J/ψ production as a function of charged-particle pseudorapidity density in p–Pb collisions at sNN=5.02TeV

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Physics

Letters

B

www.elsevier.com/locate/physletb

J/

ψ

production

as

a

function

of

charged-particle

pseudorapidity

density

in

p–Pb

collisions

at

√

s

_NN

=

5

.

02

TeV

.

ALICE

Collaboration



a

r

t

i

c

l

e

i

n

f

o

a

b

s

t

r

a

c

t

Articlehistory:

Received 6 April 2017

Received in revised form 20 October 2017 Accepted 4 November 2017

Available online 8 November 2017 Editor: L. Rolandi

WereportmeasurementsoftheinclusiveJ/ψ yieldandaveragetransversemomentumasafunctionof charged-particle pseudorapiditydensitydNch/d

η

inp–Pbcollisions at√sNN=5.02 TeV with ALICEat

theLHC.Theobservablesarenormalisedtotheircorrespondingaveragesinnon-singlediffractiveevents. AnincreaseofthenormalisedJ/ψyieldwithnormaliseddNch/d

η

,measuredatmid-rapidity,isobserved

atmid-rapidityandbackwardrapidity.Atforwardrapidity,asaturationoftherelativeyieldisobserved for highcharged-particle multiplicities.The normalisedaveragetransverse momentumatforwardand backward rapidities increases with multiplicity at low multiplicities and saturates beyond moderate multiplicities. In addition, the forward-to-backward nuclear modificationfactor ratio is alsoreported, showing an increasing suppression of J/ψ production at forward rapidity with respect to backward rapidityforincreasingcharged-particlemultiplicity.

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

1. Introduction

Quarkonium states, such as the J/

ψ

meson, are prominent probesofthedeconfinedstateofmatter,theQuark–GluonPlasma (QGP),formed inhigh-energyheavy-ioncollisions

[1]

.A suppres-sion of J/

ψ

production in nucleus–nucleus (AA) collisions with respect to that in proton–proton (pp) collisions has been ob-served by several experiments [2–10]. A remarkable feature is that, for J/

ψ

production at low transverse momentum (pT) at

the Large Hadron Collider (LHC), the suppression is significantly smallerthanthatatlowerenergies

[5,7,10]

.Themeasurementsof J/

ψ

productioninproton(deuteron)–nucleuscollisions,wherethe formationoftheQGPisnotexpected, areessentialtoquantify ef-fects(oftendenoted “cold nuclearmatter, CNM, effects”), present alsoinAAcollisions butnot associatedto theQGP formation.At LHCenergies,gluonshadowing/saturationisthemostrelevant ef-fect which was expectedto be quantified withmeasurements in p–Pbcollisions [11,12]. Furthermore,a novel effect,coherent en-ergylossinCNM(medium-inducedgluonradiation),wasproposed

[13].

Themeasurements ind–Aucollisions attheRelativistic Heavy Ion Collider (RHIC) have underlined the role of CNM effects in J/

ψ

productionat

√

sNN

=

200 GeV [14–16].At theLHC, thefirst measurementsofJ/

ψ

productioninminimum-biasp–Pbcollisions at

√

sNN

=

5

.

02 TeV [17,18]showed that J/

ψ

production inp–Pb

collisions is suppressed at forward rapidity with respect to the

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

expectation from a superposition of nucleon–nucleon collisions. The datahavebeen furtheranalysed to providemoredifferential measurements anddiscussed incomparisonwithseveral theoret-ical models

[19]

.A fairagreementis observedbetween dataand models including nuclear shadowing [12] or saturation [20,21]; alsomodelsincludingacontributionfromcoherentenergylossin CNM

[13]

describethedata.Thesemeasurementsarealsorelevant withrespect toJ/

ψ

production inPb–Pbcollisions atthe LHC

[5,

7],currentlyunderstoodtobestronglyinfluencedbythepresence of a deconfined medium. The measurements of

ϒ

production in minimum-biasp–Pbcollisions attheLHC

[22,23]

are also consis-tentwithpredictionsbasedonCNMeffects.Recentmeasurements of the

ψ

(2S) state in p–Pbcollisions have revealeda larger sup-pression than that measured forJ/

ψ

production[24,25]. Such an observationwasnotexpectedfromtheavailablepredictionsbased onCNMeffects.

Concurrently, measurements of two-particle angular correla-tions in p–Pb collisions at the LHC [26–32] revealed for high-multiplicity events features that, in Pb–Pb collisions, have been interpreted as a result of the collective expansion of a hot and densemedium.Furthermore,theidentifiedparticle

p

Tspectra

[33]

showfeaturesakintothoseinPb–Pbcollisions,wheremodels in-cludingcollective flow, assuminglocal thermalequilibrium, agree withthedata.

ThemeasurementofJ/

ψ

productionasafunctionofcentrality inp–Pbcollisions attheLHC

[34]

showedthatthenucleareffects depend on centrality.

ϒ

production has been studied as a func-tion ofcharged-particle multiplicity in pp and p–Pbcollisions by

https://doi.org/10.1016/j.physletb.2017.11.008

0370-2693/©2017 The Author. 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_.

theCMSCollaboration

[35]

.Theyieldsof

ϒ

mesonsincreasewith multiplicity,while adecrease ofthe relativeproduction of

ϒ(

2S

)

and

ϒ(

3S

)

with respect to

ϒ(

1S

)

is observed. The measurement ofD-mesonproductionasafunctionofeventmultiplicityinp–Pb collisions

[36]

exhibitsfeaturessimilartothoseobservedearlierin ppcollisions,bothforJ/

ψ

[37]andD-meson

[38]

production.

InthisLettermeasurementsoftheinclusiveJ/

ψ

yieldand aver-agetransversemomentumasafunctionofcharged-particle pseu-dorapiditydensityinp–Pbcollisions at

√

sNN

=

5

.

02 TeVare pre-sented.Performedinthreerangesofrapidity forpT

>

0 withthe

ALICEdetector atthe LHC, these measurements complementthe studies of J/

ψ

and

ψ(

2S

)

production as a function of the event centralityestimatedfromtheenergydepositedintheZeroDegree Calorimeters (ZDC) [34,39]. A measurement asa function of the charged-particle multiplicitydoesnot requireaninterpretation of theeventclasses intermsof thecollision geometry.Importantly, it enables the possibility to study rare events where collective-like effects may arise. The present data allow the investigation ofeventswithveryhighmultiplicities ofchargedparticles, corre-spondingtolessthan 1%ofthehadroniccrosssection and estab-lishaswellaconnectiontotherecentmeasurementsofD-meson productionasafunctionofeventmultiplicity

[36]

.Ameasurement oftheforward-to-backwardJ/

ψ

nuclearmodificationfactorratiois alsopresented.

