Published for SISSA by Springer Received: April 28, 2015 Accepted: June 17, 2015 Published: July 10, 2015 NN The ALICE collaboration E-mail: ALICE-publications@cern.ch Abstract: The transverse momentum (pT ) dependence of the nuclear modification factor RAA and the centrality dependence of the average transverse momentum hpT i for inclusive √ J/ψ have been measured with ALICE for Pb-Pb collisions at sNN = 2.76 TeV in the e+ e− decay channel at mid-rapidity (|y| < 0.8). The hpT i is significantly smaller than the one observed for pp collisions at the same centre-of-mass energy. Consistently, an increase of RAA is observed towards low pT . These observations might be indicative of a sizable contribution of charm quark coalescence to the J/ψ production. Additionally, the fraction of non-prompt J/ψ from beauty hadron decays, fB , has been determined in the region 1.5 < pT < 10 GeV/c in three centrality intervals. No significant centrality dependence of fB is observed. Finally, the RAA of non-prompt J/ψ is discussed and compared with model predictions. The nuclear modification in the region 4.5 < pT < 10 GeV/c is found to be stronger than predicted by most models. Keywords: Hadron-Hadron Scattering ArXiv ePrint: 1504.07151 Open Access, Copyright CERN, for the benefit of the ALICE Collaboration. Article funded by SCOAP3 . doi:10.1007/JHEP07(2015)051 JHEP07(2015)051 Inclusive, prompt and non-prompt J/ψ production at √ mid-rapidity in Pb-Pb collisions at s = 2.76 TeV Contents 1 Introduction 1 2 Data analysis 2.1 Inclusive J/ψ 2.2 Non-prompt J/ψ 2 3 8 13 4 Conclusions 19 The ALICE collaboration 26 1 Introduction Heavy-ion collisions at high energies allow the study of strongly interacting matter under extreme conditions. Calculations based on Quantum-Chromo-Dynamics (QCD) on the lattice indicate that the hot and dense medium created in these collisions behaves like a strongly coupled Quark-Gluon Plasma (QGP) [1–4]. Heavy quarks are an important probe for the properties of this state of matter, since they are produced via hard partonic collisions at a very early stage and thus experience the complete evolution of the system. Quarkonium states, i.e. bound states of a heavy quark and anti-quark such as the J/ψ meson (cc̄ state) are of particular interest. It was predicted that the J/ψ formation is suppressed in a QGP due to the screening of the cc̄ potential in the presence of free colour charges [5]. Experimentally, a suppression of the inclusive J/ψ yield in heavy-ion collisions relative to the corresponding yield in pp, scaled by the number of binary nucleon-nucleon collisions, has been observed at the Super Proton Synchrotron (SPS) [6–8] and the Relativistic Heavy Ion Collider (RHIC) [9, 10]. The level of suppression was found to be similar at SPS and RHIC, despite the significantly different collision energy. More recently, the nuclear modification of J/ψ was also measured for Pb-Pb collisions at the LHC [11–13]. While at high transverse momentum (pT > 4 GeV/c) the suppression factor is at the same level as the one observed at RHIC in the low pT region, a significant reduction of the suppression is measured towards lower pT . This has been interpreted as the effect of an additional contribution to J/ψ production at low pT , due to the combination of correlated or uncorrelated c and c̄ quarks [14, 15]. This contribution becomes sizable at LHC energies, since the number of cc̄ pairs is much higher than at lower energies. Assuming that a deconfined phase is produced and that all the J/ψ are dissociated, this process happens at the chemical freezeout stage of the fireball evolution. This is the approach followed within the statistical hadronization models described in refs. [16, 17]. Alternatively, J/ψ could be generated via coalescence throughout the full evolution of the QGP phase, if their survival probability in –1– JHEP07(2015)051 3 Results 2 Data analysis A detailed description of the ALICE detector can be found in [38]. For the analysis presented here the detectors of the central barrel have been used, in particular the Inner Tracking System (ITS) and the Time Projection Chamber (TPC). These detectors are located inside a large solenoidal magnet with a field strength of 0.5 T. They allow the –2– JHEP07(2015)051 this environment is large enough. This scenario has been implemented in several partonic transport models [18, 19]. It was found that both approaches can provide a description of the measured nuclear modification factors [12] and of the elliptic flow of inclusive J/ψ [20]. The production of open beauty hadrons is expected to be sensitive to the density of the medium created in heavy-ion collisions due to the energy loss experienced by the parent parton (a beauty quark) which hadronizes into the beauty hadron. This energy loss is expected to occur via medium-induced gluon radiation [21, 22] and elastic collisional energy loss processes [23–25] and it depends on the QCD Casimir coupling factor of the parton (larger for gluons than for quarks) and on the parton mass [26–29]. Other mechanisms, such as in-medium hadron formation and dissociation, can be envisaged as particularly relevant for heavy-flavour hadrons due to their small formation times [30–32]. Inclusive J/ψ production is the sum of several contributions. In addition to the directly produced J/ψ, the decays of heavier charmonium states, such as the χc and ψ(2S), also contribute to the inclusive J/ψ yield. These two sources (direct and charmonium decays) are defined as prompt J/ψ, where the contribution from charmonium decays is about 35% as measured in pp collisions [33]. Since heavier charmonia are less strongly bound than the J/ψ they should be more easily dissolved in a deconfined medium [34]. The J/ψ suppression measured at the SPS is indeed compatible with the assumption that only the excited states are dissolved and not the directly produced J/ψ [6, 7]. On top of the prompt J/ψ production, there is an additional non-prompt contribution to the inclusive J/ψ at high centre-of-mass energies, coming from the decay of beauty hadrons. Since these decays proceed via weak interactions, the resulting J/ψ will originate from a decay vertex that is displaced from the main interaction vertex. Their measurement provides a direct determination of the nuclear modification of beauty hadrons. By subtracting the non-prompt contribution from the inclusive J/ψ yield one can also provide an unbiased information on medium modification of prompt charmonia. The non-prompt J/ψ contribution at mid√ rapidity has already been measured in pp collisions at s = 7 TeV by ATLAS [35], CMS [36] √ and ALICE [37]. For Pb-Pb collisions at sNN = 2.76 TeV CMS has also published prompt and non-prompt J/ψ production results at mid-rapidity for pT > 6.5 GeV/c [13]. In this paper we present a differential measurement of the inclusive J/ψ production at √ mid-rapidity in Pb-Pb collisions at sNN = 2.76 TeV. The pT dependence of the nuclear modification factor and the centrality dependence of the average transverse momentum of J/ψ have been obtained, extending the set of results presented in [12]. A measurement of the prompt and non-prompt contributions to the inclusive J/ψ production is also presented. The nuclear modification factor of non-prompt J/ψ is determined down to pT = 1.5 GeV/c and compared to model predictions. 2.1 Inclusive J/ψ J/ψ candidates are reconstructed by combining opposite-sign (OS) pairs of electron/positron candidates and calculating their invariant mass mee . These candidates are selected from tracks reconstructed in the ITS and the TPC by employing the set of quality criteria described in [12, 44]. In order to reject the background from photon conversions –3– JHEP07(2015)051 measurement of J/ψ mesons via the dielectron decay channel in the central rapidity region down to zero pT . The ITS [39] consists of six layers of silicon detectors surrounding the beam pipe at radial positions between 3.9 cm and 43.0 cm. Its two innermost layers are composed of Silicon Pixel Detectors (SPD), which provide the spatial resolution to separate on a statistical basis the non-prompt J/ψ. The active volume of the TPC [40] covers the range along the beam direction −250 < z < 250 cm relative to the Interaction Point (IP) and extends in radial direction from 85 cm to 247 cm. It is the main tracking device in the central barrel and is in addition used for particle identification via the measurement of the specific ionization (dE/dx) in the detector gas. Triggering and event characterization is performed via forward detectors, the V0 [41] and two Zero Degree Calorimeters (ZDC) [42]. The V0 detectors consist of two scintillator arrays positioned at z = −90 cm and z = +340 cm and cover the pseudo-rapidity ranges −3.7 ≤ η ≤ −1.7 and 2.8 ≤ η ≤ 5.1. The ZDCs, each one consisting of two quartz fiber sampling calorimeters, are placed at a distance of 114 m relative to the IP in both directions along the beam axis and are used to detect spectator nucleons. The results presented in this article are based on data samples collected during the Pb-Pb data taking periods of the LHC in the years 2010 and 2011. In the case of the 2011 data sample the Minimum Bias (MB) Level-0 (L0) trigger condition was defined by the coincidence of signals in both V0 detectors along with a valid bunch crossing trigger. For the 2010 data sample, in addition, the detection of at least two hits in the ITS was required. Both MB trigger definitions lead to trigger efficiencies larger than 95% for inelastic Pb-Pb collisions. Electromagnetic interactions were rejected by the Level-1 (L1) trigger, which required a minimum energy deposition in the ZDC by spectator neutrons. The beam-induced background was further reduced during the offline analysis by selecting events according to the relative timing of signals in V0 and ZDC. The offline centrality selection is done using the sum of the two V0 signal amplitudes. By fitting the corresponding distribution with the results of Glauber model simulations, the average number inel for a of participants hNpart i and the average nuclear overlap function hTAA i = hNcoll i/σNN given centrality class can be determined as described in [43]. Here, hNcoll i is the average inel the inelastic nucleon-nucleon cross number of binary nucleon-nucleon collisions and σNN section. The numerical values for hNpart i, hNcoll i, and hTAA i are tabulated in [12]. The 2010 data sample consists of 1.5 × 107 events, taken with the corresponding MB trigger. The 2011 event sample was enriched with central and semi-central Pb-Pb collisions by using thresholds on the V0 multiplicity at the L0 trigger. From the latter data set we analyzed 1.9 × 107 central (0–10% of the centrality distribution) and 1.7 × 107 semi-central (10–50%) events. The summed 2010 and 2011 data samples correspond to an integrated −1 [12]. luminosity of Lint = 26.4 ± 0.3(stat.)