Search for weakly decaying Λn ¯ and ΛΛ exotic bound states in central Pb-Pb collisions at s NN − − − √ = 2.76 TeV
EEUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH
CERN-PH-EP-2015-06913 Mar 2015c (cid:13)
Search for weakly decaying Λ n and ΛΛ exotic bound statesin central Pb-Pb collisions at √ s NN = 2.76 TeV ALICE Collaboration ∗ Abstract
We present results of a search for two hypothetical strange dibaryon states, i.e. the H-dibaryon andthe possible Λ n bound state. The search is performed with the ALICE detector in central (0–10%)Pb–Pb collisions at √ s NN = .
76 TeV, by invariant mass analysis in the decay modes Λ n → d π + andH-dibaryon → Λ p π − . No evidence for these bound states is observed. Upper limits are determinedat 99% confidence level for a wide range of lifetimes and for the full range of branching ratios. Theresults are compared to thermal, coalescence and hybrid UrQMD model expectations, which describecorrectly the production of other loosely bound states, like the deuteron and the hypertriton. ∗ See Appendix A for the list of collaboration members a r X i v : . [ nu c l - e x ] M a r earch for weakly decaying dibaryon states ALICE Collaboration Particle production in Pb–Pb collisions at the Large Hadron Collider (LHC) has been extensively studied[1–3]. The observed production pattern is rather well described in equilibrium thermal models [4–7].Within this approach, the chemical freeze-out temperature T chem , the volume V and the baryo-chemicalpotential µ B are the only three free parameters. Even loosely bound states such as the deuteron andhypertriton and their anti-particles have been observed [8–10] and their rapidity densities are properlydescribed [11–17]. Consequently other loosely bound states such as the H-dibaryon and the Λ n areexpected to be produced with corresponding yields.The discovery of the H-dibaryon or the Λ n bound state would be a breakthrough in hadron spectroscopyas it would imply the existence of a six-quark state and provide crucial information on the Λ -nucleonand Λ - Λ interaction. We consequently have started the investigation on the possible existence of suchexotic bound states in pp and Pb–Pb collisions at the LHC. Searches for Λ -nucleon bound states inthe Λ p and Λ n channels have been carried out (see references [18–20]). The H-dibaryon, which is ahypothetical bound state of uuddss ( ΛΛ ) , was first predicted by Jaffe using a bag model approach [21].Experimental searches have been undertaken since then, but no evidence for a signal was found (see [22,23] and references therein). Recently, the STAR collaboration investigated the Λ - Λ interaction throughthe measurement of ΛΛ correlations [24]; this and a theoretical analysis of these data [25] did not reveala signal. Many theoretical investigations of the possible stability of the H-dibaryon have been carriedout, but predicting binding energies in the order of MeV for masses of around 2 GeV/ c is extremelydifficult and challenging [26–29].Our approach is to search for such bound states in central Pb–Pb collisions at LHC energies whererapidity densities can be well predicted by thermal [16, 17, 30] and coalescence [31] models. The modelpredictions for rapidity densities of these particles are used and tested against the experimental results.In this paper the analysis strategies for the searches of the Λ n → d π + bound state and the H-dibaryon → Λ p π − are presented. The analysis focuses on the Λ n bound state because production of anti-particles inthe detector material is strongly suppressed and thus secondary contamination of the signal is reduced.For the H-dibaryon both the Λ and the p originate from secondary vertices where knock-out backgroundis less likely. No search for the anti-H is performed yet, although it is assumed to be produced withequal yield but the measurement depends strongly on the absorption correction. We begin with a shortintroduction to the ALICE detector and a description of the particle identification technique used toidentify the decay daughters and reconstruct invariant mass distributions. To assess the possible existenceof these states we compare the experimental distributions with the model predictions. The ALICE detector [32] is specifically designed to study heavy-ion collisions. The central barrel com-prising the two main tracking detectors, the Inner Tracking System (ITS) [33] and the Time ProjectionChamber (TPC) [34] is housed in a large solenoidal magnet providing a 0.5 T field. The detector pseudo-rapidity coverage is | η | ≤ . < η < . − . < η < − .
7. The centrality selection is based on the sum of theamplitudes measured in both detectors as described in [35] and [36].The ITS consists of six cylindrical layers of three different types of silicon detectors. The innermost partcomprises two silicon pixel (SPD) and two silicon drift detector (SDD) layers. The two outer layers aredouble-sided silicon microstrip detectors (SSD). Due to the precise space points provided by the ITS a The expected masses of these states are some MeV below the sum of the mass of their constituents. µ m precision at low transverse momentum ( p T ≈
100 MeV/ c ).The TPC is the main tracking detector of ALICE and surrounds the ITS. It has a cylindrical design witha diameter of ≈
550 cm, an inner radius of 85 cm, an outer radius of 247 cm and an overall length inthe beam direction of ≈
510 cm. The 88 m gas volume of the TPC is filled with a mixture of 85.7%Ne, 9.5% CO and 4.8% N . When a charged particle is travelling through the TPC, it ionizes the gasalong its path and electrons are released. Due to the uniform electric field along the z-axis (parallel tothe beam axis and to the magnetic field) the electrons drift towards the end plates, where the electricsignals are amplified and detected in 557568 pads. These data are used to calculate a particle trajectoryin the magnetic field and thus determine the track rigidity pz (the momentum p of the particle dividedby its charge number z ). The TPC is also used for particle identification via the energy deposit d E /d x measurement (see section 3).A complete description of the performance of the ALICE sub-detectors in pp, p–Pb and Pb–Pb collisionscan be found in [37].The searches carried out and reported here are performed by analysing the data set of Pb–Pb collisionsfrom 2011. In the described analyses we use 19 . × events with a centrality of 0–10%, determinedby the aforementioned VZERO detectors from the previously mentioned campaign. The precise Particle IDentification (PID) and continuous tracking from very low p T (100 MeV/ c ) tomoderately high p T (20 GeV/ c ) is a unique feature of the ALICE detector at the LHC. The PID usedin the analysis described in this letter takes advantage of two different techniques. The energy deposit ( d E / d x ) and rigidity are measured with the TPC for each reconstructed charged-particle trajectory. Thisallows the identification of all charged stable particles, from the lightest (electron) to the heaviest ones(anti-alpha). The energy deposit resolution of the TPC in central Pb–Pb collisions (investigated here)is around 7%. The corresponding particle separation power is demonstrated in Fig. 1. This techniquewas used in the following to identify the deuterons, protons and pions. The second method makes use ofspecific topologies from weak decays, which result in typical V decay patterns. This is used here for thedetection of the Λ n bound state and the two V decay patterns of the ΛΛ , namely for the Λ identificationand the proton–pion decay vertex. The strategies of investigation for the two exotic bound states discussed here are quite similar. They bothrequire the detection of a secondary vertex, which in one case is a pure V and in the second a double V decay pattern. We discuss them separately in the following sub-sections. First we describe briefly thecommon aspects of both analyses.The tracks used in the analyses have to fulfil a set of selection criteria to ensure high tracking efficiencyand d E /d x resolution. Each track was required to have at least 70 of up to 159 clusters in the TPCattached to it, with the (rather loose) requirement, that the χ of the momentum fit is smaller than 5 percluster. Tracks with kinks due to weak decays of kaons and pions are rejected. To achieve final precisionthe accepted tracks are refit while the track finding algorithm is run inwards, outwards and inwards again(for more details on the ALICE tracking see [37] and section 5 of [41]). V decays are determined by two (or more) tracks which are emitted from a secondary vertex and whichmight come close to each other (the minimum distance is called Distance-of-Closest-Approach DCA)while each of the tracks has a certain minimum distance (DCA of the track to a vertex) to the primaryvertex. A powerful selection criterion for detecting proper V candidates is the restriction of the pointingangle, namely the angle between the reconstructed flight-line and the reconstructed momentum of the3earch for weakly decaying dibaryon states ALICE Collaboration ) c (GeV/| z /| p s i gna l ( a r b . un i t ) x / d E T P C d ALICE s NN e- p -K- p d t He He Fig. 1:
TPC d E / d x spectrum for negative particles in a sample of three different trigger types (minimum bias, semi-central and central). The dashed lines are parametrisations of the Bethe-Bloch-formula [38–40] for the differentparticle species. V particle. More details of the secondary vertex reconstruction can be found in [3, 37, 41], where alsothe clear and effective identification of Λ baryons is displayed using the aforementioned technique. Theselection criteria, described below, are optimised using a Monte Carlo set where the simulated exoticbound states are assumed to live as long as a free Λ baryon. This is a reasonable assumption for allstrange dibaryons, which are expected to live around 2–4 × − s [42–44] in the regions of bindingenergies investigated here. Selection criterion Value
Track selection criteriaTracks with kinks rejectedNumber of clusters in TPC n cl > χ / cluster < | η | < . | y | < V and kinematic selection criteriaPointing angle Θ < .
