Pion, Kaon, and Proton Production in Central Pb--Pb Collisions at $\sqrt{s_{NN}}$ = 2.76 TeV

$Page 1: Pion, Kaon, and Proton Production in Central Pb--Pb Collisions at $\sqrt{s_{NN}}$ = 2.76 TeV$
EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH

CERN-PH-EP-2012-230August 9, 2012

Pion, Kaon, and Proton Production in Central Pb–Pb Collisions at√sNN = 2.76 TeV

The ALICE Collaboration∗

Abstract

In this Letter we report the first results on π±, K±, p and p production at mid-rapidity (|y|< 0.5) incentral Pb–Pb collisions at

√sNN = 2.76 TeV, measured by the ALICE experiment at the LHC. The pT

distributions and yields are compared to previous results at√

sNN = 200 GeV and expectations fromhydrodynamic and thermal models. The spectral shapes indicate a strong increase of the radial flowvelocity with

√sNN, which in hydrodynamic models is expected as a consequence of the increasing

particle density. While the K/π ratio is in line with predictions from the thermal model, the p/π ratiois found to be lower by a factor of about 1.5. This deviation from thermal model expectations is stillto be understood.

∗See Appendix A for the list of collaboration members

CERN-PH-EP-2012-23009 August 2012


π , K, and p production in central Pb–Pb collisions at√

sNN = 2.76 TeV 1

High-energy heavy-ion collisions offer the unique possibility to study nuclear matter under extreme con-ditions, in particular the deconfined phase (Quark–Gluon Plasma, QGP [1, 2, 3]), which has been pre-dicted by lattice QCD [4]. The transverse momentum (pT) distributions and yields of identified particlesare instrumental to the study of the collective and thermal properties of this matter. Results from lowerenergies, in particular from the Relativistic Heavy-Ion Collider (RHIC,

√sNN = 200 GeV), have shown

that the bulk matter created in high-energy nuclear reactions can be quantitatively described in termsof hydrodynamic models. The initial hot and dense partonic matter rapidly expands and cools down,ultimately undergoing a transition to a hadron gas phase [5]. The observed particle abundances weredescribed in terms of thermal models. Relative particle abundances in thermal and chemical equilibriumare governed mainly by two parameters, the chemical freeze-out temperature Tch and the baryochemi-cal potential µB, where the latter describes the net baryon content of the system [6, 7, 8, 9]. Measuredparticle yields in heavy-ion collisions at RHIC, as well as SPS and AGS, are consistent with equilib-rium populations, allowing the extraction of both model parameters from fits to the measured particleratios [6, 7, 9, 10]. It has been argued that interactions modifying the relative abundances of particlespecies are negligible in the hadronic phase [11, 12], and that Tch can be linked to the phase transitiontemperature [13]. Particle momentum distributions reflect the conditions later in the evolution, at the“kinetic freeze-out” from the hadron gas phase, when elastic interactions end [14]. The pT distributionsencode information about the collective transverse expansion (radial flow) and the temperature Tkin atthe kinetic freeze-out [15, 16]. The collective expansion is driven by internal pressure gradients andquantified by the average transverse velocity 〈βT〉. Based on the success of the thermal and hydrody-namic models and based on the trend of the model parameters with

√sNN, predictions were formulated

for higher energy [7, 17]. With the advent of the LHC, it became important to check these expectationsin the new energy regime. In this Letter, we present the first results on π , K, and p production in 0-5%central Pb–Pb collisions at

√sNN = 2.76 TeV, measured by the ALICE experiment at the LHC. Previ-

ous results in pp collisions are reported in [18]. The measurement spans the pT range from ∼0.1 up to∼4.5 GeV/c at central rapidity (|y|< 0.5).

The central tracking and particle identification (PID) detectors cover the pseudorapidity window |η | <0.9 and include, from the innermost outwards, the Inner Tracking System (ITS), the Time ProjectionChamber (TPC), the Transition Radiation Detector (TRD) and the Time-Of-Flight array (TOF) [19, 20].The central detectors are operated in a 0.5 T solenoidal field. The moderate field, together with a lowmaterial budget (X/X0 ≈ 0.1 for a track going through the TPC) permits the reconstruction of low pTtracks. The data sample consists of 4 M minimum bias events. A pair of forward scintillator hodoscopes,the VZERO detectors (2.8 < η < 5.1 and −3.7 < η <−1.7), was used for triggering and for centralitydetermination [21, 22, 23]. The data were collected using a minimum bias trigger requiring a combi-nation of hits in the ITS and in the VZERO, a condition fully efficient for the event sample discussedhere [23]. The 0-5% most central collisions were selected using the signal amplitudes measured in theVZERO, fitted with a Glauber model [23]. Background events caused by beam-gas interactions, parasiticcollisions and electromagnetic processes were rejected using timing cuts on the VZERO and two neutronZero-Degree Calorimeters located on either side of the interaction point, at 114 m distance [21, 22, 23].The measurement was performed in three independent analyses, each one focusing on a sub-range ofthe total pT distribution, exploiting the capabilities of the individual detectors and specific techniquesto optimize the signal extraction. The ITS is a six-layered silicon detector. The two innermost layers,based on silicon pixels, are also used in the online trigger as mentioned above. The four outer layers,consisting of drift and strip detectors, provide identification via the specific energy loss. Using the ITSas a standalone tracker enables reconstruction and identification of low-momentum particles that do notreach the TPC, in the pT ranges 0.1-0.5, 0.2-0.5, 0.3-0.5 GeV/c for π , K, and p. For each track, at leastthree dE/dx samples were required. Only the lowest two were used in a truncated mean procedure,leading to an ∼10% resolution. The particle identity was assigned according to the distance from theexpected energy loss curves, weighted by the resolution. This procedure results in asymmetric ranges

2 The ALICE Collaboration

around the curves for π , K, and p, reflecting the Landau tails in the detector response, which are not fullysuppressed by the truncated mean. An additional 2 σ cut was applied in the case of pions, to remove thecontamination from electrons. The residual misidentification (< 10% for kaons and negligible for pionsand protons) is corrected using Monte Carlo. The other analyses combined the tracking information fromthe ITS, TPC and TRD (“global tracks”) [19]. The TPC identifies particles via the specific energy lossin the Ne-CO2-N2 (85:10:5) gas mixture. Up to 159 samples are measured, but only the lowest 60%are used in the analysis. This truncated mean procedure leads to a Gaussian distribution with an ∼6.5%resolution. The TOF is placed at a radius of 370–399 cm. It measures the time-of-flight of the particles,allowing hadron identification at higher pT. With a total time resolution of about 85 ps, PID is possibleup to pT = 3 GeV/c for π and K, and 4.5 GeV/c for p. In the intermediate pT range (0.3-1.5 GeV/c,0.3-1.3 GeV/c, 0.5-2.4 GeV/c, for π and K, and p), the identification was based on the combined TPCand TOF signals. The ranges were chosen such that the contamination from misidentification of otherspecies is negligible. It was required that the particles are within 3 σ from the expected dE/dx andtime-of-flight values. The TOF information was included starting at pT = 0.65, 0.6, 0.8 GeV/c for π , K,and p. In the third analysis, for pT > 0.5 GeV/c, the TOF signal alone was used for identification. Thetime-of-flight distribution was fitted for each pT bin with data-derived templates for π , K, and p, allowingto extract the particle yields when the separation is as low as ∼2 σ [24]. This fit was repeated for eachmass hypothesis, after applying the selection |y|< 0.5 based on the mass assumption under study [24].

