionatlowpTareconsistentwithadominantcontributiontotheJ/ψyieldoriginatingfrom

charmquark(re)combination.

©2020EuropeanOrganizationforNuclearResearch.PublishedbyElsevierB.V.Thisisanopenaccess articleundertheCCBYlicense(http://creativecommons.org/licenses/by/4.0/).FundedbySCOAP3.

1. Introduction

TheQuark-GluonPlasma(QGP)isastateofstrongly-interacting mattercharacterizedby quarkandgluondegreesoffreedom pre-dictedby QuantumChromodynamics(QCD) toexist athigh tem-perature and energy density [1,2]. Such conditions are realized duringthe initialhot anddensestagesof ultra-relativistic heavy-ioncollisions.Themediumproducedinthesecollisionshasashort lifetime,whichisoftheorderof10 fm/c attheenergies reached attheCERNLargeHadronCollider(LHC),seee.g. [3].

Dueto their large masses, charm andbeauty quarksare pro-ducedinhardpartonicscatteringsoccurringduringtheearlystage ofthecollisionandthereforeexperience thefull evolutionofthe medium.Charmonia,i.e.theboundstatesofcharmandanti-charm quarks,areofparticularinterestfortheunderstandingoftheQGP, seee.g. [4,5].Intheframeworkofcolor-screeningmodels,the sup-pressionofthecharmoniumstateJ

/ψ

isanunambiguoussignature oftheQGP [6,7].Thehighdensityofcolorchargespreventscharm andanti-charmquarks fromformingbound states.Therefore,the J

/ψ

yield is expectedto be suppressed compared to probes un-affected by the hot and dense medium or from expectations of theincoherentsuperpositionofnucleon–nucleoncollisions atthe sameenergy.Thiswasexperimentallyobservedinthemostcentral heavy-ioncollisionsatSPS [8–10] andRHIC [11–13] energies.

 _{E-mailaddress:alice -publications @cern .ch.}

At the significantly higher collision energies of the LHC, the suppression pattern of J

/ψ

mesons in heavy-ion collisions is fundamentally changed. In central Pb–Pb collisions at

√

sNN

=

2

.

76 TeV, where

√

sNN is the center-of-mass collision energy

per nucleon–nucleon pair, the suppression was found to be weaker [14–16] in comparisonwith theearlier measurements at lowerenergies mentionedabove.Theeffectwas measuredbythe ALICECollaborationatbothmid- andforwardrapidity,dominantly for J

/ψ

mesons at a low transverse momentum (pT). This

phe-nomenonisunderstoodastheresultofthecharmonium (re)gen-eration due to copiously produced charm quarks, made possible by the deconfined nature of the QGP. In addition to the weaker nuclearsuppressionofcharmonia,recentobservationsofnon-zero ellipticflowofD [17,18] andJ

/ψ

[19] mesons,suggestthatcharm quarksmaythermalizeandflowwiththebulkparticlesduringthe QGPphase.

Therearedifferentphenomenologicalscenariosavailableforthe description of charmoniumproduction in heavy-ioncollisions. In the frameworkof statisticalhadronization,all charmonium states are created at chemical equilibrium at the phase boundary and their abundancesaredetermined bythermalweights [20,21].The transport approach considers a continuous productionand disso-ciationof charmoniumstatesalready during theQGP phase gov-erned by aset ofrateequations [22]. Anotherapproach includes charmonium dissociation by the scattering of comoving partons andhadronswitha(re)generationcomponentatLHCcollision en-ergies [23].Allcurrentmodelsimplementingstatistical hadroniza-tion,microscopictransportapproaches [24,25] orcomover

interac-https://doi.org/10.1016/j.physletb.2020.135434

0370-2693/©2020 European Organization for Nuclear Research. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP3_.

isdefinedby theratiooftheproductionyieldinPb–Pb collisions and the production cross section in pp collisions normalized by thenuclearoverlapfunction



TAA



,asafunctionofeventcentrality

andJ

/ψ

pT,isobtainedusingtherecentALICEmeasurementofthe

inclusiveJ

/ψ

crosssectioninpp collisionsat

√

s

=

5

.

02 TeV [27]. Thenewpp referenceandthelargerPb–Pb datasetallowfora sig-nificant reduction of the uncertainties compared to our previous measurements at

√

sNN

=

2

.

76 TeV [14,28]. The results are

com-pared with statistical [20], microscopic parton transport [24,25], andcomover [23] modelcalculations.

Themeasurementspresentedinthispublicationprovidea sig-nificant complement to results in Pb–Pb collisions at the same collision energy by the ALICE Collaboration at forward rapid-ity [29], the measurements on J

/ψ

suppression at high pT by

the ATLAS [30] and CMS [31] Collaborations around midrapidity, as well as to results at forward rapidity in Xe–Xe collisions at

√

sNN

=

5

.

44 TeV [32].

2. Apparatusanddatasample

AdetaileddescriptionoftheALICEdetectoranditsperformance can be found in Refs. [33,34]. The ALICE central barrel detector allowsforhighresolutiontrackingandparticleidentificationover thefullazimuthalangleinthepseudorapidityrange

|

η

|

<

0

.

9.The entiresetup isplaced insideasolenoidalmagnet,whichcreatesa uniformaxialmagneticfieldofB

=

0

.

5 Talongthebeamdirection. The maindetectors used forthe J

/ψ

meson reconstruction in thee+e− decaychannel arethe Inner TrackingSystem(ITS) [35] andtheTimeProjectionChamber(TPC) [36].TheITSconsistsof6 cylindricallayers ofsilicondetectorsplaced atradial distancesto thebeamlinefrom3

.

9 cmto43 cmandprovideshigh-precision trackingclosetotheinteractionpointaswellasthedetermination oftheprimaryvertexoftheevent.Thetwoinnermostlayersform the Silicon PixelDetector (SPD), the intermediate two layers are theSiliconDriftDetector(SDD),andthe outermostlayersarethe SiliconStripDetector(SSD).

Placed around the ITS, the TPC detector is a large cylindrical driftchamber extendingradiallyfrom85 cmto 250 cmfromthe nominal interaction point (x

=

y

=

z

=

0 cm) andlongitudinally between

−

250 cmand

+

250 cm. In addition to beingthe main trackingdetector,the TPCalso providesparticle identificationvia the measurement of the specific energy loss (dE

/

dx) of charged particlesinthedetectorgas.

TheV0detectors [37] consistoftwoscintillatorarrays,V0Aand V0C, whichare located onboth sidesof the nominalinteraction pointatz

=

329 cmandz

= −

90 cmandcoverthe pseudorapid-ityinterval 2

.

8

≤

η

≤

5

.

1 and

−

3

.

7

≤

η

≤ −

1

.

7. Thecentrality of the events, expressed in fractions of the total inelastic hadronic crosssection,isdeterminedviaaGlauber fittotheV0amplitude asdescribedin [38–40].Inaddition,the V0detectorsareusedto providea minimum-biastrigger(MB), definedasthecoincidence ofsignalsinbothV0arraysandthebeamcrossing.

availableforanalysis,correspondingtoanintegratedluminosityof

Lint

≈

10

μ

b−1.