+2.1 −1.7 (syst.) µb Measurement of the inclusive J/ψ yield. The J/ψ signal counts NJ/ψ are obtained from the number of entries in the background subtracted invariant mass distributions in the range 2.92 < mee < 3.16 GeV/c2 . The uncorrelated background is evaluated with a mixed event (ME) technique. In order to achieve a good description of the background only electrons and positrons from events with similar properties in terms of centrality, primary vertex position, and event plane angle are combined. The ME distributions are scaled to the same event (SE) distributions in the mass ranges 1.5 < mee < 2.5 GeV/c2 and 3.2 < mee < 4.2 GeV/c2 , so that the J/ψ signal region is excluded. The normalization area contains the ψ(2S) signal, but its contribution is negligible and can therefore be safely ignored. Also, contributions from the tail of the J/ψ signal shape to this mass interval are below the percent level and will thus not significantly affect the normalization. Figure 1 shows a comparison of the SE and ME invariant mass distributions for the 0–40% most central Pb-Pb collisions for electron-positron pairs at mid-rapidity (|y| < 0.8) in two pT intervals: 0–2.5 GeV/c and 2.5–6 GeV/c. The agreement between the SE and ME distributions outside the signal region is very good and allows signal extraction with significances larger than eight. The J/ψ yield per MB event in a given pT interval, YJ/ψ , is obtained as YJ/ψ (pT ) = BRee NJ/ψ (pT ) . Nevts hA × i(pT ) (2.1) Here BRee is the branching ratio for the decay J/ψ → e+ e− , Nevts the number of events, and hA × i the phase space dependent product of acceptance A and reconstruction efficiency . The latter is calculated from Monte Carlo (MC) simulations as the ratio between the number of reconstructed and generated MC J/ψ, which are assumed to be unpolar√ ized. In pp collisions at s = 7 TeV the J/ψ polarization has been measured and was found to be compatible with zero at mid-rapidity (pT > 10 GeV/c) and forward rapidity (pT > 2 GeV/c) [46–48]. In heavy-ion collisions no measurement exists, but J/ψ mesons produced from the recombination of charm quarks in the medium are expected to be un- –4– JHEP07(2015)051 in the detector material, tracks are required to have a hit in one of the SPD layers. In addition, at least 70 out of a maximum of 159 space points reconstructed in the TPC must be assigned to a given track, which also needs to fulfill a quality criterion of the track fit (χ2 /ndf < 4). The tracks are required to be in the range |η| < 0.8, where the tracking and particle identification performance of the TPC is optimal, and to have pT > 0.85 GeV/c to improve the signal-to-background ratio in the J/ψ mass region. Electron candidates are selected by requiring that the dE/dx measurement in the TPC lies within a band [−1σ, +3σ] around the momentum-dependent parameterization of the expected signal, where σ is the phase space dependent dE/dx resolution (details can be found in [45]). The selection is asymmetric in order to minimize the contribution from pions. To further suppress the hadron contamination, tracks that are compatible within ±4σ with the proton expectation are rejected. A side effect of this cut is that tracks below pT = 1 GeV/c are effectively removed. polarized.1 The MC events used for the calculation of hA × i are constructed by adding to background events, generated with the HIJING model [49], J/ψ mesons decaying into e+ e− pairs, whose phase space distribution is obtained from extrapolations of other measurements [50], taking into account shadowing effects as parameterized in EKS98 [51]. The dielectron decay is simulated with the EvtGen [52] package, using the PHOTOS model [53] to describe the influence of final state radiation. This choice, together with the simulation of bremsstrahlung in the detector material, is mandatory for a proper description of the low mass tail in the measured J/ψ mass distribution and ensures that the fraction of the signal outside of the mee integration window is properly accounted for in the correction hA × i. The propagation of the simulated particles is done by GEANT3 [54] and a full simulation of the detector response is performed. The same reconstruction procedure and cuts are applied to MC events and to real data. The quality of the simulation is illustrated by the good agreement of the background-subtracted invariant mass distributions with the 1 The impact of the polarization on the acceptance was studied for extreme polarization scenarios in [44]. –5– JHEP07(2015)051 Figure 1. The invariant mass distributions of inclusive J/ψ at mid-rapidity (|y| < 0.8) for √ Pb-Pb collisions (0–40% most central) at sNN = 2.76 TeV. The left panels show the interval 0 < pT < 2.5 GeV/c and the right ones 2.5 < pT < 6 GeV/c. The upper panels display the opposite sign distributions together with the result of the mixed event procedure. In the lower panels the background subtracted distributions are shown and compared to the simulated line shape. Also, the signal-to-background ratio S/B and the significance of the signal are given. MC simulation of the J/ψ signal shape, after normalizing it to the same integral as the measured signal (see figure 1). The analysis has been performed in two slightly different centrality intervals (0–40% and 0–50%), where the larger one is used for the extraction of non-prompt J/ψ which requires a higher statistics than the inclusive measurement. Also, the pT intervals have been optimized for the different analyses. It was checked that the results for inclusive J/ψ obtained with the two centrality binnings are in good agreement. RAA (pT ) = YJ/ψ (pT ) . pp hTAA i σJ/ψ (pT ) (2.2) Since no differential J/ψ measurement at mid-rapidity at low pT is available for pp collisions √ at s = 2.76 TeV [55], the reference needed for the construction of RAA is based on an √ interpolation of the mid-rapidity measurements by PHENIX at s = 0.2 TeV [56], CDF √ √ at s = 1.96 TeV [57], and ALICE at s = 7 TeV [55]. The interpolated pT distribution is obtained by fitting the following parameterization to the available data sets [50] 1 d2 σ zT =c 2 )n . dσ/dy dzT dy (1 + a2 zT (2.3) Here, zT is defined as pT /hpT i, a = Γ(3/2) Γ(n − 3/2)/Γ(n − 1), and c = 2(n − 1) a, where n is the only free fit parameter. The value for hpT i (calculated in the pT range √ 0–10 GeV/c) at s = 2.76 TeV, which is needed to translate this parameterization into dσ/dpT , is determined by interpolating between the existing hpT i measurements for pp and pp̄ collisions [55–57]. This interpolation is done using various functional forms for the √ s dependence to determine the systematic uncertainty. For the absolute normalization of the parametrized spectrum, the same interpolated value dσ/dy = 4.25 ± 0.28(stat.) ± 0.43(syst.) µb as in [12] is used. The main sources of systematic uncertainties for the pT dependent RAA of inclusive J/ψ are the signal reconstruction procedure, the MC input kinematics, the uncertainties on the interpolated pp reference and on the nuclear overlap function. The corresponding values are summarized in table 1. While the first two components are uncorrelated between the pT intervals (type II), the uncertainty due to the nuclear overlap function is fully correlated (type I). The pp reference on the other hand introduces both uncorrelated and correlated contributions. To determine the uncertainty related to the signal reconstruction, the normalization range of the ME background and the size and positions of the mee bins have been varied. All track and electron selection criteria, such as the electron inclusion cut and the SPD hit requirement, have been relaxed and/or tightened in order to test the stability of the result, as was performed in [12]. The value of the systematic uncertainty is determined as the standard deviation of the distribution of all results obtained with the listed variations. The evaluation of the uncertainties associated with the MC input kinematics is also described in [12], while the uncertainty of the pp reference is estimated –6– JHEP07(2015)051 Determination of the pp reference for RAA . From the corrected J/ψ yield YJ/ψ (pT ) the nuclear modification factor RAA (pT ) is calculated as from the differences between the cross-section values obtained with the fitting procedure based on eq. (2.3) and the measured values used for the fit at the various energies. Determination of hpT i and hp2T i. Since the collected Pb-Pb statistics would allow the extraction of the J/ψ yield in a few pT intervals only, the average transverse momentum hpT