2. Experimentanddatasample

The ALICE central barrel detectors are located in a solenoidal magnetic field of 0.5T. The main trackingdevices in thisregion are the Inner Tracking System(ITS), which consistsof six layers of silicondetectors around the beam pipe, andthe Time Projec-tionChamber(TPC),alargecylindricalgaseousdetectorproviding trackingandparticleidentificationviaspecificenergyloss.Tracks arereconstructedintheactivevolumeoftheTPCwithinthe pseu-dorapidity range

|

η

|

<

0

.

9 in the laboratory frame. The first two layers of the ITS (

|

η

|

<

2

.

0 and

|

η

|

<

1

.

4), the Silicon Pixel De-tector (SPD), are used forthe collision vertex determination and thecharged-particlemultiplicitymeasurement.Theminimum-bias (MB)eventsaretriggeredrequiringthecoincidenceofthetwoV0 scintillatorarrayscovering2

.

8

<

η

<

5

.

1 and

−

3

.

7

<

η

<

−

1

.

7, re-spectively.ThetwoneutronZeroDegreeCalorimeters(ZDC),placed at112.5 monboth sidesoftheinteraction point,areusedto re-ject electromagnetic interactions and beam-induced background. The muon spectrometer, covering

−

4

<

η

<

−

2

.

5, consists of a front absorber, a 3 T

·

m dipole magnet, ten tracking layers, and fourtriggerlayerslocatedbehindaniron-wallfilter.Inadditionto theMBtriggercondition,thedimuontriggerrequiresthepresence oftwoopposite-sign particlesinthe muontriggerchambers. The triggercomprisesa minimumtransversemomentum requirement of

pT

>

0

.

5 GeV/c attracklevel.Thesingle-muontriggerefficiency curveisnotsharp;theefficiencyreachesaplateauvalueof

∼

96% at pT

∼

1

.

5GeV/c.TheALICEdetectorisdescribedinmoredetail

in[40]anditsperformanceisoutlinedin

[41]

.

The results presented in this Letter are obtained with data recorded in 2013 in p–Pb collisions at

√

sNN

=

5

.

02 TeV. MB

eventsareusedfortheJ/

ψ

reconstruction inthedielectron chan-nel at mid-rapidity. The dimuon-triggered data have been taken with two beam configurations, allowing the coverage of both forward and backward rapidity ranges. In the period when the dimuon-triggered data sample was collected, the MB interaction ratereachedamaximumof200kHz,correspondingtoamaximum pile-upprobabilityofabout3%.TheMB-triggeredeventsusedfor thedielectronchannelanalysiswerecollectedinoneofthebeam configurationsatalowerinteractionrate(about10kHz)and con-sequentlyhadasmallerpile-upprobabilityof0.2%.

Duetotheasymmetryofthebeamenergypernucleoninp–Pb collisionsattheLHC,thenucleon–nucleoncenter-of-massrapidity frameisshiftedinrapidityby



y

=

0

.

465 withrespecttothe lab-oratory frame inthe direction ofthe proton beam. This leads to arapiditycoverage inthenucleon–nucleoncenter-of-masssystem

−

1

.

37

<

ycms

<

0

.

43 for the MB events, while the coverage for the dimuon-triggered data forthe two different beam configura-tions is

−

4

.

46

<

ycms

<

−

2

.

96 (muonspectrometerlocatedinthe Pb-going direction) and 2

.

03

<

ycms

<

3

.

53 (muon spectrometer

locatedinthep-goingdirection).Theintegratedluminositiesused inthisanalysisare51

.

4

±

1

.

9μb−1(mid-rapidity),5

.

01

±

0

.

19nb−1 (forward

y)

and5

.

81

±

0

.

20nb−1 (backward y).

3. Charged-particlepseudorapiditydensitymeasurement

The charged-particle pseudorapidity density dNch

/

d

η

is

mea-sured at midrapidity,

|

η

|

<

1, andis based on the SPD informa-tion. Tracklets,i.e.tracksegments builtfromhitpairs inthe two SPDlayers,areusedtogetherwiththeinteractionvertexposition, which is alsodetermined with theSPD information[42].Several quality criteriaareapplied toselectonlyeventswithan accurate determinationofthe

z coordinate

ofthevertex,

zvtx

.Toensurefull SPDacceptanceforthetrackletmultiplicity

N

trk evaluationwithin

|

η

|

<

1,thecondition

|

zvtx

|

<

10 cmisappliedfortheselectionof theevents.

During the data taking period about 8% of the SPD channels were inactive, the exact fraction being time-dependent. The im-pactoftheinactivechannelsoftheSPDonthetrackletmultiplicity measurement varieswith zvtx.A zvtx-dependentcorrection factor isdeterminedfromdata,asdiscussedin

[37]

.Thisfactoralsotakes into account the time-dependent variations of thefraction of in-active SPD channels. The correction factor is randomised on an event-by-eventbasisusingaPoissondistributioninorderto emu-late thedispersion betweenthetruecharged-particle multiplicity andthemeasuredtrackletmultiplicities.

The overall inefficiency, the production of secondary parti-cles due to interactions in the detector material, particle de-cays and fake-tracklet reconstruction lead to a difference be-tween the number of reconstructed tracklets and the true pri-marycharged-particlemultiplicity

Nch

(seedetailsin

[42]

)1.Using eventssimulatedwiththeDPMJETeventgenerator

[43]

,the corre-lationbetweenthetrackletmultiplicity (afterthe zvtx-correction),

Ncorr_trk , and the generated primary charged particles Nch is deter-mined. The correction factor

β

to obtain the average dNch

/

d

η

value corresponding toa givenNcorr

trk biniscomputedfroma

lin-ear fit of the N_trkcorr–Nch correlation. The charged-particle

pseu-dorapidity density value in each multiplicity bin is given rela-tive to theevent-averagedvalue andis calculatedas: dN_chR

/

d

η

=

dNch

/

d

η

/



dNch

/

d

η



= β · 

N_trkcorr

/

(

η

· 

dNch

/

d

η

)

,where



η

=

2

and



dNch

/

d

η



is the charged-particle pseudorapidity densityfor

non-singlediffractive(NSD) collisions,whichwas measuredtobe



dNch

/

d

η



=

17

.

64

±

0

.

01

(

stat.

)

±

0

.

68

(

syst.

)

[42].The resulting

valuesforthemultiplicitybinsare summarisedin

Tables 1 and 2

for forward and mid-rapidity, respectively. For the data at back-wardrapidity,thevaluesarewellwithintheuncertaintiesofthose atforwardrapidity.