3. Analysismethods

The J

/ψ

candidates are reconstructed using the e+e− decay channel.The selectedelectroncandidatesaretracksreconstructed using both the ITS and TPC detectors. They must have a min-imum transverse momentum of 1 GeV

/

c and pseudorapidity in the range

|

η

|

<

0

.

9. Primary electrons are selected using a max-imumdistance-of-closest-approachtotheeventvertexofatmost 1 cm and 3 cm inthetransverse andlongitudinal directions, re-spectively. Additionally,kink-daughters, i.e.secondary tracksfrom long-livedweakdecaysofchargedparticles,areremovedfromthe analysis.Inordertoimprovetheresolutionoftrackreconstruction andtoreject secondaryelectrons fromphotonconversions inthe detectormaterial,thetracksareselectedtohaveatleastonehitin eitherofthetwoSPDlayers.Electronsandpositronsfromphoton conversions are further rejectedusing a prefilter method [27] in whichtrackcandidatesformingpairswithanelectron-positron in-variantmasslowerthan50 MeV

/

c2areremovedfromanyfurther pairing. In the TPC, the electron candidates are requiredto have atleast70 outof159 possiblespacepointsattachedtothetrack, whichensuresgoodtrackingandparticleidentificationresolution. Electrons areidentified by requiringthat themeasured dE

/

dx in the TPC lies within a

±

3

σ

e band around the expected value

forelectrons estimatedfromaparameterizationofthe Bethe for-mula,where

σe

istheparticleidentification(PID)resolutioninthe TPCforelectrons.Thehadroncontaminationisreducedby exclud-ing tracks compatible withthe protonor pionhypothesis within

±

3

.

5

σ

p,

π

.

The numberof observed J

/ψ

is obtainedby constructing the invariant mass distribution of all combinations of opposite-sign (OS)electron pairsfromthesameevent. Thetop panelsofFig.1

show theinvariantmassdistributions obtainedincentral (0–10%, left) and peripheral (60–90%, right) collisions together with the estimatedbackground.The backgroundisobtainedusingthe dis-tributionofOSpairsconstructedbypairingelectronsandpositrons fromdifferentevents,so-calledmixedevents(ME),whichisscaled to match the same-event OS invariant mass distribution in two massintervalsoneithersideoftheJ

/ψ

signalregion:2

.

0

<

mee

<

2

.

5 GeV

/

c2 _{and 3}

_.

₂

_<

_m

ee

<

3

.

7 GeV

/

c2, where the J

/ψ

contri-bution is expected to be negligible. The raw J

/ψ

signal is then obtainedby integratingthebackground-subtracted distributionin the mass window 2

.

92–3

.

16 GeV

/

c2. The lower panels of Fig. 1

showtheOSinvariantmassdistributionafterbackground subtrac-tion. Good agreement with the J

/ψ

invariant mass distribution from MonteCarlo(MC) simulation, normalized tothe integral of the raw signal, isobserved. The potentially remaining correlated background from semi-leptonic decays of cc and bb pairs is in-cludedinthesystematicuncertainty.

Fig. 1. Top

panels: Invariant mass distribution of opposite-sign pairs from the same event and mixed events for the 0–10% (left) and 60–90% (right) centrality classes in

Pb–Pb collisions at √sNN=5.02 TeV. Bottom panels: Background-subtracted invariant mass distributions in comparison with the expected Monte Carlo signal shape.

Thecorrected J

/ψ

pT-differential productionyield isobtained

inagivencentralityclassas

d2N

d ydpT

=

NJ/ψ

Nev

×

BRJ/ψ→ee

× (

A

×



)

× 

y

× 

pT

,

(1)

whereNJ/ψ isthenumberofreconstructedJ

/ψ

intheconsidered

centralityclass and pT and y intervals, Nev is the corresponding

numberofevents,A

×



istheacceptanceandefficiencycorrection factorandBRJ/ψ→ee

= (

5

.

971

±

0

.

032

)

% isthe branching ratioof

theJ

/ψ

decayingintothedielectronchannel [42].

MCsimulationsofPb–Pb collisionswithembeddedunpolarized J

/ψ

mesons areused toobtainthe A

×



factors.ThePb–Pb col-lisions are generated usingHIJING [43]. For the J

/ψ

,the prompt componentisgenerated usinga pT distributiontuned to the

ex-isting Pb–Pb measurements at forward rapidity while the non-prompt component is obtained from bb pairs generated with PYTHIAforcedto decayintochannelswithJ

/ψ

inthefinal state. The J

/ψ

decays into the e+e− channel are handled using PHO-TOS [44].Thetransport ofthesimulatedparticles inthedetector material is performed using a GEANT3 [45] model of the ALICE apparatusandthe samealgorithm asforthe realdatais usedto reconstructthe simulated tracks.The acceptance timesefficiency correction factors include the kinematic acceptance, the recon-struction and PID efficiencies, and the fraction of signal in the integratedinvariantmass window.The acceptancecorrection fac-tor amounts to 33% and the fraction of the signal in the mass counting window is approximately 65%. Reconstruction and PID efficiencies are centralitydependent and together amount to ap-proximately24% inthe mostcentral collisions growing monoton-icallytoapproximately32% inthemostperipheralcollisions. The correction factors are also pT dependent which, for large pT

in-tervals,induces adependenceontheMonteCarlo pT distribution

oftheembedded J

/ψ

.Thisistakenasasourceofsystematic un-certainty andis discussed in thefollowing section. The inclusive

pT-integratedJ

/ψ

productionis measured in 5 different

central-ity classes: 0–10%, 10–20%, 20–40%, 40–60% and 60–90% while the pT-differential crosssectionsare obtainedin largercentrality

classestoensure sufficientstatisticalsignificance:0–20%, 20–40% and40–90%.

The average transverse momentum of J

/ψ

,



pT



, is extracted

using a binned log-likelihood fit of the



pee_T



distribution of all electron pairsasa functionofthe invariantmass. Eachpair con-tributionisweightedbythe

(

A

×



)

−1 factorcorrespondingtoits centralityandpT.TheOS



pee_T



distributionisfittedwiththe

func-tion:



pee_T

(

mee

)

=

Nbkg

₍

_m ee

)

× 

pbkgT

(

mee

)

 +

NJ/ψ

(

mee

)

× 

pT Nbkg

₍

_m ee

)

+

NJ/ψ

(

mee

)

,

(2)

where Nbkg

(

mee

)

and NJ/ψ

(

mee

)

are the mass-dependent

distri-butions ofbackgroundandsignal pairs determinedvia thesignal extractionproceduredescribedabove.Thebackgroundmean trans-verse momentum,



pbkg_T



, dependson the invariant mass andits shape is obtainedfrom the ME technique, while its overall nor-malizationcanvaryinthefit.Fig.2illustratesthe



pT



extraction

procedureforthe mostcentral andmostperipheral centrality in-tervalsusingdielectronpairsinthetransversemomentuminterval 0

.

15

<

pT

<

10 GeV

/

c. A similar procedure is employed also for

thesecondmomentofthetransversemomentumdistribution



p2_T



. A low-pT cut-offon the J

/ψ

candidates is applied dueto the

observationofaJ

/ψ

excessforpT

<

0

.

