Centrality dependence of the pseudorapidity density distribution for charged particles in Pb-Pb collisions at √sNN=5.02TeV

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Physics Letters B

www.elsevier.com/locate/physletb

Centrality dependence of the pseudorapidity density distribution for charged particles in Pb–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 ra c t

Articlehistory:

Received9January2017

Receivedinrevisedform19June2017 Accepted9July2017

Availableonline14July2017 Editor:L.Rolandi

We present the charged-particle pseudorapidity density in Pb–Pb collisions at √_s

NN=⁵.02 TeV in centralityclassesmeasuredbyALICE.Themeasurementcoversawidepseudorapidityrangefrom−³.5 to5,whichissufficientforreliableestimatesofthetotalnumberofchargedparticlesproducedinthe collisions.Forthemostcentral(0–5%)collisionswefind21400±^{1300,whileforthemostperipheral} (80–90%)we find230±^38.Thiscorresponds toan increaseof(27±⁴)% over theresults at√_s

NN= 2.76 TeV previouslyreportedbyALICE.Theenergydependenceofthetotalnumberofchargedparticles produced inheavy-ioncollisions is foundtoobey amodifiedpower-lawlikebehaviour. Thecharged- particlepseudorapiditydensityofthemostcentralcollisionsiscomparedtomodelcalculations—none ofwhichfullydescribes themeasureddistribution.Wealsopresentanestimateoftherapiditydensity ofchargedparticles.Thewidth ofthatdistributionisfoundtoexhibitaremarkableproportionalityto thebeamrapidity,independentofthecollisionenergyfromthetopSPStoLHCenergies.

©^{2017TheAuthor(s).PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBYlicense} (http://creativecommons.org/licenses/by/4.0/).FundedbySCOAP³.

1. Introduction

Inultra-relativisticheavy-ioncollisions a denseandhot phase of nuclear matter is created [1–4]. This phase of QCD matter is consideredtobe aplasmaofstronglyinteractingquarksandglu- ons and is therefore labelled the sQGP [5]. The multiplicity of primary, charged particles produced in heavy-ion collisions is a keyobservabletocharacterisethepropertiesofthemattercreated inthese collisions [6]. The studyof theprimary charged-particle pseudorapiditydensity(dN_ch/d

η

) overa wide pseudorapidity(

η

) rangeanditsdependenceoncollidingsystem,centre-of-mass en- ergy,andcollision geometryisimportantto understandtherela- tivecontributionstoparticleproductionfromhardscatteringsand softprocesses,andmayprovideinsightintothepartonicstructure oftheinteractingnuclei.

Wehave previouslyreportedmeasurements on primarycharged- particlepseudorapiditydensitiesoverawidepseudorapidityrange inPb–Pbcollisions atthecentre-of-mass energypernucleonpair

√sNN=².76 TeV[7].InthisLetter,westudythesedistributionsin thepseudorapidityintervalfrom−³.5 to5 atacollisionenergyof

√sNN=⁵.02 TeV asa functionofthe centrality.Pseudorapidityis definedas

η

≡ −^log(tan(ϑ/2)),whereϑ istheanglebetweenthe charged-particle trajectory andthebeam axis(z-axis).Nuclei are extendedobjects,andtheircollisionscanbecharacterisedbycen- trality— the experimental proxy forthe un-measurable distance

E-mailaddress:[email protected].

between the centres of the colliding nuclei (impact parameter).

A primary particle is a particle with a mean proper lifetime

τ

larger than 1 cm/c, which is either a) produced directly in the interaction, or b) from decays of particles with

τ

smaller than 1 cm/c,restrictedtodecaychainsleadingtotheinteraction[8].In this Letter, all quantities reported are forprimary chargedparti- cles,thoughwewillomit“primary”forbrevity.

Withthe largepseudorapidity coverage available inALICE, we can reliably estimate, for all centrality classes, the total number ofchargedparticles produced inthecollisions. We thereforealso presentthefirstmeasurement ofthetotalcharged-particle multi- plicityinPb–Pbcollisions at√

sNN=⁵.02 TeV asafunctionofthe numberofnucleonsparticipatinginthecollisions(Npart).

