J/psi Elliptic Flow in Pb-Pb Collisions at root s(NN)=2.76 TeV

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J= c Elliptic Flow in Pb-Pb Collisions at p ffiffiffiffiffiffiffiffiffi s

_NN

¼ 2:76 TeV

E. Abbaset al.* (ALICE Collaboration)

(Received 24 March 2013; revised manuscript received 28 July 2013; published 17 October 2013) We report on the first measurement of inclusiveJ=celliptic flowv2in heavy-ion collisions at the LHC.

The measurement is performed with the ALICE detector in Pb-Pb collisions at ffiffiffiffiffiffiffiffi sNN

p ¼2:76 TeVin the rapidity range2:5< y <4:0. The dependence of theJ=c v2 on the collision centrality and on theJ=c transverse momentum is studied in the range0pT<10 GeV=c. For semicentral Pb-Pb collisions at

ffiffiffiffiffiffiffiffi sNN

p ¼2:76 TeV, an indication of nonzero v2 is observed with a largest measured value of v2¼ 0:1160:046ðstatÞ 0:029ðsystÞforJ=c in the transverse momentum range2pT<4 GeV=c. The elliptic flow measurement complements the previously reported ALICE results on the inclusiveJ=c nuclear modification factor and favors the scenario of a significant fraction ofJ=cproduction from charm quarks in a deconfined partonic phase.

DOI:10.1103/PhysRevLett.111.162301 PACS numbers: 25.75.Cj, 25.75.Ld, 25.75.Nq

Ultrarelativistic heavy-ion collisions enable the study of matter at high temperature and pressure where quantum chromodynamics predicts the existence of a deconfined state of partonic matter, the quark-gluon plasma (QGP).

Heavy quarks are expected to be produced in the primary partonic scatterings and to interact with this partonic medium making them ideal probes of the QGP. Quarkonia (a heavy quark and antiquark bound state) are therefore expected to be sensitive to the properties of the strongly interacting system formed in the early stages of heavy-ion collisions [1]. According to the color-screening model [2], quarkonium states are suppressed in the medium with different dissociation probabilities for the various states.

Recently, the CMS Collaboration at the Large Hadron Collider (LHC) reported about the observation of the sequential suppression in the sector [3]. The ALICE Collaboration published the inclusive [4] J=c ^nuclear modification factorRAA down to zero transverse momentum (pT) at forward rapidity in Pb-Pb collisions at ffiffiffiffiffiffiffiffi

sNN

p ¼ 2:76 TeV[5]. TheRAA compares the yields in Pb-Pb to those in pp collisions scaled by the number of binary nucleon-nucleon collisions. The inclusive J=c RAA

reported is larger than that measured at the SPS [6] and at RHIC [7,8] for central collisions and does not exhibit a significant centrality dependence. Complementarily, the CMS Collaboration measured the high pT (6:5 pT<30 GeV=c) prompt J=c RAA in the rapidity range jyj<2:4[9]. The CMS data show that high pT J=c ^are more suppressed than lowpT J=c and that this suppression does exhibit a strong centrality dependence.

The low p_T J=c RAA can be qualitatively understood with models including full [10,11] or partial [12,13] regeneration ofJ=c from deconfined charm quarks in the medium. This mechanism was first proposed by the statistical hadronization model, which assumes deconfinement and thermal equilibrium of the bulk ofccpairs to produceJ=c at the phase boundary by statistical hadronization only [10]. Later, the transport models proposed a dynamical competition between the J=c suppression by the QGP and the regeneration mechanism, which enables them to also describe the J=c RAA versusp_T [12,13]. More dif- ferential studies, like theJ=c elliptic flow, could help to assess the assumption of charm quark thermalization in the medium.

The azimuthal distribution of particles in the transverse plane is also sensitive to the dynamics of the early stages of heavy-ion collisions. In noncentral collisions, the geometrical overlap region and, therefore, the initial matter distribution are anisotropic (almond shaped). If the matter is strongly interacting, this spatial asymmetry is converted via multiple collisions into an anisotropic momentum distribution [14]. The second coefficient of the Fourier expansion describing the final state particle azimuthal distribution with respect to the reaction planev2 is called elliptic flow. The reaction plane is defined by the beam axis and the impact parameter vector of the colliding nuclei.

Within the transport model scenario [12,13] observed J=c have two origins. First, primordialJ=c produced in the initial hard scatterings traverse and interact with the created medium. During this process they may be dissoci- ated. Second, J=c could be regenerated from deconfined charm quarks in the QGP. PrimordialJ=cemitted in plane traverse a shorter path through the medium than those emitted out of plane, resulting in a small azimuthal anisotropy for the survivingJ=c. RegeneratedJ=c inherit the elliptic flow of the charm quarks in the QGP. If charm quarks do thermalize in the QGP, thenJ=c formed there

*Full author list given at the end of the article.

Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

PRL111,162301 (2013) P H Y S I C A L R E V I E W L E T T E R S 18 OCTOBER 2013

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can exhibit a large elliptic flow. In the calculation by Zhao et al.[15], thev2 ofJ=c ^atpT 2:5 GeV=cis 0.02 and 0.2 for primordial and regeneratedJ=c, respectively.

At RHIC, the (preliminary) measurements by the (PHENIX) STAR Collaboration of the J=c v2 in Au-Au collisions at ffiffiffiffiffiffiffiffi

s_NN

p ¼200 GeV [16,17] are consistent with zero albeit with large uncertainties in the pT

and centrality ranges (0–5 GeV=c) 2–10 GeV=c and (20%–60%) 10%–40%. In Pb-Pb collisions at the LHC, the higher energy density of the medium should favor the charm quark thermalization, and thus increase its flow. In addition, the large number of cc pairs produced should favor the formation ofJ=c by regeneration mechanisms.

Both effects should lead to an increase of the v2 of the observedJ=c^.

In this Letter, we report ALICE results on inclusiveJ=c elliptic flow in Pb-Pb collisions at ffiffiffiffiffiffiffiffi

sNN

p ¼2:76 TeV at forward rapidity, measured via the^þ decay channel.

The results are presented as a function of transverse momentum and collision centrality.

The ALICE detector is described in [18]. At forward rapidity (2:5< y <4) the production of quarkonia is measured in the muon spectrometer [19] down topT ¼0. The spectrometer consists of an absorber stopping the hadrons in front of five tracking stations comprising two planes of cathode pad chambers each, with the third station inside a dipole magnet. The tracking apparatus is completed by a triggering system made of four planes of resistive plate chambers downstream of an iron wall, which absorbs secondary hadrons escaping from the front absorber and low momentum muons. Also used in this analysis are two cylindrical layers of silicon pixel detectors, to determine the location of the interaction point, and two scintillator arrays (VZERO). The VZERO counters consist of two arrays of 32 scintillator sectors each distributed in four rings covering 2:85:1 (VZERO-A) and 3:7 1:7 (VZERO-C). All of these detectors have full azimuthal coverage. The data sample used for this analysis, collected in 2011, amounts to1710⁶dimuon unlike sign (MU) triggered Pb-Pb collisions and corresponds to an integrated luminosity Lint70b¹. The MU trigger requires a minimum bias (MB) trigger and at least a pair of opposite-sign (OS) track segments, each with a pT

above the threshold of the on-line trigger algorithm. This p_T threshold was set to provide 50% efficiency for muon tracks with pT ¼1 GeV=c. The MB trigger requires a signal in both VZERO-A and VZERO-C. The beam- induced background was further reduced off-line using the VZERO and the zero degree calorimeter timing infor- mation. The contribution from electromagnetic processes was removed by requiring a minimum energy deposited in the neutron zero degree calorimeters [20]. The centrality determination is based on a fit of the VZERO amplitude distribution [21,22]. The average number of participating nucleons hNparti for the centrality classes used in this

analysis (see Table I) are derived from a Glauber model calculation [21,22].