3 GeV

/

c atforwardrapidity

in peripheral Pb–Pb collisionsat

√

sNN

=

2

.

76 TeV [46], which is

foundtooriginatefromcoherentphoto-production.Sincethis pro-ductionmechanismis notnormallyincluded inhadro-production models,the low-pT interval isexcluded forenabling comparisons

withtheoreticalcalculations.Atmidrapidity,mainlyduetoabetter momentumresolution,nearlyallofthecoherentyieldiscontained in therange ofreconstructed pT

<

0

.

15 GeV

/

c,asshown by the

ALICEmeasurements of J

/ψ

photo-production inultra-peripheral collisions [47].Asmallcomponentofincoherentlyphoto-produced J

/ψ

isstillpresentintherangepT

<

1 GeV

/

c,butforthe

central-ityintervals considered inthiswork it is negligible.Thus, inthe following, unless otherwise specified, all the results refer to J

/ψ

Fig. 2. Extraction

of the J

/ψ pTin Pb–Pb collisions at √sNN=5.02 TeV for the 0–10% (left) and 60–90% (right) centrality classes in the transverse momentum interval 0.15 <pT<10 GeV/c.

The background, obtained from event-mixing, is shown by the red line.

Table 1

Average number of participant nucleons Npartand average nu-clear overlap function TAAfor the centrality classes used in this analysis. The values are derived from [40].

Centrality (%) Npart TAA(mb−1) 0–10 357.3±0.8 23.26±0.17 0–20 309.7±0.9 18.83±0.14 10–20 262.0±1.2 14.40±0.13 20–40 159.4±1.3 6.97±0.09 40–60 70.7±0.9 2.05±0.04 40–90 39.0±0.7 1.00±0.03 60–90 17.9±0.3 0.31±0.01 0–90 125.9±1.0 6.28±0.12

TheinclusiveJ

/ψ

nuclearmodificationfactoriscomputedfora givencentralityclassas

RAA

=

d2N

/

d ydpT



TAAd2

σ

pp

/

d ydpT

,

(3)

whered2N

/

d ydpTistheinclusiveJ

/ψ

yielddefinedinEquation1,

the



TAA



is the average nuclear overlap function corresponding

to the considered centrality class and d2

σ

pp

/

d ydpT is the

in-clusive J

/ψ

cross section measured by ALICE in pp collisions at

√

s

=

5

.

02 TeV [27].Thevaluesusedforthenuclearoverlap func-tionareshowninTable1andareobtainedfrom [40].

4. Systematicuncertainties

ThesystematicuncertaintiesonthemeasuredJ

/ψ

yields,



pT



,

and



p2_T



originatefromuncertaintiesontracking,electron identifi-cation,signalextractionprocedure,thekinematicsusedintheMC simulationfor estimatingthe A

×



corrections, andthe J

/ψ

de-caybranchingratio.Forthe RAAandtherAA,theuncertaintieson

theJ

/ψ

crosssectionmeasurementinpp collisions [27] and(only inthecaseoftheRAA)onthenuclearoverlapfunction



TAA



[40]

needtobeconsideredinaddition.Asummaryoftheuncertainties onthe pT-integratedandpT-differentialyieldsisgiveninTable2.

The systematic uncertainty on the tracking of the candidate electrons is mainly due to uncertainties on the ITS-TPC track matchingandonthetrackreconstructionefficiencyinboththeITS andtheTPC.Theseuncertainties,mainlyduetodifferencesinthe reconstruction efficiencybetweendata andMC, are estimatedby varyingthe maintrackselection criteriaandrepeating thewhole analysischain.Allvariations whichprovideacorrected yieldthat deviates fromthe yieldobtained withthestandard selection cri-teria by more than one standard deviation are considered [48]. Thetrackinguncertaintyisthenobtainedastheroot-mean-square

Table 2

Systematic uncertainties on the pT-integrated and on pT-differential J/ψ yields for different centrality intervals. Only the ranges of uncertainty are quoted over the considered centrality intervals. The individual contributions and the total uncertain-ties are given as percent values.

Source pT-integrated pT-differential pT rAA

Tracking 2–7 4–9 2–4 3–6

PID 3–6 1–6 1–2 2–4

Signal extraction 2–7 5–7 1–2 2–3

MC input 2 1–2 n.a. n.a.

TAA 2–5 2–5 n.a. n.a.

pp reference 7 9–12 3 5

of the distribution of all the valid variations, while the distribu-tion mean is used asthe central value. For the J

/ψ

yields, this uncertainty ranges between2% and 7%as a function of central-ity(integrated over pT) andbetween 4%and9%asafunction of

transversemomentum.Thetrackingsystematicuncertaintyonthe



pT



and



p2T



aresmallerthan thoseforthe correctedyieldsand

detailedinTable2.

Uncertaintiesontheelectron identificationareduetotheTPC electronPIDresponseandthehadronrejection.Adata-driven pro-cedure is used to improve the matching betweendata and sim-ulation forthe electronselection by employing a pure sample of electrons from tagged photon conversions in the detector mate-rial.TheresidualmismatchesareestimatedbyvaryingallthePID selection criteria following a similar procedure as for the track-ing systematic uncertainty. The extracteduncertainty onthe J

/ψ

yieldsrangesbetween1%and6%,dependingonthecentralityand transversemomentuminterval.

The uncertainty fromthe signal extractionprocedure includes twocomponents,oneduetotheJ

/ψ

signalshapeandonedueto theresidualcorrelateddielectronbackgroundintheJ

/ψ

mass re-gion.Inordertoestimatetheuncertaintyonthesignalshape,the corrected J

/ψ

yields are estimated using variations of the stan-dard signal counting mass region, 2.92-3.16 GeV

/

c2_{. For this we}

used three additional values of the lower mass limit, between 2.92 and 2.80 GeV

/

c2 and two additional values for the upper mass limit, namely 3.12 and3.20 GeV

/

c2_{. The correlated}

dielec-tron background in theinvariant massrange used to extract the signalhasgenerallyadifferentshapecomparedtothe combinato-rialbackground.SomatchingtheMEbackgroundinthesidebands ofthesame-eventOSdistributionmayleadtoabiasinthe estima-tionoftherawyields.Thisistakenasasystematicuncertaintyand is estimatedby varying themass ranges ofthe sidebands where the ME backgroundis matched.By thesevariations the widthof the sidebands was modified between 400 and 800 MeV

/

c2_{. The}

Fig. 3. Left

panel: Transverse momentum dependence of the J

/ψproduction yields in Pb–Pb collisions at √sNN=5.02 TeV at midrapidity in the centrality intervals 0–20%, 20–40%, and 40–90%. Right panel: Comparison of the pTdistribution in the centrality interval 0–20% with models [25,49].

asafunctionofcentralityandbetween5%and7%asafunctionof

pT.

TheacceptanceandefficiencycorrectionispTdependentwhich

makes correction factors averaged over large pT intervals

sensi-tivetotheJ

/ψ

pT spectrumusedinthesimulation.Sinceprecise

measurementsoftheJ

/ψ

transversemomentumspectraat midra-pidity down to pT

=

0 GeV

/

c are not available, the simulations

usedforcorrectionsrelyontheALICEmeasurementatforward ra-pidity(2

.