i is determined by a fit to the distribution of the hpT i of e+ e− pairs as a function of mee . When building such a distribution, the individual e+ e− pairs are weighted by the inverse of their acceptance times efficiency (A × )−1 , assuming that they come from the decay of a J/ψ. The resulting hpT i distributions are fitted by the expression hpT imeas =   1 S(mee ) hpT iJ/ψ + B(mee ) hpT iBkg . S(mee ) + B(mee ) (2.4) Both factors S and B depend on mee and correspond to the distribution of the J/ψ signal and of the background. For S the same background subtracted signal distribution S(mee ) is used as for the extraction of the yield (see lower panels of figure 1), while the background B is generated from the ME sample, as B(mee ) = cB BME (mee ). The normalization factor is determined by fitting cB BME (mee ) to the corresponding mee distribution of e+ e− pairs in the regions 1.5 < mee < 2.5 GeV/c2 and 3.2 < mee < 4.2 GeV/c2 , thus excluding the signal region. For the sum S(mee )+B(mee ) in the denominator of eq. (2.4), the measured OS pair mee distribution is used. The hpT iBkg , defined as the hpT i of the combinatorial background pairs, is also calculated from the ME sample. This analysis is performed in three different centrality intervals: 0–10%, 10–40%, and 40–90%. Figure 2 shows the measured hpT i of the e+ e− pairs in the pT range 0–10 GeV/c together with the results of the fit procedure. In addition, with an equivalent method, the mean square transverse momentum hp2T i is also calculated for the same centrality intervals. The systematic uncertainties of the hpT i measurement for inclusive J/ψ are mainly determined by the signal extraction, the stability of track and electron selection criteria and the fit procedure (see table 2). While the first two components are not correlated between the different centrality intervals (type II), the systematic uncertainty intrinsic to the fit procedure can affect the data points in a correlated way (type I). The uncertainties –7– JHEP07(2015)051 Figure 2. The average transverse momentum hpT i of e+ e− pairs, measured for the pT range 0– √ 10 GeV/c, as a function of the invariant mass mee in centrality selected Pb-Pb collisions at sNN = 2.76 TeV. The shown uncertainties are statistical only. The background hpT i distributions and the total fit results are also shown superimposed to the data points. Source Signal reconstruction MC input kinematics Nuclear overlap function hTAA i pp reference Type II II I I II I II Table 1. The correlated (type I) and uncorrelated (type II) systematic uncertainties (in percent) on the measurement of the nuclear modification factor RAA of inclusive J/ψ for several pT intervals √ in Pb-Pb collisions (0–40% and 0–50% most central) at sNN = 2.76 TeV. Source Signal extraction Track selection Stability of the fit procedure (from MC) Total Centrality 0–10% 10–40% 40–90% 2.0 1.6 4.5 3.1 3.9 13.7 2.0 2.0 2.0 2.0 2.0 2.0 3.7 4.2 14.4 type II II I I II Table 2. The correlated (type I) and uncorrelated (type II) systematic uncertainties (in percent) on the measurement of the average transverse momentum hpT i of inclusive J/ψ in three centrality √ intervals in Pb-Pb collisions at sNN = 2.76 TeV. related to the signal extraction have been evaluated by varying the normalization range of the ME background, the size and positions of the mee bins, the fit region and by using in addition to the ME background a linear function for the background description. In addition, the stability of the fit procedure was tested by modifying the approach, e.g. by using in the fit the direct sum of S and B, instead of the OS pair mee distribution, or by using a fit function for B, instead of ME. It was also verified by applying the above described method to MC events, which were constructed by combining signal with background events with a realistic S/B ratio. It turned out that the procedure allows to recover the hpT i of the simulated J/ψ mesons within a 2% difference. This value is assumed as correlated (type I) uncertainty. Finally, the uncertainty in the signal-to-background ratio is propagated into the statistical uncertainty of the hpT iJ/ψ . 2.2 Non-prompt J/ψ The candidate selection for the non-prompt J/ψ analysis includes, in addition to the previously described criteria, the condition that at least one of the two decay tracks has a hit in the first SPD layer, in order to enhance the resolution of secondary vertices. –8– JHEP07(2015)051 Total pT range (GeV/c) 0–40% 0–50% 0–2.5 2.5–6 0–1.5 1.5–4.5 4.5–10 10.9 11.0 22.6 8.5 10.0 3.2 5.9 1.5 4.7 5.3 3.2 3.2 3.8 3.8 3.8 12.1 12.1 12.1 12.1 12.1 4.5 4.9 5.0 4.3 10.1 12.6 12.6 12.7 12.7 12.7 12.3 13.5 23.2 10.6 15.2 The non-prompt J/ψ fraction has been determined using an unbinned two-dimensional log-likelihood fit described in detail in [37], which is performed by maximizing the quantity ln L = N X ln [fSig · FSig (x) · MSig (mee ) + (1 − fSig ) · FBkg (x) · MBkg (mee )] , (2.5) where N is the total number of OS candidates in the range 2.2 < mee < 4 GeV/c2 and x is the pseudo-proper decay length of the candidate ~ · p~T /pT ) mJ/ψ c (L . pT (2.6) ~ is the vector pointing from the primary vertex to the J/ψ decay vertex and mJ/ψ Here L the mass of the J/ψ taken from [58]. FSig (x) and FBkg (x) (MSig (mee ) and MBkg (mee )) are Probability Density Functions (p.d.f.) describing the pseudo-proper decay length (invariant mass) distribution for signal and background candidates, respectively. FSig (x) is defined as FSig (x) = fB0 · FB (x) + (1 − fB0 ) · Fprompt (x) , (2.7) where Fprompt (x) and FB (x) are the p.d.f. for prompt and non-prompt J/ψ, respectively, and fB0 is the fraction of reconstructed J/ψ coming from beauty hadron decays fB0 = NJ/ψ←hB . NJ/ψ←hB + Nprompt (2.8) A correction due to different average hA × i values, in a given pT interval, for prompt and non-prompt J/ψ, is necessary to obtain from fB0 the fraction of produced non-prompt J/ψ, fB  −1 1 − fB0 hA × iB fB = 1 + . (2.9) fB0 hA × iprompt The various ingredients for the determination of fB are described in the following: Monte Carlo pT distributions and polarization assumptions. Assuming both prompt and non-prompt J/ψ to be unpolarized, at a given pT their acceptance times efficiency values hA × i are the same. However, the pT distributions of prompt and nonprompt J/ψ can be different, resulting in different average hA × i computed over a pT range of finite size. Different hypotheses for the kinematical (pT ) distributions of both prompt and non-prompt J/ψ are considered, i.e. including or excluding shadowing or suppression effects as, e.g., those predicted in references [59–61] for non-prompt J/ψ. Due to the weak pT dependence of hA × i, the resulting uncertainty on fB is small, being ∼ 5% at low pT and ∼ 3% in the highest pT bin, and is independent of centrality. At a given pT , prompt and non-prompt J/ψ can have different polarization and therefore a different acceptance. However, the polarization of J/ψ from b-hadron decays is expected to be small due to the averaging effect caused by the admixture of various exclusive B → J/ψ +X decay channels. Indeed, in more elementary colliding systems, the sizable polarization, which is observed when the polarization axis refers to the B-meson direction [62], –9– JHEP07(2015)051 x= is strongly smeared when calculated with respect to the direction of the daughter J/ψ [63], as observed by CDF [64]. The central values of the fraction of non-prompt J/ψ are evaluated with eq. (2.9) assuming unpolarized prompt J/ψ and a polarization of non-prompt J/ψ as predicted by EVTGEN [52]. The assumption of a null polarization for non-prompt J/ψ results in a relative decrease of fB by only 1% at high pT (4.5–10 GeV/c) and 3% at low pT (1.5–4.5 GeV/c). The relative variations of fB expected in extreme scenarios for the polarization of prompt J/ψ was studied in [44]. The uncertainties related to the polarization of prompt and non-prompt J/ψ are are not further propagated to the results. P.d.f. for non-prompt J/ψ: FB (x). The shape of the x distribution of non-prompt J/ψ is estimated by using PYTHIA 6.4.21 [67] in the Perugia-0 tune [68] to generate beauty √ hadrons at s = 2.76 TeV, and the EvtGen package [52] to describe their decays. The systematic uncertainty related to this shape is estimated by assuming a softer pT distribution for the non-prompt J/ψ which is obtained by adding the suppression effects as predicted √ in [61] and a harder one taken from the same PYTHIA event generator at s = 7 TeV instead of 2.76 TeV. The resulting systematic uncertainty is within 3–4%. P.d.f. for the background: FBkg (x). The main difference of the analysis presented in this section, with respect to previous work on pp collisions [37], concerns the description of FBkg (x). In this analysis such a function includes an extra symmetric exponential tail (∝ e−|x|/λsym ) [57] and depends on the invariant mass and the pT of the dielectron pair. It is determined, for each centrality class, by a fit to the data in three pT regions (1.5–3, 3–4.5, 4.5–10 GeV/c) and in four invariant mass regions on the side-bands of the J/ψ mass peak (2.2–2.6, 2.6–2.8, 3.16–3.5, 3.5–4 GeV/c2 , labelled with the indices 1, 2, 3 and 4, respectively), for a total of 3 × 4 combinations. The background function in the invariant mass region 2.8–3.16 GeV/c2 and in each of the three pT ranges are obtained by an interpolation procedure as the weighted combination of the p.d.f. determined in the other four invariant mass regions. The weights are chosen inversely proportional to the absolute difference (or its square) between the mean of the invariant mass distribution in the given mass interval – 10 – JHEP07(2015)051 P.d.f. for prompt J/ψ: Fprompt (x). The