J=c candidates are formed by combining pairs of OS tracks reconstructed in the geometrical acceptance of the muon spectrometer. To improve the muon identification, the reconstructed tracks in the tracking chambers are required to match a track segment in the trigger system above thep_T threshold aforementioned.

TheJ=c v2 is calculated using event plane (EP) based methods. The azimuthal angle of the second harmonic EP is used to estimate the reaction plane angle [23]. is determined from the azimuthal distribution of the VZERO amplitude. A two step flattening procedure of the EP azimuthal distribution was applied as described in [24]

and [25], respectively. It results in an EP azimuthal distribution uniform to better than 2% for all centrality classes under study. The VZERO-C has a common acceptance region with the muon spectrometer. Therefore, only the VZERO-A was used for the EP determination to avoid autocorrelations. TheJ=c v2results were obtained deter- mining v2 ¼ hcos2ðÞi versus the invariant mass (m) [26], where is the OS dimuon azimuthal angle.

The resultingv2ðmÞdistribution is fitted using

v2ðmÞ ¼v^sig₂ ðmÞ þv^bkg₂ ðmÞ½1ðmÞ; (1) wherev^sig₂ andv^bkg₂ correspond to thev2of theJ=c ^signal and of the background, respectively [see Fig. 1(b)]. v^bkg₂ was parametrized using a second order polynomial. Here, ðmÞ ¼S=ðSþBÞ is the ratio of the signal over the sum of the signal plus background of the m distributions. It is extracted from fits to the OS invariant mass distribution [see Fig.1(a)] in eachp_T and centrality class.

TheJ=cline shape was described with a Crystal Ball (CB) function and the underlying continuum with either a third order polynomial or a Gaussian with a width linearly varying with mass. The CB function connects a Gaussian core with a power-law tail [27] at low mass to account for energy loss fluctuations and radiative decays. An extended CB function with an additional power-law tail at high mass, to account for alignment and calibration biases, was also used. The combination of several CB and underlying continuum parametrizations described before were tested to assess the signal and the related systematic TABLE I. hNparti and VZERO-A EP resolution for the centrality classes expressed in percentages of the nuclear cross section [21].

Centrality hNparti EP resolutionðstatÞ ðsystÞ 5%–20% 2834 0:5480:0030:009 20%–40% 1573 0:6100:0020:008 40%–60% 692 0:4510:0030:008

60%–90% 151 0:1850:0050:013

20%–60% 1133 0:5760:0020:008

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uncertainties. TheJ=c v2and its statistical uncertainty in eachp_T and centrality class were determined as the average of thev^sig2 obtained by fitting v2ðmÞusing Eq. (1) with the variousðmÞ, while the corresponding systematic uncertainties were defined as the rms of these results.

Figure1shows typical fits of the OS invariant mass distribution [1(a)] and of the hcos2ðÞi as a function of m [1(b)] in the 20%–40% centrality class. The procedure above was repeated using either a first order polynomial or its inverse asv^bkg2 parametrization. The largest deviation of the results obtained with the three different v^bkg₂ parametrizations was conservatively adopted as the systematic uncertainty related to the unknown shape of the v^bkg2 ðmÞ. This turns out to often be the dominant source of systematic uncertainties with the uncertainty from the signal extraction being the second one. It was checked that different choices of invariant mass binnings yieldv2values that are consistent within uncertainties. A similar method was used to extract the uncorrected (for detector acceptance and efficiency) average transverse momentum (hpTi^uncor) of the reconstructed J=c in each centrality andp_T class. Thehp_Ti^uncoris used to locate the data points when plotted as a function ofp_T. Consistentv2values were obtained using an alternative method [23] in which the J=c raw yield is extracted, as described before, in bins of () and v2 is evaluated by fitting the data with the functionðdN=dðÞÞ¼A½1þ2v2cos2ðÞ, where A is a normalization constant. As an additional check the first analysis procedure [26] was also applied to the same-sign (SS) dimuons. As expected, no J=c signal is seen in either the invariant mass distribution or thehcos2ðÞias a function ofmof SS dimuons. In both cases the SS dimuons exhibit the same trend as the continuum of the OS dimuons.

The finite resolution in the EP determination smears out the azimuthal distributions and lowers the value of the measured anisotropy [23]. The VZERO-A EP resolution as a function of the centrality was determined using MB events and the 3 subevent method [23]. To estimate the systematic uncertainty from the EP determination two sets of 3 subevents were used: first, VZERO-A, VZERO-C, and the time projection chamber (TPC), with pseu- dorapidity gaps V0A-TPC¼1:9, V0A-V0C¼4:5, and TPC-V0C¼0:8; second, VZERO-A, ring 0 of VZERO-C, and VZERO-C 3rd ring, with pseudorapi- dity gaps V0A-V0C0¼6:0, V0C0-V0C3¼1:0, and V0A-V0C3 ¼4:5. The differences between the EP resolution for VZERO-A obtained from these two sets of subevents are taken as systematic uncertainties. Since v2

is measured here in a wide centrality class, the resolution must reflect the distribution of events with a J=c ^within the class. Therefore, the EP resolution for each wide class was calculated as the average of the values obtained in finer centrality classes weighted by the number of recon- structedJ=c^{. Table}^Ishows the corresponding resolution for each centrality class which is applied to the results reported in this Letter.

The J=c reconstruction efficiency depends on the detector occupancy, which could bias the v2 measurement.

This effect was evaluated by embedding azimuthally iso- tropic simulated J=c !^þ decays into real events.

The measuredv2of those embeddedJ=c does not deviate from zero by more than 0.015 in the centrality and pT

classes considered. This value is used as a conservative systematic uncertainty on all measuredv2values.

Figure2shows thepTdependence of the inclusiveJ=c v2for semicentral (20%–40%) Pb-Pb collisions at ffiffiffiffiffiffiffiffi

sNN

p ¼ 2:76 TeV. The vertical bars show the statistical uncertainties while the boxes indicate the point-to-point uncorrelated systematic uncertainties, which include those from

) c (GeV/

pT

0 1 2 3 4 5 6 7 8 9 10

2v

-0.1 0 0.1 0.2 0.3

< 4.0 y = 2.76 TeV), centrality 20%-40%, 2.5 <

sNN

ALICE (Pb-Pb

1.3%

± global syst =

FIG. 2 (color online). Inclusive J=c v2ðp_TÞfor semicentral (20%–40%) Pb-Pb collisions at ffiffiffiffiffiffiffiffi

sNN

p ¼2:76 TeV(see text for details on uncertainties). The usedpTranges are 0–2, 2–4, 4–6, and6–10 GeV=c.