In this Letter, results for “primary” particles are presented, defined as prompt particles produced inthe collision, including decay products, except those from weak decays of strange particles. Both ITSstandalone and global tracks provide very good transverse impact parameter resolution relative to theprimary vertex (DCAxy), of order 200 µm at pT = 300 MeV/c and 35 µm at pT = 5 GeV/c, allowingto separate primary and secondary particles. The residual contamination was estimated from data byfitting the DCAxy distribution with three Monte Carlo templates: primary particles, secondaries frommaterial and secondaries from weak decays [25, 18]. This contamination can reach 35% at pT = 300MeV/c for protons. It quickly decreases with increasing pT, becoming negligible at pT ∼2.5 GeV/c.The efficiency correction and the templates used in the correction procedure were computed with 1 MMonte Carlo events, using the Hijing [26] event generator (tuned to reproduce the dNch/dη measuredfor central collisions [22]), transported through a GEANT3 [27] model of the detector. The results ofthe three analyses were consistent in the regions of overlap and therefore combined using the (largelyindependent) systematic uncertainties as weights.

The main sources of systematic uncertainties are summarized in Table 1. The uncertainties due to thesecondary subtraction procedure were estimated for all analyses varying the range of the DCAxy fit, usingdifferent track selections (for instance using TPC-only tracks), applying different cuts on the longitudinalDCAz and varying the composition of the Monte Carlo templates used in the fit. The uncertainty on theenergy loss correction was estimated in a simulation with the material budget scaled by ±7%. In orderto account for the uncertainties due to poorly-known hadronic interactions with the detector material,different transport codes (GEANT3, GEANT4 [28] and FLUKA [29]) were tested. The interaction crosssection used in the models for π , K, and p were separately validated by comparison with the few existingmeasurements [30, 31, 32, 33, 34].The main systematic uncertainty on the ITS standalone analysis comesfrom the tracking, due to the high occupancy and small number of tracking points. This was estimatedfrom data using global tracks as a reference. The other systematic uncertainties are smaller, and includethe effect of the magnetic field configuration (E×B effect), of the track selection and of the PID cuts.Similarly, the uncertainties related to the tracking efficiency in the TPC were investigated comparingdifferent sets of tracks in data and Monte Carlo and by a variation of the track cuts. The uncertaintyrelated to the combined TPC/TOF PID procedure was estimated varying the PID cut between 2 and5 σ . The tracks reaching the TOF detector have to cross a substantial amount of additional material(X/X0 ≈ 0.23), mostly due to the TRD [20]. Since the TRD was not fully installed in 2010, the analysiswas repeated for regions in azimuth with and without installed TRD modules, allowing one to determine


sNN = 2.76 TeV 3

Table 1: Main sources of systematic uncertainty. See text for details.

effect π± K± p and p

pT range (GeV/c) 0.1 3 0.2 3 0.35 4.5correction for

1.5% 1% negl. 4% 1%secondaries

material5% negl. 3% negl. 3% negl.

budget

hadronic2% 1% 4% 1%

6% 1% (p)interactions 4% negl. (p)

pT range (GeV/c) 0.1 0.5 0.2 0.5 0.35 0.65ITS tracking

10% 10% 10%efficiency

ITS PID 2% 4% 4.5%

pT range (GeV/c) 0.3 0.65 0.3 0.6 0.5 0.8global tracking

4% 4% 4%efficiency

TPC PID 3% 5% 1.5%

pT range (GeV/c) 0.5 3 0.5 3 0.5 4.5TOF matching

3% 6% 3%efficiency

TOF PID 2% 7% 3% 15% 5% 25%

the uncertainty due to the aditional material. The systematics related to the PID extraction in the TOFanalysis were estimated varying the parameters of the expected sources by ±10%.

The pT distributions of positive and negative particles were found to be compatible within errors, wetherefore show results for summed charge states in Fig. 1. The spectra are compared to RHIC resultsin Au–Au collisions at

√sNN = 200 GeV [35, 36] and to hydrodynamic models. The spectral shapes

show a significant change from RHIC to LHC energies, having a distinctly harder distribution. Withinhydrodynamic models, this indicates a significantly stronger radial flow. In the range pT < 1.5 GeV/cVISH2+1 [37], a viscous hydrodynamic model, reproduces fairly well the pion and kaon distributions,but misses the protons, both in shape and absolute abundance. In this model, the particle yields are takento be thermal at Tch = 165 MeV (see below). The difference is possibly due to the lack of an explicitdescription of the hadronic phase in the model. This interpretation is supported by the comparison withHKM [38, 39], a similar model in which, after the hydrodynamic phase, particles are injected into ahadronic cascade model (UrQMD [40, 41]), which further transports them until final decoupling. Thehadronic phase builds additional radial flow, mostly due to elastic interactions, and affects particle ra-tios due to inelastic interactions. HKM yields a better description of the data. At the LHC, hadronicfinal state interactions, and in particular antibaryon-baryon annihilation, may therefore be an impor-tant ingredient for the description of particle yields [42, 39], contradicting the scenario of negligibleabundance-changing processes in the hadronic phase. The third model shown in Fig. 1 (Krakow [43, 44])introduces non-equilibrium corrections due to viscosity at the transition from the hydrodynamic descrip-tion to particles, which change the effective Tch, leading to a good agreement with the data. In the regionpT . 3 GeV/c (Krakow) and pT . 1.5 GeV/c (HKM) the last two models reproduce the experimentaldata within ∼20%, supporting a hydrodynamic interpretation of the transverse momentum spectra at theLHC. These models also describe correctly other features of the space-time evolution of the system, asmeasured by ALICE with charged pion correlations [45]. In order to quantify the kinetic freeze-out pa-


Dat

a/M

odel

-2 )c)

(GeV

/yd

Tp

/(d

N2

dT

pπ 1

/2ev

N1/

)c (GeV/T

p

)c (GeV/T

p0 1 2 3 4 5

-310

-110

10

310

510

610

0-5% Central collisions

100)× (-π + +π

10)× (- + K +K

1)× (pp +

= 2.76 TeVNNsALICE, Pb-Pb

= 200 GeVNNsSTAR, Au-Au,

= 200 GeVNNsPHENIX, Au-Au,

Blast Wave FitVISH2+1HKM

kowKra

0 1 2 3 4 50

1

2-π + +π

0 1 2 3 4 50

1

2- + K+K

0 1 2 3 4 50

1

2 pp +

Fig. 1: (color online) Transverse momentum distributions of the sum of positive and negative particles (box:systematic errors; statistical errors smaller than the symbol for most data points), fitted individually with a blastwave function, compared to RHIC data and hydrodynamic models.

rameters at√

sNN = 2.76 TeV, we performed a combined fit with a blast wave function [15]. It shouldbe noted that the value of the Tkin parameter extracted from the fit is sensitive to the fit range used forthe pions, because of the large contribution from resonance decays (mostly at low pT), which tend toreduce Tkin. For this reason, the pT ranges 0.5-1 GeV/c, 0.2-1.5 GeV/c, 0.3-3 GeV/c for π , K, and pwere used. These hydro-motivated fits do not replace a full hydrodynamic calculation, but allow oneto compare with a few parameters the measurements of different experiments. The data are well de-scribed by the combined blast wave fit with a collective radial flow velocity 〈βT〉 = 0.65± 0.02, and akinetic freeze-out temperature of Tkin = 96± 10 MeV. As compared to fits to central Au–Au collisionsat√

sNN = 200 GeV/c, in similar pT ranges [35, 46], 〈βT〉 at the LHC is ∼10% higher while Tkin iscomparable within errors.