5

<

y

<

4

.

0)inPb–Pb collisionsat

√

sNN

=

5

.

02 TeV [29].

The measured spectrum including the statistical and systematic uncertaintiesis fittedusinga powerlawfunction andthefit pa-rameters are varied randomly within their allowed uncertainties takingintoaccount their correlation matrix.The resulting uncer-tainty amounts to 2% for the pT-integrated corrected yields and

rangesbetween1%to2%intheconsidered pTintervals.

Systematicuncertaintiesontheextractionof



pT



and



p2T



are

obtainedby repeating thefitprocedurewithsimilar variationsof trackingand PID selectionsasfor the yield estimation.Since for thismeasurementthe A

×



correctionisappliedforeach dielec-tronpairusingafine-binneddistributionofthecorrectionfactors, thesystematicuncertaintyduetothekinematicsoftheJ

/ψ

used intheMC simulationisnegligible.In addition,the



pT



and



p2_T



are also extractedby directly fittingthe corrected J

/ψ

spectrum withapowerlawfunctionandarefoundtobe compatibletothe valuesobtainedfromthefitwithEquation2.

Systematicuncertaintiesonthetracking,PIDandMC kinemat-icsare consideredtobe partlycorrelated overboththecentrality and the transverse momentum. The systematic uncertainties on signal extraction are considered as uncorrelated. The uncertain-ties on the nuclear overlap function are taken as uncorrelated over centrality and fully correlated over pT within a given

cen-tralityinterval.The uncertaintyonthe pT-integratedpp reference

isconsidered tobe fullycorrelated overcentrality, whilethe un-certainties on the pT-differential values are fully correlated over

centralityandhighlycorrelatedover pT.

5. Resultsanddiscussions

The inclusiveJ

/ψ

pT-differential yields evaluated using

Equa-tion1 are shownin the left panel ofFig. 3 (left) forthe 0–20%, 20–40%,and40–90%centralityintervals.Theverticalerrorbars in-dicate statisticaluncertainties whilethe systematic uncertainties, independentlyof their degree ofcorrelation, are shownas boxes aroundthedatapoints.Thehorizontalerrorbarsshowthe evalu-atedpT-rangewiththedatapointplacedinthecenter.

The experimental results are compared with different phe-nomenologicalmodelsofthecharmoniumproductionin relativis-tic heavy-ion collisions, i.e. the statistical hadronization model

(SHM)byAndronicetal.[21],thecomoverinteractionmodel(CIM) by Ferreiro [23,50] and two differentmicroscopic transport mod-els,byZhaoetal.(TM1) [24] andbyZhouetal.(TM2) [25].

In the SHM, all heavy quarks are produced during the initial hard partonicinteractionsfollowedby their thermalizationinthe QGP andthe subsequentformation of bound statesatthe phase boundary according to their thermal weights. The pT-integrated

charmed-hadronyields depend only onthe totalcc cross section inheavy-ioncollisionsandonthechemicalfreeze-outparameters, which are determined by fitting measured light-flavored hadron yields. In addition to the high-density core part in the QGP, a corona contribution is added for the casethat the nuclear den-sity decreases below10% ofits maximal value, where noQGP is assumed andthe number ofJ

/ψ

is calculated fromyields in pp collisions scaled by the number ofbinary nucleon–nucleon colli-sion.Arecent updateofthe SHM [49] usesa MUSIC(3+1)D [51] hydrodynamical simulationtoextractthe transverseflowvelocity andtheradialvelocityprofileofthefreeze-outhyper-surface,such thattheJ

/ψ

pTcanbeextractedfromablast-wave

parameteriza-tionwhichfollowsaHubble-likeexpansion [52].

The CIM [23] was developedspecificallyforthedescription of charmonium suppression in heavy-ion collisions via its interac-tions with a comovingmedium, either hadronicor partonic.The hotmediumeffectsaremodeledusingarateequationwhich con-tains a loss term for charmonium dissociation, and a gain term for(re)generation.Inthismodel,thecharmoniumdissociationrate dependsonthedensityofcomovers,obtainedfromexperimental measurements andon thecharmonium dissociationcrosssection which is an energy-independent parameter of the model, fixed fromfitstolowenergydata.Charmoniumdissociationisbalanced bythe(re)generationcomponentwhichdependsontheprimordial charm-quarkcrosssection.

Both microscopic transport models considered here, TM1 [24] andTM2 [25], solve theBoltzmannequation forcharmonia (J

/ψ

,

χ

cand

ψ

)withdissociationandrecombinationterms.Eachmodel considersthefireballevolutionusingimplementationsofideal hy-drodynamicswhichincludeboththedeconfined andthehadronic phase separated by a first order phase transition. The dissocia-tion rate in both models depends on the medium density and on a lattice-QCD-inspired charmonium binding energy (in TM1) orsquaredradius ofthe boundstate (in TM2),all ofthem being functionsoftemperature. The(re)generationcomponentis imple-mented using differentapproaches. Inthe TM1 calculations, it is based on the assumption that the charm quarks reach statistical equilibrationaftera relaxationtimeofaboutafew fm/c,whilein theTM2calculationsthecharm quarksarerecombinedusing the

Fig. 4. J/ψ pT(left) and rAA(right) at midrapidity as a function of the mean number of participant nucleons Npart. The ALICE measurements at √sNN=5.02 TeV are compared with previous results in pp and Pb–Pb collisions at 2.76 TeV [28], Pb–Pb collisions at 5.02 at forward rapidity [53], and with those at lower collision energies at SPS [54] and RHIC [11,55,56]. The red box around unity at Npart≈400 in the right panel indicates the correlated uncertainty of the ALICE data points due to the p2Tin pp collisions.

Fig. 5. Inclusive

J

/ψpT(left) and rAA(right) in pp [27] and Pb–Pb collisions at √sNN=5.02 TeV at midrapidity as a function of the mean number of participating nucleons. The ALICE results are compared with calculations from the transport models [57,58] and the SHM [49]. The colored bands represent model uncertainties. As in Fig.4, the red box around unity at Npart≈400 in the right panel indicates the correlated uncertainty of the ALICE data points due to the p2Tin pp collisions.

samecrosssection asforthedissociationprocessanda thermal-izeddistributionofcharmquarks.

Theprimordial cc productioncrosssection inPb–Pb collisions isacommoninputforalloftheabovementionedmodels.Thereis sofarnomeasurementofthecc crosssectioninPb–Pb orpp col-lisionsat

√

sNN

=

5

.

02 TeVatmidrapidity, whichleaddominantly

totheuncertainty ofthemodels.The crosssectionin Pb–Pb col-lisions isobtainedfromthe totalcc crosssection inpp collisions d

σ

cc

/

d y scaled by the average numberofnucleon–nucleon

colli-sions



Ncoll



in a given centrality class of Pb–Pb collisions with

additionalCNM effectstakenintoaccount. Fortherapidity inter-valusedinthiswork,

|

y

|

<

0

.

9,thevalueofd

σ

cc

/

d y estimatedfor

MBPb–Pb collisionsis0

.

53

±

0

.

10 mbfortheSHM,0

.