)2cCounts/ (50 MeV/ ₅₀₀

1000 1500 2000

(a)

c < 4.0 GeV/

pT

≤ < 4.0, 2.0 y = 2.76 TeV, centrality 20% - 40%, 2.5 <

sNN Pb-Pb

Opposite sign pairs Fit total Fit signal Fit background

2) c (GeV/

µ

mµ

2 2.5 3 3.5 4 4.5 5

〉)Ψ - φ cos 2(〈 ⁰ 0.05

0.1 Opposite sign pairs

µ) mµ 2( v Fit total

(b)

FIG. 1 (color online). Invariant mass distribution (a) and hcos2ðÞi as a function of m (b) of OS dimuons with 2pT<4 GeV=cand2:5< y <4in semicentral (20%–40%) Pb-Pb collisions.

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the signal extraction, thev^bkg₂ shape, and the reconstruction efficiency. The global correlated relative systematic uncertainty on the EP resolution is 1.3%. A nonzero v2 is observed in the intermediate p_T range 2p_T <

6 GeV=c. Including statistical and systematic uncertainties the combined significance of a nonzerov2in thisp_T range is 2:7. At lower and higherp_T the inclusive J=c v2 is compatible with zero within uncertainties.

To study the centrality dependence of thev2 we select J=c ^with ¹:5pT<10 GeV=c. Indeed, below 1:5 GeV=c the v2 of the J=c is expected to be small [15] and the signal to background ratio is also low. Since the initial spatial anisotropy for head-on collisions is small, the expectedv2 is also small. In addition, for the 0%–5%

centrality range the VZERO-A EP resolution is quite low and has higher systematic uncertainties. Therefore, the 0%–5% centrality range was excluded. Figure3(a)shows v2 for inclusive J=c ^with ¹:5p_T<10 GeV=c as a function of hNparti in Pb-Pb collisions at ffiffiffiffiffiffiffiffi

s_NN p ¼ 2:76 TeV. Here, the point-to-point uncorrelated systematic uncertainties (boxes) also include, in addition to those discussed above, the uncertainty from the EP resolution determination. The measuredv2 depends on thep_T distribution of the reconstructedJ=c, which could vary with the collision centrality. Therefore, hp_Ti^uncor of the reconstructed J=c is also shown in Fig. 3(b). The error bar indicates the statistical uncertainties while the boxes show the systematic uncertainties due to the J=c ^signal extraction. For the most central collisions, 5%–20% and 20%–40%, the inclusive J=c v2 for 1:5pT <

10 GeV=c are 0:1010:044ðstatÞ 0:032ðsystÞ and 0:1160:045ðstatÞ 0:041ðsystÞ, respectively. The combined significance of a nonzero v2 is 2:9. For more peripheral Pb-Pb collisions, thev2 is consistent with zero within uncertainties. Although there is a small variation

with centrality, the hp_Ti^uncor stays in the range 3:0–3:3 GeV=c, indicating that the bulk of the recon- structedJ=c are in the samepT range for all centralities.

Thus, the observed centrality dependence of the v2 for inclusiveJ=c ^with¹:5pT<10 GeV=cdoes not result from any bias in the sampled pT distributions. For J=c with pT<1:5 GeV=c (not shown), the v2 is compatible with zero within 1 standard deviation for the four centrality classes. The hpTi^uncor ranges from about 0.75 to 0:9 GeV=c.

To allow a direct comparison with current model calculations, the inclusiveJ=c v2ðpTÞwas also calculated in a broader centrality range, namely, 20%–60%, and it is shown in Fig. 4. In this broader centrality range, the measured v2 signal in the pT range2–4 GeV=cdeviates from zero by2. The same trend ofv2ðp_TÞis observed in the 20%–60% and in the 20%–40% centrality classes. This trend seems qualitatively different from that of the STAR measurement [17] at lower collision energy, which is compatible with zero for p_T 2 GeV=c albeit in somewhat different (10%–40% and 0%–80%) centrality ranges. Also shown in Fig.4are two transport model calculations that include a J=c regeneration component from deconfined charm quarks in the medium [15,28]. In both models about 30% of the measured J=c in the 20%–60% centrality range are regenerated. First, thermalized charm quarks in the medium transfer a significant elliptic flow to regenerated J=c. Second, primordialJ=c emitted out of plane traverse a longer path through the medium than those emitted in plane, resulting in a small apparent v2. The predicted maximum v2 at pT2:5 GeV=c results from an interplay between the regeneration component, dominant at lower p_T, and the primordial J=c ^component which takes over at higher p_T. The first model [28] is shown for the hypothesis of thermalization (full line) and

part〉

〈N

0 50 100 150 200 250 300 350 400

)c (GeV/uncor〉Tp〈

3 3.5

(b)

2v

-0.1 0 0.1 0.2 0.3

(a) c < 10.0 GeV/

pT

≤ < 4.0, 1.5 y = 2.76 TeV, 2.5 <

sNN

Pb-Pb

FIG. 3 (color online). v2(a) andhp_Tiûncor(b) of inclusiveJ=c with 1:5pT<10 GeV=c as a function of hNparti in Pb-Pb collisions at ffiffiffiffiffiffiffiffi

sNN

p ¼2:76 TeV (see text for details on uncertainties).

) c (GeV/

pT

0 1 2 3 4 5 6 7 8 9 10

2v

-0.1 0 0.1 0.2 0.3

< 4.0 y = 2.76 TeV), centrality 20%-60%, 2.5 <

sNN

ALICE (Pb-Pb Y. Liu et al., b thermalized Y. Liu et al., b not thermalized X. Zhao et al., b thermalized

1.4%

± global syst =

FIG. 4 (color online). Inclusive J=c v2ðp_TÞ for noncentral (20%–60%) Pb-Pb collisions at ffiffiffiffiffiffiffiffi

sNN

p ¼2:76 TeV(see text for details on uncertainties). The usedpTranges are 0–2, 2–4, 4–6, and 6–10 GeV=c. Calculations from two transport models [15,28] are also shown (see text for details).

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nonthermalization (dashed line) of b quarks. The LHCb Collaboration measured the fraction ofJ=c ^fromBhadron decays inppcollisions at ﬃﬃ

ps

¼2:76and 7 TeV [29,30] in the rapidity acceptance used for this measurement. At 7 TeV this fraction increases from 7% atp_T0to 15%

at pT7 GeV=c, while at 2.76 TeV it is about 7% for pT<12 GeV=c. In Pb-Pb collisions this fraction could increase up to 11% if theB hadronRAA¼1. Ifbquarks do thermalize, then their elliptic flow will be transferred to Bmesons at hadronization and to theJ=c ^{at the}Bmeson decay. In the second model [15] (dash-dotted line) only the case assuming b quark thermalization is shown. Both models qualitatively describe the p_T dependence of the v2 and theRAAof inclusiveJ=c ^[5].