Finally, we transform the measured dN_ch/d

η

distribution for the5%mostcentralcollisionsintocharged-particlerapiditydensity (dN_ch/dy),andweexaminethecentre-of-massenergydependence of the width of that distribution. The rapidity (y) of a particle withenergyEandmomentumcomponentpzalongthebeamaxis isdefinedas y≡¹₂^log([^E+^pz]/[^E−^pz])^{.Thecomparisonofthe} width of the dNch/dy atdifferent collision energies provides an insight intotheconstraints onthe overall productionmechanism ofchargedparticles.

2. Experimentalsetup

A detailed description of ALICE and its performance can be found elsewhere [9,10]. In the following, we briefly describe the detectorsrelevanttothisanalysis.

http://dx.doi.org/10.1016/j.physletb.2017.07.017

0370-2693/©^{2017TheAuthor(s).PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBYlicense}(http://creativecommons.org/licenses/by/4.0/).Fundedby SCOAP³.

TheSiliconPixelDetector(SPD),theinnermostpartoftheInner TrackingSystem(ITS), consistsoftwo cylindricallayers ofhybrid siliconpixelassembliescovering|

η

_|<2 and|

η

_|<1.4 fortheinner andouterlayers,respectively.Combinationsofhitsoneachofthe twolayers consistent withtracksoriginatingfromtheinteraction pointformtracklets.

TheForwardMultiplicityDetector(FMD)isasiliconstripdetec- torwhich,recordstheenergydepositedbyparticlestraversingthe it.Thedetectorcoversthepseudorapidityregions−³.5<

η

<−¹.8 and1.8<

η

<5,andhasalmostfullcoverageinazimuth(

ϕ

),and highgranularityintheradial(

η

)direction.

The third detector system used in this analysis is the V0. It consistsoftwosub-detectors:V0-AandV0-C coveringthepseudo- rapidity regions 2.8<

η

<5.1 and −³.7<

η

<−¹.7,respectively, eachmadeup ofscintillatortileswithatiming resolution<1 ns.

The fast signals from eitherof V0-A or V0-C are combined in a programmable logic to form a trigger signal and to reject back- groundevents.Furthermore,the combined pulseheight signal of bothsub-detectors formsthebasis fortheclassificationofevents intodifferentcentralityclasses[11].

The Zero-Degree Calorimeter (ZDC) measures the energy of spectator (non-interacting) nucleons with two components: one measures protons and the other measures neutrons. The ZDC is locatedatabout112.5 mfromtheinteractionpointonbothsides ofthe experiment [9]. The ZDCalsoprovides timing information usedtoselectcollisionsintheoff-linedataprocessing.

3. Datasampleandanalysismethod

Theresults presentedherearebasedon datacollected by AL- ICEin2015during thePb–Pbcollision runofthe LHCat√

sNN= 5.02 TeV. About 100000 eventswitha minimumbias triggerre- quirement[12] were analysed inthe centralityrange from0% to 90%.TheminimumbiastriggerforPb–PbcollisionsinALICE,which definesthe so-called visiblecross-section, is definedas a coinci- dencebetweentheA(z>0)andC(z<0)sidesoftheV0detector.

Thestandard ALICEeventselection[13] andcentralityestima- torbasedontheV0–amplitude[11]areusedinthisanalysis.The eventselection consistsof: exclusionof backgroundevents using the timing information fromthe ZDC andV0 detectors; verifica- tionofthetriggerconditions;andareconstructed positionofthe collision.Asdiscussedelsewhere[11],the90–100%centralityclass hassubstantialcontributionsfromQEDprocessesandistherefore notincludedintheresultspresentedhere.