x distribution Fprompt (x) for prompt J/ψ, which decay at the primary vertex, coincides with the resolution function R(x), which describes the accuracy by which x can be reconstructed. It also enters in the p.d.f. describing the x distributions of non-prompt J/ψ, FB (x), and of the background candidates, FBkg (x). The determination of R(x) is based on the same MC data sample as used for the inclusive J/ψ analysis (see section 2.1). The systematic uncertainty on R(x) was estimated with a MC approach by propagating the maximum observed discrepancies of the track parameters (space and momentum variables) between data and MC to the x variable [45, 65, 66] and was found to be at most 10%. To propagate this systematic uncertainty to the final results the fits are repeated after modifying in the log-likelihood function the resolution to (1/(1 + δ)) × R (x/(1 + δ)). In this expression δ parameterizes the relative variation of the RMS of the resolution function and is varied between −10% and +10%. The systematic uncertainty due to the resolution function is smaller in the highest pT bin, because of the better resolution in the x variable and the higher values of the signal-to-background ratio. and that in the interpolated region FBkg interp (x) = 4 X wi FBkg i (x); wi ∝ |hmee ii − hmee iinterp |−n (n = 1 or 2). (2.10) i=1 P.d.f. for the invariant mass distribution of the signal: MSig (mee ). The shape of the invariant mass distribution for the signal is determined by the same MC simulations described in section 2.1. The influence of detector material budget is studied with dedicated MC simulations, where the material budget is varied within its uncertainty (±6%) [69]. The resulting contribution to the systematic uncertainty on fB slightly increases for central events, and ranges from 2 to 4%. P.d.f. for the invariant mass distribution of the background: MBkg (mee ). The shape of the invariant mass distribution for the background candidates is determined from ME pairs. The related systematic uncertainty on fB is evaluated using the like-sign distribution, instead of the ME one. The uncertainty increases at higher centrality and in the lowest pT interval due to the decrease of the S/B ratio. As an example in figure 3 the projections of the best fit function for n = 1 and w1 = w4 = 0 are shown superimposed to the invariant mass (upper panel) and x (lower panel) distributions of the candidates in the centrality range 10–50% for 1.5 < pT < 10 GeV/c. A summary of the systematic uncertainties on the determination of the non-prompt J/ψ fraction is provided in table 3 for the three centrality intervals in the integrated pT range and, in the two pT ranges where the results will be given, for the most central collisions (0–10%). The value of fB is determined in two pT bins (1.5–4.5 and 4.5–10 GeV/c) for the 0– 50% centrality range and in three centrality classes (0–10%, 10–40% and 40–90%) for 1.5 < pT < 10 GeV/c. The fB measurements are then combined with the nuclear modification factors of inclusive J/ψ to get the non-prompt and prompt J/ψ RAA non−prompt J/ψ RAA = fBPb−Pb incl. RAA fBpp J/ψ , prompt J/ψ RAA = 1 − fBPb−Pb incl. RAA 1 − fBpp J/ψ . (2.11) √ pp interpolation. The value of fB in pp collision at s = 2.76 TeV, fBpp , is needed to compute the RAA for prompt and non-prompt J/ψ mesons, see eq. (2.11). It is determined by an interpolation procedure. Therefore, a fit is performed to the existing measurements of – 11 – JHEP07(2015)051 Optionally, only the two adjacent mass regions can be considered in the interpolation procedure, corresponding to the condition w1 = w4 = 0. The central value of fB has been determined as the average of the values obtained with the different assumptions (n = 1 or n = 2, with or without the condition w1 = w4 = 0). The RMS of the distributions of the relative variations obtained for fB is used to define the systematic uncertainty. It becomes larger for central events and in the lowest pT interval, where the signal-to-background ratio S/B is lower. This approach allows to cope with the much lower S/B ratio in Pb-Pb than in pp collisions. √ fB as a function of pT in mid-rapidity pp collisions at s = 7 TeV (ALICE [37], ATLAS [35] and CMS [70]). The function used to fit the data is chosen as , phenom. FONLL dσJ/ψ dσJ/ψ←h B model fB (pT ) = , (2.12) dpT dpT which is the ratio of the differential cross section for non-prompt J/ψ obtained by an implementation of pQCD calculations at fixed order with next-to leading-log resummation (FONLL) [71] to that for inclusive J/ψ, parameterized by the phenomenological function defined in eq. (2.3). A similar fit is then performed to the CDF results [57] in pp̄ collisions √ √ at s = 1.96 TeV. Finally, the fBpp (pT ) value at s = 2.76 TeV is determined by an energy interpolation, which gives fBpp = 0.122 ± 0.010 in the integrated pT range 1.5– – 12 – JHEP07(2015)051 Figure 3. The invariant mass (upper panel) and pseudo-proper decay length (lower panel) distributions for e+ e− pairs with pT > 1.5 GeV/c in Pb-Pb collisions in the centrality interval 10– √ 50% at sNN = 2.76 TeV. The projections of the maximum likelihood fit used to extract fB are superimposed to the data. 1.5 < pT < 10 GeV/c Centr. 0–10% Type Centr. Centr. Centr. pT pT 0–10% 10–40% 40–90% 1.5–4.5 GeV/c 4.5–10 GeV/c Resolution function 23 15 10 28 12 I P.d.f. for non-prompt J/ψ 4 3 3 4 3 I P.d.f. for the background 22 15 5 23 19 II MC pT distribution 5 5 5 5 3 I P.d.f. for the invariant mass of signal 5 3 2 5 3 I P.d.f. for the invariant mass of background 7 5 3 7 5 II Total 34 23 13 38 24 Source 10 GeV/c. The quoted uncertainty includes: (i) a component from the fit procedure, which depends on the uncertainties of both data and FONLL predictions; (ii) the systematic uncertainty due to the energy interpolation, which has been estimated by considering √ different functional forms of the s dependency (linear, exponential and power law); (iii) an additional systematic uncertainty, which has been obtained by repeating the whole fitting procedure after excluding, one at a time, the data samples used for the fB fit in pp √ collisions at s = 7 TeV. 3 Results Figure 4 shows the hpT i of inclusive J/ψ for the three analyzed centrality intervals. The numerical values for hpT i are summarized in table 4. As a reference, the hpT i in pp collisions at the same centre-of-mass energy, as determined by the interpolation method described in section 2.1, is also presented. The hpT i for Pb-Pb collisions is significantly smaller than that for pp collisions. Such a behaviour is not observed at smaller centre-of-mass energies (see left panel of figure 4), for which no significant system size dependence of hpT i is seen. This might indicate the onset of processes which either deplete the high pT region or enhance the J/ψ production at low pT in heavy-ion collisions at the LHC. The latter effect would be expected as a consequence of a significant contribution from cc̄ coalescence. It has been suggested [77] that the observable rAA = hp2T iAA /hp2T ipp should be particularly sensitive to medium modifications affecting the J/ψ transverse momentum distribu√ tions. The measured hp2T i values for Pb-Pb collisions at sNN = 2.76 TeV are summarized in table 4. The corresponding rAA values as a function of hNpart i are shown in figure 5 and are found to be significantly below unity. This is in contrast to results from lower √ centre-of-mass energies, where either values consistent with unity (PHENIX at sNN = √ 0.2 TeV [9, 72]) or around 1.5 (NA50 at sNN = 17.3 GeV [73]) were obtained (see left panel of figure 5). The measured hNpart i dependences of hpT i and rAA are compared with a transport model for inclusive J/ψ by Zhao et al. [75, 76] in the right panels of figures 4 and 5. This model includes regeneration and dissociation processes, based on in-medium – 13 – JHEP07(2015)051 Table 3. Systematic uncertainties (in percent) on the measurement of the fraction fB of J/ψ from the decay of beauty hadrons, for different centrality intervals in the transverse momentum range 1.5 < pT < 10 GeV/c, and in the two pT intervals for the most central collisions. The contributions which are fully correlated between the different centrality classes are denoted as type I, the uncorrelated ones as type II. Centrality 0–10% 10–40% 40–90% pp hpT i (GeV/c) 2.23 ± 0.10 ± 0.08 2.01 ± 0.12 ± 0.08 2.02 ± 0.19 ± 0.29 2.54 ± 0.02 ± 0.01 hp2T i (GeV 2 /c2 ) 5.50 ± 0.58 ± 0.25 4.97 ± 0.65 ± 0.34 5.15 ± 1.05 ± 1.23 9.07 ± 0.15 ± 0.07 Table 4. The numerical values of hpT i and hp2T i calculated in the range 0 < pT < 10 GeV/c for the three analyzed centrality intervals in Pb-Pb collisions (the first uncertainty is the statistical and the second is the uncorrelated systematic (type II), the correlated uncertainty has a value of 2%, see table 2). The values for pp collisions obtained by the interpolation procedure are given as a reference. J/ψ spectral functions, throughout the evolution of a thermally expanding fireball. It also incorporates nuclear shadowing by reducing the input charm cross section by a factor of up to 1/3, with a centrality dependence as estimated in [78]. There is a fair agreement between our hpT i results and the model calculation, while the rAA is not described by this prediction. Our hpT i and rAA results are also compared with the calculations by Zhou et al. [74]. These calculations are also based on a transport approach and incorporate dissociation and regeneration of J/ψ and heavier charmonia, as well as nuclear shadowing – 14 – JHEP07(2015)051 Figure 4. The average transverse momentum hpT i of inclusive J/ψ measured at mid-rapidity (|y| < 0.8) in centrality selected Pb-Pb collisions (filled circles) and pp collisions (open circles) at √ sNN = 2.76 TeV as a function of the number of participants hNpart i. The uncorrelated systematic uncertainties (type II) are depicted by the open boxes. Left panel: a comparison to results obtained √ by the PHENIX collaboration for Au-Au and Cu-Cu collisions at sNN = 0.2 TeV [9, 72] (open √ and filled diamonds) and by the NA50 collaboration for Pb-Pb collisions at sNN = 17.3 GeV [73] (crosses). The hpT i values are calculated for NA50 and PHENIX in the pT interval 0–5 GeV/c, while for ALICE the pT interval is 0–10 GeV/c. Right panel: hpT i is compared to theory predictions by Zhou et al. [74] and Zhao et al. [75, 76] for the pT interval 0–10 GeV/c. according to EKS98 [51]. While the most central data point is matched by the prediction, it does not describe the evolution of rAA towards peripheral collisions. It must be noted that our results from Pb-Pb collisions at forward rapidity [79] exhibit a continuous decrease of hpT i and rAA from peripheral towards central events and are thus closer to the theory predictions, while the behaviour of mid-rapidity Pb-Pb results is more compatible with a flat hNpart i dependence. The RAA of inclusive J/ψ in three pT intervals is shown in figure 6 along with the results by the CMS collaboration for the interval 6.5 < pT < 30 GeV/c [13], both in 0–40% most central Pb-Pb collisions. The corresponding numerical values are 0.82 ± 0.11(stat.) ± 0.10(syst.) for the interval 0 < pT < 2.5 GeV/c and 0.58 ± 0.06(stat.) ± 0.08(syst.) for 2.5 < pT < 6 GeV/c, where the systematic uncertainties quoted here are the uncorrelated (type II) ones, as listed in table 1. The data point for 4.5 < pT < 10 GeV/c corresponds to the RAA value given in table 5 (centrality range 0–50%). Table 5 also contains the RAA values for prompt J/ψ, which are numerically identical to the ones for inclusive J/ψ. The inclusive RAA values below pT = 6 GeV/c are significantly higher than those measured at higher pT , corresponding to a decrease of RAA with increasing pT , while the high pT data point is close to the CMS measurement. This pT dependence is similar to the one observed at forward rapidity [12], and is in clear contrast to the pT dependence measured at lower – 15 – JHEP07(2015)051 Figure 5. The ratio rAA = hp2T iAA /hp2T ipp in the pT interval 0–10 GeV/c for inclusive J/ψ mea√ sured at mid-rapidity (|y| < 0.8) in centrality selected Pb-Pb collisions (filled circles) at sNN = 2.76 TeV as a function of the number of participants hNpart i. The uncorrelated systematic uncertainties (type II) are depicted by the open boxes, while correlated uncertainty (type I) is shown as the filled box at unity. Left panel: a comparison to results obtained by the PHENIX collaboration √ for Au-Au and Cu-Cu collisions at sNN = 0.2 TeV [9, 72] (filled diamonds) and by the NA50 √ collaboration for Pb-Pb collisions at sNN = 17.3 GeV [73] (crosses). The PHENIX and NA50 rAA values are calculated in the pT interval 0–5 GeV/c. Right panel: rAA is compared to theory predictions by Zhou et al. [74] and Zhao et al. [75, 76] for the pT interval 0–10 GeV/c. √ centre-of-mass energies by the PHENIX collaboration for sNN = 0.2 TeV [9]. Figure 6 also shows the model predictions by Zhou et al. [74]. The value of the predicted RAA is systematically below the measurement and exhibits a pT dependence similar to the one in the data. The prediction by Zhao et al. [75, 76] is close to our result. In both models, the rise of RAA towards pT = 0 is due to the dominant contribution from J/ψ regeneration via coalescence. The fraction of non-prompt J/ψ in the pT range 1.5–10 GeV/c is shown as a function of the number of participants for the centrality intervals 40–90% (hNpart i = 38), 10–40% (hNpart i = 192), and 0–10% (hNpart i = 356) in the left panel of figure 7. Within uncertainties, no centrality dependence is observed. The pT dependence of fB (centrality: 0–50%) is shown in the right panel of figure 7 and compared with the measurements by CMS in the centrality interval 0–100% and pT > 6.5 GeV/c (for the numerical values see table 5). Our results at low transverse momenta extend the CMS measurements in Pb-Pb collisions √ towards lower pT . Also shown are results at mid-rapidity in pp at s = 7 TeV (ALICE [37], √ ATLAS [35] and CMS [70]) and in pp̄ collisions at s = 1.96 TeV (CDF [57]). Considering the ALICE and CMS results in Pb-Pb collisions together, a similar pT dependence as in pp – 16 – JHEP07(2015)051 Figure 6. The nuclear modification factor RAA of inclusive J/ψ, measured at mid-rapidity √ (|y| < 0.8) in Pb-Pb collisions (0–40% most central) at sNN = 2.76 TeV, as a function of transverse momentum pT . The filled symbols are placed at the measured pT for the given interval. Since for the data point in 4.5 < pT < 10 GeV/c (open symbol, 0–50% most central) hpT i is not available due to the limited statistics, it is plotted at the centre of the pT interval. The uncorrelated systematic uncertainties (type II) are depicted by the open boxes, while the correlated uncertainties (type I) are shown as the filled boxes at unity. The data are compared to corresponding results by PHENIX √ for Au-Au collisions (0–40% most central) at sNN = 0.2 TeV [9], by CMS for Pb-Pb collisions √ (0–40% most central) at sNN = 2.76 TeV [13], and to predictions by the model of Zhou et al. [74] and Zhao et al. [75, 76]. pT (GeV/c) fB (%) RAA (inclusive J/ψ) RAA (prompt J/ψ) RAA (non-prompt J/ψ) 0.0–1.5 – 0.89±0.20±0.21 – – 1.5–4.5 10.7±4.8±2.5 0.76±0.09±0.08 0.76±0.10±0.08 0.73±0.34±0.20 4.5–10.0 17.0±6.1±2.2 0.38±0.07±0.06 0.38±0.07±0.06 0.37±0.15±0.09 Table 5. The numerical values on the fraction of J/ψ from beauty hadron decays fB at midrapidity and the nuclear modification factors RAA of inclusive, prompt and non-prompt J/ψ for √ Pb-Pb collisions at s = 2.76 TeV. These results correspond to the centrality interval 0–50%. The first uncertainty is statistical and the second uncorrelated systematic (type II). is observed. However, this similarity could be coincidental, being due to a compensation of the medium effects on the prompt component (J/ψ dissociation and recombination) and on the non-prompt part (b-quark energy loss). In figure 8 the nuclear modification factor for non-prompt J/ψ for 1.5 < pT < 4.5 GeV/c and 4.5 < pT < 10 GeV/c is shown together with the result by CMS for 6.5 < pT < 30 GeV/c [13] and with theoretical model predictions [30, 31, 59–61, 80–85]. One should note that the centrality ranges are not the same for ALICE (0–50%) and CMS (0–20% and 20–100%). However, the results obtained by CMS for these two centrality bins are compatible with each other, and also compatible with our measurement in the high pT interval (4.5 < pT < 10 GeV/c). The model by Uphoff et al. [61] follows a partonic transport approach based on the Boltzmann equation, which allows interactions among all partons. It does not include radiative processes for heavy quarks. The calculation has been – 17 – JHEP07(2015)051 Figure 7. The fraction of J/ψ from beauty hadron decays fB at mid-rapidity measured in the √ pT interval 1.5 < pT < 10 GeV/c for centrality selected Pb-Pb collisions at sNN = 2.76 TeV (left). √ √ The pT dependence of fB at mid-rapidity for Pb-Pb ( sNN = 2.76 TeV, |yJ/ψ | < 0.8) and pp ( s = 7 TeV, |yJ/ψ | < 0.9) [37] collisions is compared with measurements by CDF (|yJ/ψ | < 0.6) [57], ATLAS (|yJ/ψ | < 0.75) [35], and CMS (|yJ/ψ | < 0.9) [13, 70] (right). performed for a fixed impact parameter b = 5 fm. In the model of Alberico et al. [59, 60] the propagation of the heavy quarks in the medium is described by the relativistic Langevin equation. The predicted pT dependence of RAA is strongly influenced by the choice of transport coefficients. Two values are considered, either as provided by a perturbative calculation (hard thermal loop approach) or extracted from lattice-QCD simulations. The calculations have been provided for the centrality range 0–50%. A transport approach, which is based on a strong-coupling scheme, is employed in the model of He et al. [80]. The transport is implemented using non-perturbative interactions for heavy quarks and mesons through the QGP, hadronization and hadronic phases of a nuclear collision. In particular, the elastic heavy-quark scattering in the QGP is evaluated within a thermodynamic T-matrix approach, by generating resonances close to the critical temperature that can in turn recombine into B mesons, followed by hadronic diffusion using effective hadronic scattering amplitudes. The hydrodynamic evolution of the system is quantitatively constrained by the measured transverse momentum distributions and elliptic flow of light hadrons. Radiative processes, which should improve the description at high pT , are not included in this approach. The calculations have been performed in the centrality range 0–50%. The model of Vitev et al. [30, 31] assumes the existence of open heavy flavour bound-state solutions in the QGP in the vicinity of the critical temperature. A description of beauty quark quenching is combined with B meson inelastic breakup processes. Furthermore, modified – 18 – JHEP07(2015)051 Figure 8. The nuclear modification factor RAA at mid-rapidity (|y| < 0.8) for non-prompt √ J/ψ in Pb-Pb collisions at sNN = 2.76 TeV as a function of transverse momentum pT . The ALICE measurement corresponds to the 0–50% centrality range and to the pT intervals 1.5 < pT < 4.5 GeV/c and 4.5 < pT < 10 GeV/c. The uncorrelated systematic uncertainties (type II) are depicted by the open boxes, while the correlated uncertainties (type I) are shown as filled boxes at unity. Results by CMS for higher pT in the centrality range 0–20% and 20–100% [13] are also shown (the two points have been slightly displaced horizontally for better visibility). The data are compared to theoretical predictions at mid-rapidity (see text for details). In the right panel, the ALICE result in the pT interval 4.5 < pT < 10 GeV/c is compared to theoretical predictions integrated over the same pT range. 