In summary, we reported the ALICE measurement of inclusive J=c elliptic flow in the range 0pT <

10 GeV=c at forward rapidity in Pb-Pb collisions at ffiffiffiffiffiffiffiffi

s_NN

p ¼2:76 TeV. For semicentral collisions indications of a nonzeroJ=c v2 are observed in the intermediatepT

range. This measurement complements the results on the J=c RAA, where a smaller suppression was seen at lowp_T at the LHC compared to RHIC. Both results seem in agreement with the global picture in which a significant fraction of the observedJ=c is produced from deconfined charm quarks in the QGP phase.

The ALICE Collaboration would like to thank all its engineers and technicians for their invaluable contributions to the construction of the experiment and the CERN ac- celerator teams for the outstanding performance of the LHC complex. The ALICE Collaboration acknowledges the following funding agencies for their support in building and running the ALICE detector: State Committee of Science, World Federation of Scientists (WFS) and Swiss Fonds Kidagan, Armenia, Conselho Nacional de Desenvolvimento Cientı´fico e Tecnolo´gico (CNPq), Financiadora de Estudos e Projetos (FINEP), Fundaçaõ de Amparo a` Pesquisa do Estado de Saõ Paulo (FAPESP); National Natural Science Foundation of China (NSFC), the Chinese Ministry of Education (CMOE), and the Ministry of Science and Technology of China (MSTC); Ministry of Education and Youth of the Czech Republic; Danish Natural Science Research Council, the Carlsberg Foundation, and the Danish National Research Foundation; The European Research Council under the European Community’s Seventh Framework Programme; Helsinki Institute of Physics and the Academy of Finland; French CNRS-IN2P3, the

‘‘Region Pays de Loire,’’ ‘‘Region Alsace,’’ ‘‘Region Auvergne,’’ and CEA, France; German BMBF and the Helmholtz Association; General Secretariat for Research and Technology, Ministry of Development, Greece;

Hungarian OTKA and National Office for Research and Technology (NKTH); Department of Atomic Energy and Department of Science and Technology of the Government of India; Istituto Nazionale di Fisica Nucleare (INFN) and

Centro Fermi-Museo Storico della Fisica e Centro Studi e Ricerche ‘‘Enrico Fermi,’’ Italy; MEXT Grant-in-Aid for Specially Promoted Research, Japan; Joint Institute for Nuclear Research, Dubna; National Research Foundation of Korea (NRF); CONACYT, DGAPA, Me´xico, ALFA-EC, and the EPLANET Program (European Particle Physics Latin American Network);

Stichting voor Fundamenteel Onderzoek 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 Nat¸ionala˘ pentru Cercetare S¸tiint¸ifica˘-ANCS); Ministry of Education and Science of Russian Federation, Russian Academy of Sciences, Russian Federal Agency of Atomic Energy, Russian Federal Agency for Science and Innovations, and The Russian Foundation for Basic Research; Ministry of Education of Slovakia; Department of Science and Technology, South Africa; CIEMAT, EELA, Ministerio de Economıá y Competitividad (MINECO) of Spain, Xunta de Galicia (Consellerıá de Educacioń), CEADEN, Cubaenergıá, Cuba, and IAEA (International Atomic Energy Agency); Swedish Research Council (VR) and Knut & Alice Wallenberg Foundation (KAW); Ukraine Ministry of Education and Science; United Kingdom Science and Technology Facilities Council (STFC); U.S.

Department of Energy, U.S. National Science Foundation, the State of Texas, and the State of Ohio.

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E. Abbas,¹B. Abelev,²J. Adam,³D. Adamova´,⁴A. M. Adare,⁵M. M. Aggarwal,⁶G. Aglieri Rinella,⁷M. Agnello,^8,9 A. G. Agocs,¹⁰A. Agostinelli,¹¹Z. Ahammed,¹²N. Ahmad,¹³A. Ahmad Masoodi,¹³S. A. Ahn,¹⁴S. U. Ahn,¹⁴

I. Aimo,^15,8,9M. Ajaz,¹⁶A. Akindinov,¹⁷D. Aleksandrov,¹⁸B. Alessandro,⁸A. Alici,^19,20A. Alkin,²¹ E. Almara´z Avin˜a,²²J. Alme,²³T. Alt,²⁴V. Altini,²⁵S. Altinpinar,²⁶I. Altsybeev,²⁷C. Andrei,²⁸A. Andronic,²⁹

V. Anguelov,³⁰J. Anielski,³¹C. Anson,³²T. Anticˇic´,³³F. Antinori,³⁴P. Antonioli,¹⁹L. Aphecetche,³⁵ H. Appelsha¨user,³⁶N. Arbor,³⁷S. Arcelli,¹¹A. Arend,³⁶N. Armesto,³⁸R. Arnaldi,⁸T. Aronsson,⁵I. C. Arsene,²⁹ M. Arslandok,³⁶A. Asryan,²⁷A. Augustinus,⁷R. Averbeck,²⁹T. C. Awes,³⁹J. A¨ ysto¨,⁴⁰M. D. Azmi,^13,41M. Bach,²⁴ A. Badala`,⁴²Y. W. Baek,^43,44R. Bailhache,³⁶R. Bala,^45,8A. Baldisseri,⁴⁶F. Baltasar Dos Santos Pedrosa,⁷J. Ba´n,⁴⁷ R. C. Baral,⁴⁸R. Barbera,⁴⁹F. Barile,²⁵G. G. Barnafo¨ldi,¹⁰L. S. Barnby,⁵⁰V. Barret,⁴³J. Bartke,⁵¹M. Basile,¹¹ N. Bastid,⁴³S. Basu,¹²B. Bathen,³¹G. Batigne,³⁵B. Batyunya,⁵²P. C. Batzing,⁵³C. Baumann,³⁶I. G. Bearden,⁵⁴ H. Beck,³⁶N. K. Behera,⁵⁵I. Belikov,⁵⁶F. Bellini,¹¹R. Bellwied,⁵⁷E. Belmont-Moreno,²²G. Bencedi,¹⁰S. Beole,¹⁵ I. Berceanu,²⁸A. Bercuci,²⁸Y. Berdnikov,⁵⁸D. Berenyi,¹⁰A. A. E. Bergognon,³⁵R. A. Bertens,⁵⁹D. Berzano,^15,8 L. Betev,⁷A. Bhasin,⁴⁵A. K. Bhati,⁶J. Bhom,⁶⁰N. Bianchi,⁶¹L. Bianchi,¹⁵C. Bianchin,⁵⁹J. Bielcˇı´k,³J. Bielcˇı´kova´,⁴

A. Bilandzic,⁵⁴S. Bjelogrlic,⁵⁹F. Blanco,⁵⁷F. Blanco,⁶²D. Blau,¹⁸C. Blume,³⁶M. Boccioli,⁷S. Bo¨ttger,⁶³ A. Bogdanov,⁶⁴H. Bøggild,⁵⁴M. Bogolyubsky,⁶⁵L. Boldizsa´r,¹⁰M. Bombara,⁶⁶J. Book,³⁶H. Borel,⁴⁶ A. Borissov,⁶⁷F. Bossu´,⁴¹M. Botje,⁶⁸E. Botta,¹⁵E. Braidot,⁶⁹P. Braun-Munzinger,²⁹M. Bregant,³⁵T. Breitner,⁶³ T. A. Broker,³⁶T. A. Browning,⁷⁰M. Broz,⁷¹R. Brun,⁷E. Bruna,^15,8G. E. Bruno,²⁵D. Budnikov,⁷²H. Buesching,³⁶ S. Bufalino,^15,8P. Buncic,⁷O. Busch,³⁰Z. Buthelezi,⁴¹D. Caffarri,^73,34X. Cai,⁷⁴H. Caines,⁵E. Calvo Villar,⁷⁵