The mid-rapidity (|y|< 0.5) pT-integrated particle yields were extracted by fitting the π , K, and p spectraindividually with a blast wave function, in order to extrapolate to zero pT. The individual fits are shownin Fig. 1 as solid curves; the fraction of extrapolated yield is small: about 7%, 6%, and 4% for π , K, andp. Its uncertainty was estimated using different fit functions [24]. The particle ratios are compared inFig. 2 to results at

√sNN = 200 GeV and to the predictions from thermal models, using µB = 1 MeV and a

Tch of 164 MeV [7] or 170 MeV [17]. The value for µB is based on extrapolation from lower energy data.Tch was found to be constant above a center-of-mass energy of a few ten GeV, so the value obtained fromfits to RHIC data was used. The systematic uncertainties on the particle ratios were computed taking intoaccount the correlated sources of uncertainty (mainly due to the tracking efficiency for different particlesand to PID and extrapolation for anti-particle over particle ratios). In the following we quote the total er-ror for the ratios, as the statistical error is negligible. The anti-particle/particle ratios are all unity withinerrors, consistent with a vanishing baryochemical potential µB. In order to minimize the sensitivity toµB, the ratios K/π = (K++K−)/(π++π−) and p/π = (p+ p)/(π++π−) are also shown. The ratio


sNN = 2.76 TeV 5

Fig. 2: (color online) Mid-rapidity particle ratios, compared to RHIC results and predictions from thermal modelsfor central Pb-Pb collisions at the LHC (combined statistical and systematic errors).

K/π = 0.149± 0.010, is similar to the lower energy values and agrees with the expectations from thethermal model [7]. However, the ratio p/π = 0.046± 0.003, is significantly lower than expected, by afactor ∼1.5–1.9 (p/π' 0.07− 0.09 for [7] and [17] respectively). The two models differ mainly in thehadron mass spectrum implementation, but were both successful in describing RHIC data. The compar-ison with RHIC data also hints at a slight decrease of the p/π ratio with energy (by a factor ∼1.2), whileessentially no change was predicted. The thermal models proved to be very successful over a wide rangeof energies (from

√sNN= 2 GeV to

√sNN = 200 GeV [9, 7, 6, 10]): such a large difference for one of the

most abundantly produced particle species was therefore unexpected. In retrospect, some disagreementbetween data and the thermal model is also apparent in the RHIC data, with the proton measurementsbeing about 20% lower than predictions [6, 46, 47]. However, this difference was not considered tobe significant, because of the differences between model implementations, model uncertainties [48] andexperimental uncertainties in the subtraction of secondary particles in the RHIC experiments. This is-sue will likely be clarified by a thermal analysis including strange and multi-strange baryons at the LHC.Current speculations are that final state interactions in the hadronic phase, in particular via the large crosssection channel for antibaryon-baryon annihilation [42], could explain the significant deviation from theusual thermal ratios. A similar conclusion is implied by the HKM model, where p/π = 0.052, consistentwith our measurement [39]. An alternative scenario conjectures the existence of flavor and mass depen-dent pre-hadronic bound states in the QGP phase, as suggested by recent lattice QCD calculation andQCD-inspired models [49, 50].

In summary, we presented the first measurements of π , K, and p production in central Pb-Pb collisions at√sNN = 2.76 TeV at the LHC. The pT distributions are harder than previously measured at RHIC. They

are well described by hydrodynamic models including a refined description of the late fireball stages.Fitting the spectra with a hydro-inspired blast wave model results in the highest radial flow parameterever measured, 〈βT〉=0.65 ± 0.02. The integrated particle ratios were compared with expectations fromthermal models. While the K/π ratio was found to agree with these expectations, p/π is a factor & 1.5lower.

1 Acknowledgments

We are grateful to P. Bozek, U. Heinz, Y. Karpenko, C. Shen, Y. Sinyukov, H. Song and K. Werner forproviding the theoretical calculations and for the useful discussion and to colleagues from the BRAHMS,PHENIX and STAR collaborations for the helpful discussions and clarifications on their measurements.

The ALICE collaboration would like to thank all its engineers and technicians for their invaluable con-tributions to the construction of the experiment and the CERN accelerator teams for the outstandingperformance of the LHC complex. The ALICE collaboration acknowledges the following funding agen-


cies for their support in building and running the ALICE detector: Calouste Gulbenkian Foundationfrom Lisbon and Swiss Fonds Kidagan, Armenia; Conselho Nacional de Desenvolvimento Cientıfico eTecnologico (CNPq), Financiadora de Estudos e Projetos (FINEP), Fundacao de Amparo a Pesquisa doEstado de Sao Paulo (FAPESP); National Natural Science Foundation of China (NSFC), the ChineseMinistry of Education (CMOE) and the Ministry of Science and Technology of China (MSTC); Ministryof Education and Youth of the Czech Republic; Danish Natural Science Research Council, the CarlsbergFoundation and the Danish National Research Foundation; The European Research Council under theEuropean Community’s Seventh Framework Programme; Helsinki Institute of Physics and the Academyof Finland; French CNRS-IN2P3, the ‘Region Pays de Loire’, ‘Region Alsace’, ‘Region Auvergne’ andCEA, France; German BMBF and the Helmholtz Association; Hungarian OTKA and National Officefor Research and Technology (NKTH); Department of Atomic Energy and Department of Science andTechnology of the Government of India; Istituto Nazionale di Fisica Nucleare (INFN) of Italy; MEXTGrant-in-Aid for Specially Promoted Research, Japan; Joint Institute for Nuclear Research, Dubna; Na-tional Research Foundation of Korea (NRF); CONACYT, DGAPA, Mexico, ALFA-EC and the HELENProgram (High-Energy physics Latin-American–European Network); Stichting voor Fundamenteel On-derzoek der Materie (FOM) and the Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO),Netherlands; Research Council of Norway (NFR); Polish Ministry of Science and Higher Education;National Authority for Scientific Research - NASR (Autoritatea Nationala pentru Cercetare Stiintifica- ANCS); Federal Agency of Science of the Ministry of Education and Science of Russian Federation,International Science and Technology Center, Russian Academy of Sciences, Russian Federal Agencyof Atomic Energy, Russian Federal Agency for Science and Innovations and CERN-INTAS; Ministry ofEducation of Slovakia; CIEMAT, EELA, Ministerio de Educacion y Ciencia of Spain, Xunta de Gali-cia (Consellerıa de Educacion), CEADEN, Cubaenergıa, Cuba, and IAEA (International Atomic EnergyAgency); The Ministry of Science and Technology and the National Research Foundation (NRF), SouthAfrica; Swedish Reseach Council (VR) and Knut & Alice Wallenberg Foundation (KAW); Ukraine Min-istry of Education and Science; United Kingdom Science and Technology Facilities Council (STFC); TheUnited States Department of Energy, the United States National Science Foundation, the State of Texas,and the State of Ohio.