045 radDCA between the V daughters DCA < . p tot of the anti-deuteron p tot > . / c Energy deposit d E /d x anti-deuteron d E /d x >
110 (from Fig. 1)PID cut for daughters ± σ (TPC) Table 1:
Selection criteria for Λ n analysis. Λ n bound state In analogy to recent hypertriton measurements [8, 9] we focus here on the expected two-body decay Λ n → d π + . For the data analysis the following strategy is used: first displaced vertices are identifiedusing ITS and TPC information. In a second step the negative track of the V candidate is identified as ananti-deuteron via the TPC d E / d x information. If the second daughter is identified as a pion, the invariant4earch for weakly decaying dibaryon states ALICE Collaboration ) c ) (GeV/ + p dInvariant mass (2 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 ) c C oun t s / ( M e V / n L = 2.76 TeV NN s Pb-Pb (0-10% central)ALICE
Fig. 2:
Invariant mass distribution for d π + for the Pb–Pb data corresponding to 19 . × central events. Thearrow indicates the sum of the mass of the constituents ( Λ n) of the assumed bound state. A signal for the boundstate is expected in the region below this sum. The dashed line represents an exponential fit outside the expectedsignal region to estimate the background. mass of the pair is reconstructed. Both particles are required to lie within a 3 standard deviations ( σ )band of the expected Bethe-Bloch lines of the corresponding particles. To identify the secondary vertexthe two daughter tracks have to have a DCA smaller than 0.3 cm. Another condition is that the maximumpointing angle is smaller than 0.045 rad (see description above). Deuterons are cleanly identified in therigidity region of 400 MeV/ c to 1.75 GeV/ c . To limit contamination from other particle species, thed E /d x has to be above 110 units of the TPC signal, shown in Fig. 1.The selection criteria are summarised in Table 1. The resulting invariant mass distribution, reflecting thekinematic range of identified daughter tracks, is displayed in Fig. 2. The search for the H-dibaryon is performed in the decay channel H → Λ p π − , with a mass lying in therange 2 .
200 GeV / c < m H < .
231 GeV / c (see Fig. 3 below). The analysis strategy for the H-dibaryonis similar as for the Λ n bound state described above, except that here a second V -type decay particle isinvolved.One V candidate originating from the H-dibaryon decay vertex has to be identified as a Λ decaying into aproton and a pion. In addition another V decay pattern reconstructed from a proton and a pion is requiredto be found at the decay vertex of the H-dibaryon. First the invariant mass of the Λ is reconstructed andthen the candidates in the invariant mass window of 1 .
111 GeV / c < m Λ < .
120 GeV / c are combinedwith the four-vectors of the proton and pion at the decay vertex. A 3 σ d E /d x cut in the TPC is used toidentify the protons and the pions for both the Λ candidate and the V topology at the H-dibaryon decayvertex.To cope with the huge background caused by primary and secondary pions additional selection criteriahave to be applied. Each track is required to be at least 2 cm away from the primary vertex and the trackscombined to a V are required to have a minimum distance below 1 cm. The pointing angle is requiredto be below 0.05 rad. All selection criteria are summarised in Table 2. The resulting invariant mass isshown in Fig. 3. The shape of the invariant mass distribution is caused by the kinematic range of theidentified daughter tracks. 5earch for weakly decaying dibaryon states ALICE Collaboration Selection criterion Value
Track selection criteriaTracks with kinks rejectedNumber of clusters in TPC n cl > χ / cluster < | η | < . | y | < V selection criteriaDCA V daughters DCA < V daughter - H decay vertex DCA > V daughter - H decay vertex DCA > > > < Θ < .