76

±

0

.

13 mb forTM1,0

.

78

±

0

.

09 mbforTM2and0

.

56

±

0

.

11 mbforCIM.

The right panel of Fig. 3 shows a comparison of the inclu-siveJ

/ψ

transversemomentumspectruminthe20% mostcentral Pb–Pb collisions to calculations fromthe SHM and TM2models. The bands indicate model uncertainties mainly due to the as-sumptions on the d

σ

cc

/

d y. Good agreement between data and

the SHM predictions is observed inthe low-pT region, while for pT



5 GeV

/

c the calculations underestimate the data. The TM2

calculationsunderestimatethemeasuredyieldsoverthemeasured

pTrange.

In order to facilitate the comparison of the J

/ψ

pT spectra

obtainedin thiswork withother measurements ortheory calcu-lations, the J

/ψ



pT



and



p2T



are extracted inseveral centrality

intervals, using the method described in Sec. 3. The left panel

of Fig. 4 shows the J

/ψ



pT



dependence on the mean

num-ber of participant nucleons



Npart



. The



pT



in Pb–Pb collisions

at

√

sNN

=

5

.

02 TeV showsa monotonic decrease fromthe most

peripheral collisions, where it is compatibleto the measurement in pp collisions at

√

s

=

5

.

02 TeV,to the most central collisions, which hints towards a strong contribution from (re)combination processes.Thistrendisnotclearlyvisibleforthemeasurementat

√

sNN

=

2

.

76 TeV,whichsufferedfromlargestatisticaland

system-aticuncertainties.

The rAA ratio, defined as



p2_T



PbPb

/



p2T



pp, which is shown in

the right panel of Fig. 4, is a measure of the broadness of the

pT spectra in heavy-ioncollisions relative to pp collisionsat the

same energy. A strong decrease of the rAA is observed in Pb–Pb

collisionsat

√

sNN

=

5

.

02 TeVbetweenperipheral,whereitis

con-sistentwithunity,andcentralcollisionswhererAAreachesavalue

of0

.

6 atmidrapidityand0

.

75 atforwardrapidity [53].When com-paringwithmeasurementsatlowerenergiesfromRHIC [11,55,56] and SPS [54], a very different picture emerges. While the RHIC measurements for both



pT



andrAA are compatiblewitha

con-stant trend asa function of



Npart



[25], the SPS resultsshow a

monotonicincrease ofboth



pT



andrAA asafunctionofcollision

centralitywhich,atthisenergy,canbe explainedbyabroadening ofthepT distributionduetotheCronineffect [59].

Theresultsforthe



pT



andrAA inPb–Pb collisionsat

√

sNN

=

5

.

02 TeVarecomparedwithmodelcalculationsinFig.5.The sta-tisticalhadronizationmodelagreeswiththedataonlyforthemost central collisions butunderestimates the measurements formore

Fig. 6. Inclusive

J

/ψnuclear modification factor at midrapidity, integrated over pT, as a function of Npartin Pb–Pb collisions at √sNN=5.02 TeV compared with results at

√_s

NN=2.76 TeV [14] (left panel) and with calculations from the CIM [23], SHM [49], TM1 [58] and TM2 [25] models (right panel). The yields in the left panel are shown without the low-pTcut-off in order to be able to compare with the lower energy data which are obtained for pT>0. The calculations are shown as bands indicating the model uncertainties. Boxes around unity at Npart≈400 in both panels indicate the correlated uncertainty of the data points due to the cross section in pp collisions.

peripheralcollisions. Agooddescription ofthecentralitytrendis obtainedwiththetransportmodelTM1calculation,whichincludes adetailedimplementationofthefireballevolution,withthe excep-tionofmostcentralcollisionswherethemodeloverestimatesboth theJ

/ψ



pT



andrAA.

The pT-integratednuclear modificationfactorforinclusiveJ

/ψ

inPb–Pb collisionsat

√

sNN

=

5

.

02 TeVobtainedusingEquation3

is shown in the left panel of Fig. 6 as a function of the mean number of participants and compared with a measurement at

√

sNN

=

2

.

76 TeV [14]. The boxes shown around unity indicate

thecorrelatedsystematicuncertaintiesandincludethe uncertain-tiesonthepp reference.Besidesthemostcentralcollisionswhere there is a hint of an increase of the RAA with collision energy,

theresults at thetwo energies are compatiblewithin uncertain-ties.Acomparisonoftheexperimentalresultsat

√

sNN

=

5

.

02 TeV

withcalculationsbasedon themodelsdescribed beforeisshown inthe rightpanel ofFig. 6.The calculationsare shownasbands thatindicatemodeluncertainties, dominatedbythe uncertainties on the cc cross section and on the CNM effects. The SHM cal-culation showsa good agreement with the data over the entire centralityrange.CIM,TM1andTM2calculationsunderestimatethe experimentalresultstowardsthedatapointscorrespondingtothe mostcentralcollisionsdespitethefactthat thetotalcc cross sec-tionassumedinTM1andTM2issignificantly largercomparedto theSHMandtheCIM.Thelargemodeluncertaintiesdonotallow a conclusion to be madeon the phenomenology of charmonium productionin nuclear collisions. This emphasizes the importance ofaprecisemeasurementofthetotalcc crosssection,butalsothe needofusingconsistentmodelinputs,includingthetotalcc cross section,thepp referenceJ

/ψ

crosssectionandCNMeffects.

The inclusive J

/ψ

nuclear modification factor in Pb–Pb colli-sionsas afunction of pT is shownin theleft panel of Fig.7 for

thecentrality intervals 0–20%, 20–40% and40–90%. The system-aticuncertainties shownasboxesaround thedatapoints include thesystematicuncertaintiesfromthePb–Pb analysiswhilethe un-certainties from the pp reference, correlated over centrality, are shownasthegray band aroundunity. The coloredboxes athigh

pT around unity indicate the correlated uncertainties due to the



TAA



valuesused forthe RAA calculation.Theseresultsare

com-patiblewithbinaryscalingforpT

<

3 GeV

/

c,withtheexceptionof

thedatapointaround2 GeV

/

c whichshowsadownward statisti-calfluctuation for40–90% centrality,while theJ

/ψ

productionis suppressedathigher pT.Withthecurrentuncertainties itis

diffi-culttoextractacentralitytrendexceptforthehighestpTinterval,

5–10 GeV

/

c,whereastrongersuppressionisobservedinthemost central collisions relative to the moreperipheral centrality

inter-vals at a significance level ofabout 3

σ

. The results for the 20% mostcentralcollisionsare comparedwithmodelcalculationsand shownintherightpanelofFig.7.Both theSHMandTM1models describequalitativelythedata.Inthesemodels,theincreasing RAA

towardslow pT isaconsequenceofthedominantcontributionof

(re)generated J

/ψ

.At high pT, the contribution from

recombina-tiondecreases,andtheJ

/ψ

productionissuppressedduetocolor chargesinthemedium. ThemainJ

/ψ

sourcesathigh pT are

pri-mordialproductionandfeed-downfrombeautydecays.TheSHM, wheretheJ

/ψ

athigh pT are producedonlyinthecorona,

over-estimatesthedegreeofJ

/ψ

suppression.