The fractionof theMB cross sectioncontained ineach multi-plicity bin (

σ

/

σ

M B, derived from the respective event counts in the multiplicity bins andtotalnumber ofMB events)is reported in Tables 1 and 2.The softest MB events, whichlead to absence

1 _{In this context, we regard as primary charged-particles all prompt charged} par-ticles including all decay products except products from weak decays of light flavour hadrons and of muons.

Table 1

Average charged-particle pseudorapidity density values (absolute and relative) in each multiplicity bin, obtained from Ncorr

trk measured in the range |η|<1. The values correspond to the data sample used for the forward rapidity analysis. Only system-atic uncertainties are shown since the statistical ones are negligible. The fraction of the MB cross section for each multiplicity bin is also indicated.

dNch/dη dNchR/dη σ/σM B 4.8±0.2 0.27±0.01 26.4% 10.9±0.4 0.62±0.03 14.3% 14.6±0.5 0.83±0.03 7.9% 17.8±0.5 1.01±0.04 9.6% 21.4±0.7 1.22±0.05 8.5% 25.0±0.8 1.42±0.06 7.2% 28.6±0.8 1.62±0.06 6.0% 32.7±1.0 1.85±0.07 6.7% 37.8±1.1 2.14±0.08 4.6% 44.2±1.3 2.51±0.10 4.2% 54.3±1.6 3.08±0.12 2.4% 71.4±2.1 4.05±0.16 0.3% Table 2

As Table 1, but for the analysis of J/ψproduction at mid-rapidity.

dNch/dη dNchR/dη σ/σM B

6.9±0.2 0.39±0.02 47.2%

22.9±0.6 1.30±0.05 39.7%

42.3±1.1 2.40±0.10 10.9%

64.4±1.6 3.65±0.15 1.0%

oftracklets in

|

η

|

<

1 arenot accountedforinthisanalysis.They correspond to1.2% of

σ

M B for the MB-triggeredevents and1.9% forthemuon-triggereddata;thedifferenceisduetothedifferent fractionofinactivechannelsinSPDandaffects,albeitina negligi-bleway,onlyourfirstmultiplicitybin.

Themultiplicityselection inthisanalysisallowstosample the datain bins containing a small fractionof the MB cross section. Therefore, it gives the possibility to study the J/

ψ

production in rare high-multiplicity events which were not accessible in the centrality-basedanalysis

[34]

(wherethemost-centraleventclass correspondstotherange2–10%in

σ

/

σ

M B).

4. J/

ψ

measurement

FortheJ/

ψ

analysisatforwardandbackward rapidities,muon candidatesareselectedbyrequiringthereconstructedtrackinthe muonchamberstomatchatracksegmentinthetriggerchambers. Furthermore,theradial distanceofthe muon trackswithrespect tothe beamaxis atthe endof the front absorber isrequired to be between17.6 and89.5cm. Thiscriterion rejects tracks cross-ingthehigh-densitypartoftheabsorber,wherethescatteringand energy-loss effects are large. Aselection onthe muon pseudora-pidity

−

4

<

η

<

−

2

.

5 isalsoappliedtorejectmuonsattheedges ofthespectrometer’sacceptance.

When building the invariant mass distributions, each dimuon pair(ofagiven pT andy) iscorrectedbythedetectoracceptance timesefficiencyfactor1/( A

×

ε

(pT, y)).The A

×

ε

(pT, y)mapis

ob-tainedfromaparticle-gunMonteCarlo(MC)simulationbasedon GEANT 3 [44] and simulating the detector response as in [18]. Since the A

×

ε

-factor does not depend on the multiplicity for theeventmultiplicities relevantforthe p–Pbanalyses,the simu-latedeventsonlycontainadimuonpairatthegeneratorlevel.The simulations assume an unpolarised J/

ψ

production. The same re-constructionprocedureandselectioncutsareappliedtoMCevents andto real data.The extractionof the J/

ψ

signal in the dimuon channel is performed via a fit to the A

×

ε

-corrected opposite-sign(OS)dimuon invariant massdistributions obtained for pT

<

15GeV/c.Thefittingprocedureissimilarto thatusedina previ-ousJ/

ψ

analysisinp–Pbcollisions

[18]

.Thedistributionsarefitted

usinga superpositionofJ/

ψ

and

ψ(

2S

)

signalsanda background shape.TheresonancesareparameterizedusingaCrystalBall func-tion with asymmetric tails while for the background a Gaussian withits widthlinearlyvarying withmassis used.In thepresent analysis,theparametersofthenon-Gaussian tailsoftheresonance shapearedetermined fromfitsoftheMCJ/

ψ

signal,andfixed in thedatafittingprocedure.Examplesoffitsofthe A

×

ε

-corrected dimuoninvariantmassdistributionsfortwoselectedbins,lowand highmultiplicities,aregivenintheleftpanelof

Fig. 1

.

Inthedielectrondecaychannel,electronsandpositronsare re-constructedinthecentralbarreldetectorsbyrequiringaminimum of 70out ofmaximally 159track points in the TPCand a max-imum value of 4 for the track fit

χ

2 _{over the number of track}

points. Furthermore,onlytracks withatleasttwo associatedhits intheITS, oneoftheminthe innermostlayer, areaccepted.This selectionreducestheamountofelectronsandpositronsfrom pho-ton conversions in the material of the detector beyond the first ITSlayer. Inaddition a vetocut ontopologically identifiedtracks fromphoton conversions isapplied. The electronidentification is achieved by the measurement of the energy deposition of the track in the TPC, which is required to be compatible with that expected for electrons within 3 standard deviations. Tracks with specificenergylossbeingconsistentwiththatofthepionor pro-ton hypothesis within 3.5standard deviationsare rejected. These selectioncriteriaareidenticaltothoseusedin[34].Electronsand positronsareselectedinthepseudorapidityrange

|

η

|

<

0

.

9 andin thetransversemomentumrangepT

>

1GeV/c.

The background in the OS invariant mass distribution is es-timated with dielectron pairs formed with tracks from differ-ent events (mixed-event background). The background shape is normalised such that its integral over ranges of the invariant mass in the sidebands of the J/

ψ

mass peak equals the num-ber of measured OS dielectron pairs in the same ranges (typical ranges usedare

[

3

.

2

,

3

.

7

]

GeV/c2 _and

_[

₂

_.

₀

_,

₂

_.

₅

_]

_GeV/c2_).The

sig-nal itselfis extractedby countingtheentries inthe background-subtractedinvariant massdistribution(the standardrangeusedis

[

2

.

92

,

3

.