sNN = 2.76 TeV 7

A The ALICE Collaboration

B. Abelev68 , J. Adam34 , D. Adamova73 , A.M. Adare120 , M.M. Aggarwal77 , G. Aglieri Rinella30 ,A.G. Agocs60 , A. Agostinelli19 , S. Aguilar Salazar56 , Z. Ahammed116 , N. Ahmad14 , A. Ahmad Masoodi14 ,S.A. Ahn62 , S.U. Ahn37 , A. Akindinov46 , D. Aleksandrov88 , B. Alessandro94 , R. Alfaro Molina56 ,A. Alici97 ,10 , A. Alkin2 , E. Almaraz Avina56 , J. Alme32 , T. Alt36 , V. Altini28 , S. Altinpinar15 , I. Altsybeev117 ,C. Andrei70 , A. Andronic85 , V. Anguelov82 , J. Anielski54 , C. Anson16 , T. Anticic86 , F. Antinori93 ,P. Antonioli97 , L. Aphecetche102 , H. Appelshauser52 , N. Arbor64 , S. Arcelli19 , A. Arend52 , N. Armesto13 ,R. Arnaldi94 , T. Aronsson120 , I.C. Arsene85 , M. Arslandok52 , A. Asryan117 , A. Augustinus30 , R. Averbeck85 ,T.C. Awes74 , J. Aysto38 , M.D. Azmi14 ,79 , M. Bach36 , A. Badala99 , Y.W. Baek63 ,37 , R. Bailhache52 ,R. Bala94 , R. Baldini Ferroli10 , A. Baldisseri12 , A. Baldit63 , F. Baltasar Dos Santos Pedrosa30 , J. Ban47 ,R.C. Baral48 , R. Barbera25 , F. Barile28 , G.G. Barnafoldi60 , L.S. Barnby90 , V. Barret63 , J. Bartke104 ,M. Basile19 , N. Bastid63 , S. Basu116 , B. Bathen54 , G. Batigne102 , B. Batyunya59 , C. Baumann52 ,I.G. Bearden71 , H. Beck52 , I. Belikov58 , F. Bellini19 , R. Bellwied110 , E. Belmont-Moreno56 , G. Bencedi60 ,S. Beole23 , I. Berceanu70 , A. Bercuci70 , Y. Berdnikov75 , D. Berenyi60 , A.A.E. Bergognon102 , D. Berzano94 ,L. Betev30 , A. Bhasin80 , A.K. Bhati77 , J. Bhom114 , L. Bianchi23 , N. Bianchi65 , C. Bianchin20 , J. Bielcık34 ,J. Bielcıkova73 , A. Bilandzic72 ,71 , S. Bjelogrlic45 , F. Blanco8 , F. Blanco110 , D. Blau88 , C. Blume52 ,M. Boccioli30 , N. Bock16 , S. Bottger51 , A. Bogdanov69 , H. Bøggild71 , M. Bogolyubsky43 , L. Boldizsar60 ,M. Bombara35 , J. Book52 , H. Borel12 , A. Borissov119 , S. Bose89 , F. Bossu23 , M. Botje72 , E. Botta23 ,B. Boyer42 , E. Braidot67 , P. Braun-Munzinger85 , M. Bregant102 , T. Breitner51 , T.A. Browning83 , M. Broz33 ,R. Brun30 , E. Bruna23 ,94 , G.E. Bruno28 , D. Budnikov87 , H. Buesching52 , S. Bufalino23 ,94 , O. Busch82 ,Z. Buthelezi79 , D. Caballero Orduna120 , D. Caffarri20 ,93 , X. Cai5 , H. Caines120 , E. Calvo Villar91 ,P. Camerini21 , V. Canoa Roman9 , G. Cara Romeo97 , F. Carena30 , W. Carena30 , N. Carlin Filho107 ,F. Carminati30 , A. Casanova Dıaz65 , J. Castillo Castellanos12 , J.F. Castillo Hernandez85 , E.A.R. Casula22 ,V. Catanescu70 , C. Cavicchioli30 , C. Ceballos Sanchez7 , J. Cepila34 , P. Cerello94 , B. Chang38 ,123 ,S. Chapeland30 , J.L. Charvet12 , S. Chattopadhyay116 , S. Chattopadhyay89 , I. Chawla77 , M. Cherney76 ,C. Cheshkov30 ,109 , B. Cheynis109 , V. Chibante Barroso30 , D.D. Chinellato108 , P. Chochula30 , M. Chojnacki45 ,S. Choudhury116 , P. Christakoglou72 , C.H. Christensen71 , P. Christiansen29 , T. Chujo114 , S.U. Chung84 ,C. Cicalo96 , L. Cifarelli19 ,30 ,10 , F. Cindolo97 , J. Cleymans79 , F. Coccetti10 , F. Colamaria28 , D. Colella28 ,G. Conesa Balbastre64 , Z. Conesa del Valle30 , P. Constantin82 , G. Contin21 , J.G. Contreras9 , T.M. Cormier119 ,Y. Corrales Morales23 , P. Cortese27 , I. Cortes Maldonado1 , M.R. Cosentino67 , F. Costa30 , M.E. Cotallo8 ,E. Crescio9 , P. Crochet63 , E. Cruz Alaniz56 , E. Cuautle55 , L. Cunqueiro65 , A. Dainese20 ,93 , H.H. Dalsgaard71 ,A. Danu50 , I. Das42 , D. Das89 , K. Das89 , S. Dash40 , A. Dash108 , S. De116 , G.O.V. de Barros107 ,A. De Caro26 ,10 , G. de Cataldo98 , J. de Cuveland36 , A. De Falco22 , D. De Gruttola26 , H. Delagrange102 ,A. Deloff100 , V. Demanov87 , N. De Marco94 , E. Denes60 , S. De Pasquale26 , A. Deppman107 , G. D Erasmo28 ,R. de Rooij45 , M.A. Diaz Corchero8 , D. Di Bari28 , T. Dietel54 , C. Di Giglio28 , S. Di Liberto95 , A. Di Mauro30 ,P. Di Nezza65 , R. Divia30 , Ø. Djuvsland15 , A. Dobrin119 ,29 , T. Dobrowolski100 , I. Domınguez55 ,B. Donigus85 , O. Dordic18 , O. Driga102 , A.K. Dubey116 , A. Dubla45 , L. Ducroux109 , P. Dupieux63 ,A.K. Dutta Majumdar89 , M.R. Dutta Majumdar116 , D. Elia98 , D. Emschermann54 , H. Engel51 , B. Erazmus102 ,H.A. Erdal32 , B. Espagnon42 , M. Estienne102 , S. Esumi114 , D. Evans90 , G. Eyyubova18 , D. Fabris20 ,93 ,J. Faivre64 , D. Falchieri19 , A. Fantoni65 , M. Fasel85 , R. Fearick79 , A. Fedunov59 , D. Fehlker15 ,L. Feldkamp54 , D. Felea50 , B. Fenton-Olsen67 , G. Feofilov117 , A. Fernandez Tellez1 , A. Ferretti23 ,R. Ferretti27 , A. Festanti20 , J. Figiel104 , M.A.S. Figueredo107 , S. Filchagin87 , D. Finogeev44 , F.M. Fionda28 ,E.M. Fiore28 , M. Floris30 , S. Foertsch79 , P. Foka85 , S. Fokin88 , E. Fragiacomo92 , A. Francescon30 ,20 ,U. Frankenfeld85 , U. Fuchs30 , C. Furget64 , M. Fusco Girard26 , J.J. Gaardhøje71 , M. Gagliardi23 , A. Gago91 ,M. Gallio23 , D.R. Gangadharan16 , P. Ganoti74 , C. Garabatos85 , E. Garcia-Solis11 , I. Garishvili68 , J. Gerhard36 ,M. Germain102 , C. Geuna12 , M. Gheata50 ,30 , A. Gheata30 , B. Ghidini28 , P. Ghosh116 , P. Gianotti65 ,M.R. Girard118 , P. Giubellino30 , E. Gladysz-Dziadus104 , P. Glassel82 , R. Gomez106 , E.G. Ferreiro13 ,L.H. Gonzalez-Trueba56 , P. Gonzalez-Zamora8 , S. Gorbunov36 , A. Goswami81 , S. Gotovac103 , V. Grabski56 ,L.K. Graczykowski118 , R. Grajcarek82 , A. Grelli45 , C. Grigoras30 , A. Grigoras30 , V. Grigoriev69 ,S. Grigoryan59 , A. Grigoryan121 , B. Grinyov2 , N. Grion92 , P. Gros29 , J.F. Grosse-Oetringhaus30 ,J.-Y. Grossiord109 , R. Grosso30 , F. Guber44 , R. Guernane64 , C. Guerra Gutierrez91 , B. Guerzoni19 , M.Guilbaud109 , K. Gulbrandsen71 , T. Gunji113 , R. Gupta80 , A. Gupta80 , H. Gutbrod85 , Ø. Haaland15 ,C. Hadjidakis42 , M. Haiduc50 , H. Hamagaki113 , G. Hamar60 , B.H. Han17 , L.D. Hanratty90 , A. Hansen71 ,Z. Harmanova-Tothova35 , J.W. Harris120 , M. Hartig52 , D. Hasegan50 , D. Hatzifotiadou97 ,A. Hayrapetyan30 ,121 , S.T. Heckel52 , M. Heide54 , H. Helstrup32 , A. Herghelegiu70 , G. Herrera Corral9 ,N. Herrmann82 , B.A. Hess115 , K.F. Hetland32 , B. Hicks120 , P.T. Hille120 , B. Hippolyte58 , T. Horaguchi114 ,