Since thecharm quark density,i.e.thecc cross section, is ex-pectedto decreasetowardslargerrapidity,thecomparisonto the forward-rapiditymeasurementsisavaluablesourceofinformation. IntheleftpanelofFig.8,thepTdependenceoftheJ

/ψ

RAAinthe

20%mostcentralPb–Pb collisionsatmidrapidityiscomparedwith theALICEresultsmeasuredatforwardrapidity(2

.

5

<

y

<

4) [29]. Theboxes aroundthedatapoints representsystematic uncertain-ties, while the boxes drawn around RAA

=

1 show global

uncer-taintiesonthepp referenceduetouncertaintiesonthebeam lu-minosityand



TAA



.Inthelow-pTrange(pT

<

5 GeV

/

c)thesedata

indicatelargerRAAvaluesatmidrapiditycomparedtothoseat

for-wardrapidity,withacombinedstatisticalsignificanceofnearly4

σ

, compatible withexpectations froma (re)generation scenario due tothelargerprimordialcc densityatmidrapidity.Therapidity de-pendence ofthe inclusiveJ

/ψ

suppression,integrated over pT, is

shownintherightpanelofFig.8forthe0–90%centralityinterval. ThevalueoftheRAAatmidrapidityis0

.

97

±

0

.

05

(

stat.

)

±

0

.

1

(

syst.

)

,

and a monothonic decrease is observed towards forward rapid-ity [29,53].

6. Conclusions

ThemeasurementsoftheinclusiveJ

/ψ

yieldsandnuclear mod-ification factorsat midrapidity(

|

y

|

<

0

.

9) were performedin the dielectron decay channel in Pb–Pb collisions at a center-of-mass energy

√

sNN

=

5

.

02 TeVusing an integratedluminosityof Lint

≈

10

μ

b−1 collected by the ALICE Collaboration. The results were presentedasa functionoftransversemomentumindifferent col-lisioncentralityclasses.

The J

/ψ

transverse momentum dependent yields in central Pb–Pb collisions are well reproduced in the low pT range by an

updated SHM calculation [49] and underestimated for large pT.

TheTM2 [25] transportcalculationsunderestimatetheJ

/ψ

yields overtheentiremeasured pTrange.TheJ

/ψ



pT



and



p2T



showa

Fig. 7. Inclusive

J

/ψ RAAat midrapidity in Pb–Pb collisions at √sNN=5.02 TeV as a function of pT for different centrality intervals (left) and compared with model calculations [49,58] for the centrality interval 0–20% (right).

Fig. 8. Left:

Inclusive J

/ψ RAAin the 20% most central Pb–Pb collisions at √sNN=5.02 TeV as a function of pT, at midrapidity and at forward rapidity [29,53]. Right: Rapidity dependence of the inclusive J/ψ RAAin the centrality interval 0–90%. The error bars represent statistical uncertainties, while the boxes around the data points represent systematic uncertainties. The boxes around unity represent global uncertainties on the pp reference due to normalization and TAA. In the right panel, the correlated uncertainty of the point at midrapidity is included in the box around the data point.

values observed inpp collisions, towards most central collisions. This centrality-dependentbehavior is qualitatively different com-paredtotheobservationsatlowerenergiesfromRHICandSPSand canbeexplainedthroughtheinterplaybetweenthe(re)generation process, dominantatlow pT for central eventsatthe LHC, color

screening,andCNMeffectslikegluonshadowing.Agood descrip-tion ofthe observed trends is providedby theTM1 calculations, whilethe SHM calculationsagree withthe dataforcentral colli-sionsonly.

The pT-integratednuclear modificationfactor asa function of

the number of participant nucleons shows a moderate level of suppressionin therange50

<



Npart



<

300,andindicates an

in-creasetowardscentralcollisions.Inthemostperipheralcollisions, ourresultsare compatiblewithbinaryscalingoftheJ

/ψ

produc-tion.Thenuclearmodificationfactorasafunctionofthetransverse momentumshowsastrongsuppression, centralitydependent,for

pT

>

3 GeV

/

c but is compatible with unity or with a small

en-hancementatsmall pT, suggestiveof thelarge contributionfrom

the(re)generationprocess.Furthermore,fromthesemeasurements weobservesignificantlylargervaluesforRAA comparedtothe

re-sultsatforwardrapidity [29] forboththe pT-integratedvaluesin

the0–90%centralityintervalandforthe pT-differentialRAAinthe

low pTregion(pT

<

5 GeV

/

c)inthecentralityinterval0–20%.

Consequently,theseresultsstrenghtenthehypothesisthat char-moniumatlow pTisproducedpredominantlyvia(re)generationin

thelatestagesofthecollisionattheLHC.However,duetothe re-mainingexperimentalandtheoreticaluncertainties,theexact

phe-nomenology leading to these observations cannot be determined yet.

Declarationofcompetinginterest

Theauthorsdeclarethattheyhavenoknowncompeting finan-cialinterestsorpersonalrelationshipsthatcouldhaveappearedto influencetheworkreportedinthispaper.

Acknowledgements

The ALICECollaboration would like to thank all its engineers andtechniciansfortheirinvaluablecontributionstothe construc-tion of the experiment and the CERN accelerator teams for the outstanding performance of the LHC complex. The ALICE Collab-oration gratefully acknowledges the resources and support pro-videdbyallGridcentresandtheWorldwideLHCComputingGrid (WLCG) collaboration. The ALICE Collaboration acknowledges the following fundingagenciesfortheir supportin buildingand run-ningtheALICEdetector:A.I.AlikhanyanNationalScience Labora-tory(YerevanPhysicsInstitute)Foundation (ANSL),State Commit-teeofScienceandWorldFederationofScientists(WFS),Armenia; Austrian Academy of Sciences, Austrian Science Fund (FWF): [M 2467-N36] and Nationalstiftung für Forschung, Technologie und Entwicklung,Austria;MinistryofCommunicationsandHigh Tech-nologies, National Nuclear Research Center, Azerbaijan; Conselho Nacional de Desenvolvimento Científico e Tecnológico(CNPq), Fi-nanciadora de Estudose Projetos (Finep),Fundação de Amparo à