P. Camerini,⁷⁶V. Canoa Roman,⁷⁷G. Cara Romeo,¹⁹W. Carena,⁷F. Carena,⁷N. Carlin Filho,⁷⁸F. Carminati,⁷ A. Casanova Dı´az,⁶¹J. Castillo Castellanos,⁴⁶J. F. Castillo Hernandez,²⁹E. A. R. Casula,⁷⁹V. Catanescu,²⁸ C. Cavicchioli,⁷C. Ceballos Sanchez,⁸⁰J. Cepila,³P. Cerello,⁸B. Chang,^40,81S. Chapeland,⁷J. L. Charvet,⁴⁶ S. Chattopadhyay,⁸²S. Chattopadhyay,¹²M. Cherney,⁸³C. Cheshkov,^7,84B. Cheynis,⁸⁴V. Chibante Barroso,⁷ D. D. Chinellato,⁵⁷P. Chochula,⁷M. Chojnacki,⁵⁴S. Choudhury,¹²P. Christakoglou,⁶⁸C. H. Christensen,⁵⁴

P. Christiansen,⁸⁵T. Chujo,⁶⁰S. U. Chung,⁸⁶C. Cicalo,⁸⁷L. Cifarelli,^11,20F. Cindolo,¹⁹J. Cleymans,⁴¹ F. Colamaria,²⁵D. Colella,²⁵A. Collu,⁷⁹G. Conesa Balbastre,³⁷Z. Conesa del Valle,^7,88M. E. Connors,⁵ G. Contin,⁷⁶J. G. Contreras,⁷⁷T. M. Cormier,⁶⁷Y. Corrales Morales,¹⁵P. Cortese,⁸⁹I. Corte´s Maldonado,⁹⁰ M. R. Cosentino,⁶⁹F. Costa,⁷M. E. Cotallo,⁶²E. Crescio,⁷⁷P. Crochet,⁴³E. Cruz Alaniz,²²R. Cruz Albino,⁷⁷

E. Cuautle,⁹¹L. Cunqueiro,⁶¹A. Dainese,^73,34R. Dang,⁷⁴A. Danu,⁹²D. Das,⁸²K. Das,⁸²S. Das,⁹³I. Das,⁸⁸ A. Dash,⁹⁴S. Dash,⁵⁵S. De,¹²G. O. V. de Barros,⁷⁸A. De Caro,^95,20G. de Cataldo,⁹⁶J. de Cuveland,²⁴A. De Falco,⁷⁹

D. De Gruttola,^95,20H. Delagrange,³⁵A. Deloff,⁹⁷N. De Marco,⁸E. De´nes,¹⁰S. De Pasquale,⁹⁵A. Deppman,⁷⁸ G. D’Erasmo,²⁵R. de Rooij,⁵⁹M. A. Diaz Corchero,⁶²D. Di Bari,²⁵T. Dietel,³¹C. Di Giglio,²⁵S. Di Liberto,⁹⁸

A. Di Mauro,⁷P. Di Nezza,⁶¹R. Divia`,⁷Ø. Djuvsland,²⁶A. Dobrin,^67,85,59T. Dobrowolski,⁹⁷B. Do¨nigus,²⁹ O. Dordic,⁵³O. Driga,³⁵A. K. Dubey,¹²A. Dubla,⁵⁹L. Ducroux,⁸⁴P. Dupieux,⁴³A. K. Dutta Majumdar,⁸²D. Elia,⁹⁶

D. Emschermann,³¹H. Engel,⁶³B. Erazmus,^7,35H. A. Erdal,²³D. Eschweiler,²⁴B. Espagnon,⁸⁸M. Estienne,³⁵ S. Esumi,⁶⁰D. Evans,⁵⁰S. Evdokimov,⁶⁵G. Eyyubova,⁵³D. Fabris,^73,34J. Faivre,³⁷D. Falchieri,¹¹A. Fantoni,⁶¹

M. Fasel,³⁰D. Fehlker,²⁶L. Feldkamp,³¹D. Felea,⁹²A. Feliciello,⁸B. Fenton-Olsen,⁶⁹G. Feofilov,²⁷ PRL111,162301 (2013) P H Y S I C A L R E V I E W L E T T E R S 18 OCTOBER 2013

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A. Ferna´ndez Te´llez,⁹⁰A. Ferretti,¹⁵A. Festanti,⁷³J. Figiel,⁵¹M. A. S. Figueredo,⁷⁸S. Filchagin,⁷²D. Finogeev,⁹⁹ F. M. Fionda,²⁵E. M. Fiore,²⁵E. Floratos,¹⁰⁰M. Floris,⁷S. Foertsch,⁴¹P. Foka,²⁹S. Fokin,¹⁸E. Fragiacomo,¹⁰¹ A. Francescon,^7,73U. Frankenfeld,²⁹U. Fuchs,⁷C. Furget,³⁷M. Fusco Girard,⁹⁵J. J. Gaardhøje,⁵⁴M. Gagliardi,¹⁵

A. Gago,⁷⁵M. Gallio,¹⁵D. R. Gangadharan,³²P. Ganoti,³⁹C. Garabatos,²⁹E. Garcia-Solis,¹⁰²C. Gargiulo,⁷ I. Garishvili,²J. Gerhard,²⁴M. Germain,³⁵C. Geuna,⁴⁶A. Gheata,⁷M. Gheata,^92,7B. Ghidini,²⁵P. Ghosh,¹² P. Gianotti,⁶¹M. R. Girard,¹⁰³P. Giubellino,⁷E. Gladysz-Dziadus,⁵¹P. Gla¨ssel,³⁰R. Gomez,^104,77E. G. Ferreiro,³⁸

L. H. Gonza´lez-Trueba,²²P. Gonza´lez-Zamora,⁶²S. Gorbunov,²⁴A. Goswami,¹⁰⁵S. Gotovac,¹⁰⁶ L. K. Graczykowski,¹⁰³R. Grajcarek,³⁰A. Grelli,⁵⁹A. Grigoras,⁷C. Grigoras,⁷V. Grigoriev,⁶⁴A. Grigoryan,¹⁰⁷