4 Conclusions √ A study of J/ψ production at mid-rapidity in Pb-Pb collisions at sNN = 2.76 TeV has been presented. A reduction of the inclusive J/ψ hpT i is observed in Pb-Pb collisions in comparison to pp. The ratio rAA = hp2T iAA /hp2T ipp is found to be significantly below unity, corresponding to a medium-induced change in the shape of the pT spectra. The nuclear modification factor RAA depends on pT . It is around 0.8 for pT < 2.5 GeV/c and reaches, at higher pT , almost the same level of suppression as observed at RHIC energies at low pT . These observations might be indicative of a sizable contribution of charm quark coalescence to the J/ψ production at low pT . Transport models including this additional component are able to qualitatively describe the features seen in the data. The fraction of J/ψ from beauty hadron decays is determined as a function of centrality and pT . No significant centrality dependence is observed. By combining this measurement with the inclusive J/ψ results the RAA of non-prompt J/ψ is obtained in the region 1.5 < pT < 10 GeV/c, thus extending the coverage of CMS to the low pT region. The nuclear modification in the region 4.5 < pT < 10 GeV/c is found to be stronger than predicted by most of the models. – 19 – JHEP07(2015)051 beauty parton distribution functions and beauty fragmentation functions in a co-moving plasma are implemented in this calculation. The prediction is shown for a fixed centrality, corresponding to hNpart i = 200, a value very close to the average number of participants in the centrality range 0–50%. In the model, a sizable fraction of the suppression is ascribed to the inelastic break-up processes (collisional dissociation), as can be deduced from figure 8 by comparing the full model prediction with and without the contribution of this specific process. The model of Djordjevic [81], shown in figure 8 for the centrality range 0–50%, uses a formalism that takes into account finite size dynamical QCD medium with finite magnetic mass effects and running coupling. In the WHDG model [82] (centrality range 0–50%) the energy loss is computed using perturbative QCD and considering both elastic and inelastic partonic collisions and path length fluctuations. The approach of Aichelin et al. [83, 84] includes a contribution of radiative gluon emission in the interaction of heavy quarks with light quarks, which are considered as dynamical scattering centers. In this model the relative contribution to the energy loss by radiative processes, as compared to collisional ones, is influenced by introducing a finite gluon mass. The results of the model shown in figure 8, which are obtained for the centrality range 0–50%, correspond to either a pure collisional scenario or a combination of collisional and radiative energy loss. Finally, in the model of Horowitz and Gyulassy [85], also applied to the centrality interval 0–50%, the string inspired AdS/CFT gravity-gauge theory correspondence [86, 87] is applied to the case of heavy quark energy loss. In the right hand inset of figure 8, the ALICE RAA value, integrated over the range 4.5 < pT < 10 GeV/c, is compared to theoretical predictions computed in the same pT range. Most of the models predict a larger value of RAA than observed in the measurement. However, more precise data are needed to discriminate among the different models. The next LHC run will provide increased statistics for this measurement. Acknowledgments – 20 – JHEP07(2015)051 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 accelerator teams for the outstanding performance of the LHC complex. The ALICE Collaboration gratefully acknowledges the resources and support 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 building and running the ALICE detector: State Committee of Science, World Federation of Scientists (WFS) and Swiss Fonds Kidagan, Armenia, Conselho Nacional de Desenvolvimento Cientı́fico e Tecnológico (CNPq), Financiadora de Estudos e Projetos (FINEP), Fundação de Amparo à Pesquisa do Estado de São 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 Bundesministerium fur Bildung, Wissenschaft, Forschung und Technologie (BMBF) and the Helmholtz Association; General Secretariat for Research and Technology, Ministry of Development, Greece; Hungarian Orszagos Tudomanyos Kutatasi Alappgrammok (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); Consejo Nacional de Cienca y Tecnologia (CONACYT), Direccion General de Asuntos del Personal Academico(DGAPA), México, Amerique Latine Formation academique – European Commission(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); National Science Centre, Poland; Ministry of National Education/Institute for Atomic Physics and Consiliul National al Cercetǎrii Ştiintifice – Executive Agency for Higher Education Research Development and Innovation Funding (CNCS-UEFISCDI) – Romania; 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; Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas (CIEMAT), E-Infrastructure shared between Europe and Latin America (EELA), Ministerio de Economı́a y Competitividad (MINECO) of Spain, Xunta de Galicia (Consellerı́a de Educación), Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear (CEADEN), Cubaenergı́a, 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); The United States Department of Energy, the United States National Science Foundation, the State of Texas, and the State 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 References [1] F. Karsch, Lattice simulations of the thermodynamics of strongly interacting elementary particles and the exploration of new phases of matter in relativistic heavy ion collisions, J. Phys. Conf. Ser. 46 (2006) 122 [hep-lat/0608003] [INSPIRE]. [2] Wuppertal-Budapest collaboration, S. Borsányi et al., Is there still any Tc mystery in lattice QCD? Results with physical masses in the continuum limit III, JHEP 09 (2010) 073 [arXiv:1005.3508] [INSPIRE]. [3] S. Borsányi et al., The QCD equation of state with dynamical quarks, JHEP 11 (2010) 077 [arXiv:1007.2580] [INSPIRE]. [4] A. Bazavov et al., The chiral and deconfinement aspects of the QCD transition, Phys. Rev. D 85 (2012) 054503 [arXiv:1111.1710] [INSPIRE]. [5] T. Matsui and H. Satz, J/ψ Suppression by Quark-Gluon Plasma Formation, Phys. Lett. B 178 (1986) 416 [INSPIRE]. [6] NA50 collaboration, B. Alessandro et al., A new measurement of J/ψ suppression in Pb-Pb collisions at 158-GeV per nucleon, Eur. Phys. J. C 39 (2005) 335 [hep-ex/0412036] [INSPIRE]. [7] NA60 collaboration, R. Arnaldi, J/ψ production in p-A and A-A collisions at fixed target experiments, Nucl. Phys. A 830 (2009) 345C–352C [arXiv:0907.5004] [INSPIRE]. [8] N. Brambilla et al., Heavy quarkonium: progress, puzzles and opportunities, Eur. Phys. J. C 71 (2011) 1534 [arXiv:1010.5827] [INSPIRE]. [9] PHENIX collaboration, A. Adare et al., J/ψ Production vs Centrality, Transverse √ Momentum and Rapidity in Au+Au Collisions at sN N = 200 GeV, Phys. Rev. Lett. 98 (2007) 232301 [nucl-ex/0611020] [INSPIRE]. [10] PHENIX collaboration, A. Adare et al., J/ψ suppression at forward rapidity in Au+Au √ collisions at sN N = 200 GeV, Phys. Rev. C 84 (2011) 054912 [arXiv:1103.6269] [INSPIRE]. [11] ALICE collaboration, J/ψ suppression at forward rapidity in Pb-Pb collisions at √ sN N = 2.76 TeV, Phys. Rev. Lett. 109 (2012) 072301 [arXiv:1202.1383] [INSPIRE]. [12] ALICE collaboration, Centrality, rapidity and transverse momentum dependence of J/ψ √ suppression in Pb-Pb collisions at sNN = 2.76 TeV, Phys. Lett. B 734 (2014) 314 [arXiv:1311.0214] [INSPIRE]. – 21 – JHEP07(2015)051 Open Access. This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited. [13] CMS collaboration, Suppression of non-prompt J/ψ, prompt J/ψ and Y(1S) in PbPb √ collisions at sN N = 2.76 TeV, JHEP 05 (2012) 063 [arXiv:1201.5069] [INSPIRE]. [14] P. Braun-Munzinger and J. Stachel, (Non)thermal aspects of charmonium production and a new look at J/ψ suppression, Phys. Lett. B 490 (2000) 196 [nucl-th/0007059] [INSPIRE]. [15] R.L. Thews, M. Schroedter and J. Rafelski, Enhanced J/ψ production in deconfined quark matter, Phys. Rev. C 63 (2001) 054905 [hep-ph/0007323] [INSPIRE]. [16] M.I. Gorenstein, A.P. Kostyuk, H. Stoecker and W. Greiner, Statistical coalescence model with exact charm conservation, Phys. Lett. B 509 (2001) 277 [hep-ph/0010148] [INSPIRE]. [18] X. Zhao and R. Rapp, Transverse Momentum Spectra of J/ψ in Heavy-Ion Collisions, Phys. Lett. B 664 (2008) 253 [arXiv:0712.2407] [INSPIRE]. [19] Y.-p. Liu, Z. Qu, N. Xu and P.-f. Zhuang, J/ψ Transverse Momentum Distribution in High Energy Nuclear Collisions at RHIC, Phys. Lett. B 678 (2009) 72 [arXiv:0901.2757] [INSPIRE]. √ [20] ALICE collaboration, J/ψ Elliptic Flow in Pb-Pb Collisions at sNN = 2.76 TeV, Phys. Rev. Lett. 111 (2013) 162301 [arXiv:1303.5880] [INSPIRE]. [21] M. Gyulassy and M. Plumer, Jet Quenching in Dense Matter, Phys. Lett. B 243 (1990) 432 [INSPIRE]. [22] R. Baier, Y.L. Dokshitzer, A.H. Mueller, S. Peigne and D. Schiff, Radiative energy loss and pT broadening of high-energy partons in nuclei, Nucl. Phys. B 484 (1997) 265 [hep-ph/9608322] [INSPIRE]. [23] M.H. Thoma and M. Gyulassy, Quark Damping and Energy Loss in the High Temperature QCD, Nucl. Phys. B 351 (1991) 491 [INSPIRE]. [24] E. Braaten and M.H. Thoma, Energy loss of a heavy fermion in a hot plasma, Phys. Rev. D 44 (1991) 1298 [INSPIRE]. [25] E. Braaten and M.H. Thoma, Energy loss of a heavy quark in the quark-gluon plasma, Phys. Rev. D 44 (1991) 2625 [INSPIRE]. [26] Y.L. Dokshitzer and D.E. Kharzeev, Heavy quark colorimetry of QCD matter, Phys. Lett. B 519 (2001) 199 [hep-ph/0106202] [INSPIRE]. [27] N. Armesto, C.A. Salgado and U.A. Wiedemann, Medium induced gluon radiation off massive quarks fills the dead cone, Phys. Rev. D 69 (2004) 114003 [hep-ph/0312106] [INSPIRE]. [28] S. Wicks, W. Horowitz, M. Djordjevic and M. Gyulassy, Heavy quark jet quenching with collisional plus radiative energy loss and path length fluctuations, Nucl. Phys. A 783 (2007) 493 [nucl-th/0701063] [INSPIRE]. [29] B.