16

]

GeV/c2_{). Due to bremsstrahlung of the electron and}

positron inthe detectormaterial andradiative correctionsof the decayvertex, theJ/

ψ

signalshapehasatailtowardslower invari-antmasses.The standardrangeforthesignalextractioncontains, according to MC simulations, about 69% of the J/

ψ

signal. The numberofreconstructedJ/

ψ

mesonsanditsstatisticaluncertainty are derived from the mean obtainedwhen varying the counting window for the signal extraction and the invariant mass ranges usedforthenormalisationofthebackground.The variationsthat are taken intoaccount are thesame asin [34].Examples of the dielectron invariant mass distributions in data, for two selected analysisbinsatlow andhighmultiplicities,aregivenintheright panelof

Fig. 1

.

The correction for the acceptance and efficiency of the raw yieldsisbasedonsimulatedp–PbcollisionswiththeHIJINGevent generator[45]withaninjectedJ/

ψ

signal.Thedielectrondecayis simulatedwiththeEVTGENpackage[46]usingPHOTOS[47,48]to describethefinal stateradiation.Theproductionisassumedtobe unpolarisedasinthe muondecaychannel analysis. The propaga-tionofthesimulatedparticlesisdonebyGEANT 3[44]andafull simulationofthedetectorresponseisperformed.Thesame recon-struction procedure and selection cuts are applied to MC events andtorealdata.

The inclusive J/

ψ

yield per event is obtained in each multi-plicity bin as NJ/ψ

=

NcorrJ/ψ

/

NMB, where N

corr

J/ψ is the number of

reconstructed J/

ψ

mesons corrected for the acceptance times ef-ficiencyfactor.Inthedimuondecaychannelanalysis, thenumber ofMBeventsequivalentto theanalysed dimuonsample(NMB) in

trig-Fig. 1. Opposite-sign

invariant mass distributions of selected muon (left panel, for the forward rapidity) and electron (right panel) pairs, for selected multiplicity bins. In the

left panel, the distributions are corrected for A×ε. The curves show the fit functions for signal, background and combined signal with background (see text for details). In the right panel, the background is evaluated with the event-mixing technique, and the overlaid signal is obtained from Monte Carlo (see text for details).

gers(NDIMU),throughthenormalisationfactorofdimuon-triggered

toMB-triggeredevents F2μ/MB,as

NMB

=

F2μ/MB

·

NDIMU.This

fac-toriscomputedusingtwodifferentmethods,asdiscussedin

[34]

. TheJ/

ψ

crosssectionvaluesforminimum-biaseventsobtainedin thedimuonchannelatforwardandbackwardrapidities,andinthe dielectronchannelatmid-rapidityarecompatiblewiththose pre-sented in [18] and[19], respectively. The results presented here areprovidedrelativetotheyieldinNSDevents,



dNJ/ψ

/

d y



.The

event-averagedyieldisnormalisedtotheNSDeventclass;the nor-malisationuncertaintyis3.1%

[42]

.

Inpreviousanalyses,e.g.

[19]

,theJ/

ψ

yieldwasextractedin

pT

bins,andthe resultingdistribution was fittedto extract the



pT



value.Thepresentanalysisaimsatstudyingeffectsthatmayarise athighcharged-particle multiplicities,wheretheusualmethodis no longersuitable due tostatistical limitations.The method pre-sentedheredoesnotrequiretosample thedatainpT bins,hence allowing the analysis infiner multiplicity bins. The extractionof theaveragetransversemomentumofJ/

ψ

mesonsisdoneviaafit to the dimuon meantransverse momentum as a function ofthe invariant mass,



pμ_T+μ−

(

_mμ+_μ−

)

.Acorrectionforthe acceptance times efficiencyhas to be applied when building these distribu-tions.Hence, thecontributionofeachdimuonpairwithacertain

pT and y in a given invariant mass bin is weighted with the two-dimensional A

×

ε

(pT, y).InordertoextracttheJ/

ψ



pT



,the A

×

ε

-corrected



p_Tμ+μ−

(

_mμ+μ−

)

distributions, whichare shown in

Fig. 2

,arefittedusingthefollowingfunctionalshape:



pμ_T+μ−

(

m_μ+_μ−

)

=

α

J/ψ

₍

_m μ+μ−

)

× 

pTJ/ψ



+

α

ψ (2S)

₍

_m μ+μ−

)

× 

pψ (T 2S)



+



1

−

α

J/ψ

(

m_μ+_μ−

)

−

α

ψ (2S)

(

m_μ+_μ−

)



× 

pbkg_T



(1)

Fig. 2. Average

transverse momentum of opposite-sign muon pairs as a function of

the invariant mass at forward rapidity, for two multiplicity bins. The curves are fits of the background and combined signal and background (see text).

where

α

(

mμ+_μ−

)

=

S

(

mμ+_μ−

)/(

S

(

mμ+_μ−

)

+

B

(

mμ+_μ−

))

; the sig-nal (S)andbackground(B)dependenceon thedimuoninvariant massisextractedfromthecorrectedinvariant massspectrumfits mentionedabove.TheJ/

ψ

and

ψ(

2S

)

averagetransversemomenta,

Table 3

The relative systematic uncertainties of the relative J/ψyield measurement in the three rapidity ranges. The values in parentheses correspond to the absolute yield measurement when different from the relative ones. The ranges represent the minimum and maximum values of the uncertainties over the multiplicity bins. For the vertex quality selection, the uncertainties marked with ∗_{refer only to the lowest-multiplicity bin; for all other bins the value is 0.3%. The trigger,} tracking and matching efficiency uncertainties are not listed in the table.

Source 2.03<ycms<3.53 −4.46<ycms<−2.96 −1.37<ycms<0.43

Sig. Extr. 0.6–1.9% 0.5–1.8% 3.2–8.4%

F2μ/M Bmethod 0.3–3.9% 0.3–3.9% Not applicable

A×ε/bin-flow 1–5.9% 1.4–3.9% 3.1–9.9%

Pile-up 1–4% 1–1.5% Negligible

Signal tails 0.5% (2%) 0.5% (2%) Not applicable

Vertex quality sel. 0.3%–0.6%∗(0.9%∗) 0.3%–0.6%∗(0.9%∗) Negligible

Total 2.1–8.3% (3.0–8.6%) 2.1–6.0% (2.9–6.4%) 4.5–13%



p_TJ/ψ



and



p_Tψ (2S)



, respectively, are fit parameters assumed to beindependentof theinvariantmass,while thebackgroundone,



pbkg_T



,isparameterizedwithasecondorderpolynomialfunction. Notethat,asfortheyieldextraction,thequantity



pψ (_T 2S)



isnot a measurement ofthe

ψ(

2S

)

mean transverse momentum, since the A

×

ε

isobtainedonlyfromJ/

ψ

signalsinthesimulation.The



pT



resultspresentedhereforbinsinmultiplicity are relativeto thevalueobtainedforinclusiveevents,



pT



MB[19].