05 radPID cut for daughters ± σ (TPC) Λ mass window ± σ Table 2:
Selection criteria used for ΛΛ (H-dibaryon) analysis. ) c ) (GeV/ - p p L Invariant mass (2.2 2.21 2.22 2.23 2.24 2.25 2.26 2.27 ) c C oun t s / ( M e V / LL p X = 2.76 TeV NN s Pb-Pb (0-10% central)ALICE
Fig. 3:
Invariant mass distribution for Λ p π − for the Pb–Pb data corresponding to 19 . × central events. Theleft arrow indicates the sum of the masses of the constituents ( ΛΛ ) of the possible bound state. A signal for thebound state is expected in the region below this sum. For the speculated resonant state a signal is expected betweenthe ΛΛ and the Ξ p (indicated by the right arrow) thresholds. The dashed line is an exponential fit to estimate thebackground. Monte Carlo samples have been produced to estimate the efficiency for the detection of the Λ n boundstate and the H-dibaryon. The kinematical distributions of the hypothetical bound states were generateduniformly in rapidity y and in transverse momentum p T . In order to deal with the unknown lifetime,different decay lengths are investigated, ranging from 4 cm up to 3 m. The lower limit is determined bythe secondary vertex finding efficiency and the upper limit by the requirement that there is a significantprobability for decays inside the TPC (the final acceptance × efficiency drops down to 1% for the Λ n and For the H-dibaryon there is also a theoretical maximal decay length calculated for the investigated decay channel [45]. − for the H-dibaryon). The shape of transverse momentum spectra in heavy-ion collisions is describedwell by the blast-wave approach, with radial flow parameter (cid:104) β (cid:105) and kinetic freeze-out temperature T kin as in [46]. The true shape of the p T spectrum is also not known, therefore it is estimated from theextrapolation of blast-wave fits to deuterons and He spectra at the same energy [10]. To obtain finalefficiencies, the resulting blast-wave distributions constructed for the exotic bound states are normalisedto unity and convoluted with the correction factors (efficiency × acceptance).Typical values of the final efficiency are of the order of a few percent assuming the lifetime of the free Λ . The uncertainty in the shape of the p T distributions is the main source of systematic error. Blast-wavefits of deuteron and He spectra are employed to explore the range of systematic uncertainties. Analysesof these results lead to a systematic uncertainty in the overall yield of around 25%.Other systematic uncertainties are estimated by varying the cuts described in Table 1 and Table 2 withinthe limits consistent with the detector resolution. The contributions of these systematic uncertainties aretypically found to be in the percent range. The combination of the different sources leads to a globalsystematic uncertainty of around 30% for both analyses, when all uncertainties are added in quadrature.For the Λ n bound state analysis the possible absorption of the anti-deuterons and the bound state itselfwhen crossing material has to be taken into account. For this, the same procedure as used for the anti-hypertriton analysis [9] is utilised. The absorption correction ranges from 3 to 40% (depending onthe lifetime of the Λ n bound state, which determines the amount of material crossed) with an overalluncertainty of 7%. No significant signal in the invariant mass distributions has been observed for both cases, as visiblefrom Fig. 2 and Fig. 3 . The shape of the invariant mass distribution of d π + is of purely kinematicorigin, reflecting the momentum distribution of the particles used. The selection criteria listed in Table 1are tuned to select secondary decays. The secondary anti-deuterons involved in the analysis originatemainly from two sources: The first and dominating source are daughters from three-body decays ofthe anti-hypertriton ( Λ H → ¯d¯p π + and Λ H → ¯d¯n π ) where the other decay daughters are not detected.The invariant mass spectrum is obtained by combining theses anti-deuterons with pions generated in thecollision. The second source is due to prompt anti-deuterons which are incorrectly labelled as displaced,because they have such low momenta that the DCA resolution of these tracks is not sufficient to separateprimary from secondary particles.Since no signal in the invariant mass distributions is observed upper limits are estimated. For the estima-tion of upper limits for the rapidity density d N /d y the method discussed in [47] is utilised. In particular,we apply the software package T Rolke as implemented in
ROOT [48]. This method needs as input massand experimental width (3 σ ) of the hypothetical bound states. The observed counts are therefore com-pared to a smooth background as given by an exponential fit outside the signal region (as indicated bythe line in Fig. 2 and Fig. 3). For both candidates Λ n and H-dibaryon we assume a binding energy of1 MeV. The width is determined by the experimental resolution and obtained from Monte Carlo simu-lations. In addition, the final efficiency which is discussed in section 5 is required. Further, values ofbranching ratios of the assumed bound states are needed. These depend strongly on the binding energy.With a 1 MeV binding energy for the Λ n bound state the branching ratio in the d + π + decay channelis expected to be 54% [49]. The branching ratio for a 1 MeV or less bound H-dibaryon decaying into Λ p π − is predicted to be 64%, see [44].The resulting upper limits, for 99% CL, are shown in Fig. 4 as a function of the different lifetimes; forthe Λ n bound state in the upper panel and for the H-dibaryon in the lower panel. These upper limits Note that a hypothetical H-dibaryon with a mass above the Ξ p threshold would not be observable in the present analysis. Λ n the absorption corrections are also considered in the figure,which causes the upper limits to be shifted upwards.The obtained upper limits can now be compared to model predictions. The rapidity densities d N / d y from a thermal model prediction for a chemical freeze-out temperature of, for example, 156 MeV, ared N / d y = . × − for the Λ n bound state and d N / d y = . × − for the H-dibaryon [16]. Thesevalues are indicated with the (blue) dashed lines in Fig. 