France; Bundesministerium für Bildung und Forschung (BMBF) andGSIHelmholtzzentrumfürSchwerionenforschungGmbH, Ger-many;GeneralSecretariatforResearchandTechnology,Ministryof Education,Research andReligions,Greece; NationalResearch De-velopmentandInnovationOffice,Hungary;DepartmentofAtomic Energy, Government of India (DAE), Department of Science and Technology, Government of India (DST), University Grants Com-mission,GovernmentofIndia(UGC) andCouncil ofScientificand Industrial Research (CSIR), India; Indonesian Institute of Science, Indonesia;CentroFermi- MuseoStoricodellaFisicaeCentroStudi e Ricerche Enrico Fermi and Istituto Nazionale di Fisica Nucle-are (INFN),Italy; Institute forInnovativeScience andTechnology, Nagasaki Institute of Applied Science (IIST), Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT) and JapanSocietyforthePromotionofScience(JSPS)KAKENHI,Japan; Consejo Nacional de Ciencia (CONACYT) y Tecnología, through FondodeCooperaciónInternacionalenCienciayTecnología (FON-CICYT)andDirecciónGeneralde Asuntosdel PersonalAcademico (DGAPA),Mexico; Nederlandse OrganisatievoorWetenschappelijk Onderzoek(NWO),Netherlands; The ResearchCouncil ofNorway, Norway; Commission on Science and Technology for Sustainable Development in the South (COMSATS), Pakistan; Pontificia Uni-versidad Católicadel Perú, Peru; Ministry of Science and Higher EducationandNationalScience Centre,Poland;Korea Institute of ScienceandTechnology Information andNationalResearch Foun-dation of Korea (NRF), Republic of Korea; Ministry of Education andScientificResearch,InstituteofAtomicPhysicsandMinistryof ResearchandInnovationandInstituteofAtomicPhysics,Romania; Joint Institute for Nuclear Research (JINR), Ministry of Education andScience of the Russian Federation, National Research Centre KurchatovInstitute,RussianScienceFoundationandRussian Foun-dation forBasic Research, Russia; Ministry ofEducation, Science, ResearchandSportoftheSlovak Republic, Slovakia; National Re-searchFoundationofSouthAfrica,SouthAfrica; SwedishResearch Council (VR) and Knut & Alice Wallenberg Foundation (KAW), Sweden;EuropeanOrganizationforNuclearResearch,Switzerland; Suranaree University of Technology (SUT), National Science and TechnologyDevelopmentAgency(NSDTA)andOfficeoftheHigher Education Commission under NRU project of Thailand, Thailand; TurkishAtomic Energy Agency (TAEK),Turkey; NationalAcademy ofSciences ofUkraine,Ukraine; ScienceandTechnology Facilities Council (STFC), United Kingdom; National Science Foundation of theUnitedStatesofAmerica(NSF)andUnitedStatesDepartment of Energy, Office of Nuclear Physics (DOE NP), United States of America.