5. Systematicuncertainties

The systematic uncertainty of the overall average charged-particle pseudorapidity density was estimated to be 3.8% [42]. This includes effects related to the uncertainties in the simula-tions,detectoracceptanceandeventselection efficiency,anditis dominatedby the normalisation tothe NSD eventclass.Possible correlationbetweentheaveragemultiplicityandthatevaluatedin agivenbinwouldleadtoapartialcancellationofcertain sources ofuncertaintywhencomputingtherelativemultiplicity.Asa con-servative estimate, the uncertainty on the relative multiplicity is consideredtobe equaltotheuncertaintyontheoverall charged-particlepseudorapiditydensity.

Theinfluenceofvariationsofthe

η

distributioninthe calcula-tionof the

β

correction factors, isestimated fromthe difference between the average number of tracklets obtained in the data takenwiththetwodifferentbeamconfigurations.The correspond-inguncertainty onthemultiplicity determination amountsto 1%. Theuncertainties arising fromthe fit procedureof the Ncorr_trk –Nch

correlationinsimulatedevents,usedtoobtainthecorrection fac-tors, are also included.This uncertainty ranges between0.2% (at high multiplicity) and 2% (at low multiplicity). The event selec-tionrelated to the vertexquality has a 1% effecton the average multiplicity in the lowest multiplicity bin anda negligible effect fortheother bins.Duetotheuncertaintyonthedeterminationof themultiplicity ofthe individual events,there couldbe a migra-tionofeventsamongthemultiplicitybins(bin-flow).Thisbin-flow effectisdeterminedbyrunningtheanalysisseveraltimeswith dif-ferent seeds for the random factor of the multiplicity correction (bin-flow test). The bin-flow uncertainties are obtainedfrom the dispersionofthe averagemultiplicity valuesinthebin-flowtests foreach multiplicity bin. Finally,the effect of pile-up is studied usingatoymodelthatreproducesthemainfeaturesofthe multi-plicitydetermination,andtakesintoaccountthemis-identification ofmultiplecollisionsinthesameevent. Thecontributionsof bin-flow and pile-up to the measured multiplicities are found to be negligibleforallthedatasets(takenatdifferentinteractionrates). Thebin-dependentuncertaintyisaddedinquadraturetothe3.8% uncertaintyof



dNch

/

d

η



,resultingina systematicuncertaintyof

therelative charged-particle multiplicity of 4–4.5% depending on themultiplicitybin.

The yields reported here are provided relative to the event-averageyieldandtheuncertaintiesareestimatedforthisratio.The systematicuncertainties related totrigger, tracking andmatching efficiencyare correlated betweenthe multiplicity-differential and theintegrateddeterminations.Theycancelouttoalargeextent.

In the dimuon analysis, a combined systematic uncertainty whichincludesthe A

×

ε

variations duetotheuncertaintyofthe J/

ψ

pTandrapidityinputdistributionsusedinthesimulationand multiplicitybin-floweffectsisderived.Duetothemultiplicity bin-flow, andthe fact that the invariant mass and



p_Tμ+μ−

(

_mμ+_μ−

)

spectra are weighted by A

×

ε

, these uncertainties can not be computedseparately. Thecombined uncertaintyis obtainedfrom ther.m.s. oftherelative yieldvaluesobtainedrunningthe analy-sisseveraltimeswithdifferentseeds fortherandomfactorofthe multiplicity correction. In additionthe systematicuncertainty for the signal extraction isestimated asthe r.m.s. ofthe results ob-tainedusingdifferentfittingassumptionsforagivenbin-flowtest. The fit procedure is varied by adoptinga pseudo-Gaussian func-tionforthesignal,apolynomialtimesanexponentialfunctionfor thebackgroundandbyusingtwoadditionalfittingranges.The un-certaintyduetothedeterminationoftheparametersofthesignal tailsis estimatedbyusingseveralsets ofparameters from differ-ent MC simulations. The uncertainty related to the computation method of the relative F2μ/M B is estimated considering the dif-ference betweenthetwoavailable methodstomeasurethefactor inmultiplicity bins

[34]

.Theeffectofthevertexqualityselection is estimatedfromthe difference ofthe obtained yields withand without this selection. Finally, in order to determine the pile-up effectonthe measuredyield ineach multiplicitybin,the pile-up toy model is extended by including the production of J/

ψ

using as input the measured yields as a function of multiplicity. The difference between the measured andtoy MC yields is taken as systematicuncertainty.Alltheseeffectsareuncorrelatedwithina givenmultiplicitybin,hencetheyareaddedquadraticallytoobtain the systematic uncertainty of the relative yield in a multiplicity bin.Also, thesesystematicuncertainties are consideredas uncor-relatedbetweenthedifferentrapidityintervals. Asummaryofthe maximumandminimumrelativeyieldsystematicuncertainties is shownin Table 3. Inaddition, the3.1% uncertaintyof the event-averageyieldnormalisationtoNSD,isreportedseparately.

Thesystematicuncertaintiesarecomputedalsofortheabsolute yieldsinmultiplicitybinsatforwardandbackwardrapidities.The absoluteyieldsareusedtocomputetheratioofthenuclear mod-ificationfactorsatforwardandbackward rapidities.Thevaluesof theuncertaintiesontheabsoluteyields areshowninparentheses in

Table 3

,whentheyaredifferentfromtheonesobtainedforthe relativeyield.Inaddition,fortheabsoluteyieldmeasurement,the muontracking,triggerandmatchingefficiencyuncertainties need tobe takenintoaccount

[18]

.Theyamountto4% (6%),3% (3.4%) and1%(1%)atforward(backward)rapidities.

Table 4

The systematic uncertainties for the relative pT measurement at forward and backward rapidities. The values represent the minimum and maximum values of the uncertainties over the multiplicity bins. The uncertainties marked with ∗_only refer to the two highest-multiplicity bins.

Source 2.03<ycms<3.53 −4.46<ycms<−2.96

Sig. extr. 0.2–1.2% 0.2–0.5%

A×ε/bin-flow 0.5–2.0% 0.7–2.7%

Pile-up 0.2–0.7%∗ 0.2–0.8%∗

Total 0.6–2.4% 0.7–2.9%

Forthe dielectron decay channel, the signal extraction uncer-tainty is derived basedon the r.m.s.value of thedifferent signal yieldratiosobtainedforthevariationsofthebackgroundandthe signalintegrationwindowasin

[34]

.Theuncertaintyislargestfor thehighestmultiplicitybins.Sincethe pT distributionofJ/

ψ

may

depend on multiplicity, the unmeasured pT spectrum leads to a multiplicity-dependent uncertainty, determinedas in[34]. As ex-plained in section 2, the pile-up contamination is very low and the induced uncertainty is negligible for all the multiplicity in-tervals.The uncertaintyrelatedto bin-flowisestimatedwiththe samemethodasinthedimuonanalysis. Thetotalsystematic un-certaintyvariesasafunctionofmultiplicitybetween4.5%and13%, see

Table 3

.