4. For the investigated range of lifetimes theupper limit of the Λ n bound state is at least a factor 20 below this prediction. For the H-dibaryon theupper limits depend more strongly on the lifetime since it has a different decay topology and all fourfinal state tracks have to be reconstructed. The upper limit is a factor of 20 below the thermal modelprediction for the lifetime of the free Λ and becomes less stringent at higher lifetimes since the detectionefficiency becomes small. For a lifetime of 10 − s, corresponding to a decay length of 3 m, the differencebetween model and upper limit reduces to a factor two.In order to take the uncertainties in the branching ratio into account, we plot in Fig. 5 the products of theupper limit of the rapidity density times the branching ratio together with several theory predictions [16,30, 31, 50]. The curves are obtained using the value for the Λ -lifetime of Fig. 4.The (red) arrows in the figures indicate the branching ratio from the theory predictions [44, 49]. Theobtained upper limits are a factor of more than 5 below all theory predictions for a branching ratio of atleast 5% for the Λ n bound state and at least 20% for the H-dibaryon. decay length (m) -1
10 1 y / d N d -4 -3 -2 -1 n L ALICE Upper limits (99% CL, 0-10% central)Pb-Pb = 2.76 TeV NN s Thermal model prediction (156 MeV) L Decay length of free
Decay length (m) -2 · -1 -1 · y / d N d -4 -3 -2 LL Fig. 4:
Upper limit of the rapidity density as function of the decay length shown for the Λ n bound state in theupper panel and for the H-dibaryon in the lower panel. Here a branching ratio of 64% was used for the H-dibaryonand a branching ratio of 54% for the Λ n bound state. The horizontal (dashed) lines indicate the expectation of thethermal model with a temperature of 156 MeV. The vertical line shows the lifetime of the free Λ baryon. The limits obtained on the rapidity density of the investigated exotic compound objects are found to bemore than one order of magnitude below the expectations of particle production models, when using arealistic branching ratio and a reasonable lifetime. It has to be noted that simultaneously, a clear signalwas observed for the very loosely bound hypertriton (binding energy <
150 keV) for which productionyields have been measured [9]. These yields along with those of nuclei A = 2,3,4 agree well with the8earch for weakly decaying dibaryon states ALICE Collaboration
BR0 0.2 0.4 0.6 0.8 1 ) y / d N B R x ( d -4 -3 -2 -1 (99% CL)n L Upper limit Preferred BR from theory = 2.76 TeV NN s Pb-Pb (0-10% central)ALICE
Branching Ratio (BR)0 0.2 0.4 0.6 0.8 1 ) y / d N B R x ( d -5 -4 -3 -2
10 Upper limit H-dibaryon (99% CL)Preferred BR from theory
Fig. 5:
Experimentally determined upper limit, under the assumption of the lifetime of a free Λ . In the upper panelshown for the Λ n bound state and for the H-dibaryon in the lower panel. It includes 30% systematic uncertaintyfor each particle and 6% correction for absorption with an uncertainty of 7% for the Λ n bound state. The theorylines are drawn for different theoretical branching ratios (BR) in blue for the equilibrium thermal model from [16]for two temperatures (164 MeV the full line and 156 MeV the dashed line), in green the non-equilibrium thermalmodel from [30] and in yellow the predictions from a hybrid UrQMD calculation [50]. The H-dibaryon is alsocompared with predictions from coalescence models, where the full red line visualises the prediction assumingquark coalescence and the dashed red line corresponds to hadron coalescence [31]. predictions of the thermal model discussed above and decrease with each additional baryon number byroughly a factor 300. One would therefore assume that the yield of the Λ n, if such particle existed, shouldalso be predicted by this model and with a value for the rapidity density of about a factor 300 higher thanthe measured hypertriton yield. Similar considerations hold for the H-dibaryon. A search is reported for the existence of loosely bound strange dibaryons ΛΛ and Λ n whose possibleexistence has been discussed widely in the literature. No signals are observed. On the other hand,loosely bound objects with baryon number A =3 such as the hypertriton have been measured in the samedata sample. The yields of nuclei [10] and of the hypertriton [9] are quantitatively understood within athermal model calculation. The present analysis provides stringent upper limits at 99% confidence levelfor the production of H-dibaryon and Λ n bound state, in general significantly below the thermal modelpredictions. The upper limits are obtained for different lifetimes. The values are well below the modelpredictions when realistic branching ratios and reasonable lifetimes are assumed. Thus, our results donot support the existence of the H-dibaryon and the Λ n bound state. Acknowledgements
We thank S. Beane, M. Petr´aˇn, J. Schaffner-Bielich and J. Steinheimer for useful correspondence.9earch for weakly decaying dibaryon states ALICE CollaborationThe 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 gratefully acknowledges the resources andsupport provided by all Grid centres and the Worldwide LHC Computing Grid (WLCG) collaboration.The ALICE Collaboration acknowledges the following funding agencies for their support in buildingand running the ALICE detector: State Committee of Science, World Federation of Scientists (WFS)and Swiss Fonds Kidagan, Armenia, Conselho Nacional de Desenvolvimento Cient´ıfico e Tecnol´ogico(CNPq), Financiadora de Estudos e Projetos (FINEP), Fundac¸ ˜ao de Amparo `a Pesquisa do Estado de S˜aoPaulo (FAPESP); National Natural Science Foundation of China (NSFC), the Chinese Ministry of Edu-cation (CMOE) and the Ministry of Science and Technology of China (MSTC); Ministry of Educationand Youth of the Czech Republic; Danish Natural Science Research Council, the Carlsberg Foundationand the Danish National Research Foundation; The European Research Council under the EuropeanCommunity’s Seventh Framework Programme; Helsinki Institute of Physics and the Academy of Fin-land; French CNRS-IN2P3, the ‘Region Pays de Loire’, ‘Region Alsace’, ‘Region Auvergne’ and CEA,France; German Bundesministerium fur Bildung, Wissenschaft, Forschung