Y. Hori113 , P. Hristov30 , I. Hrivnacova42 , M. Huang15 , T.J. Humanic16 , D.S. Hwang17 , R. Ichou63 , R. Ilkaev87 ,I. Ilkiv100 , M. Inaba114 , E. Incani22 , G.M. Innocenti23 , P.G. Innocenti30 , M. Ippolitov88 , M. Irfan14 , C. Ivan85 ,M. Ivanov85 , A. Ivanov117 , V. Ivanov75 , O. Ivanytskyi2 , P. M. Jacobs67 , H.J. Jang62 , R. Janik33 , M.A. Janik118 ,P.H.S.Y. Jayarathna110 , S. Jena40 , D.M. Jha119 , R.T. Jimenez Bustamante55 , L. Jirden30 , P.G. Jones90 ,H. Jung37 , A. Jusko90 , A.B. Kaidalov46 , V. Kakoyan121 , S. Kalcher36 , P. Kalinak47 , T. Kalliokoski38 ,A. Kalweit53 ,30 , J.H. Kang123 , V. Kaplin69 , A. Karasu Uysal30 ,122 , O. Karavichev44 , T. Karavicheva44 ,E. Karpechev44 , A. Kazantsev88 , U. Kebschull51 , R. Keidel124 , P. Khan89 , M.M. Khan14 , S.A. Khan116 ,A. Khanzadeev75 , Y. Kharlov43 , B. Kileng32 , M.Kim37 , D.J. Kim38 , D.W. Kim37 , J.H. Kim17 , J.S. Kim37 ,T. Kim123 , M. Kim123 , S.H. Kim37 , S. Kim17 , B. Kim123 , S. Kirsch36 , I. Kisel36 , S. Kiselev46 , A. Kisiel118 ,J.L. Klay4 , J. Klein82 , C. Klein-Bosing54 , M. Kliemant52 , A. Kluge30 , M.L. Knichel85 , A.G. Knospe105 ,K. Koch82 , M.K. Kohler85 , T. Kollegger36 , A. Kolojvari117 , V. Kondratiev117 , N. Kondratyeva69 ,A. Konevskikh44 , A. Korneev87 , R. Kour90 , M. Kowalski104 , S. Kox64 , G. Koyithatta Meethaleveedu40 ,J. Kral38 , I. Kralik47 , F. Kramer52 , I. Kraus85 , T. Krawutschke82 ,31 , M. Krelina34 , M. Kretz36 ,M. Krivda90 ,47 , F. Krizek38 , M. Krus34 , E. Kryshen75 , M. Krzewicki85 , Y. Kucheriaev88 , T. Kugathasan30 ,C. Kuhn58 , P.G. Kuijer72 , I. Kulakov52 , J. Kumar40 , P. Kurashvili100 , A.B. Kurepin44 , A. Kurepin44 ,A. Kuryakin87 , S. Kushpil73 , V. Kushpil73 , H. Kvaerno18 , M.J. Kweon82 , Y. Kwon123 , P. Ladron de Guevara55 ,I. Lakomov42 , R. Langoy15 , S.L. La Pointe45 , C. Lara51 , A. Lardeux102 , P. La Rocca25 , C. Lazzeroni90 ,R. Lea21 , Y. Le Bornec42 , M. Lechman30 , K.S. Lee37 , G.R. Lee90 , S.C. Lee37 , F. Lefevre102 , J. Lehnert52 ,L. Leistam30 , M. Lenhardt85 , V. Lenti98 , H. Leon56 , M. Leoncino94 , I. Leon Monzon106 , H. Leon Vargas52 ,P. Levai60 , J. Lien15 , R. Lietava90 , S. Lindal18 , V. Lindenstruth36 , C. Lippmann85 ,30 , M.A. Lisa16 , L. Liu15 ,V.R. Loggins119 , V. Loginov69 , S. Lohn30 , D. Lohner82 , C. Loizides67 , K.K. Loo38 , X. Lopez63 ,E. Lopez Torres7 , G. Løvhøiden18 , X.-G. Lu82 , P. Luettig52 , M. Lunardon20 , J. Luo5 , G. Luparello45 ,L. Luquin102 , C. Luzzi30 , K. Ma5 , R. Ma120 , D.M. Madagodahettige-Don110 , A. Maevskaya44 , M. Mager53 ,30 ,D.P. Mahapatra48 , A. Maire82 , M. Malaev75 , I. Maldonado Cervantes55 , L. Malinina59 ,,i, D. Mal’Kevich46 ,P. Malzacher85 , A. Mamonov87 , L. Manceau94 , L. Mangotra80 , V. Manko88 , F. Manso63 , V. Manzari98 ,Y. Mao5 , M. Marchisone63 ,23 , J. Mares49 , G.V. Margagliotti21 ,92 , A. Margotti97 , A. Marın85 ,C.A. Marin Tobon30 , C. Markert105 , I. Martashvili112 , P. Martinengo30 , M.I. Martınez1 ,A. Martınez Davalos56 , G. Martınez Garcıa102 , Y. Martynov2 , A. Mas102 , S. Masciocchi85 , M. Masera23 ,A. Masoni96 , L. Massacrier102 , A. Mastroserio28 , Z.L. Matthews90 , A. Matyja104 ,102 , C. Mayer104 ,J. Mazer112 , M.A. Mazzoni95 , F. Meddi24 , A. Menchaca-Rocha56 , J. Mercado Perez82 , M. Meres33 ,Y. Miake114 , L. Milano23 , J. Milosevic18 , , A. Mischke45 , A.N. Mishra81 , D. Miskowiec85 ,30 , C. Mitu50 ,J. Mlynarz119 , B. Mohanty116 , L. Molnar60 ,30 , L. Montano Zetina9 , M. Monteno94 , E. Montes8 , T. Moon123 ,M. Morando20 , D.A. Moreira De Godoy107 , S. Moretto20 , A. Morsch30 , V. Muccifora65 , E. Mudnic103 ,S. Muhuri116 , M. Mukherjee116 , H. Muller30 , M.G. Munhoz107 , L. Musa30 , A. Musso94 , B.K. Nandi40 ,R. Nania97 , E. Nappi98 , C. Nattrass112 , N.P. Naumov87 , S. Navin90 , T.K. Nayak116 , S. Nazarenko87 ,G. Nazarov87 , A. Nedosekin46 , M. Nicassio28 , M.Niculescu50 ,30 , B.S. Nielsen71 , T. Niida114 , S. Nikolaev88 ,V. Nikolic86 , S. Nikulin88 , V. Nikulin75 , B.S. Nilsen76 , M.S. Nilsson18 , F. Noferini97 ,10 , P. Nomokonov59 ,G. Nooren45 , N. Novitzky38 , A. Nyanin88 , A. Nyatha40 , C. Nygaard71 , J. Nystrand15 , A. Ochirov117 ,H. Oeschler53 ,30 , S. Oh120 , S.K. Oh37 , J. Oleniacz118 , C. Oppedisano94 , A. Ortiz Velasquez29 ,55 , G. Ortona23 ,A. Oskarsson29 , P. Ostrowski118 , J. Otwinowski85 , K. Oyama82 , K. Ozawa113 , Y. Pachmayer82 , M. Pachr34 ,F. Padilla23 , P. Pagano26 , G. Paic55 , F. Painke36 , C. Pajares13 , S.K. Pal116 , A. Palaha90 , A. Palmeri99 ,V. Papikyan121 , G.S. Pappalardo99 , W.J. Park85 , A. Passfeld54 , B. Pastircak47 , D.I. Patalakha43 , V. Paticchio98 ,A. Pavlinov119 , T. Pawlak118 , T. Peitzmann45 , H. Pereira Da Costa12 , E. Pereira De Oliveira Filho107 ,D. Peresunko88 , C.E. Perez Lara72 , E. Perez Lezama55 , D. Perini30 , D. Perrino28 , W. Peryt118 , A. Pesci97 ,V. Peskov30 ,55 , Y. Pestov3 , V. Petracek34 , M. Petran34 , M. Petris70 , P. Petrov90 , M. Petrovici70 , C. Petta25 ,S. Piano92 , A. Piccotti94 , M. Pikna33 , P. Pillot102 , O. Pinazza30 , L. Pinsky110 , N. Pitz52 , D.B. Piyarathna110 ,M. Planinic86 , M. Płoskon67 , J. Pluta118 , T. Pocheptsov59 , S. Pochybova60 , P.L.M. Podesta-Lerma106 ,M.G. Poghosyan30 ,23 , K. Polak49 , B. Polichtchouk43 , A. Pop70 , S. Porteboeuf-Houssais63 , V. Pospısil34 ,B. Potukuchi80 , S.K. Prasad119 , R. Preghenella97 ,10 , F. Prino94 , C.A. Pruneau119 , I. Pshenichnov44 ,S. Puchagin87 , G. Puddu22 , A. Pulvirenti25 , V. Punin87 , M. Putis35 , J. Putschke119 ,120 , E. Quercigh30 ,H. Qvigstad18 , A. Rachevski92 , A. Rademakers30 , T.S. Raiha38 , J. Rak38 , A. Rakotozafindrabe12 ,L. Ramello27 , A. Ramırez Reyes9 , S. Raniwala81 , R. Raniwala81 , S.S. Rasanen38 , B.T. Rascanu52 ,D. Rathee77 , K.F. Read112 , J.S. Real64 , K. Redlich100 ,57 , P. Reichelt52 , M. Reicher45 , R. Renfordt52 ,A.R. Reolon65 , A. Reshetin44 , F. Rettig36 , J.-P. Revol30 , K. Reygers82 , L. Riccati94 , R.A. Ricci66 , T. Richert29 ,M. Richter18 , P. Riedler30 , W. Riegler30 , F. Riggi25 ,99 , B. Rodrigues Fernandes Rabacal30 ,M. Rodrıguez Cahuantzi1 , A. Rodriguez Manso72 , K. Røed15 , D. Rohr36 , D. Rohrich15 , R. Romita85 ,