Fortherelative J/

ψ



pT



,theeffectsof theuncertaintyonthe determinationof

A

×

ε

,the



pT



extractionprocedureandbin-flow are computed together following the same procedure asfor the relativeyield.The



pT



extractionuncertaintyisobtainedfromthe dispersionoftheresultsusingdifferentfitcombinations,including variations of the invariant mass signal and background parame-terisations,fittingrangeandtheuseofasecond orderpolynomial timesanexponentialfunctionforthe



pT



ofbackgrounddimuons. TheeffectofconsideringtheJ/

ψ



pT



asindependentofthe invari-antmassinthe



p_Tμ+μ−



fitsisfoundtobenegligible.Theimpact offixing thesignal andbackgroundparametersduring the fitting procedureisobservedtobenegligibleaswell.Theeventsremoved bythevertexqualityselectiondonot havereconstructed J/

ψ

and thereforethe



pT



remainsunmodified.Finally,usingapile-uptoy

model,itisshownthatthepile-uphasnoeffectonthe



pT



mea-surement, except for the two bins corresponding to the largest multiplicities.Alltheseeffectsareconsideredasuncorrelatedina givenmultiplicity binandhencetheirrespectiveuncertaintiesare added quadraticallyto obtain the relative



pT



systematic uncer-tainty ineachmultiplicity bin.Thesesystematicuncertainties are consideredasuncorrelatedbetweenthedifferentrapidityintervals. Theresultsoftheuncertainties enteringintherelative



pT



mea-surementarereportedin

Table 4

.

6. Resultsanddiscussion

The dependence of the relative J/

ψ

yield on the relative charged-particle pseudorapidity density for three J/

ψ

rapidity rangesispresentedin

Fig. 3

.Anincreaseoftherelativeyieldwith charged-particle multiplicity is observed forall rapidity domains, with a similar behaviour at low multiplicities. At multiplicities beyond 1.5–2 times the event-average multiplicity, two different trendsare observed.Therelativeyields atmid-rapidityand back-wardrapiditykeep growingwiththerelativemultiplicity inp–Pb collisions similarly to the observation in pp collisions at 7 TeV

[37]. At forward rapidity the trend is different. In this rapidity window a saturation of the relative yield sets in for high mul-tiplicities. In lack of theoretical model calculations, it is unclear at the moment what is the causeof this observation. We recall thatthe exploredBjorken

x ranges

intheforwardrapidityregion

Fig. 3. Relative

yield of inclusive J/

ψmesons, measured in three rapidity regions, as a function of relative charged-particle pseudorapidity, measured at mid-rapidity. The error bars show the statistical uncertainties, and the boxes the systematic ones. The dashed line is the first diagonal, plotted to guide the eye.

Fig. 4. Relative yield of inclusive J/ψmesons as a function of relative charged-particle pseudorapidity density, measured at mid-rapidity, in comparison to D mesons (average of D0_{, D}+_{, and D}∗+ _{species), for the pTinterval 2–4 GeV/c[36].} The error bars show the statistical uncertainties, and the boxes the systematic ones (additional systematic uncertainties due to the b feed-down contributions and the event normalisation are not shown for the D mesons).

are in thedomain ofshadowing/saturation, andthat a variety of models [12,13,49,20,21] arefairly successfulin describingthe re-cent centrality-integratedanddifferential measurements ofALICE

[19,34],whichcorrespondintermsofourrelativemultiplicitiesto dNch

/

d

η

/



dNch

/

d

η





2

.

5 atmost.

In Fig. 4the J/

ψ

measurementatmid-rapidity iscompared to that forprompt Dmesons (average ofD0, D+, andD∗+ species) for the pT range 2–4GeV/c [36]. Similar trends are seen forthe J/

ψ

andDmesons,asobservedearlierinppcollisions

[38]

.

ThenuclearmodificationfactorforJ/

ψ

productioninp–Pb col-lisions (RpPb) as a function of centrality was presented in [34].

The relationship betweengeometry-related quantities, that quan-tifythecentralityofthecollision,andexperimentalobservablesin p–Pbcollisionsmaybesubjecttoaselectionbias

[50]

whichneeds careininterpretation.Byperformingtheratioofthenuclear mod-ification factors atforwardandbackward rapidities asa function of multiplicity,the dependenceon geometry-related quantities is eluded. Theforward-to-backwardnuclearmodificationfactorratio isdefinedas:

RFB

=

RpPb

(

2

.

03

<

ycms

<

3

.

53

)

Fig. 5. RFB of inclusive J/ψin p–Pb collisions at √sNN=5.02 TeV as a function of relative charged-particle pseudorapidity density, measured at mid-rapidity. The filled box at unity represents the global uncertainty. The error bars show the statis-tical uncertainties, and the boxes the systematic ones.

=

Y J/ψ pPb

(

2

.

03

<

ycms

<

3

.

53

)

Y_pPbJ/ψ

(

−

4

.

46

<

ycms

<

−

2

.

96

)

×

d

σ

J/ψ pp

/

d y

(

−

4

.

46

<

ycms

<

−

2

.

96

)

d

σ

ppJ/ψ

/

d y

(

2

.

03

<

ycms

<

3

.

53

)

(2)

Since theaverage charged-particle multiplicities andtheir uncer-taintiesareconsistentwitheachotherforthetwosetsofdata,the valuesof RFB are shown versus the average value of the two in eachmultiplicitybin.Notethat,differentlythanforthecaseofthe nuclearmodification factor measurement in

[18]

,for the present measurementtherapidity ranges arenot symmetricwithrespect to ycms

=

0 totake advantageofallthesignal yield,allowingthe

studyuptohighmultiplicities.Thevaluesofthereferencepp cross sectionwereobtainedbymeansofaninterpolationprocedure us-ing measurements at center-of-massenergies of 2.76 and 7 TeV

[51]. The resulting backward-to-forward ratio of J/

ψ

production crosssectionsinpp collisionsis0

.

691

±

0

.

048,leadingtoaglobal uncertaintyonthe RFBmeasurementof6.9%.