und Technologie (BMBF)and the Helmholtz Association; General Secretariat for Research and Technology, Ministry of Develop-ment, Greece; Hungarian Orszagos Tudomanyos Kutatasi Alappgrammok (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) and Centro Fermi- Museo Storico della Fisica e Centro Studi e Ricerche ”Enrico Fermi”, Italy; MEXT Grant-in-Aidfor Specially Promoted Research, Japan; Joint Institute for Nuclear Research, Dubna; National ResearchFoundation of Korea (NRF); Consejo Nacional de Cienca y Tecnologia (CONACYT), Direccion Generalde Asuntos del Personal Academico(DGAPA), M´exico, Amerique Latine Formation academique - Euro-pean Commission (ALFA-EC) and the EPLANET Program (European Particle Physics Latin AmericanNetwork); Stichting voor Fundamenteel Onderzoek der Materie (FOM) and the Nederlandse Organisatievoor Wetenschappelijk Onderzoek (NWO), Netherlands; Research Council of Norway (NFR); NationalScience Centre, Poland; Ministry of National Education/Institute for Atomic Physics and National Coun-cil of Scientific Research in Higher Education (CNCSI-UEFISCDI), Romania; Ministry of Educationand Science of Russian Federation, Russian Academy of Sciences, Russian Federal Agency of AtomicEnergy, Russian Federal Agency for Science and Innovations and The Russian Foundation for Basic Re-search; Ministry of Education of Slovakia; Department of Science and Technology, South Africa; Centrode Investigaciones Energeticas, Medioambientales y Tecnologicas (CIEMAT), E-Infrastructure sharedbetween Europe and Latin America (EELA), Ministerio de Econom´ıa y Competitividad (MINECO) ofSpain, Xunta de Galicia (Conseller´ıa de Educaci´on), Centro de Aplicaciones Tecnolgicas y DesarrolloNuclear (CEADEN), Cubaenerg´ıa, Cuba, and IAEA (International Atomic Energy Agency); SwedishResearch Council (VR) and Knut & Alice Wallenberg Foundation (KAW); Ukraine Ministry of Edu-cation and Science; United Kingdom Science and Technology Facilities Council (STFC); The UnitedStates Department of Energy, the United States National Science Foundation, the State of Texas, and theState of Ohio; Ministry of Science, Education and Sports of Croatia and Unity through Knowledge Fund,Croatia. Council of Scientific and Industrial Research (CSIR), New Delhi, India
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A The ALICE Collaboration
J. Adam , D. Adamov´a , M.M. Aggarwal , G. Aglieri Rinella , M. Agnello , N. Agrawal ,Z. Ahammed , I. Ahmed , S.U. Ahn , I. Aimo
93 ,110 , S. Aiola , M. Ajaz , A. Akindinov ,S.N. Alam , D. Aleksandrov
99 ,99 , B. Alessandro , D. Alexandre , R. Alfaro Molina , A. Alici
104 ,12 ,A. Alkin , J. Alme , T. Alt , S. Altinpinar
18 ,18 , I. Altsybeev , C. Alves Garcia Prado , C. Andrei ,A. Andronic , V. Anguelov , J. Anielski , T. Antiˇci´c , F. Antinori , P. Antonioli , L. Aphecetche ,H. Appelsh¨auser , S. Arcelli , N. Armesto , R. Arnaldi , T. Aronsson , I.C. Arsene , M. Arslandok ,A. Augustinus , R. Averbeck , M.D. Azmi
19 ,19 , M. Bach , A. Badal`a , Y.W. Baek , S. Bagnasco ,R. Bailhache , R. Bala , A. Baldisseri , M. Ball , F. Baltasar Dos Santos Pedrosa , R.C. Baral ,A.M. Barbano , R. Barbera , F. Barile , G.G. Barnaf¨oldi , L.S. Barnby , V. Barret , P. Bartalini ,J. Bartke , E. Bartsch , M. Basile , N. Bastid , S. Basu , B. Bathen , G. Batigne , A. BatistaCamejo , B. Batyunya , P.C. Batzing , I.G. Bearden , H. Beck , C. Bedda , N.K. Behera
48 ,47 ,I. Belikov , F. Bellini , H. Bello Martinez , R. Bellwied , R. Belmont , E. Belmont-Moreno ,V. Belyaev , G. Bencedi , S. Beole , I. Berceanu , A. Bercuci , Y. Berdnikov , D. Berenyi ,R.A. Bertens , D. Berzano
36 ,27 , L. Betev , A. Bhasin , I.R. Bhat , A.K. Bhati , B. Bhattacharjee ,J. Bhom , L. Bianchi
27 ,120 , N. Bianchi , C. Bianchin
133 ,56 , J. Bielˇc´ık , J. Bielˇc´ıkov´a , A. Bilandzic
79 ,79 ,S. Biswas
78 ,78 , S. Bjelogrlic , F. Blanco , D. Blau , C. Blume , F. Bock
73 ,92 , A. Bogdanov ,H. Bøggild , L. Boldizs´ar , M. Bombara , J. Book , H. Borel , A. Borissov , M. Borri , F. Boss´u ,M. Botje , E. Botta , S. B¨ottger , P. Braun-Munzinger , M. Bregant , T. Breitner , T.A. Broker ,T.A. Browning , M. Broz , E.J. Brucken
45 ,45 , E. Bruna , G.E. Bruno , D. Budnikov , H. Buesching ,S. Bufalino
36 ,110 , P. Buncic , O. Busch , Z. Buthelezi , J.T. Buxton , D. Caffarri
36 ,30 , X. Cai ,H. Caines , L. Calero Diaz , A. Caliva , E. Calvo Villar , P. Camerini , F. Carena , W. Carena ,J. Castillo Castellanos , A.J. Castro , E.A.R. Casula
25 ,25 , C. Cavicchioli , C. Ceballos Sanchez ,J. Cepila
39 ,39 , P. Cerello , B. Chang , S. Chapeland , M. Chartier , J.L. Charvet ,S. Chattopadhyay , S. Chattopadhyay , V. Chelnokov , M. Cherney , C. Cheshkov , B. Cheynis ,V. Chibante Barroso , D.D. Chinellato , P. Chochula , K. Choi , M. Chojnacki , S. Choudhury ,P. Christakoglou , C.H. Christensen , P. Christiansen , T. Chujo , S.U. Chung , C. Cicalo ,L. Cifarelli
12 ,28 , F. Cindolo , J. Cleymans , F. Colamaria , D. Colella , A. Collu , M. Colocci ,G. Conesa Balbastre , Z. Conesa del Valle , M.E. Connors , J.G. Contreras
39 ,11 , T.M. Cormier ,Y. Corrales Morales , I. Cort´es Maldonado , P. Cortese , M.R. Cosentino , F. Costa , P. Crochet ,R. Cruz Albino , E. Cuautle , L. Cunqueiro , T. Dahms , A. Dainese , A. Danu , D. Das ,I. Das
100 ,50 , S. Das , A. Dash , S. Dash , S. De
130 ,118 , A. De Caro
31 ,12 , G. de Cataldo , J. deCuveland , A. De Falco , D. De Gruttola
12 ,31 , N. De Marco , S. De Pasquale , A. Deisting
96 ,92 ,A. Deloff , E. D´enes , G. D’Erasmo , D. Di Bari , A. Di Mauro , P. Di Nezza , M.A. Diaz Corchero ,T. Dietel , P. Dillenseger , R. Divi`a , Ø. Djuvsland , A. Dobrin
56 ,80 , T. Dobrowolski
76 ,i , D. DomenicisGimenez , B. D¨onigus , O. Dordic , A.K. Dubey , A. Dubla , L. Ducroux , P. Dupieux ,R.J. Ehlers , D. Elia , H. Engel , B. Erazmus
112 ,36 , F. Erhardt , D. Eschweiler , B. Espagnon ,M. Estienne , S. Esumi , D. Evans , S. Evdokimov , G. Eyyubova , L. Fabbietti , D. Fabris ,J. Faivre , A. Fantoni , M. Fasel , L. Feldkamp , D. Felea , A. Feliciello , G. Feofilov ,J. Ferencei , A. Fern´andez T´ellez , E.G. Ferreiro , A. Ferretti , A. Festanti , J. Figiel ,M.A.S. Figueredo , S. Filchagin , D. Finogeev , F.M. Fionda , E.M. Fiore , M.G. Fleck , M. Floris ,S. Foertsch , P. Foka , S. Fokin , E. Fragiacomo , A. Francescon