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ALICECollaboration

S. Acharya

141

,

D. Adamová

94

,

A. Adler

74

,

J. Adolfsson

80

,

M.M. Aggarwal

99

,

G. Aglieri Rinella

33

,

M. Agnello

30

,

N. Agrawal

10

,

53

,

Z. Ahammed

141

,

S. Ahmad

16

,

S.U. Ahn

76

,

A. Akindinov

91

,

M. Al-Turany

106

,

S.N. Alam

141

,

D.S.D. Albuquerque

122

,

D. Aleksandrov

87

,

B. Alessandro

58

,

H.M. Alfanda

6

,

R. Alfaro Molina

71

,

B. Ali

16

,

Y. Ali

14

,

A. Alici

10

,

26

,

53

,

A. Alkin

2

,

J. Alme

21

,

T. Alt

68

,

L. Altenkamper

21

,

I. Altsybeev

112

,

M.N. Anaam

6

,

C. Andrei

47

,

D. Andreou

33

,

H.A. Andrews

110

,

A. Andronic

144

,

M. Angeletti

33

,

V. Anguelov

103

,

C. Anson

15

,

T. Antiˇci ´c

107

,

F. Antinori

56

,

P. Antonioli

53

,

R. Anwar

125

,

N. Apadula

79

,

L. Aphecetche

114

,

H. Appelshäuser

68

,

S. Arcelli

26

,

R. Arnaldi

58

,

M. Arratia

79

,

I.C. Arsene

20

,

M. Arslandok

103

,

A. Augustinus

33

,

R. Averbeck

106

,

S. Aziz

61

,

M.D. Azmi

16

,

A. Badalà

55

,

Y.W. Baek

40

,

S. Bagnasco

58

,

X. Bai

106

,

R. Bailhache

68

,

R. Bala

100

,

A. Baldisseri

137

,

M. Ball

42

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S. Balouza

104

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R. Barbera

27

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L. Barioglio

25

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G.G. Barnaföldi

145

,

L.S. Barnby

93

,

V. Barret

134

,

P. Bartalini

6

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K. Barth

33

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E. Bartsch

68

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F. Baruffaldi

28

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N. Bastid

134

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S. Basu

143

,

G. Batigne

114

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B. Batyunya

75

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D. Bauri

48

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J.L. Bazo Alba

111

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I.G. Bearden

88

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C. Bedda

63

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N.K. Behera

60

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I. Belikov

136

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A.D.C. Bell Hechavarria

144

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F. Bellini

33

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R. Bellwied

125

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V. Belyaev

92

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G. Bencedi

145

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S. Beole

25

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A. Bercuci

47

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Y. Berdnikov

97

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D. Berenyi

145

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R.A. Bertens

130

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D. Berzano

58

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M.G. Besoiu

67

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L. Betev

33

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A. Bhasin

100

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I.R. Bhat

100

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M.A. Bhat

3

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H. Bhatt

48

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B. Bhattacharjee

41

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A. Bianchi

25

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L. Bianchi

25

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N. Bianchi

51

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J. Bielˇcík

36

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J. Bielˇcíková

94

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A. Bilandzic

104

,

117

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G. Biro

145

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R. Biswas

3

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S. Biswas

3

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J.T. Blair

119

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D. Blau

87

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C. Blume

68

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G. Boca

139

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F. Bock

33

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95

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A. Bogdanov

92

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S. Boi

23

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L. Boldizsár

145

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A. Bolozdynya

92

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M. Bombara

37

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G. Bonomi

140

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H. Borel

137

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A. Borissov

92

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144

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H. Bossi

146

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E. Botta

25

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L. Bratrud

68

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P. Braun-Munzinger

106

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M. Bregant

121

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M. Broz

36

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E.J. Brucken

43

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E. Bruna

58

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G.E. Bruno

105

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M.D. Buckland

127

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D. Budnikov

108

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H. Buesching

68

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S. Bufalino

30

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O. Bugnon

114

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P. Buhler

113

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P. Buncic

33

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Z. Buthelezi

72

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131

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J.B. Butt

14

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J.T. Buxton

96

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S.A. Bysiak

118

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D. Caffarri

89

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A. Caliva

106

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E. Calvo Villar

111

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R.S. Camacho

44

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P. Camerini

24

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A.A. Capon

113

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F. Carnesecchi

10

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26

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R. Caron

137

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J. Castillo Castellanos

137

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A.J. Castro

130

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E.A.R. Casula

54

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F. Catalano

30

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C. Ceballos Sanchez

52

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P. Chakraborty

48

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S. Chandra

141

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W. Chang

6

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S. Chapeland

33

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M. Chartier

127

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S. Chattopadhyay

141

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S. Chattopadhyay

109

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A. Chauvin

23

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C. Cheshkov

135

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B. Cheynis

135

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V. Chibante Barroso

33

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D.D. Chinellato

122

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S. Cho

60

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P. Chochula

33

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T. Chowdhury

134

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P. Christakoglou

89

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C.H. Christensen

88

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P. Christiansen

80

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T. Chujo

133

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C. Cicalo

54

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L. Cifarelli

10

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26

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F. Cindolo

53

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B. Erazmus

,

F. Erhardt

,

A. Erokhin

,

M.R. Ersdal

,

B. Espagnon

,

G. Eulisse

,

D. Evans

,

S. Evdokimov

90

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L. Fabbietti

104

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117

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M. Faggin

28

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J. Faivre

78

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F. Fan

6

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A. Fantoni

51

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M. Fasel

95

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P. Fecchio

30

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A. Feliciello

58

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G. Feofilov

112

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A. Fernández Téllez

44

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A. Ferrero

137

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A. Ferretti

25

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A. Festanti

33

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V.J.G. Feuillard

103

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J. Figiel

118

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S. Filchagin

108

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D. Finogeev

62

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F.M. Fionda

21

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G. Fiorenza

52

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F. Flor

125

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S. Foertsch

72

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P. Foka

106

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S. Fokin

87

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E. Fragiacomo

59

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U. Frankenfeld

106

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U. Fuchs

33

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C. Furget

78

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A. Furs

62

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M. Fusco Girard

29

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J.J. Gaardhøje

88

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M. Gagliardi

25

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A.M. Gago

111

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A. Gal

136

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C.D. Galvan

120

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P. Ganoti

83

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C. Garabatos

106

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E. Garcia-Solis

11

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K. Garg

27

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C. Gargiulo

33

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A. Garibli

86

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K. Garner

144

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P. Gasik

104

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117

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E.F. Gauger

119

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M.B. Gay Ducati

70

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M. Germain

114

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J. Ghosh

109

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P. Ghosh

141

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S.K. Ghosh

3

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P. Gianotti

51

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P. Giubellino

58

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106

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P. Giubilato

28

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P. Glässel

103

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D.M. Goméz Coral

71

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A. Gomez Ramirez

74

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V. Gonzalez

106

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P. González-Zamora

44

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S. Gorbunov

38

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L. Görlich

118

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S. Gotovac

34

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V. Grabski

71

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L.K. Graczykowski

142

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K.L. Graham

110

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L. Greiner

79

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A. Grelli

63

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C. Grigoras

33

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V. Grigoriev

92

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A. Grigoryan

1

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S. Grigoryan

75

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O.S. Groettvik

21

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F. Grosa

30

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J.F. Grosse-Oetringhaus

33

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R. Grosso

106

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R. Guernane

78

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M. Guittiere

114

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K. Gulbrandsen

88

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T. Gunji

132

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A. Gupta

100

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R. Gupta

100

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I.B. Guzman

44

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R. Haake

146

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M.K. Habib

106

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C. Hadjidakis

61

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H. Hamagaki

81

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G. Hamar

145

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M. Hamid

6

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R. Hannigan

119

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M.R. Haque

63

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85

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A. Harlenderova

106

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J.W. Harris

146

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A. Harton

11

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J.A. Hasenbichler

33

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H. Hassan

95

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D. Hatzifotiadou

10

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53

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P. Hauer

42

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S. Hayashi

132

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S.T. Heckel

68

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104

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E. Hellbär

68

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H. Helstrup

35

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A. Herghelegiu

47

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T. Herman

36

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E.G. Hernandez

44

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G. Herrera Corral

9

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F. Herrmann

144

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K.F. Hetland

35

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T.E. Hilden

43

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H. Hillemanns

33

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C. Hills

127

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B. Hippolyte

136

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B. Hohlweger

104

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D. Horak

36

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A. Hornung

68

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S. Hornung

106

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R. Hosokawa

15

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133

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P. Hristov

33

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C. Huang

61

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C. Hughes

130

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P. Huhn

68

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T.J. Humanic

96

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H. Hushnud

109

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L.A. Husova

144

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N. Hussain

41

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S.A. Hussain

14

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D. Hutter

38

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J.P. Iddon

33

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127

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R. Ilkaev

108

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M. Inaba

133

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G.M. Innocenti

33

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M. Ippolitov

87

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A. Isakov

94

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M.S. Islam

109

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M. Ivanov

106

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V. Ivanov

97

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V. Izucheev

90

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B. Jacak

79

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N. Jacazio

53

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P.M. Jacobs

79

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S. Jadlovska

116

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J. Jadlovsky

116

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S. Jaelani

63

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C. Jahnke

121

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M.J. Jakubowska

142

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M.A. Janik

142

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T. Janson

74

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M. Jercic

98

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O. Jevons

110

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R.T. Jimenez Bustamante

106

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M. Jin

125

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F. Jonas

95

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144

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P.G. Jones

110

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J. Jung

68

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M. Jung

68

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A. Jusko

110

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P. Kalinak

64

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A. Kalweit

33

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V. Kaplin

92

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S. Kar

6

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A. Karasu Uysal

77

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O. Karavichev

62

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T. Karavicheva

62

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P. Karczmarczyk

33

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E. Karpechev

62

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A. Kazantsev

87

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U. Kebschull

74

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R. Keidel

46

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M. Keil

33

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B. Ketzer

42

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Z. Khabanova

89

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A.M. Khan

6

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S. Khan

16

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S.A. Khan

141

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A. Khanzadeev

97

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Y. Kharlov

90

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A. Khatun

16

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A. Khuntia

118

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B. Kileng

35

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B. Kim

60

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B. Kim

133

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D. Kim

147

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D.J. Kim

126

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E.J. Kim

73

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H. Kim

17

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147

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J. Kim

147

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J.S. Kim

40

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J. Kim

103

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J. Kim

147

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J. Kim

73

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M. Kim

103

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S. Kim

18

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T. Kim

147

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T. Kim

147

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S. Kirsch

38

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68

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I. Kisel

38

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S. Kiselev

91

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A. Kisiel

142

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J.L. Klay

5

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C. Klein

68

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J. Klein

58

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S. Klein

79

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C. Klein-Bösing

144

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M. Kleiner

68

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A. Kluge

33

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M.L. Knichel

33

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A.G. Knospe

125

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C. Kobdaj

115

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M.K. Köhler

103

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T. Kollegger

106

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A. Kondratyev

75

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N. Kondratyeva

92

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90

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J. Konig

68

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P.J. Konopka

33

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L. Koska

116

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O. Kovalenko

84

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V. Kovalenko

112

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M. Kowalski

118

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I. Králik

64

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A. Kravˇcáková

37

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L. Kreis

106

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M. Krivda

64

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110

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F. Krizek

94

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K. Krizkova Gajdosova

36

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M. Krüger

68

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E. Kryshen

97

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M. Krzewicki

38

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A.M. Kubera

96

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V. Kuˇcera

60

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C. Kuhn

136

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P.G. Kuijer

89

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L. Kumar

99

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S. Kumar

48

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S. Kundu

85

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P. Kurashvili

84

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A. Kurepin

62

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62

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A. Kuryakin

108

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S. Kushpil

94

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J. Kvapil

110

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M.J. Kweon

60

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60

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Y. Kwon

147

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38

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P. La Rocca

27

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79

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R. Langoy

129

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33

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A. Lardeux

20

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P. Larionov

51

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33

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R. Lavicka

36

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T. Lazareva

112

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R. Lea

24

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L. Leardini

103

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J. Lee

133

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147

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89

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113

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38

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93

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I. León Monzón

120

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19

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12

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6

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J. Lien

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R. Lietava

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127

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C. Lippmann

106

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96

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43

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19

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96

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W.J. Llope

143

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