sNN = 2.76 TeV 9

F. Ronchetti65 , P. Rosnet63 , S. Rossegger30 , A. Rossi30 ,20 , P. Roy89 , C. Roy58 , A.J. Rubio Montero8 , R. Rui21 ,R. Russo23 , E. Ryabinkin88 , A. Rybicki104 , S. Sadovsky43 , K. Safarık30 , R. Sahoo41 , P.K. Sahu48 , J. Saini116 ,H. Sakaguchi39 , S. Sakai67 , D. Sakata114 , C.A. Salgado13 , J. Salzwedel16 , S. Sambyal80 , V. Samsonov75 ,X. Sanchez Castro58 , L. Sandor47 , A. Sandoval56 , M. Sano114 , S. Sano113 , R. Santo54 , R. Santoro98 ,30 ,10 ,J. Sarkamo38 , E. Scapparone97 , F. Scarlassara20 , R.P. Scharenberg83 , C. Schiaua70 , R. Schicker82 ,H.R. Schmidt115 , C. Schmidt85 , S. Schreiner30 , S. Schuchmann52 , J. Schukraft30 , Y. Schutz30 ,102 ,K. Schwarz85 , K. Schweda85 ,82 , G. Scioli19 , E. Scomparin94 , P.A. Scott90 , R. Scott112 , G. Segato20 ,I. Selyuzhenkov85 , S. Senyukov27 ,58 , J. Seo84 , S. Serci22 , E. Serradilla8 ,56 , A. Sevcenco50 , A. Shabetai102 ,G. Shabratova59 , R. Shahoyan30 , N. Sharma77 , S. Sharma80 , S. Rohni80 , K. Shigaki39 , M. Shimomura114 ,K. Shtejer7 , Y. Sibiriak88 , M. Siciliano23 , E. Sicking30 , S. Siddhanta96 , T. Siemiarczuk100 , D. Silvermyr74 ,C. Silvestre64 , G. Simatovic55 ,86 , G. Simonetti30 , R. Singaraju116 , R. Singh80 , S. Singha116 , V. Singhal116 ,T. Sinha89 , B.C. Sinha116 , B. Sitar33 , M. Sitta27 , T.B. Skaali18 , K. Skjerdal15 , R. Smakal34 , N. Smirnov120 ,R.J.M. Snellings45 , C. Søgaard71 , R. Soltz68 , H. Son17 , J. Song84 , M. Song123 , C. Soos30 , F. Soramel20 ,I. Sputowska104 , M. Spyropoulou-Stassinaki78 , B.K. Srivastava83 , J. Stachel82 , I. Stan50 , I. Stan50 ,G. Stefanek100 , M. Steinpreis16 , E. Stenlund29 , G. Steyn79 , J.H. Stiller82 , D. Stocco102 , M. Stolpovskiy43 ,K. Strabykin87 , P. Strmen33 , A.A.P. Suaide107 , M.A. Subieta Vasquez23 , T. Sugitate39 , C. Suire42 ,M. Sukhorukov87 , R. Sultanov46 , M. Sumbera73 , T. Susa86 , T.J.M. Symons67 , A. Szanto de Toledo107 ,I. Szarka33 , A. Szczepankiewicz104 ,30 , A. Szostak15 , M. Szymanski118 , J. Takahashi108 , J.D. Tapia Takaki42 ,A. Tauro30 , G. Tejeda Munoz1 , A. Telesca30 , C. Terrevoli28 , J. Thader85 , D. Thomas45 , R. Tieulent109 ,A.R. Timmins110 , D. Tlusty34 , A. Toia36 ,20 ,93 , H. Torii113 , L. Toscano94 , V. Trubnikov2 , D. Truesdale16 ,W.H. Trzaska38 , T. Tsuji113 , A. Tumkin87 , R. Turrisi93 , T.S. Tveter18 , J. Ulery52 , K. Ullaland15 , J. Ulrich61 ,51 ,A. Uras109 , J. Urban35 , G.M. Urciuoli95 , G.L. Usai22 , M. Vajzer34 ,73 , M. Vala59 ,47 , L. Valencia Palomo42 ,S. Vallero82 , P. Vande Vyvre30 , M. van Leeuwen45 , L. Vannucci66 , A. Vargas1 , R. Varma40 , M. Vasileiou78 ,A. Vasiliev88 , V. Vechernin117 , M. Veldhoen45 , M. Venaruzzo21 , E. Vercellin23 , S. Vergara1 , R. Vernet6 ,M. Verweij45 , L. Vickovic103 , G. Viesti20 , O. Vikhlyantsev87 , Z. Vilakazi79 , O. Villalobos Baillie90 ,Y. Vinogradov87 , A. Vinogradov88 , L. Vinogradov117 , T. Virgili26 , Y.P. Viyogi116 , A. Vodopyanov59 ,S. Voloshin119 , K. Voloshin46 , G. Volpe28 ,30 , B. von Haller30 , D. Vranic85 , G. Øvrebekk15 , J. Vrlakova35 ,B. Vulpescu63 , A. Vyushin87 , V. Wagner34 , B. Wagner15 , R. Wan5 , Y. Wang5 , M. Wang5 , D. Wang5 ,Y. Wang82 , K. Watanabe114 , M. Weber110 , J.P. Wessels30 ,54 , U. Westerhoff54 , J. Wiechula115 , J. Wikne18 ,M. Wilde54 , A. Wilk54 , G. Wilk100 , M.C.S. Williams97 , B. Windelband82 , L. Xaplanteris Karampatsos105 ,C.G. Yaldo119 , Y. Yamaguchi113 , S. Yang15 , H. Yang12 , S. Yasnopolskiy88 , J. Yi84 , Z. Yin5 , I.-K. Yoo84 ,J. Yoon123 , W. Yu52 , X. Yuan5 , I. Yushmanov88 , V. Zaccolo71 , C. Zach34 , C. Zampolli97 , S. Zaporozhets59 ,A. Zarochentsev117 , P. Zavada49 , N. Zaviyalov87 , H. Zbroszczyk118 , P. Zelnicek51 , I.S. Zgura50 , M. Zhalov75 ,H. Zhang5 , X. Zhang63 ,5 , D. Zhou5 , Y. Zhou45 , F. Zhou5 , J. Zhu5 , X. Zhu5 , J. Zhu5 , A. Zichichi19 ,10 ,A. Zimmermann82 , G. Zinovjev2 , Y. Zoccarato109 , M. Zynovyev2 , M. Zyzak52

Affiliation notesi Also at: M.V.Lomonosov Moscow State University, D.V.Skobeltsyn Institute of Nuclear Physics, Moscow,

Russia

Collaboration Institutes1 Benemerita Universidad Autonoma de Puebla, Puebla, Mexico2 Bogolyubov Institute for Theoretical Physics, Kiev, Ukraine3 Budker Institute for Nuclear Physics, Novosibirsk, Russia4 California Polytechnic State University, San Luis Obispo, California, United States5 Central China Normal University, Wuhan, China6 Centre de Calcul de l’IN2P3, Villeurbanne, France7 Centro de Aplicaciones Tecnologicas y Desarrollo Nuclear (CEADEN), Havana, Cuba8 Centro de Investigaciones Energeticas Medioambientales y Tecnologicas (CIEMAT), Madrid, Spain9 Centro de Investigacion y de Estudios Avanzados (CINVESTAV), Mexico City and Merida, Mexico

10 Centro Fermi – Centro Studi e Ricerche e Museo Storico della Fisica “Enrico Fermi”, Rome, Italy11 Chicago State University, Chicago, United States12 Commissariat a l’Energie Atomique, IRFU, Saclay, France13 Departamento de Fısica de Partıculas and IGFAE, Universidad de Santiago de Compostela, Santiago de

Compostela, Spain


14 Department of Physics Aligarh Muslim University, Aligarh, India15 Department of Physics and Technology, University of Bergen, Bergen, Norway16 Department of Physics, Ohio State University, Columbus, Ohio, United States17 Department of Physics, Sejong University, Seoul, South Korea18 Department of Physics, University of Oslo, Oslo, Norway19 Dipartimento di Fisica dell’Universita and Sezione INFN, Bologna, Italy20 Dipartimento di Fisica dell’Universita and Sezione INFN, Padova, Italy21 Dipartimento di Fisica dell’Universita and Sezione INFN, Trieste, Italy22 Dipartimento di Fisica dell’Universita and Sezione INFN, Cagliari, Italy23 Dipartimento di Fisica dell’Universita and Sezione INFN, Turin, Italy24 Dipartimento di Fisica dell’Universita ‘La Sapienza’ and Sezione INFN, Rome, Italy25 Dipartimento di Fisica e Astronomia dell’Universita and Sezione INFN, Catania, Italy26 Dipartimento di Fisica ‘E.R. Caianiello’ dell’Universita and Gruppo Collegato INFN, Salerno, Italy27 Dipartimento di Scienze e Innovazione Tecnologica dell’Universita del Piemonte Orientale and Gruppo