The measurement ofthe charged-particle pseudorapidity den- sityat mid-rapidity (|

η

|<2) is obtainedfroma tracklet analysis usingthetwolayersoftheSPD.Theanalysismethodusedisiden- ticaltowhat haspreviously beenpresented [12,14,15]. Notethat noattemptismadetocorrectforknowndeficiencies,suchasdevi- ationsinthenumberofstrangeparticlesortransversemomentum (pT)distributionscomparedtoexperimentalmeasurements[11,16, 17], in the eventgenerators used to obtain the corrections from simulations (e.g.,HIJING). It isfound, through simulationstudies, thattrackletreconstructionfirstandforemostdependsonthelocal hit density andonly weakly on particle mix andtransverse mo- mentum.Forexample,thedeficitofstrangeparticlesintheevent generatoreffectstheresultbylessthan2%.Sincetheeventgenera- torsgenerally,afterdetectorsimulation,producealocalhitdensity thatisconsistentwithwhatisobservedindata,weobserveacor- respondencebetweenthetrackletsamplesofbothsimulationsand data.Ontheother hand,changingthenumberoftracklets corre- spondingtostrangeparticlesapostioritomatchthemeasuredrel- ativeyieldsdramaticallybiasesthesimulatedtrackletsampleaway fromthemeasured,thusentailingsystematicuncertaintiesthatare beyondtheeffect oftheknown eventgeneratordeficiencies, and

Fig. 1.[Colour online.] Charged-particlepseudorapidity density forten centrality classesoverabroadηrangeinPb–Pbcollisionsat√

sNN=5.02 TeV.Boxesaround the pointsreflectthe totaluncorrelated systematicuncertainties,whilethe filled squares on the right reflect the correlated systematicuncertainty (evaluated at η=^0).Statisticalerrorsaregenerallyinsignificantandsmallerthanthemarkers.

Alsoshownisthereflectionofthe3.5<η<5 valuesaroundη=^{0 (opencircles).}

Thelinecorrespondstofitsofthedifference betweentwoGaussianscentredat η=0 (fGG)[7]tothedata.

assuchdonotimprovetheaccuracyofthemeasurements.Instead, variationsontheeventgeneratorsareusedtoestimatethesystem- aticuncertaintiesasdetailedelsewhere[12,14,15].

Intheforwardregions (−³.5<

η

<−¹.8 and 1.8<

η

<5),the measurement isprovidedby theanalysisofthedepositedenergy signal intheFMD.The analysismethodusedisidenticaltowhat haspreviouslybeenpresented[7,14]:a statisticalapproachtocal- culatetheinclusivenumberofchargedparticles;andadata-driven correction — derived from previous satellite-main collisions — to removethelargebackgroundfromsecondaryparticles.

4. Systematicuncertainties

For the measurements at mid-rapidity the sources and de- pendencies ofthesystematicuncertaintiesare detailedelsewhere [7,12,15]. The magnitude of the systematic uncertainties is un- changed withrespecttoprevious results,andamounts to2.6% at

η

₌0 and 2.9% at

η

₌2,mostofwhichiscorrelatedover|

η

_|<2, andlargelyindependentofcentrality.

Thesystematicuncertaintyontheforwardanalysisisevaluated usingthesametechnique asforpreviousresults[7].Wefindthat theuncertaintyisuncorrelatedacross

η

anthatitamountsto6.9%

for

η

>3.5 and6.4% elsewherewithintheforwardregions.

The systematic uncertainty on dN_ch/d

η

due to the centrality classdefinitionisestimatedas0.6% forthemostcentraland9.5%

for the most peripheral class [15]. The uncertainty is estimated by usingalternative centrality definitions basedon SPD hit mul- tiplicitiesandbyvaryingthefractionofthevisiblehadroniccross- section. The 80–90% centrality class has some residual contam- ination from electromagnetic processes detailed elsewhere [11], which givesrisetoa 4% additionalsystematicuncertainty onthe measurements.

In summary,thetotal systematicuncertaintyvariesfrom2.6%

atmid-rapidityinthemostcentralcollisionsto12.4% atthevery forwardrapiditiesforthemostperipheralcollisions.

5. Results

Fig. 1 presents the charged-particle pseudorapidity densityas a function of pseudorapidity for ten centralityclasses. The mea- surements from the SPD and FMD are combined in regions of overlap (1.8<|

η

|<2) between the two detectors by taking the weighted average using the non-shared uncertainties as weights.