S. Grigoryan,⁵²B. Grinyov,²¹N. Grion,¹⁰¹P. Gros,⁸⁵J. F. Grosse-Oetringhaus,⁷J.-Y. Grossiord,⁸⁴R. Grosso,⁷ F. Guber,⁹⁹R. Guernane,³⁷B. Guerzoni,¹¹M. Guilbaud,⁸⁴K. Gulbrandsen,⁵⁴H. Gulkanyan,¹⁰⁷T. Gunji,¹⁰⁸ A. Gupta,⁴⁵R. Gupta,⁴⁵R. Haake,³¹Ø. Haaland,²⁶C. Hadjidakis,⁸⁸M. Haiduc,⁹²H. Hamagaki,¹⁰⁸G. Hamar,¹⁰ B. H. Han,¹⁰⁹L. D. Hanratty,⁵⁰A. Hansen,⁵⁴Z. Harmanova´-To´thova´,⁶⁶J. W. Harris,⁵M. Hartig,³⁶A. Harton,¹⁰² D. Hatzifotiadou,¹⁹S. Hayashi,¹⁰⁸A. Hayrapetyan,^7,107S. T. Heckel,³⁶M. Heide,³¹H. Helstrup,²³A. Herghelegiu,²⁸ G. Herrera Corral,⁷⁷N. Herrmann,³⁰B. A. Hess,¹¹⁰K. F. Hetland,²³B. Hicks,⁵B. Hippolyte,⁵⁶Y. Hori,¹⁰⁸P. Hristov,⁷

I. Hrˇivna´cˇova´,⁸⁸M. Huang,²⁶T. J. Humanic,³²D. S. Hwang,¹⁰⁹R. Ichou,⁴³R. Ilkaev,⁷²I. Ilkiv,⁹⁷M. Inaba,⁶⁰ E. Incani,⁷⁹P. G. Innocenti,⁷G. M. Innocenti,¹⁵M. Ippolitov,¹⁸M. Irfan,¹³C. Ivan,²⁹M. Ivanov,²⁹V. Ivanov,⁵⁸

A. Ivanov,²⁷O. Ivanytskyi,²¹A. Jachołkowski,⁴⁹P. M. Jacobs,⁶⁹C. Jahnke,⁷⁸H. J. Jang,¹⁴M. A. Janik,¹⁰³ P. H. S. Y. Jayarathna,⁵⁷S. Jena,⁵⁵D. M. Jha,⁶⁷R. T. Jimenez Bustamante,⁹¹P. G. Jones,⁵⁰H. Jung,⁴⁴A. Jusko,⁵⁰

A. B. Kaidalov,¹⁷S. Kalcher,²⁴P. Kalinˇa´k,⁴⁷T. Kalliokoski,⁴⁰A. Kalweit,⁷J. H. Kang,⁸¹V. Kaplin,⁶⁴S. Kar,¹² A. Karasu Uysal,^7,111,112O. Karavichev,⁹⁹T. Karavicheva,⁹⁹E. Karpechev,⁹⁹A. Kazantsev,¹⁸U. Kebschull,⁶³ R. Keidel,¹¹³B. Ketzer,^36,114S. A. Khan,¹²M. M. Khan,¹³P. Khan,⁸²K. H. Khan,¹⁶A. Khanzadeev,⁵⁸Y. Kharlov,⁶⁵

B. Kileng,²³M. Kim,⁸¹S. Kim,¹⁰⁹M. Kim,⁴⁴J. S. Kim,⁴⁴J. H. Kim,¹⁰⁹T. Kim,⁸¹B. Kim,⁸¹D. J. Kim,⁴⁰ D. W. Kim,^44,14S. Kirsch,²⁴I. Kisel,²⁴S. Kiselev,¹⁷A. Kisiel,¹⁰³J. L. Klay,¹¹⁵J. Klein,³⁰C. Klein-Bo¨sing,³¹ M. Kliemant,³⁶A. Kluge,⁷M. L. Knichel,²⁹A. G. Knospe,¹¹⁶M. K. Ko¨hler,²⁹T. Kollegger,²⁴A. Kolojvari,²⁷ M. Kompaniets,²⁷V. Kondratiev,²⁷N. Kondratyeva,⁶⁴A. Konevskikh,⁹⁹V. Kovalenko,²⁷M. Kowalski,⁵¹S. Kox,³⁷

G. Koyithatta Meethaleveedu,⁵⁵J. Kral,⁴⁰I. Kra´lik,⁴⁷F. Kramer,³⁶A. Kravcˇa´kova´,⁶⁶M. Krelina,³M. Kretz,²⁴ M. Krivda,^50,47F. Krizek,⁴⁰M. Krus,³E. Kryshen,⁵⁸M. Krzewicki,²⁹V. Kucera,⁴Y. Kucheriaev,¹⁸T. Kugathasan,⁷ C. Kuhn,⁵⁶P. G. Kuijer,⁶⁸I. Kulakov,³⁶J. Kumar,⁵⁵P. Kurashvili,⁹⁷A. Kurepin,⁹⁹A. B. Kurepin,⁹⁹A. Kuryakin,⁷²

S. Kushpil,⁴V. Kushpil,⁴H. Kvaerno,⁵³M. J. Kweon,³⁰Y. Kwon,⁸¹P. Ladro´n de Guevara,⁹¹I. Lakomov,⁸⁸ R. Langoy,^26,117S. L. La Pointe,⁵⁹C. Lara,⁶³A. Lardeux,³⁵P. La Rocca,⁴⁹R. Lea,⁷⁶M. Lechman,⁷S. C. Lee,⁴⁴

G. R. Lee,⁵⁰I. Legrand,⁷J. Lehnert,³⁶R. C. Lemmon,¹¹⁸M. Lenhardt,²⁹V. Lenti,⁹⁶H. Leoń,²²M. Leoncino,¹⁵ I. Leoń Monzoń,¹⁰⁴P. Le´vai,¹⁰S. Li,^43,74J. Lien,^26,117R. Lietava,⁵⁰S. Lindal,⁵³V. Lindenstruth,²⁴C. Lippmann,^29,7

M. A. Lisa,³²H. M. Ljunggren,⁸⁵D. F. Lodato,⁵⁹P. I. Loenne,²⁶V. R. Loggins,⁶⁷V. Loginov,⁶⁴D. Lohner,³⁰ C. Loizides,⁶⁹K. K. Loo,⁴⁰X. Lopez,⁴³E. Lo´pez Torres,⁸⁰G. Løvhøiden,⁵³X.-G. Lu,³⁰P. Luettig,³⁶M. Lunardon,⁷³

J. Luo,⁷⁴G. Luparello,⁵⁹C. Luzzi,⁷R. Ma,⁵K. Ma,⁷⁴D. M. Madagodahettige-Don,⁵⁷A. Maevskaya,⁹⁹ M. Mager,^119,7D. P. Mahapatra,⁴⁸A. Maire,³⁰M. Malaev,⁵⁸I. Maldonado Cervantes,⁹¹L. Malinina,^52,120 D. Mal’Kevich,¹⁷P. Malzacher,²⁹A. Mamonov,⁷²L. Manceau,⁸L. Mangotra,⁴⁵V. Manko,¹⁸F. Manso,⁴³ N. Manukyan,¹⁰⁷V. Manzari,⁹⁶Y. Mao,⁷⁴M. Marchisone,^43,15J. Maresˇ,¹²¹G. V. Margagliotti,^76,101A. Margotti,¹⁹

A. Marıń,²⁹C. Markert,¹¹⁶M. Marquard,³⁶I. Martashvili,¹²²N. A. Martin,²⁹P. Martinengo,⁷M. I. Martıńez,⁹⁰ A. Martıńez Davalos,²²G. Martıńez Garcıá,³⁵Y. Martynov,²¹A. Mas,³⁵S. Masciocchi,²⁹M. Masera,¹⁵A. Masoni,⁸⁷