Forthe RFB ratio,thesystematic uncertainties ofthe absolute yields inp–Pbcollisions (Table 3) are considered asuncorrelated betweenforwardandbackwardrapidities,andthereforeaddedin quadrature.Theuncorrelated systematicuncertainties ofthe pro-ductioncrosssectionsinpp collisionsare thesameasafunction ofmultiplicity,sothey areaddedinquadratureto theglobal un-certainty (quadratic sumof muon tracking, trigger andmatching efficiencyuncertainties)ofthep–Pbdata,resultinginatotal rela-tiveuncertaintyof11%.

The RFB ratio is shownas a function ofthe relative

charged-particle pseudorapidity density inFig. 5. In multiplicity-inclusive collisions for symmetric y ranges at forward and backward ra-pidities

[18]

, RFB issmallerthanunityanddescribed by

theoreti-calmodels.Thepresentmeasurementshowsthatthesuppression of J/

ψ

production at forward rapidity with respect to backward rapidity increases significantly with charged-particle multiplicity, since RFB reaches values as low as 0.34

±

0.06 (stat.)

±

0.05 (syst.). A forward–backward asymmetry can be noticed for in-clusive charged-particle production studied in [50]. Even though therangeofrelativecharged-particle multiplicitiesprobedinthat measurement is not as large as in the present measurement of J/

ψ

production,theapparent similarityofthetrendseenin

Fig. 5

tosoftparticleproductionisintriguing.

In Fig. 6 the relative



pT



of J/

ψ

mesons at backward and forwardrapidity is shown asa function of the relative charged-particlepseudorapiditydensity.The resultsaresimilaratforward

Fig. 6. RelativepTof J/ψmesons for backward and forward rapidity as a function of the relative charged-particle pseudorapidity density, measured at mid-rapidity. The bars show the statistical uncertainties, and the boxes the systematic ones. The data for charged particles (h±_{) [52]are included for comparison. The latter are for}

|ηcms|<0.3 and with pT in the range 0.15 to 10 GeV/c and have an additional normalisation uncertainty of 3.4%.

andbackwardrapidities.Anincreaseoftherelative



pT



with mul-tiplicity at low charged-particle multiplicity is observed, but for multiplicities beyond 1.5 times the average multiplicity it satu-rates.Forbackwardrapidity,thesimultaneousincreaseoftheyield andthe saturation of the relative



pT



could be an indication of J/

ψ

productionfromanincoherentsuperpositionofparton–parton interactions,assuggestedbydataoncorrelationsofjet-likeyields pertriggerparticle

[32]

.

The pT broadening observedin theanalysisof J/

ψ

production inp–Pbcollisionsasafunctionofcentrality

[34]

iswelldescribed by initialandfinal-statemultiplescatteringofpartonswithinthe nuclear medium [53]. The comparisonof data to model calcula-tions, performed in [34], corresponds in terms of relative mul-tiplicities to a range up to roughly dNch

/

d

η

/



dNch

/

d

η



=

2

.

5. It

remains to be seen whether such models can explain the satu-rationobserved inthe relative



pT



oftheJ/

ψ

mesons forevents withhighermultiplicities.

It is interesting to contrast the observed saturation of



pT



for J/

ψ

mesons withthe monotonic increase of



pT



for charged hadrons(dominatedbypionproduction)

[54]

withthemultiplicity measuredatmid-rapidityalsoshownin

Fig. 6

.Notethatthis mea-surementisforparticlesin

|

η

cms

|

<

0

.

3 andwithpT intherange

0.15 to 10 GeV/c, and it is relative to events with at least one particleinthiskinematicrange(forwhich



Nch



=

11

.

9

±

0

.

5 and



pT



=

0

.

696

±

0

.

024 GeV/c[54]).Althoughthedifferentkinematic regionsmayplayaroleandcareisneededintheinterpretation,it isapparent that thetwo observables, characterisedby rather dif-ferent production mechanisms (and momentum-transfer) exhibit different patterns in the multiplicity dependence of the average transversemomentum.

7. Conclusions

Measurementsoftherelative J/

ψ

yieldandaverage transverse momentum asa functionofthe relativecharged-particle pseudo-rapiditydensityinp–Pbcollisions attheLHCat

√

sNN

=

5

.

02TeV

have been presented inthis letter. The measurements were per-formedwithALICEinthreerangesofrapidity.Thecharged-particle multiplicity was measured atmid-rapidity; multiplicities up to 4 times the value of NSD events were reached, corresponding to rareeventsoflessthan1% ofthetotalhadronicinteraction cross section.AnincreaseoftherelativeJ/

ψ

yieldwiththerelative mul-tiplicityisobserved,withatrendtowardssaturationathigh

mul-tiplicityforthe forwardrapidity (proton-goingdirection).Forthe J/

ψ

dataatmid-rapidity,acomparisontocorresponding measure-ments ofD-meson yieldsis performed, revealingsimilarpatterns for the two meson species. At forward and backward rapidities, therelativeaveragetransversemomentaexhibitasaturationabove moderatevaluesofrelativemultiplicity.

Thepresentdataareexpectedtoconstituteastringenttestfor theoreticalmodels ofJ/

ψ

production inp–Pb collisionsandhelp tounderstandtheeffects associatedwiththe productionofa de-confinedmediuminPb–Pbcollisions.