Finally,basedonthe symmetryofthecollisionsystem, theresult issymmetrisedaround

η

=^{0,andextendedintothe}non-measured

Fig. 2.[Colouronline.]Totalnumberofchargedparticlesasafunctionofthemean numberofparticipating nucleons [11]. The totalcharged-particle multiplicity is givenastheintegraloverdNch/dηoverthemeasuredregion(−³.5<η<5)and extrapolationsfromfittedfunctionsintheunmeasuredregions.Thecontribution fromunmeasured ηregions amounts to≈^{30% ofthe totalnumberofcharged} particles.Theuncertaintyontheextrapolationtotheunmeasuredpseudorapidity regionissmallerthanthesizeofthemarkers.Thecontributiontothesystematic uncertaintiesfromthecentralitydeterminationandelectromagneticprocessesare vanishingcomparedtothecontributionfromthelargestdifferencesbetweenthe fittedfunctions.Afunctioninspiredbyfactorisation[18]isfittedtothedata,and thebestfityieldsa=⁵¹.5±⁷.3,b=⁰.16±⁰.05.

region−⁵<

η

<−³.5 byreflectingthe3.5<

η

<5 valuesaround

η

=^0. Complementing resultpreviously reported atmid-rapidity [15],wefind dN_ch/d

η

|_|η_|<0.5=¹⁷.52±⁰.05(stat)±¹.84(sys)and Npart=⁷.3±⁰.1 inthe80–90%centralityclass.

Themeasured distributions arefittedwithfourfunctions fGG, f_P, f_T,and f_B [7],whichare the differenceof twoGaussian dis- tributions centredat

η

=^{0; a}parametrisation proposed by PHO- BOS[18];atrapezoidalform;andaplateauconnectedtoGaussian tails, respectively. To extract the total number of charged parti- cles,wecalculatetheintegralanduncertaintyfromthedatainthe measured region and use the integrals of the fitted functionsin theunmeasuredregions uptothe beamrapidity±^ybeam= ±⁸.6.

Asforthepreviousmeasurementsat√

sNN=⁵.02 TeV,thecentral value inthe unmeasuredregions (−⁸.6<

η

<−³.5 and 5<

η

<

8.6)istakenfromthefitofthefunction f_T,whiletheuncertainty isevaluatedasthelargestdifferencebetweenthe fittedfunctions scaled by 1/√

3 [7,14]. The total charged-particle multiplicity is shownin Fig. 2versus the meannumber of participatingnucle- ons (^Npart^{) estimated from a Glauber} calculation [11,15]. After removing correlated systematic uncertainties, we observe an in- creaseinthe totalnumberofchargedparticles of(27±⁴)% with respectto the measurements at√

sNN=².76 TeV[7] forall cen- trality classes. The line shown in Fig. 2 corresponds to a fit of a function inspired by factorisation [18]. The function illustrates scalingby numberofparticipantpairs,witha smallperturbation proportional to the cubic rootof the number of participants. As the number of nucleon–nucleon collisions (Ncoll) scales roughly likethesquareofthenumberofparticipantsNcoll≈^N2part[19],we seenoindication of scalingby numberofnucleon–nucleon colli- sions.The observed total N_ch dependenceon ^Npart^{provides no} evidenceofanysignificantincreaseinthenumberofhardscatter- ingsbetweentheparticipatingnucleonsandpartons.

InFig. 3,wecomparethecharged-particle pseudorapidityden- sity for the 0–5% most central collisions to three models: HI- JING [20]; EPOS–LHC [21]; and KLN [22,23], also for the 0–5%

mostcentral,exceptforKLNwhichisshownforthe0–6%central- ityclass.TwoversionsofHIJINGareused:version 1.383,withjet quenchingdisabled,shadowing enabled, anda hard pT cut-offof 2.3 GeV;andthenewerversion 2.1[24].Botharetwo-component models witha softand hard sector definedby a pT cut-offsep- arating the two. In the 2.1 implementation, HIJING uses an up- graded parametrisation of the nuclear parton distribution func-

Fig. 3.[Colouronline.]ComparisonofdNch/dη inthe0–5%(0–6%forKLN)most centralcollisionsoftwoversionsofHIJING,KLN,andEPOS–LHCmodelcalculations tothemeasureddistribution.