-W. Zhang, E. Wang and X.-N. Wang, Heavy quark energy loss in nuclear medium, Phys. Rev. Lett. 93 (2004) 072301 [nucl-th/0309040] [INSPIRE]. [30] R. Sharma, I. Vitev and B.-W. Zhang, Light-cone wave function approach to open heavy flavor dynamics in QCD matter, Phys. Rev. C 80 (2009) 054902 [arXiv:0904.0032] [INSPIRE]. [31] R. Sharma and I. Vitev, High transverse momentum quarkonium production and dissociation in heavy ion collisions, Phys. Rev. C 87 (2013) 044905 [arXiv:1203.0329] [INSPIRE]. – 22 – JHEP07(2015)051 [17] A. Andronic, P. Braun-Munzinger, K. Redlich and J. Stachel, Statistical hadronization of charm in heavy ion collisions at SPS, RHIC and LHC, Phys. Lett. B 571 (2003) 36 [nucl-th/0303036] [INSPIRE]. [32] A. Adil and I. Vitev, Collisional dissociation of heavy mesons in dense QCD matter, Phys. Lett. B 649 (2007) 139 [hep-ph/0611109] [INSPIRE]. [33] P. Faccioli, C. Lourenco, J. Seixas and H.K. Woehri, Study of ψ 0 and χc decays as feed-down sources of J/ψ hadro-production, JHEP 10 (2008) 004 [arXiv:0809.2153] [INSPIRE]. [34] A. Mócsy and P. Petreczky, Color screening melts quarkonium, Phys. Rev. Lett. 99 (2007) 211602 [arXiv:0706.2183] [INSPIRE]. [37] ALICE collaboration, Measurement of prompt J/ψ and beauty hadron production cross √ sections at mid-rapidity in pp collisions at s = 7 TeV, JHEP 11 (2012) 065 [arXiv:1205.5880] [INSPIRE]. [38] ALICE collaboration, The ALICE experiment at the CERN LHC, 2008 JINST 3 S08002 [INSPIRE]. [39] ALICE collaboration, Alignment of the ALICE Inner Tracking System with cosmic-ray tracks, 2010 JINST 5 P03003 [arXiv:1001.0502] [INSPIRE]. [40] J. Alme et al., The ALICE TPC, a large 3-dimensional tracking device with fast readout for ultra-high multiplicity events, Nucl. Instrum. Meth. A 622 (2010) 316 [arXiv:1001.1950] [INSPIRE]. [41] ALICE collaboration, Performance of the ALICE VZERO system, 2013 JINST 8 P10016 [arXiv:1306.3130] [INSPIRE]. [42] ALICE collaboration, Measurement of the Cross Section for Electromagnetic Dissociation √ with Neutron Emission in Pb-Pb Collisions at sN N = 2.76 TeV, Phys. Rev. Lett. 109 (2012) 252302 [arXiv:1203.2436] [INSPIRE]. √ [43] ALICE collaboration, Centrality determination of Pb-Pb collisions at sN N = 2.76 TeV with ALICE, Phys. Rev. C 88 (2013) 044909 [arXiv:1301.4361] [INSPIRE]. [44] ALICE collaboration, Rapidity and transverse momentum dependence of inclusive J/ψ √ production in pp collisions at s = 7 TeV, Phys. Lett. B 704 (2011) 442 [arXiv:1105.0380] [INSPIRE]. [45] ALICE collaboration, Performance of the ALICE Experiment at the CERN LHC, Int. J. Mod. Phys. A 29 (2014) 1430044 [arXiv:1402.4476] [INSPIRE]. √ [46] ALICE collaboration, J/ψ polarization in pp collisions at s = 7 TeV, Phys. Rev. Lett. 108 (2012) 082001 [arXiv:1111.1630] [INSPIRE]. [47] CMS collaboration, Measurement of the prompt J/ψ and ψ(2S) polarizations in pp collisions √ at s = 7 TeV, Phys. Lett. B 727 (2013) 381 [arXiv:1307.6070] [INSPIRE]. √ [48] LHCb collaboration, Measurement of J/ψ polarization in pp collisions at s = 7 TeV, Eur. Phys. J. C 73 (2013) 2631 [arXiv:1307.6379] [INSPIRE]. [49] X.-N. Wang and M. Gyulassy, HIJING: A Monte Carlo model for multiple jet production in p p, p A and A A collisions, Phys. Rev. D 44 (1991) 3501 [INSPIRE]. [50] F. Bossu et al., Phenomenological interpolation of the inclusive J/ψ cross section to proton-proton collisions at 2.76 TeV and 5.5 TeV, arXiv:1103.2394 [INSPIRE]. – 23 – JHEP07(2015)051 [35] ATLAS collaboration, Measurement of the differential cross-sections of inclusive, prompt √ and non-prompt J/ψ production in proton-proton collisions at s = 7 TeV, Nucl. Phys. B 850 (2011) 387 [arXiv:1104.3038] [INSPIRE]. √ [36] CMS collaboration, J/ψ and ψ(2S) production in pp collisions at s = 7 TeV, JHEP 02 (2012) 011 [arXiv:1111.1557] [INSPIRE]. [51] K.J. Eskola, V.J. Kolhinen and C.A. Salgado, The Scale dependent nuclear effects in parton distributions for practical applications, Eur. Phys. J. C 9 (1999) 61 [hep-ph/9807297] [INSPIRE]. [52] D.J. Lange, The EvtGen particle decay simulation package, Nucl. Instrum. Meth. A 462 (2001) 152 [INSPIRE]. [53] E. Barberio and Z. Was, PHOTOS: A Universal Monte Carlo for QED radiative corrections. Version 2.0, Comput. Phys. Commun. 79 (1994) 291 [INSPIRE]. [56] PHENIX collaboration, A. Adare et al., J/ψ production versus transverse momentum and √ rapidity in p+ p collisions at s = 200-GeV, Phys. Rev. Lett. 98 (2007) 232002 [hep-ex/0611020] [INSPIRE]. [57] CDF collaboration, Measurement of the J/ψ meson and b−hadron production cross sections √ in pp̄ collisions at s = 1960 GeV, Phys. Rev. D 71 (2005) 032001 [hep-ex/0412071] [INSPIRE]. [58] Particle Data Group collaboration, K. Olive et al., Review of Particle Physics, Chin. Phys. C 38 (2014) 090001. [59] W.M. Alberico et al., Heavy-flavour spectra in high energy nucleus-nucleus collisions, Eur. Phys. J. C 71 (2011) 1666 [arXiv:1101.6008] [INSPIRE]. [60] W.M. Alberico, et al., Heavy flavors in AA collisions: production, transport and final spectra, Eur. Phys. J. C 73 (2013) 2481 [arXiv:1305.7421] [INSPIRE]. [61] J. Uphoff, O. Fochler, Z. Xu and C. Greiner, Open Heavy Flavor in Pb+Pb Collisions at √ s = 2.76 TeV within a Transport Model, Phys. Lett. B 717 (2012) 430 [arXiv:1205.4945] [INSPIRE]. [62] BaBar collaboration, B. Aubert et al., Study of inclusive production of charmonium mesons in B decay, Phys. Rev. D 67 (2003) 032002 [hep-ex/0207097] [INSPIRE]. √ [63] LHCb collaboration, Measurement of J/ψ production in pp collisions at s = 7 TeV, Eur. Phys. J. C 71 (2011) 1645 [arXiv:1103.0423] [INSPIRE]. [64] CDF collaboration, Polarization of J/ψ and ψ2S mesons produced in pp̄ collisions at √ s = 1.96-TeV, Phys. Rev. Lett. 99 (2007) 132001 [arXiv:0704.0638] [INSPIRE]. [65] ALICE collaboration, Suppression of high transverse momentum D mesons in central Pb-Pb √ collisions at sN N = 2.76 TeV, JHEP 09 (2012) 112 [arXiv:1203.2160] [INSPIRE]. [66] ALICE collaboration, Technical Design Report for the Upgrade of the ALICE Inner Tracking System, J. Phys. G 41 (2014) 087002 [INSPIRE]. [67] T. Sjöstrand, S. Mrenna and P.Z. Skands, PYTHIA 6.4 Physics and Manual, JHEP 05 (2006) 026 [hep-ph/0603175] [INSPIRE]. [68] P.Z. Skands, Tuning Monte Carlo Generators: The Perugia Tunes, Phys. Rev. D 82 (2010) 074018 [arXiv:1005.3457] [INSPIRE]. [69] ALICE collaboration, K. Koch, π 0 and η measurement with photon conversions in ALICE √ in proton-proton collisions at s = 7 TeV, Nucl. Phys. A 855 (2011) 281 [arXiv:1103.2217] [INSPIRE]. – 24 – JHEP07(2015)051 [54] R. Brun, F. Carminati and S. Giani, GEANT Detector Description and Simulation Tool, CERN-W5013, CERN-W-5013 (1994). √ [55] ALICE collaboration, Inclusive J/ψ production in pp collisions at s = 2.76 TeV, Phys. Lett. B 718 (2012) 295 [arXiv:1203.3641] [INSPIRE]. [70] CMS collaboration, Prompt and non-prompt J/ψ production in pp collisions at Eur. Phys. J. C 71 (2011) 1575 [arXiv:1011.4193] [INSPIRE]. √ s = 7 TeV, [71] M. Cacciari et al., Theoretical predictions for charm and bottom production at the LHC, JHEP 10 (2012) 137 [arXiv:1205.6344] [INSPIRE]. √ [72] PHENIX collaboration, A. Adare et al., J/ψ Production in sN N = 200 GeV Cu+Cu Collisions, Phys. Rev. Lett. 101 (2008) 122301 [arXiv:0801.0220] [INSPIRE]. [73] NA50 collaboration, M.C. Abreu et al., Transverse momentum distributions of J/ψ, ψ 0 , Drell-Yan and continuum dimuons produced in Pb Pb interactions at the SPS, Phys. Lett. B 499 (2001) 85 [INSPIRE]. [75] X. Zhao and R. Rapp, Charmonium in Medium: From Correlators to Experiment, Phys. Rev. C 82 (2010) 064905 [arXiv:1008.5328] [INSPIRE]. [76] X. Zhao and R. Rapp, Medium Modifications and Production of Charmonia at LHC, Nucl. Phys. A 859 (2011) 114 [arXiv:1102.2194] [INSPIRE]. [77] K. Zhou, N. Xu and P. Zhuang, Quarkonium Production and Medium Effects in High Energy Nuclear Collisions, arXiv:1309.7520 [INSPIRE]. [78] K. Tuchin, Forward hadron production in high energy pA collisions: From RHIC to LHC, Nucl. Phys. A 798 (2008) 61 [arXiv:0705.2193] [INSPIRE]. [79] ALICE collaboration, Differential studies of J/ψ and ψ(2S) production in Pb-Pb collisions √ at sN N = 2.76 TeV, arXiv:1506.08804. [80] M. He, R.J. Fries and R. Rapp, Heavy Flavor at the Large Hadron Collider in a Strong Coupling Approach, Phys. Lett. B 735 (2014) 445 [arXiv:1401.3817] [INSPIRE]. [81] M. Djordjevic and M. Djordjevic, LHC jet suppression of light and heavy flavor observables, Phys. Lett. B 734 (2014) 286 [arXiv:1307.4098] [INSPIRE]. [82] S. Wicks, W. Horowitz, M. Djordjevic and M. Gyulassy, Elastic, inelastic and path length fluctuations in jet tomography, Nucl. Phys. A 784 (2007) 426 [nucl-th/0512076] [INSPIRE]. [83] J. Aichelin, P.B. Gossiaux and T. Gousset, Gluon radiation by heavy quarks at intermediate energies, Phys. Rev. D 89 (2014) 074018 [arXiv:1307.5270] [INSPIRE]. [84] P.B. Gossiaux et al., Gluon radiation by heavy quarks at intermediate energies and consequences for the mass hierarchy of energy loss, Nucl. Phys. A 931 (2014) 581 [arXiv:1409.0900] [INSPIRE]. [85] W.A. Horowitz and M. Gyulassy, Heavy quark jet tomography of Pb + Pb at LHC: AdS/CFT drag or pQCD energy loss?, Phys. Lett. B 666 (2008) 320 [arXiv:0706.2336] [INSPIRE]. [86] J.M. Maldacena, The