Acknowledgements

The ALICE Collaboration would like to thank all its engineers andtechnicians fortheir invaluablecontributionstothe 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-videdbyall GridcentresandtheWorldwide LHCComputingGrid (WLCG) collaboration. The ALICE Collaboration acknowledges the followingfundingagencies fortheirsupport inbuildingand run-ningtheALICEdetector: A.I. AlikhanyanNationalScience Labora-tory(YerevanPhysicsInstitute)Foundation(ANSL),State Commit-teeofScienceandWorldFederationofScientists(WFS),Armenia; AustrianAcademyofSciencesandÖsterreichischeNationalstiftung für Forschung, Technologie undEntwicklung, Austria; Ministry of CommunicationsandHighTechnologies,NationalNuclearResearch Center,Azerbaijan;Conselho NacionaldeDesenvolvimento Cientí-ficoeTecnológico(CNPq), UniversidadeFederaldo RioGrande do Sul(UFRGS), Financiadorade Estudose Projetos(Finep)and Fun-dação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), Brazil; Ministry of Science & Technology of China (MSTC), Na-tional Natural Science Foundation of China (NSFC) and Ministry of Education of China (MOEC), China; Ministry of Science, Edu-cation and Sportand Croatian Science Foundation, Croatia; Min-istryofEducation,YouthandSportsoftheCzech Republic,Czech Republic; The Danish Council for Independent Research — Natu-ral Sciences, the Carlsberg Foundation and Danish National Re-search Foundation (DNRF), Denmark;Helsinki Institute ofPhysics (HIP),Finland;Commissariatàl’EnergieAtomique(CEA)and Insti-tut Nationalde Physique Nucléaire etde Physique desParticules (IN2P3)and Centre Nationalde laRecherche Scientifique(CNRS), France; Bundesministerium für Bildung, Wissenschaft, Forschung undTechnologie (BMBF)andGSI Helmholtzzentrum für Schweri-onenforschung GmbH, Germany; Ministry of Education, Research andReligiousAffairs,Greece;NationalResearch,Developmentand Innovation Office, Hungary; Department of Atomic Energy, Gov-ernment of India (DAE) and Council of Scientific and Industrial Research(CSIR),NewDelhi,India;IndonesianInstituteofScience, Indonesia;CentroFermi–MuseoStoricodellaFisicaeCentroStudi e Ricerche Enrico Fermi and Istituto Nazionale di Fisica Nucle-are (INFN), Italy; Institute forInnovativeScience and Technology, Nagasaki Institute ofApplied Science(IIST), Japan Societyforthe PromotionofScience(JSPS)KAKENHIandJapaneseMinistryof Ed-ucation, Culture, Sports, Science and Technology (MEXT), Japan; Consejo Nacional de Ciencia (CONACYT) y Tecnología, through FondodeCooperaciónInternacionalenCienciayTecnología (FON-CICYT)andDirección GeneraldeAsuntos delPersonalAcademico (DGAPA), Mexico;Nederlandse Organisatievoor Wetenschappelijk Onderzoek(NWO), Netherlands;The ResearchCouncil ofNorway, Norway; Commission on Science andTechnology for Sustainable Development in the South (COMSATS), Pakistan; Pontificia Uni-versidad Católica del Perú, Peru; Ministry of Science and Higher EducationandNationalScience Centre, Poland;Korea Institute of Science andTechnology InformationandNationalResearch

Foun-dation of Korea (NRF), Republic of Korea; Ministry of Education andScientific Research,Institute ofAtomicPhysics andRomanian National Agency for Science, Technology and Innovation, Roma-nia; JointInstitute forNuclearResearch(JINR),Ministryof Educa-tion andScience oftheRussianFederationandNationalResearch Centre KurchatovInstitute,Russia; MinistryofEducation,Science, Research andSport oftheSlovak Republic, Slovakia; National Re-search Foundation of South Africa, South Africa; Centro de Apli-cacionesTecnológicasyDesarrolloNuclear(CEADEN),Cubaenergía, Cuba, Ministerio de Ciencia e Innovacion andCentro de Investi-gaciones Energéticas, Medioambientales y Tecnológicas(CIEMAT), Spain;SwedishResearchCouncil(VR)andKnut&AliceWallenberg Foundation(KAW),Sweden;EuropeanOrganizationforNuclear Re-search,Switzerland;NationalScienceandTechnologyDevelopment Agency(NSDTA),SuranareeUniversityofTechnology(SUT)and Of-fice of the Higher Education Commission under NRU project of Thailand,Thailand;TurkishAtomicEnergyAgency(TAEK),Turkey; National Academy of Sciences of Ukraine, Ukraine; Science and TechnologyFacilitiesCouncil(STFC),UnitedKingdom;National Sci-ence Foundation of the United States of America (NSF) and U.S. DepartmentofEnergy,OfficeofNuclear Physics(DOENP),United StatesofAmerica.

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ALICECollaboration

D. Adamová

87

,

M.M. Aggarwal

91

,

G. Aglieri Rinella

34

,

M. Agnello

30

,

N. Agrawal

47

,

Z. Ahammed

139

,

N. Ahmad

17

,

S.U. Ahn

69

,

S. Aiola

143

,

A. Akindinov

54

,

S.N. Alam

139

,

D.S.D. Albuquerque

124

,

D. Aleksandrov

83

,

B. Alessandro

113

,

D. Alexandre

104

,

R. Alfaro Molina

64

,

A. Alici

26,12,107

,

A. Alkin

3

,

J. Alme

21

,

T. Alt

41

,

I. Altsybeev

138

,

C. Alves Garcia Prado

123

,

M. An

7

,

C. Andrei

80

,

H.A. Andrews

104

,

A. Andronic

100

,

V. Anguelov

96

,

C. Anson

90

,

T. Antiˇci ´c

101

,

F. Antinori

110

,

P. Antonioli

107

,

R. Anwar

126

,

L. Aphecetche

116

,

H. Appelshäuser

60

,

S. Arcelli

26

,

R. Arnaldi

113

,

O.W. Arnold

97,35

,

I.C. Arsene

20

,

M. Arslandok

60

,

B. Audurier

116

,

A. Augustinus

34

,

R. Averbeck

100

,

M.D. Azmi

17

,

A. Badalà

109

,

Y.W. Baek

68

,

S. Bagnasco

113

,

R. Bailhache

60

,

R. Bala

93

,

A. Baldisseri

65

,

M. Ball

44

,

R.C. Baral

57

,

A.M. Barbano

25

,

R. Barbera

27

,

F. Barile

32,106

,

L. Barioglio

25

,

G.G. Barnaföldi

142

,

L.S. Barnby

34,104

,

V. Barret

71

,

P. Bartalini

7

,

K. Barth

34

,

J. Bartke

120,i

,

E. Bartsch

60

,

M. Basile

26

,

N. Bastid

71

,

S. Basu

139

,

B. Bathen

61

,

G. Batigne

116

,

A. Batista Camejo

71

,

B. Batyunya

67

,

P.C. Batzing

20

,

I.G. Bearden

84

,

H. Beck

96

,

C. Bedda

30

,

N.K. Behera

50

,

I. Belikov

135

,

F. Bellini

26

,

H. Bello Martinez

2

,

R. Bellwied

126

,

L.G.E. Beltran

122

,

V. Belyaev

76

,

G. Bencedi

142

,

S. Beole

25

,

A. Bercuci

80

,

Y. Berdnikov

89

,

D. Berenyi

142

,

R.A. Bertens

53,129

,

D. Berzano

34

,

L. Betev

34

,

A. Bhasin

93

,

I.R. Bhat

93

,

A.K. Bhati

91

,

B. Bhattacharjee

43

,

J. Bhom

120

,

L. Bianchi

126

,

N. Bianchi

73

,

C. Bianchin

141

,

J. Bielˇcík

38

,

J. Bielˇcíková

87

,

A. Bilandzic

35,97

,

G. Biro

142

,

R. Biswas

4

,

S. Biswas

4

,

J.T. Blair

121

,

D. Blau

83

,

C. Blume

60

,

G. Boca

136

,

F. Bock

75,96

,