Fig. 4.[Colouronline.]Totalnumberofchargedparticlesasafunctionof√ sNNfor themostcentralcollisionsatAGS (0–5%Au–Au)[25,26],SPS (0–5%Pb–Pb)[27,28], RHIC (0–5%and0–6%Au–Au)[18,29,30],andLHC (0–5%Pb–Pb)[14].Thedotted, dashed,andfulllinesareextrapolationsfromfitstolowerenergyresults[14],while thedash-dottedlineisafitoverallenergies,including√_s

NN=⁵.02 TeV.

tions.Thisresultsinalargercrosssectionforsoftprocessesanda smallercrosssectionforjetproduction.TheKLN modelisbasedon Colour-Glass-Condensate initial conditions, while EPOS-LHC uses so-called parton-ladders which hadronise in a medium. While noneofthethreemodels describethemeasured charged-particle pseudorapiditydensityoverthefull pseudorapidityrange,weob- serve some differences: HIJING 1.383 over-predicts the charged- particle production especially away from

η

_≈0; EPOS–LHC and HIJING 2.1 consistently under-predict the charge-particle produc- tion; whereas KLN, EPOS–LHC, and HIJING 2.1 give a shape rea- sonably close to the observed distribution. Not shown in Fig. 3, forbothHIJING 1.383andEPOS–LHC,theseobservationsholdover allcentralityclassesi.e.,HIJING 1.383consistentlyproducesfartoo manyparticlesawayfrommid-rapidityandEPOS–LHCconsistently under-predicts the charged-particle yield over the full

η

range.

Thesetrends becomeincreasingly morepronouncedformorepe- ripheralcollisions.

Fig. 4 showsthe total number of charged particles produced in themostcentral heavy-ion collisions asa functionof thecol- lisionenergy,ranging from√

sNN=².6 GeV to 5.02 TeV [14].The dotted,dashed,andfull-drawnlinesinthefigurerepresentextrap- olationsfromlowerenergyresultstothecurrenttopLHCenergyof

√sNN=⁵.02 TeV.Noneofthesepredictionsfullydescribethedata.

A refitofthesimplemodelofalogarithmic-dampenedpower-law inthesquarecollisionenergy(s)includingfromthelowesttothe highestenergyresults,shownasthedash-dottedline, doesaccu- ratelydescribethetotalnumberofchargedparticlesatallavailable energies.

Fig. 5.[Colour online.] Estimate ofdNch/dy in the most central (0–5%)Pb–Pb collisionsat √

sNN=5.02 TeV. Alsoshown arethe Landau–Wong [31], Landau–

Carruthers[32],Gaussian,anddouble-Gaussiandistributions.

Fig. 6.[Colour online.]Scalingbehaviourasafunction√_s

NN ofthewidthofthe charged-particleor-pionrapidity-densitydistributionwithrespecttotheLandau–

Carrutherswidth(top)andrapidityrange(bottom).Charged-pionpointsfromAGS andSPSareadaptedfromtheliterature[33],whilethePHOBOS(filledcrosses)[34]

andBRAHMS(opencrosses)[30]charged-hadronpointsaretranslatedfromthecor- respondingdNch/dηresults.

We can calculate the Jacobian transform from

η

to rapidity y by assuming the same transverse momentum distribution of (anti-)protons, and charged kaons andpions, andthe same par- ticleratios inPb–Pb collisions at √

sNN=⁵.02 TeV as in √ sNN= 2.76 TeV.TheresultispresentedinFig. 5forthe0–5%mostcen- tral collisions. The effect on the Jacobian fromthe changeof pT

spectraandparticleratioswhenincreasingthecollisionenergyby almosta factortwoisevaluated usingtheEPOS–LHC model[21].