36 ,30 , U. Frankenfeld , U. Fuchs ,C. Furget , A. Furs , M. Fusco Girard , J.J. Gaardhøje , M. Gagliardi , A.M. Gago , M. Gallio ,D.R. Gangadharan , P. Ganoti , C. Gao , C. Garabatos , E. Garcia-Solis , C. Gargiulo , P. Gasik ,M. Germain , A. Gheata , M. Gheata
61 ,36 , P. Ghosh , S.K. Ghosh , P. Gianotti , P. Giubellino
36 ,110 ,P. Giubilato , E. Gladysz-Dziadus , P. Gl¨assel , A. Gomez Ramirez , P. Gonz´alez-Zamora ,S. Gorbunov , L. G¨orlich , S. Gotovac , V. Grabski , L.K. Graczykowski , A. Grelli , A. Grigoras ,C. Grigoras , V. Grigoriev , A. Grigoryan , S. Grigoryan , B. Grinyov , N. Grion ,J.F. Grosse-Oetringhaus , J.-Y. Grossiord , R. Grosso , F. Guber , R. Guernane , B. Guerzoni ,K. Gulbrandsen , H. Gulkanyan , T. Gunji , A. Gupta , R. Gupta , R. Haake , Ø. Haaland ,C. Hadjidakis , M. Haiduc , H. Hamagaki , G. Hamar , L.D. Hanratty , A. Hansen , J.W. Harris ,H. Hartmann , A. Harton , D. Hatzifotiadou , S. Hayashi , S.T. Heckel , M. Heide , H. Helstrup ,A. Herghelegiu , G. Herrera Corral , B.A. Hess , K.F. Hetland , T.E. Hilden , H. Hillemanns ,B. Hippolyte , P. Hristov , M. Huang , T.J. Humanic , N. Hussain , T. Hussain , D. Hutter ,D.S. Hwang , R. Ilkaev , I. Ilkiv , M. Inaba , C. Ionita , M. Ippolitov
75 ,99 , M. Irfan , M. Ivanov ,V. Ivanov , V. Izucheev , A. Jachołkowski , P.M. Jacobs , C. Jahnke , H.J. Jang , M.A. Janik , P.H.S.Y. Jayarathna , C. Jena
30 ,30 , S. Jena , R.T. Jimenez Bustamante , P.G. Jones , H. Jung ,A. Jusko , P. Kalinak , A. Kalweit , J. Kamin , J.H. Kang , V. Kaplin , S. Kar , A. Karasu Uysal ,O. Karavichev , T. Karavicheva , E. Karpechev , U. Kebschull , R. Keidel , D.L.D. Keijdener ,M. Keil , K.H. Khan , M.M. Khan , P. Khan , S.A. Khan , A. Khanzadeev , Y. Kharlov ,B. Kileng , B. Kim , D.W. Kim
67 ,43 , D.J. Kim , H. Kim , J.S. Kim , M. Kim , M. Kim ,S. Kim , T. Kim , S. Kirsch , I. Kisel , S. Kiselev , A. Kisiel , G. Kiss , J.L. Klay , C. Klein ,J. Klein , C. Klein-B¨osing , A. Kluge , M.L. Knichel
92 ,92 , A.G. Knospe , T. Kobayashi ,C. Kobdaj , M. Kofarago , M.K. K¨ohler , T. Kollegger
96 ,42 , A. Kolojvari , V. Kondratiev ,N. Kondratyeva , E. Kondratyuk , A. Konevskikh , C. Kouzinopoulos , V. Kovalenko ,M. Kowalski
115 ,36 , S. Kox , G. Koyithatta Meethaleveedu , J. Kral , I. Kr´alik , A. Kravˇc´akov´a ,M. Krelina , M. Kretz , M. Krivda
58 ,101 , F. Krizek , E. Kryshen , M. Krzewicki
42 ,96 , A.M. Kubera ,V. Kuˇcera , Y. Kucheriaev
99 ,i , T. Kugathasan , C. Kuhn , P.G. Kuijer , I. Kulakov , J. Kumar ,L. Kumar
78 ,86 , P. Kurashvili
76 ,76 , A. Kurepin , A.B. Kurepin , A. Kuryakin , S. Kushpil , M.J. Kweon ,Y. Kwon , S.L. La Pointe , P. La Rocca , C. Lagana Fernandes , I. Lakomov
50 ,36 , R. Langoy ,C. Lara , A. Lardeux , A. Lattuca , E. Laudi , R. Lea , L. Leardini , G.R. Lee , S. Lee ,I. Legrand , J. Lehnert , R.C. Lemmon , V. Lenti , E. Leogrande , I. Le´on Monz´on , M. Leoncino ,P. L´evai , S. Li , X. Li , J. Lien , R. Lietava , S. Lindal , V. Lindenstruth , C. Lippmann ,M.A. Lisa , H.M. Ljunggren , D.F. Lodato , P.I. Loenne , V.R. Loggins , V. Loginov , C. Loizides ,X. Lopez , E. L´opez Torres , A. Lowe
134 ,134 , X.-G. Lu , P. Luettig , M. Lunardon , G. Luparello
26 ,56 ,A. Maevskaya , M. Mager , S. Mahajan , S.M. Mahmood , A. Maire , R.D. Majka , M. Malaev ,I. Maldonado Cervantes , L. Malinina , D. Mal’Kevich , P. Malzacher , A. Mamonov , L. Manceau ,V. Manko , F. Manso , V. Manzari
36 ,103 , M. Marchisone , J. Mareˇs , G.V. Margagliotti , A. Margotti ,J. Margutti , A. Mar´ın , C. Markert , M. Marquard , I. Martashvili , N.A. Martin , J. MartinBlanco , P. Martinengo , M.I. Mart´ınez , G. Mart´ınez Garc´ıa , M. Martinez Pedreira , Y. Martynov ,A. Mas , S. Masciocchi , M. Masera , A. Masoni , L. Massacrier , A. Mastroserio , A. Matyja ,C. Mayer , J. Mazer , M.A. Mazzoni , D. Mcdonald , F. Meddi , A. Menchaca-Rocha ,E. Meninno , J. Mercado P´erez , M. Meres , Y. Miake , M.M. Mieskolainen , K. Mikhaylov
57 ,65 ,L. Milano , J. Milosevic
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130 ,78 , L. Molnar , L. Monta˜no Zetina ,E. Montes , M. Morando , S. Moretto , A. Morreale , A. Morsch , V. Muccifora , E. Mudnic ,D. M¨uhlheim , S. Muhuri , M. Mukherjee , H. M¨uller , J.D. Mulligan , M.G. Munhoz ,S. Murray , L. Musa , J. Musinsky , B.K. Nandi , R. Nania , E. Nappi , M.U. Naru , C. Nattrass ,K. Nayak , T.K. Nayak , S. Nazarenko , A. Nedosekin , L. Nellen , F. Ng , M. Nicassio
96 ,96 ,M. Niculescu
36 ,61 ,61 , J. Niedziela , B.S. Nielsen , S. Nikolaev , S. Nikulin , V. Nikulin ,F. Noferini
104 ,12 , P. Nomokonov , G. Nooren , J. Norman , A. Nyanin , J. Nystrand , H. Oeschler ,S. Oh , S.K. Oh , A. Ohlson , A. Okatan , T. Okubo , L. Olah , J. Oleniacz , A.C. Oliveira DaSilva , M.H. Oliver , J. Onderwaater , C. Oppedisano , A. Ortiz Velasquez , A. Oskarsson ,J. Otwinowski
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96 ,96 , S. Parmar , A. Passfeld , V. Paticchio , B. Paul , T. Pawlak , T. Peitzmann ,H. Pereira Da Costa , E. Pereira De Oliveira Filho , D. Peresunko
75 ,99 , C.E. P´erez Lara , V. Peskov
52 ,52 ,Y. Pestov , V. Petr´aˇcek , V. Petrov , M. Petrovici , C. Petta , S. Piano , M. Pikna , P. Pillot ,O. Pinazza
104 ,36 , L. Pinsky , D.B. Piyarathna , M. Płosko´n , M. Planinic , J. Pluta ,S. Pochybova , P.L.M. Podesta-Lerma
117 ,117 , M.G. Poghosyan , B. Polichtchouk , N. Poljak ,W. Poonsawat , A. Pop , S. Porteboeuf-Houssais , J. Porter , J. Pospisil , S.K. Prasad ,R. Preghenella
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92 ,36 , X. Ren , R. Renfordt , A.R. Reolon , A. Reshetin , F. Rettig , J.-P. Revol ,K. Reygers , V. Riabov , R.A. Ricci , T. Richert , M. Richter
22 ,22 , P. Riedler , W. Riegler , F. Riggi ,C. Ristea , A. Rivetti , E. Rocco , M. Rodr´ıguez Cahuantzi
11 ,2 ,11 , A. Rodriguez Manso , K. Røed ,E. Rogochaya , D. Rohr , D. R¨ohrich , R. Romita , F. Ronchetti , L. Ronflette , P. Rosnet ,A. Rossi , F. Roukoutakis , A. Roy , C. Roy , P. Roy , A.J. Rubio Montero , R. Rui , R. Russo ,E. Ryabinkin , Y. Ryabov , A. Rybicki , S. Sadovsky , K. ˇSafaˇr´ık , B. Sahlmuller , P. Sahoo ,R. Sahoo , S. Sahoo , P.K. Sahu , J. Saini , S. Sakai , M.A. Saleh , C.A. Salgado , J. Salzwedel , S. Sambyal , V. Samsonov , X. Sanchez Castro , L. ˇS´andor , A. Sandoval , M. Sano , G. Santagati ,D. Sarkar , E. Scapparone , F. Scarlassara , R.P. Scharenberg , C. Schiaua , R. Schicker ,C. Schmidt , H.R. Schmidt , S. Schuchmann , J. Schukraft , M. Schulc , T. Schuster , Y. Schutz