L. Massacrier,³⁵A. Mastroserio,²⁵A. Matyja,⁵¹C. Mayer,⁵¹J. Mazer,¹²²M. A. Mazzoni,⁹⁸F. Meddi,¹²³ A. Menchaca-Rocha,²²J. Mercado Pe´rez,³⁰M. Meres,⁷¹Y. Miake,⁶⁰K. Mikhaylov,^52,17L. Milano,^7,15 J. Milosevic,^53,124A. Mischke,⁵⁹A. N. Mishra,^105,125D. Mis´kowiec,²⁹C. Mitu,⁹²S. Mizuno,⁶⁰J. Mlynarz,⁶⁷ B. Mohanty,^12,126L. Molnar,^10,56L. Montan˜o Zetina,⁷⁷M. Monteno,⁸E. Montes,⁶²T. Moon,⁸¹M. Morando,⁷³ D. A. Moreira De Godoy,⁷⁸S. Moretto,⁷³A. Morreale,⁴⁰A. Morsch,⁷V. Muccifora,⁶¹E. Mudnic,¹⁰⁶S. Muhuri,¹²

M. Mukherjee,¹²H. Mu¨ller,⁷M. G. Munhoz,⁷⁸S. Murray,⁴¹L. Musa,⁷J. Musinsky,⁴⁷B. K. Nandi,⁵⁵R. Nania,¹⁹ E. Nappi,⁹⁶C. Nattrass,¹²²T. K. Nayak,¹²S. Nazarenko,⁷²A. Nedosekin,¹⁷M. Nicassio,^25,29M. Niculescu,^92,7 B. S. Nielsen,⁵⁴T. Niida,⁶⁰S. Nikolaev,¹⁸V. Nikolic,³³S. Nikulin,¹⁸V. Nikulin,⁵⁸B. S. Nilsen,⁸³M. S. Nilsson,⁵³ F. Noferini,^19,20P. Nomokonov,⁵²G. Nooren,⁵⁹A. Nyanin,¹⁸A. Nyatha,⁵⁵C. Nygaard,⁵⁴J. Nystrand,²⁶A. Ochirov,²⁷

H. Oeschler,^119,7,30S. Oh,⁵S. K. Oh,⁴⁴J. Oleniacz,¹⁰³A. C. Oliveira Da Silva,⁷⁸C. Oppedisano,⁸ A. Ortiz Velasquez,^85,91A. Oskarsson,⁸⁵P. Ostrowski,¹⁰³J. Otwinowski,²⁹K. Oyama,³⁰K. Ozawa,¹⁰⁸ PRL111,162301 (2013) P H Y S I C A L R E V I E W L E T T E R S 18 OCTOBER 2013

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Y. Pachmayer,³⁰M. Pachr,³F. Padilla,¹⁵P. Pagano,⁹⁵G. Paic´,⁹¹F. Painke,²⁴C. Pajares,³⁸S. K. Pal,¹²A. Palaha,⁵⁰ A. Palmeri,⁴²V. Papikyan,¹⁰⁷G. S. Pappalardo,⁴²W. J. Park,²⁹A. Passfeld,³¹D. I. Patalakha,⁶⁵V. Paticchio,⁹⁶ B. Paul,⁸²A. Pavlinov,⁶⁷T. Pawlak,¹⁰³T. Peitzmann,⁵⁹H. Pereira Da Costa,⁴⁶E. Pereira De Oliveira Filho,⁷⁸ D. Peresunko,¹⁸C. E. Pe´rez Lara,⁶⁸D. Perrino,²⁵W. Peryt,¹⁰³A. Pesci,¹⁹Y. Pestov,¹²⁷V. Petra´cˇek,³M. Petran,³ M. Petris,²⁸P. Petrov,⁵⁰M. Petrovici,²⁸C. Petta,⁴⁹S. Piano,¹⁰¹M. Pikna,⁷¹P. Pillot,³⁵O. Pinazza,⁷L. Pinsky,⁵⁷

N. Pitz,³⁶D. B. Piyarathna,⁵⁷M. Planinic,³³M. Płoskon´,⁶⁹J. Pluta,¹⁰³T. Pocheptsov,⁵²S. Pochybova,¹⁰ P. L. M. Podesta-Lerma,¹⁰⁴M. G. Poghosyan,⁷K. Pola´k,¹²¹B. Polichtchouk,⁶⁵N. Poljak,^59,33A. Pop,²⁸ S. Porteboeuf-Houssais,⁴³V. Pospı´sˇil,³B. Potukuchi,⁴⁵S. K. Prasad,⁶⁷R. Preghenella,^19,20F. Prino,⁸C. A. Pruneau,⁶⁷ I. Pshenichnov,⁹⁹G. Puddu,⁷⁹V. Punin,⁷²M. Putisˇ,⁶⁶J. Putschke,⁶⁷H. Qvigstad,⁵³A. Rachevski,¹⁰¹A. Rademakers,⁷

T. S. Ra¨iha¨,⁴⁰J. Rak,⁴⁰A. Rakotozafindrabe,⁴⁶L. Ramello,⁸⁹S. Raniwala,¹⁰⁵R. Raniwala,¹⁰⁵S. S. Ra¨sa¨nen,⁴⁰ B. T. Rascanu,³⁶D. Rathee,⁶W. Rauch,⁷K. F. Read,¹²²J. S. Real,³⁷K. Redlich,^97,128R. J. Reed,⁵A. Rehman,²⁶ P. Reichelt,³⁶M. Reicher,⁵⁹R. Renfordt,³⁶A. R. Reolon,⁶¹A. Reshetin,⁹⁹F. Rettig,²⁴J.-P. Revol,⁷K. Reygers,³⁰

L. Riccati,⁸R. A. Ricci,¹²⁹T. Richert,⁸⁵M. Richter,⁵³P. Riedler,⁷W. Riegler,⁷F. Riggi,^49,42 M. Rodrı´guez Cahuantzi,⁹⁰A. Rodriguez Manso,⁶⁸K. Røed,^26,53E. Rogochaya,⁵²D. Rohr,²⁴D. Ro¨hrich,²⁶ R. Romita,^29,118F. Ronchetti,⁶¹P. Rosnet,⁴³S. Rossegger,⁷A. Rossi,^7,73P. Roy,⁸²C. Roy,⁵⁶A. J. Rubio Montero,⁶² R. Rui,⁷⁶R. Russo,¹⁵E. Ryabinkin,¹⁸A. Rybicki,⁵¹S. Sadovsky,⁶⁵K. Sˇafarˇı´k,⁷R. Sahoo,¹²⁵P. K. Sahu,⁴⁸J. Saini,¹²