Itisfound,thattheeffectisatmost3‰onbothdN_ch/dyandy— muchsmallerthanthesystematicuncertaintyand

η

resolutionof theanalysis.Fig. 5alsoshowstheexpectedcharged-particlerapid- itydensities from the Landau–Carruthers [32] andLandau–Wong [31] models,both assuming Landauhydrodynamics i.e., basedon areactionscenariowithfullstoppingofthereactionpartnersand asubsequentthermodynamic evolution.Themeasurements,how- ever,areseentobeconsistentwithaGaussiandistributionwitha widthof4.12±⁰.10,much widerthan thewidth expectedfrom thetwomodels.Abestparameterfitofthesumoftwo Gaussian distributionswithmeanssymmetricaroundy=^0,isindistinguish- ablefromthesingleGaussiancase.

In the top part of Fig. 6 we compare the widths of the charged-particle or -pion rapidity density distribution extracted frommeasurements tothe expectedwidth

σ

_L-C² =^log(√

sNN/2mp) from Landau–Carruthers, where mp is the proton mass, at colli- sion energies ranging from2.6 GeV up to 5.02 TeV. An increase of ≈^{7% of}

σ

dNX/dy/

σ

L-C is seen from the √

sNN=².76 TeV AL- ICE measurements [14]. The full evolution is consistent with an almost linearriseasa function oflog√

sNN fromthe topSPS en- ergyat√

sNN=¹⁷.3 GeV. Itcanbe shown[35] thatthe widthof

the rapidity-density distribution in Landau hydrodynamics scales as

σ

dN_X/dy∝¹/(1−^c2s),wherecsisthespeedofsoundinthemat- ter.The lifetimeofthe systemscales inverselywithcs,andgiven that the measured widthis larger than the predicted by Landau hydrodynamics, it is an indication that, given the considerations above,thelifetimeisshorterthansuggested.

In the bottom part of Fig. 6 we compare the width of the dN_ch/dy distribution totheavailable rapidityrange(2y_beam). We observe no dependence ofthis ratio from √

sNN=¹⁷.3 GeV and upward, indicating that the available phase–space constrains the width of that distribution. The charged-hadron measurements at RHIC (crosses) from the BRAHMS [30] and PHOBOS [34] mea- surements ofdN_ch/d

η

areconverted to dN_ch/dy usingthe same method as applied to the ALICE data. Previously, charged-pion measurements fromBRAHMShavebeenreported[33].Thesedata arenotincludedbecauseare-evaluationusingRHICRun-4Au–Au datahasnotbeenfinalised[36].

Fromtheobserveds^p scalingofthecharged-particlepseudora- pidity densityatmid-rapidity[15] weexpect a20% increaseover

√sNN=².76 TeV in thelevelof dN_ch/d

η

|_|η_|<0.5 andfromtheex- tractedwidthofdN_ch/dy weobserveanadditional7%,consistent withtheincreaseof27% over√

sNN=².76 TeV inthetotalnumber ofchargedparticlesproducedin√

sNN=⁵.02 TeV collisions.

6. Conclusions

Thecharged-particlepseudorapiditydensityismeasuredinPb–

Pb collisions at √

sNN=⁵.02 TeV over the psuedorapidity range

−³.5<

η

<5. The totalnumber ofchargedparticles produced is determined owing to the large pseudorapidity acceptance of AL- ICE.Thelatterincreasesbytwoordersofmagnitudefromthemost peripheralto themostcentralcollisions andscales approximately with the number of participating nucleons. The increase in the totalnumberofchargedparticlesrelativeto√

sNN=².76 TeV ises- timated tobe(27±⁴)%. Thecharged-particle rapidity densityfor themostcentralcollisions isextracted, andthewidthofthatdis- tribution is compared to predictionsfrom theLandau–Carruthers andLandau–Wonghydrodynamicmodels.Itisfoundthatthemea- suredcharged-particlerapiditydensitybecomesincreasinglywider as a function of collision energy than predicted by Landau hy- drodynamics. The width of the charged-particle rapidity density is seen to scale with the beam rapidity, which implies that the available phase space determines the longitudinal extend of the charged-particle production.Thephase spacedominancestarts at thetopSPSenergyandpersistfortwo ordersofmagnitudeupto thetopLHCenergy.