112 ,36 ,K. Schwarz , K. Schweda , G. Scioli , E. Scomparin , R. Scott , K.S. Seeder , J.E. Seger ,Y. Sekiguchi , I. Selyuzhenkov
96 ,96 , K. Senosi , J. Seo
66 ,95 , E. Serradilla
10 ,63 , A. Sevcenco ,A. Shabanov , A. Shabetai , O. Shadura , R. Shahoyan , A. Shangaraev , A. Sharma ,N. Sharma
60 ,123 , K. Shigaki , K. Shtejer , Y. Sibiriak , S. Siddhanta , K.M. Sielewicz ,T. Siemiarczuk , D. Silvermyr
83 ,34 , C. Silvestre , G. Simatovic , G. Simonetti , R. Singaraju ,R. Singh
89 ,78 , S. Singha
78 ,130 , V. Singhal , B.C. Sinha , T. Sinha , B. Sitar , M. Sitta , T.B. Skaali ,M. Slupecki , N. Smirnov , R.J.M. Snellings , T.W. Snellman , C. Søgaard , R. Soltz , J. Song ,M. Song , Z. Song , F. Soramel , S. Sorensen , M. Spacek , E. Spiriti , I. Sputowska ,M. Spyropoulou-Stassinaki , B.K. Srivastava , J. Stachel , I. Stan , G. Stefanek , M. Steinpreis ,E. Stenlund , G. Steyn , J.H. Stiller , D. Stocco , P. Strmen , A.A.P. Suaide , T. Sugitate ,C. Suire , M. Suleymanov , R. Sultanov , M. ˇSumbera , T.J.M. Symons , A. Szabo , A. Szanto deToledo
118 ,i , I. Szarka , A. Szczepankiewicz , M. Szymanski , J. Takahashi , N. Tanaka ,M.A. Tangaro , J.D. Tapia Takaki ,ii,50 , A. Tarantola Peloni , M. Tariq , M.G. Tarzila , A. Tauro ,G. Tejeda Mu˜noz , A. Telesca , K. Terasaki , C. Terrevoli
30 ,25 , B. Teyssier , J. Th¨ader
96 ,73 ,D. Thomas
56 ,116 , R. Tieulent , A.R. Timmins , A. Toia , S. Trogolo , V. Trubnikov , W.H. Trzaska ,T. Tsuji , A. Tumkin , R. Turrisi , T.S. Tveter , K. Ullaland , A. Uras
128 ,128 , G.L. Usai ,A. Utrobicic , M. Vajzer , M. Vala , L. Valencia Palomo , S. Vallero , J. Van Der Maarel , J.W. VanHoorne , M. van Leeuwen , T. Vanat , P. Vande Vyvre , D. Varga , A. Vargas , M. Vargyas ,R. Varma , M. Vasileiou , A. Vasiliev , A. Vauthier , V. Vechernin , A.M. Veen , M. Veldhoen ,A. Velure , M. Venaruzzo , E. Vercellin , S. Vergara Lim´on , R. Vernet , M. Verweij , L. Vickovic ,G. Viesti
30 ,i , J. Viinikainen , Z. Vilakazi , O. Villalobos Baillie , A. Vinogradov , L. Vinogradov ,Y. Vinogradov , T. Virgili , V. Vislavicius , Y.P. Viyogi , A. Vodopyanov , M.A. V¨olkl , K. Voloshin ,S.A. Voloshin , G. Volpe
36 ,134 , B. von Haller , I. Vorobyev , D. Vranic
96 ,36 , J. Vrl´akov´a ,B. Vulpescu , A. Vyushin , B. Wagner , J. Wagner , H. Wang , M. Wang , Y. Wang ,D. Watanabe , M. Weber
36 ,120 , S.G. Weber , J.P. Wessels , U. Westerhoff , J. Wiechula , J. Wikne ,M. Wilde , G. Wilk , J. Wilkinson , M.C.S. Williams , B. Windelband , M. Winn , C.G. Yaldo ,Y. Yamaguchi , H. Yang
56 ,56 , P. Yang , S. Yano , S. Yasnopolskiy , Z. Yin , H. Yokoyama ,I.-K. Yoo , V. Yurchenko , I. Yushmanov , A. Zaborowska , V. Zaccolo , A. Zaman , C. Zampolli ,H.J.C. Zanoli , S. Zaporozhets , A. Zarochentsev , P. Z´avada , N. Zaviyalov , H. Zbroszczyk ,I.S. Zgura , M. Zhalov , H. Zhang
18 ,7 , X. Zhang , Y. Zhang , C. Zhao , N. Zhigareva , D. Zhou ,Y. Zhou , Z. Zhou , H. Zhu , J. Zhu , X. Zhu , A. Zichichi
12 ,28 , A. Zimmermann ,M.B. Zimmermann
53 ,36 , G. Zinovjev , M. Zyzak Affiliation notes i Deceased ii Also at: University of Kansas, Lawrence, Kansas, United States
Collaboration Institutes A.I. Alikhanyan National Science Laboratory (Yerevan Physics Institute) Foundation, Yerevan, Armenia Benem´erita Universidad Aut´onoma de Puebla, Puebla, Mexico Bogolyubov Institute for Theoretical Physics, Kiev, Ukraine Bose Institute, Department of Physics and Centre for Astroparticle Physics and Space Science (CAPSS),Kolkata, India Budker Institute for Nuclear Physics, Novosibirsk, Russia California Polytechnic State University, San Luis Obispo, California, United States Central China Normal University, Wuhan, China Centre de Calcul de l’IN2P3, Villeurbanne, France Centro de Aplicaciones Tecnol´ogicas y Desarrollo Nuclear (CEADEN), Havana, Cuba Centro de Investigaciones Energ´eticas Medioambientales y Tecnol´ogicas (CIEMAT), Madrid, Spain Centro de Investigaci´on y de Estudios Avanzados (CINVESTAV), Mexico City and M´erida, Mexico Centro Fermi - Museo Storico della Fisica e Centro Studi e Ricerche “Enrico Fermi”, Rome, Italy Chicago State University, Chicago, Illinois, USA China Institute of Atomic Energy, Beijing, China Commissariat `a l’Energie Atomique, IRFU, Saclay, France COMSATS Institute of Information Technology (CIIT), Islamabad, Pakistan Departamento de F´ısica de Part´ıculas and IGFAE, Universidad de Santiago de Compostela, Santiago deCompostela, Spain Department of Physics and Technology, University of Bergen, Bergen, Norway Department of Physics, Aligarh Muslim University, Aligarh, India Department of Physics, Ohio State University, Columbus, Ohio, United States Department of Physics, Sejong University, Seoul, South Korea Department of Physics, University of Oslo, Oslo, Norway Dipartimento di Elettrotecnica ed Elettronica del Politecnico, Bari, Italy Dipartimento di Fisica dell’Universit`a ’La Sapienza’ and Sezione INFN Rome, Italy Dipartimento di Fisica dell’Universit`a and Sezione INFN, Cagliari, Italy Dipartimento di Fisica dell’Universit`a and Sezione INFN, Trieste, Italy Dipartimento di Fisica dell’Universit`a and Sezione INFN, Turin, Italy Dipartimento di Fisica e Astronomia dell’Universit`a and Sezione INFN, Bologna, Italy Dipartimento di Fisica e Astronomia dell’Universit`a and Sezione INFN, Catania, Italy Dipartimento di Fisica e Astronomia dell’Universit`a and Sezione INFN, Padova, Italy Dipartimento di Fisica ‘E.R. Caianiello’ dell’Universit`a and Gruppo Collegato INFN, Salerno, Italy Dipartimento di Scienze e Innovazione Tecnologica dell’Universit`a del Piemonte Orientale and GruppoCollegato INFN, Alessandria, Italy Dipartimento Interateneo di Fisica ‘M. Merlin’ and Sezione INFN, Bari, Italy Division of Experimental High Energy Physics, University of Lund, Lund, Sweden Eberhard Karls Universit¨at T¨ubingen, T¨ubingen, Germany European Organization for Nuclear Research (CERN), Geneva, Switzerland Faculty of Engineering, Bergen University College, Bergen, Norway Faculty of Mathematics, Physics and