H. Sakaguchi,¹³⁰S. Sakai,⁶⁹D. Sakata,⁶⁰C. A. Salgado,³⁸J. Salzwedel,³²S. Sambyal,⁴⁵V. Samsonov,⁵⁸ X. Sanchez Castro,⁵⁶L. Sˇa´ndor,⁴⁷A. Sandoval,²²M. Sano,⁶⁰G. Santagati,⁴⁹R. Santoro,^7,20J. Sarkamo,⁴⁰ D. Sarkar,¹²E. Scapparone,¹⁹F. Scarlassara,⁷³R. P. Scharenberg,⁷⁰C. Schiaua,²⁸R. Schicker,³⁰H. R. Schmidt,¹¹⁰ C. Schmidt,²⁹S. Schuchmann,³⁶J. Schukraft,⁷T. Schuster,⁵Y. Schutz,^7,35K. Schwarz,²⁹K. Schweda,²⁹G. Scioli,¹¹

E. Scomparin,⁸R. Scott,¹²²P. A. Scott,⁵⁰G. Segato,⁷³I. Selyuzhenkov,²⁹S. Senyukov,⁵⁶J. Seo,⁸⁶S. Serci,⁷⁹ E. Serradilla,^62,22A. Sevcenco,⁹²A. Shabetai,³⁵G. Shabratova,⁵²R. Shahoyan,⁷N. Sharma,¹²²S. Sharma,⁴⁵ S. Rohni,⁴⁵K. Shigaki,¹³⁰K. Shtejer,⁸⁰Y. Sibiriak,¹⁸E. Sicking,³¹S. Siddhanta,⁸⁷T. Siemiarczuk,⁹⁷D. Silvermyr,³⁹

C. Silvestre,³⁷G. Simatovic,^91,33G. Simonetti,⁷R. Singaraju,¹²R. Singh,⁴⁵S. Singha,^12,126V. Singhal,¹² B. C. Sinha,¹²T. Sinha,⁸²B. Sitar,⁷¹M. Sitta,⁸⁹T. B. Skaali,⁵³K. Skjerdal,²⁶R. Smakal,³N. Smirnov,⁵ R. J. M. Snellings,⁵⁹C. Søgaard,⁸⁵R. Soltz,²M. Song,⁸¹J. Song,⁸⁶C. Soos,⁷F. Soramel,⁷³I. Sputowska,⁵¹

M. Spyropoulou-Stassinaki,¹⁰⁰B. K. Srivastava,⁷⁰J. Stachel,³⁰I. Stan,⁹²G. Stefanek,⁹⁷M. Steinpreis,³² E. Stenlund,⁸⁵G. Steyn,⁴¹J. H. Stiller,³⁰D. Stocco,³⁵M. Stolpovskiy,⁶⁵P. Strmen,⁷¹A. A. P. Suaide,⁷⁸ M. A. Subieta Va´squez,¹⁵T. Sugitate,¹³⁰C. Suire,⁸⁸R. Sultanov,¹⁷M. Sˇumbera,⁴T. Susa,³³T. J. M. Symons,⁶⁹ A. Szanto de Toledo,⁷⁸I. Szarka,⁷¹A. Szczepankiewicz,^51,7M. Szyman´ski,¹⁰³J. Takahashi,⁹⁴M. A. Tangaro,²⁵ J. D. Tapia Takaki,⁸⁸A. Tarantola Peloni,³⁶A. Tarazona Martinez,⁷A. Tauro,⁷G. Tejeda Mun˜oz,⁹⁰A. Telesca,⁷

A. Ter Minasyan,¹⁸C. Terrevoli,²⁵J. Tha¨der,²⁹D. Thomas,⁵⁹R. Tieulent,⁸⁴A. R. Timmins,⁵⁷D. Tlusty,³ A. Toia,^24,73,34H. Torii,¹⁰⁸L. Toscano,⁸V. Trubnikov,²¹D. Truesdale,³²W. H. Trzaska,⁴⁰T. Tsuji,¹⁰⁸A. Tumkin,⁷²

R. Turrisi,³⁴T. S. Tveter,⁵³J. Ulery,³⁶K. Ullaland,²⁶J. Ulrich,^131,63A. Uras,⁸⁴G. M. Urciuoli,⁹⁸G. L. Usai,⁷⁹ M. Vajzer,^3,4M. Vala,^52,47L. Valencia Palomo,⁸⁸P. Vande Vyvre,⁷J. W. Van Hoorne,⁷M. van Leeuwen,⁵⁹

L. Vannucci,¹²⁹A. Vargas,⁹⁰R. Varma,⁵⁵M. Vasileiou,¹⁰⁰A. Vasiliev,¹⁸V. Vechernin,²⁷M. Veldhoen,⁵⁹ M. Venaruzzo,⁷⁶E. Vercellin,¹⁵S. Vergara,⁹⁰R. Vernet,¹³²M. Verweij,⁵⁹L. Vickovic,¹⁰⁶G. Viesti,⁷³ J. Viinikainen,⁴⁰Z. Vilakazi,⁴¹O. Villalobos Baillie,⁵⁰Y. Vinogradov,⁷²L. Vinogradov,²⁷A. Vinogradov,¹⁸ T. Virgili,⁹⁵Y. P. Viyogi,¹²A. Vodopyanov,⁵²M. A. Vo¨lkl,³⁰S. Voloshin,⁶⁷K. Voloshin,¹⁷G. Volpe,⁷B. von Haller,⁷

I. Vorobyev,²⁷D. Vranic,^29,7J. Vrla´kova´,⁶⁶B. Vulpescu,⁴³A. Vyushin,⁷²B. Wagner,²⁶V. Wagner,³R. Wan,⁷⁴ Y. Wang,⁷⁴M. Wang,⁷⁴Y. Wang,³⁰K. Watanabe,⁶⁰M. Weber,⁵⁷J. P. Wessels,^7,31U. Westerhoff,³¹J. Wiechula,¹¹⁰

J. Wikne,⁵³M. Wilde,³¹G. Wilk,⁹⁷M. C. S. Williams,¹⁹B. Windelband,³⁰L. Xaplanteris Karampatsos,¹¹⁶ C. G. Yaldo,⁶⁷Y. Yamaguchi,¹⁰⁸S. Yang,²⁶P. Yang,⁷⁴H. Yang,^46,59S. Yasnopolskiy,¹⁸J. Yi,⁸⁶Z. Yin,⁷⁴

I.-K. Yoo,⁸⁶J. Yoon,⁸¹W. Yu,³⁶X. Yuan,⁷⁴I. Yushmanov,¹⁸V. Zaccolo,⁵⁴C. Zach,³C. Zampolli,¹⁹ S. Zaporozhets,⁵²A. Zarochentsev,²⁷P. Za´vada,¹²¹N. Zaviyalov,⁷²H. Zbroszczyk,¹⁰³P. Zelnicek,⁶³ I. S. Zgura,⁹²M. Zhalov,⁵⁸H. Zhang,⁷⁴X. Zhang,^69,43,74Y. Zhang,⁷⁴D. Zhou,⁷⁴F. Zhou,⁷⁴Y. Zhou,⁵⁹H. Zhu,⁷⁴

J. Zhu,⁷⁴X. Zhu,⁷⁴J. Zhu,⁷⁴A. Zichichi,^11,20A. Zimmermann,³⁰G. Zinovjev,²¹Y. Zoccarato,⁸⁴ M. Zynovyev,²¹and M. Zyzak³⁶

(ALICE Collaboration)