Acknowledgements

The ALICECollaboration would like to thank all its engineers andtechniciansfortheirinvaluablecontributionstotheconstruc- 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 buildingandrun- ningthe ALICEdetector:A.I. AlikhanyanNationalScience Labora- tory(YerevanPhysicsInstitute)Foundation (ANSL),State Commit- teeofScienceandWorldFederationofScientists(WFS),Armenia;

Austrian Academyof SciencesandNationalstiftung fürForschung, Technologie und Entwicklung, Austria; Conselho Nacionalde De- senvolvimento Científico e Tecnológico (CNPq), Universidade Fed- eral do Rio Grande do Sul (UFRGS), Financiadora de Estudos e Projetos (Finep) and Fundação de Amparo à Pesquisa do Estado

deSãoPaulo(FAPESP),Brazil;MinistryofScience&Technologyof China(MSTC),NationalNaturalScienceFoundationofChina(NSFC) andMinistryofEducationofChina(MOEC),China;MinistryofSci- ence,EducationandSportandCroatianScienceFoundation,Croa- tia;MinistryofEducation,YouthandSportsoftheCzechRepublic, Czech Republic; The Danish Council for Independent Research–

NaturalSciences,theCarlsbergFoundationandDanishNationalRe- search Foundation (DNRF), Denmark;Helsinki Institute ofPhysics (HIP),Finland;Commissariatàl’EnergieAtomique(CEA)andInsti- tut Nationalde Physique Nucléaire etde Physique des Particules (IN2P3)andCentre National de laRecherche Scientifique (CNRS), France; Bundesministerium für Bildung, Wissenschaft, Forschung undTechnologie(BMBF)and GSI Helmholtzzentrumfür 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), New Delhi, India; Indonesian Institute of Sci- ence,Indonesia;CentroFermi- Museo StoricodellaFisica eCen- troStudi e Ricerche EnricoFermi andIstitutoNazionale di Fisica Nucleare(INFN), Italy; Institute forInnovative Science and Tech- nology, Nagasaki Institute of Applied Science (IIST), Japan Soci- ety for the Promotion of Science (JSPS) KAKENHI and Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan;Consejo Nacional de Ciencia y Tecnología(CONA- CYT), through Fondo de Cooperación Internacional en Ciencia y Tecnología(FONCICYT)andDirecciónGeneralde AsuntosdelPer- sonal Academico (DGAPA), Mexico; Nationaal instituut voor sub- atomaire fysica (Nikhef), Netherlands; The Research Council of Norway,Norway;CommissiononScienceandTechnologyforSus- tainableDevelopmentintheSouth(COMSATS),Pakistan;Pontificia UniversidadCatólicadelPerú,Peru;MinistryofScienceandHigher EducationandNationalScience Centre,Poland;Korea Institute of ScienceandTechnology Information andNationalResearchFoun- dation of Korea (NRF), Republic of Korea; Ministry of Education andScientific Research,InstituteofAtomic PhysicsandRomanian National Agency for Science, Technology and Innovation, Roma- nia;JointInstituteforNuclearResearch(JINR),MinistryofEduca- tionandScienceoftheRussian FederationandNationalResearch CentreKurchatovInstitute, Russia;MinistryofEducation,Science, ResearchandSportoftheSlovak Republic, Slovakia; NationalRe- search Foundation of South Africa, South Africa; Centrode Apli- cacionesTecnológicasyDesarrolloNuclear(CEADEN),Cubaenergía, Cuba, Ministerio de Ciencia e Innovacion and Centro de Investi- gacionesEnergéticas, Medioambientales y Tecnológicas (CIEMAT), Spain;SwedishResearchCouncil(VR)andKnut&AliceWallenberg Foundation(KAW),Sweden;EuropeanOrganizationforNuclearRe- search,Switzerland;NationalScienceandTechnologyDevelopment Agency(NSDTA),SuranareeUniversityofTechnology(SUT)andOf- 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;NationalSci- enceFoundationoftheUnitedStatesofAmerica(NSF)andUnited StatesDepartmentofEnergy, Office ofNuclear Physics(DOE NP), UnitedStatesofAmerica.

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