Informatics, Comenius University, Bratislava, Slovakia Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, Prague,Czech Republic Faculty of Science, P.J. ˇSaf´arik University, Koˇsice, Slovakia Faculty of Technology, Buskerud and Vestfold University College, Vestfold, Norway Frankfurt Institute for Advanced Studies, Johann Wolfgang Goethe-Universit¨at Frankfurt, Frankfurt,Germany Gangneung-Wonju National University, Gangneung, South Korea Gauhati University, Department of Physics, Guwahati, India Helsinki Institute of Physics (HIP), Helsinki, Finland Hiroshima University, Hiroshima, Japan Indian Institute of Technology Bombay (IIT), Mumbai, India Indian Institute of Technology Indore, Indore (IITI), India Inha University, Incheon, South Korea Institut de Physique Nucl´eaire d’Orsay (IPNO), Universit´e Paris-Sud, CNRS-IN2P3, Orsay, France Institut f¨ur Informatik, Johann Wolfgang Goethe-Universit¨at Frankfurt, Frankfurt, Germany Institut f¨ur Kernphysik, Johann Wolfgang Goethe-Universit¨at Frankfurt, Frankfurt, Germany Institut f¨ur Kernphysik, Westf¨alische Wilhelms-Universit¨at M¨unster, M¨unster, Germany Institut Pluridisciplinaire Hubert Curien (IPHC), Universit´e de Strasbourg, CNRS-IN2P3, Strasbourg,France Institute for Nuclear Research, Academy of Sciences, Moscow, Russia Institute for Subatomic Physics of Utrecht University, Utrecht, Netherlands Institute for Theoretical and Experimental Physics, Moscow, Russia Institute of Experimental Physics, Slovak Academy of Sciences, Koˇsice, Slovakia Institute of Physics, Academy of Sciences of the Czech Republic, Prague, Czech Republic Institute of Physics, Bhubaneswar, India Institute of Space Science (ISS), Bucharest, Romania Instituto de Ciencias Nucleares, Universidad Nacional Aut´onoma de M´exico, Mexico City, Mexico Instituto de F´ısica, Universidad Nacional Aut´onoma de M´exico, Mexico City, Mexico iThemba LABS, National Research Foundation, Somerset West, South Africa Joint Institute for Nuclear Research (JINR), Dubna, Russia Konkuk University, Seoul, South Korea Korea Institute of Science and Technology Information, Daejeon, South Korea KTO Karatay University, Konya, Turkey Laboratoire de Physique Corpusculaire (LPC), Clermont Universit´e, Universit´e Blaise Pascal,CNRS–IN2P3, Clermont-Ferrand, France Laboratoire de Physique Subatomique et de Cosmologie, Universit´e Grenoble-Alpes, CNRS-IN2P3,Grenoble, France Laboratori Nazionali di Frascati, INFN, Frascati, Italy Laboratori Nazionali di Legnaro, INFN, Legnaro, Italy Lawrence Berkeley National Laboratory, Berkeley, California, United States Lawrence Livermore National Laboratory, Livermore, California, United States Moscow Engineering Physics Institute, Moscow, Russia National Centre for Nuclear Studies, Warsaw, Poland National Institute for Physics and Nuclear Engineering, Bucharest, Romania National Institute of Science Education and Research, Bhubaneswar, India Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark Nikhef, National Institute for Subatomic Physics, Amsterdam, Netherlands Nuclear Physics Group, STFC Daresbury Laboratory, Daresbury, United Kingdom Nuclear Physics Institute, Academy of Sciences of the Czech Republic, ˇReˇz u Prahy, Czech Republic Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States Petersburg Nuclear Physics Institute, Gatchina, Russia Physics Department, Creighton University, Omaha, Nebraska, United States Physics Department, Panjab University, Chandigarh, India Physics Department, University of Athens, Athens, Greece Physics Department, University of Cape Town, Cape Town, South Africa Physics Department, University of Jammu, Jammu, India Physics Department, University of Rajasthan, Jaipur, India Physik Department, Technische Universit¨at M¨unchen, Munich, Germany Physikalisches Institut, Ruprecht-Karls-Universit¨at Heidelberg, Heidelberg, Germany Politecnico di Torino, Turin, Italy Purdue University, West Lafayette, Indiana, United States Pusan National University, Pusan, South Korea Research Division and ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum f¨urSchwerionenforschung, Darmstadt, Germany Rudjer Boˇskovi´c Institute, Zagreb, Croatia Russian Federal Nuclear Center (VNIIEF), Sarov, Russia Russian Research Centre Kurchatov Institute, Moscow, Russia
Saha Institute of Nuclear Physics, Kolkata, India
School of Physics and Astronomy, University of Birmingham, Birmingham, United Kingdom
Secci´on F´ısica, Departamento de Ciencias, Pontificia Universidad Cat´olica del Per´u, Lima, Peru
Sezione INFN, Bari, Italy
Sezione INFN, Bologna, Italy
Sezione INFN, Cagliari, Italy
Sezione INFN, Catania, Italy
Sezione INFN, Padova, Italy
Sezione INFN, Rome, Italy
Sezione INFN, Trieste, Italy
Sezione INFN, Turin, Italy
SSC IHEP of NRC Kurchatov institute, Protvino, Russia
SUBATECH, Ecole des Mines de Nantes, Universit´e de Nantes, CNRS-IN2P3, Nantes, France
Suranaree University of Technology, Nakhon Ratchasima, Thailand
Technical University of Split FESB, Split, Croatia
The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Cracow, Poland
The University of Texas at Austin, Physics Department, Austin, Texas, USA
Universidad Aut´onoma de Sinaloa, Culiac´an, Mexico
Universidade de S˜ao Paulo (USP), S˜ao Paulo, Brazil
Universidade Estadual de Campinas (UNICAMP), Campinas, Brazil
University of Houston, Houston, Texas, United States
University of Jyv¨askyl¨a, Jyv¨askyl¨a, Finland
University of Liverpool, Liverpool, United Kingdom
University of Tennessee, Knoxville, Tennessee, United States
University of the Witwatersrand, Johannesburg, South Africa
University of Tokyo, Tokyo, Japan
University of Tsukuba, Tsukuba, Japan
University of Zagreb, Zagreb, Croatia
Universit´e de Lyon, Universit´e Lyon 1, CNRS/IN2P3, IPN-Lyon, Villeurbanne, France
V. Fock Institute for Physics, St. Petersburg State University, St. Petersburg, Russia
Variable Energy Cyclotron Centre, Kolkata, India
Vinˇca Institute of Nuclear Sciences, Belgrade, Serbia
Warsaw University of Technology, Warsaw, Poland
Wayne State University, Detroit, Michigan, United States
Wigner Research Centre for Physics, Hungarian Academy of Sciences, Budapest, Hungary
Yale University, New Haven, Connecticut, United States
Yonsei University, Seoul, South Korea