Collegato INFN, Alessandria, Italy28 Dipartimento Interateneo di Fisica ‘M. Merlin’ and Sezione INFN, Bari, Italy29 Division of Experimental High Energy Physics, University of Lund, Lund, Sweden30 European Organization for Nuclear Research (CERN), Geneva, Switzerland31 Fachhochschule Koln, Koln, Germany32 Faculty of Engineering, Bergen University College, Bergen, Norway33 Faculty of Mathematics, Physics and Informatics, Comenius University, Bratislava, Slovakia34 Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, Prague,

Czech Republic35 Faculty of Science, P.J. Safarik University, Kosice, Slovakia36 Frankfurt Institute for Advanced Studies, Johann Wolfgang Goethe-Universitat Frankfurt, Frankfurt,

Germany37 Gangneung-Wonju National University, Gangneung, South Korea38 Helsinki Institute of Physics (HIP) and University of Jyvaskyla, Jyvaskyla, Finland39 Hiroshima University, Hiroshima, Japan40 Indian Institute of Technology Bombay (IIT), Mumbai, India41 Indian Institute of Technology Indore (IIT), Indore, India42 Institut de Physique Nucleaire d’Orsay (IPNO), Universite Paris-Sud, CNRS-IN2P3, Orsay, France43 Institute for High Energy Physics, Protvino, Russia44 Institute for Nuclear Research, Academy of Sciences, Moscow, Russia45 Nikhef, National Institute for Subatomic Physics and Institute for Subatomic Physics of Utrecht University,

Utrecht, Netherlands46 Institute for Theoretical and Experimental Physics, Moscow, Russia47 Institute of Experimental Physics, Slovak Academy of Sciences, Kosice, Slovakia48 Institute of Physics, Bhubaneswar, India49 Institute of Physics, Academy of Sciences of the Czech Republic, Prague, Czech Republic50 Institute of Space Sciences (ISS), Bucharest, Romania51 Institut fur Informatik, Johann Wolfgang Goethe-Universitat Frankfurt, Frankfurt, Germany52 Institut fur Kernphysik, Johann Wolfgang Goethe-Universitat Frankfurt, Frankfurt, Germany53 Institut fur Kernphysik, Technische Universitat Darmstadt, Darmstadt, Germany54 Institut fur Kernphysik, Westfalische Wilhelms-Universitat Munster, Munster, Germany55 Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Mexico City, Mexico56 Instituto de Fısica, Universidad Nacional Autonoma de Mexico, Mexico City, Mexico57 Institut of Theoretical Physics, University of Wroclaw58 Institut Pluridisciplinaire Hubert Curien (IPHC), Universite de Strasbourg, CNRS-IN2P3, Strasbourg,

France59 Joint Institute for Nuclear Research (JINR), Dubna, Russia60 KFKI Research Institute for Particle and Nuclear Physics, Hungarian Academy of Sciences, Budapest,

Hungary61 Kirchhoff-Institut fur Physik, Ruprecht-Karls-Universitat Heidelberg, Heidelberg, Germany62 Korea Institute of Science and Technology Information, Daejeon, South Korea63 Laboratoire de Physique Corpusculaire (LPC), Clermont Universite, Universite Blaise Pascal,


sNN = 2.76 TeV 11

CNRS–IN2P3, Clermont-Ferrand, France64 Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Universite Joseph Fourier, CNRS-IN2P3,

Institut Polytechnique de Grenoble, Grenoble, France65 Laboratori Nazionali di Frascati, INFN, Frascati, Italy66 Laboratori Nazionali di Legnaro, INFN, Legnaro, Italy67 Lawrence Berkeley National Laboratory, Berkeley, California, United States68 Lawrence Livermore National Laboratory, Livermore, California, United States69 Moscow Engineering Physics Institute, Moscow, Russia70 National Institute for Physics and Nuclear Engineering, Bucharest, Romania71 Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark72 Nikhef, National Institute for Subatomic Physics, Amsterdam, Netherlands73 Nuclear Physics Institute, Academy of Sciences of the Czech Republic, Rez u Prahy, Czech Republic74 Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States75 Petersburg Nuclear Physics Institute, Gatchina, Russia76 Physics Department, Creighton University, Omaha, Nebraska, United States77 Physics Department, Panjab University, Chandigarh, India78 Physics Department, University of Athens, Athens, Greece79 Physics Department, University of Cape Town, iThemba LABS, Cape Town, South Africa80 Physics Department, University of Jammu, Jammu, India81 Physics Department, University of Rajasthan, Jaipur, India82 Physikalisches Institut, Ruprecht-Karls-Universitat Heidelberg, Heidelberg, Germany83 Purdue University, West Lafayette, Indiana, United States84 Pusan National University, Pusan, South Korea85 Research Division and ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum fur

Schwerionenforschung, Darmstadt, Germany86 Rudjer Boskovic Institute, Zagreb, Croatia87 Russian Federal Nuclear Center (VNIIEF), Sarov, Russia88 Russian Research Centre Kurchatov Institute, Moscow, Russia89 Saha Institute of Nuclear Physics, Kolkata, India90 School of Physics and Astronomy, University of Birmingham, Birmingham, United Kingdom91 Seccion Fısica, Departamento de Ciencias, Pontificia Universidad Catolica del Peru, Lima, Peru92 Sezione INFN, Trieste, Italy93 Sezione INFN, Padova, Italy94 Sezione INFN, Turin, Italy95 Sezione INFN, Rome, Italy96 Sezione INFN, Cagliari, Italy97 Sezione INFN, Bologna, Italy98 Sezione INFN, Bari, Italy99 Sezione INFN, Catania, Italy

100 Soltan Institute for Nuclear Studies, Warsaw, Poland101 Nuclear Physics Group, STFC Daresbury Laboratory, Daresbury, United Kingdom102 SUBATECH, Ecole des Mines de Nantes, Universite de Nantes, CNRS-IN2P3, Nantes, France103 Technical University of Split FESB, Split, Croatia104 The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Cracow, Poland105 The University of Texas at Austin, Physics Department, Austin, TX, United States106 Universidad Autonoma de Sinaloa, Culiacan, Mexico107 Universidade de Sao Paulo (USP), Sao Paulo, Brazil108 Universidade Estadual de Campinas (UNICAMP), Campinas, Brazil109 Universite de Lyon, Universite Lyon 1, CNRS/IN2P3, IPN-Lyon, Villeurbanne, France110 University of Houston, Houston, Texas, United States111 University of Technology and Austrian Academy of Sciences, Vienna, Austria112 University of Tennessee, Knoxville, Tennessee, United States113 University of Tokyo, Tokyo, Japan114 University of Tsukuba, Tsukuba, Japan115 Eberhard Karls Universitat Tubingen, Tubingen, Germany116 Variable Energy Cyclotron Centre, Kolkata, India


117 V. Fock Institute for Physics, St. Petersburg State University, St. Petersburg, Russia118 Warsaw University of Technology, Warsaw, Poland119 Wayne State University, Detroit, Michigan, United States120 Yale University, New Haven, Connecticut, United States121 Yerevan Physics Institute, Yerevan, Armenia122 Yildiz Technical University, Istanbul, Turkey123 Yonsei University, Seoul, South Korea124 Zentrum fur Technologietransfer und Telekommunikation (ZTT), Fachhochschule Worms, Worms,

Germany

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Pion, Kaon, and Proton Production in Central Pb--Pb Collisions at $\sqrt{s_{NN}}$ = 2.76 TeV

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