Large-N limit of superconformal field theories and supergravity, Int. J. Theor. Phys. 38 (1999) 1113 [hep-th/9711200] [INSPIRE]. [87] S.S. Gubser, I.R. Klebanov and A.M. Polyakov, Gauge theory correlators from noncritical string theory, Phys. Lett. B 428 (1998) 105 [hep-th/9802109] [INSPIRE]. – 25 – JHEP07(2015)051 [74] K. Zhou, N. Xu, Z. Xu and P. Zhuang, Medium effects on charmonium production at ultrarelativistic energies available at the CERN Large Hadron Collider, Phys. Rev. C 89 (2014) 054911 [arXiv:1401.5845] [INSPIRE]. The ALICE collaboration – 26 – JHEP07(2015)051 J. Adam40 , D. Adamová83 , M.M. Aggarwal87 , G. Aglieri Rinella36 , M. Agnello111 , N. Agrawal48 , Z. Ahammed132 , S.U. Ahn68 , I. Aimo94 ,111 , S. Aiola137 , M. Ajaz16 , A. Akindinov58 , S.N. Alam132 , D. Aleksandrov100 , B. Alessandro111 , D. Alexandre102 , R. Alfaro Molina64 , A. Alici105 ,12 , A. Alkin3 , J. Alme38 , T. Alt43 , S. Altinpinar18 , I. Altsybeev131 , C. Alves Garcia Prado120 , C. Andrei78 , A. Andronic97 , V. Anguelov93 , J. Anielski54 , T. Antičić98 , F. Antinori108 , P. Antonioli105 , L. Aphecetche113 , H. Appelshäuser53 , S. Arcelli28 , N. Armesto17 , R. Arnaldi111 , I.C. Arsene22 , M. Arslandok53 , B. Audurier113 , A. Augustinus36 , R. Averbeck97 , M.D. Azmi19 , M. Bach43 , A. Badalà107 , Y.W. Baek44 , S. Bagnasco111 , R. Bailhache53 , R. Bala90 , A. Baldisseri15 , F. Baltasar Dos Santos Pedrosa36 , R.C. Baral61 , A.M. Barbano111 , R. Barbera29 , F. Barile33 , G.G. Barnaföldi136 , L.S. Barnby102 , V. Barret70 , P. Bartalini7 , K. Barth36 , J. Bartke117 , E. Bartsch53 , M. Basile28 , N. Bastid70 , S. Basu132 , B. Bathen54 , G. Batigne113 , A. Batista Camejo70 , B. Batyunya66 , P.C. Batzing22 , I.G. Bearden80 , H. Beck53 , C. Bedda111 , N.K. Behera49 ,48 , I. Belikov55 , F. Bellini28 , H. Bello Martinez2 , R. Bellwied122 , R. Belmont135 , E. Belmont-Moreno64 , V. Belyaev76 , G. Bencedi136 , S. Beole27 , I. Berceanu78 , A. Bercuci78 , Y. Berdnikov85 , D. Berenyi136 , R.A. Bertens57 , D. Berzano36 ,27 , L. Betev36 , A. Bhasin90 , I.R. Bhat90 , A.K. Bhati87 , B. Bhattacharjee45 , J. Bhom128 , L. Bianchi122 , N. Bianchi72 , C. Bianchin135 ,57 , J. Bielčı́k40 , J. Bielčı́ková83 , A. Bilandzic80 , R. Biswas4 , S. Biswas79 , S. Bjelogrlic57 , F. Blanco10 , D. Blau100 , C. Blume53 , F. Bock74 ,93 , A. Bogdanov76 , H. Bøggild80 , L. Boldizsár136 , M. Bombara41 , J. Book53 , H. Borel15 , A. Borissov96 , M. Borri82 , F. Bossú65 , M. Botje81 , E. Botta27 , S. Böttger52 , P. Braun-Munzinger97 , M. Bregant120 , T. Breitner52 , T.A. Broker53 , T.A. Browning95 , M. Broz40 , E.J. Brucken46 , E. Bruna111 , G.E. Bruno33 , D. Budnikov99 , H. Buesching53 , S. Bufalino111 ,36 , P. Buncic36 , O. Busch93 ,128 , Z. Buthelezi65 , J.T. Buxton20 , D. Caffarri36 , X. Cai7 , H. Caines137 , L. Calero Diaz72 , A. Caliva57 , E. Calvo Villar103 , P. Camerini26 , F. Carena36 , W. Carena36 , J. Castillo Castellanos15 , A.J. Castro125 , E.A.R. Casula25 , C. Cavicchioli36 , C. Ceballos Sanchez9 , J. Cepila40 , P. Cerello111 , J. Cerkala115 , B. Chang123 , S. Chapeland36 , M. Chartier124 , J.L. Charvet15 , S. Chattopadhyay132 , S. Chattopadhyay101 , V. Chelnokov3 , M. Cherney86 , C. Cheshkov130 , B. Cheynis130 , V. Chibante Barroso36 , D.D. Chinellato121 , P. Chochula36 , K. Choi96 , M. Chojnacki80 , S. Choudhury132 , P. Christakoglou81 , C.H. Christensen80 , P. Christiansen34 , T. Chujo128 , S.U. Chung96 , Z. Chunhui57 , C. Cicalo106 , L. Cifarelli12 ,28 , F. Cindolo105 , J. Cleymans89 , F. Colamaria33 , D. Colella33 , A. Collu25 , M. Colocci28 , G. Conesa Balbastre71 , Z. Conesa del Valle51 , M.E. Connors137 , J.G. Contreras11 ,40 , T.M. Cormier84 , Y. Corrales Morales27 , I. Cortés Maldonado2 , P. Cortese32 , M.R. Cosentino120 , F. Costa36 , P. Crochet70 , R. Cruz Albino11 , E. Cuautle63 , L. Cunqueiro36 , T. Dahms92 ,37 , A. Dainese108 , A. Danu62 , D. Das101 , I. Das51 ,101 , S. Das4 , A. Dash121 , S. Dash48 , S. De120 , A. De Caro31 ,12 , G. de Cataldo104 , J. de Cuveland43 , A. De Falco25 , D. De Gruttola12 ,31 , N. De Marco111 , S. De Pasquale31 , A. Deisting97 ,93 , A. Deloff77 , E. Dénes136 , G. D’Erasmo33 , D. Di Bari33 , A. Di Mauro36 , P. Di Nezza72 , M.A. Diaz Corchero10 , T. Dietel89 , P. Dillenseger53 , R. Divià36 , Ø. Djuvsland18 , A. Dobrin57 ,81 , T. Dobrowolski77 , i , D. Domenicis Gimenez120 , B. Dönigus53 , O. Dordic22 , A.K. Dubey132 , A. Dubla57 , L. Ducroux130 , P. Dupieux70 , R.J. Ehlers137 , D. Elia104 , H. Engel52 , B. Erazmus36 ,113 , I. Erdemir53 , F. Erhardt129 , D. Eschweiler43 , B. Espagnon51 , M. Estienne113 , S. Esumi128 , J. Eum96 , D. Evans102 , S. Evdokimov112 , G. Eyyubova40 , L. Fabbietti37 ,92 , D. Fabris108 , J. Faivre71 , A. Fantoni72 , M. Fasel74 , L. Feldkamp54 , D. Felea62 , A. Feliciello111 , G. Feofilov131 , J. Ferencei83 , A. Fernández Téllez2 , E.G. Ferreiro17 , – 27 – JHEP07(2015)051 A. Ferretti27 , A. Festanti30 , V.J.G. Feuillard15 , J. Figiel117 , M.A.S. Figueredo124 , S. Filchagin99 , D. Finogeev56 , F.M. Fionda104 , E.M. Fiore33 , M.G. Fleck93 , M. Floris36 , S. Foertsch65 , P. Foka97 , S. Fokin100 , E. Fragiacomo110 , A. Francescon36 ,30 , U. Frankenfeld97 , U. Fuchs36 , C. Furget71 , A. Furs56 , M. Fusco Girard31 , J.J. Gaardhøje80 , M. Gagliardi27 , A.M. Gago103 , M. Gallio27 , D.R. Gangadharan74 , P. Ganoti88 , C. Gao7 , C. Garabatos97 , E. Garcia-Solis13 , C. Gargiulo36 , P. Gasik92 ,37 , M. Germain113 , A. Gheata36 , M. Gheata62 ,36 , P. Ghosh132 , S.K. Ghosh4 , P. Gianotti72 , P. Giubellino36 , P. Giubilato30 , E. Gladysz-Dziadus117 , P. Glässel93 , A. Gomez Ramirez52 , P. González-Zamora10 , S. Gorbunov43 , L. Görlich117 , S. Gotovac116 , V. Grabski64 , L.K. Graczykowski134 , K.L. Graham102 , A. Grelli57 , A. Grigoras36 , C. Grigoras36 , V. Grigoriev76 , A. Grigoryan1 , S. Grigoryan66 , B. Grinyov3 , N. Grion110 , J.F. Grosse-Oetringhaus36 , J.-Y. Grossiord130 , R. Grosso36 , F. Guber56 , R. Guernane71 , B. Guerzoni28 , K. Gulbrandsen80 , H. Gulkanyan1 , T. Gunji127 , A. Gupta90 , R. Gupta90 , R. Haake54 , Ø. Haaland18 , C. Hadjidakis51 , M. Haiduc62 , H. Hamagaki127 , G. Hamar136 , A. Hansen80 , J.W. Harris137 , H. Hartmann43 , A. Harton13 , D. Hatzifotiadou105 , S. Hayashi127 , S.T. Heckel53 , M. Heide54 , H. Helstrup38 , A. Herghelegiu78 , G. Herrera Corral11 , B.A. Hess35 , K.F. Hetland38 , T.E. Hilden46 , H. Hillemanns36 , B. Hippolyte55 , P. Hristov36 , M. Huang18 , T.J. Humanic20 , N. Hussain45 , T. Hussain19 , D. Hutter43 , D.S. Hwang21 , R. Ilkaev99 , I. Ilkiv77 , M. Inaba128 , C. Ionita36 , M. Ippolitov76 ,100 , M. Irfan19 , M. Ivanov97 , V. Ivanov85 , V. Izucheev112 , P.M. Jacobs74 , S. Jadlovska115 , C. Jahnke120 , H.J. Jang68 , M.A. Janik134 , P.H.S.Y. Jayarathna122 , C. Jena30 , S. Jena122 , R.T. Jimenez Bustamante97 , P.G. Jones102 , H. Jung44 , A. Jusko102 , P. Kalinak59 , A. Kalweit36 , J. Kamin53 , J.H. Kang138 , V. Kaplin76 , S. Kar132 , A. Karasu Uysal69 , O. Karavichev56 , T. Karavicheva56 , E. Karpechev56 , U. Kebschull52 , R. Keidel139 , D.L.D. Keijdener57 , M. Keil36 , K.H. Khan16 , M.M. Khan19 , P. Khan101 , S.A. Khan132 , A. Khanzadeev85 , Y. Kharlov112 , B. Kileng38 , B. Kim138 , D.W. Kim68 ,44 , D.J. Kim123 , H. Kim138 , J.S. Kim44 , M. Kim44 , M. Kim138 , S. Kim21 , T. Kim138 , S. Kirsch43 , I. Kisel43 , S. Kiselev58 , A. Kisiel134 , G. Kiss136 , J.L. Klay6 , C. Klein53 , J. Klein93 , C. Klein-Bösing54 , A. Kluge36 , M.L. Knichel93 , A.G. Knospe118 , T. Kobayashi128 , C. Kobdaj114 , M. Kofarago36 , T. Kollegger97 ,43 , A. Kolojvari131 , V. Kondratiev131 , N. Kondratyeva76 , E. Kondratyuk112 , A. Konevskikh56 , M. Kopcik115 , C. Kouzinopoulos36 , O. Kovalenko77 , V. Kovalenko131 , M. Kowalski117 , S. Kox71 , G. Koyithatta Meethaleveedu48 , J. Kral123 , I. Králik59 , A. Kravčáková41 , M. Krelina40 , M. Kretz43 , M. Krivda102 ,59 , F. Krizek83 , E. Kryshen36 , M. Krzewicki43 , A.M. Kubera20 , V. Kučera83 , T. Kugathasan36 , C. Kuhn55 , P.G. Kuijer81 , I. Kulakov43 , J. Kumar48 , L. Kumar79 ,87 , P. Kurashvili77 , A. Kurepin56 , A.B. Kurepin56 , A. Kuryakin99 , S. Kushpil83 , M.J. Kweon50 , Y. Kwon138 , S.L. La Pointe111 , P. La Rocca29 , C. Lagana Fernandes120 , I. Lakomov36 , R. Langoy42 , C. Lara52 , A. Lardeux15 , A. Lattuca27 , E. Laudi36 , R. Lea26 , L. Leardini93 , G.R. Lee102 , S. Lee138 , I. Legrand36 , R.C. Lemmon82 , V. Lenti104 , E. Leogrande57 , I. León Monzón119 , M. Leoncino27 , P. Lévai136 , S. Li7 ,70 , X. Li14 , J. Lien42 , R. Lietava102 , S. Lindal22 , V. Lindenstruth43 , C. Lippmann97 , M.A. Lisa20 , H.M. Ljunggren34 , D.F. Lodato57 , P.I. Loenne18 , V.R. Loggins135 , V. Loginov76 , C. Loizides74 , X. Lopez70 , E. López Torres9 , A. Lowe136 , P. Luettig53 , M. Lunardon30 , G. Luparello26 , P.H.F.N.D. Luz120 , A. Maevskaya56 , M. Mager36 , S. Mahajan90 , S.M. Mahmood22 , A. Maire55 , R.D. Majka137 , M. Malaev85 , I. Maldonado Cervantes63 , L. Malinina66 , D. Mal’Kevich58 , P. Malzacher97 , A. Mamonov99 , L. Manceau111 , V. Manko100 , F. Manso70 , V. Manzari104 ,36 , M. Marchisone27 , J. Mareš60 , G.V. Margagliotti26 , A. Margotti105 , J. Margutti57 , A. Marı́n97 , C. Markert118 , M. Marquard53 , N.A. Martin97 , J. Martin Blanco113 , P. Martinengo36 , M.I. Martı́nez2 , G. Martı́nez Garcı́a113 , M. Martinez Pedreira36 , Y. Martynov3 , A. Mas120 , S. Masciocchi97 , M. Masera27 , A. Masoni106 , L. Massacrier113 , – 28 – JHEP07(2015)051 A. Mastroserio33 , H. Masui128 , A. Matyja117 , C. Mayer117 , J. Mazer125 , M.A. Mazzoni109 , D. Mcdonald122 , F. Meddi24 , A. Menchaca-Rocha64 , E. Meninno31 , J. Mercado Pérez93 , M. Meres39 , Y. Miake128 , M.M. Mieskolainen46 , K. Mikhaylov58 ,66 , L. Milano36 , J. Milosevic22 ,133 , L.M. Minervini23 ,104 , A. Mischke57 , A.N. Mishra49 , D. Miśkowiec97 , J. Mitra132 , C.M. Mitu62 , N. Mohammadi57 , B. Mohanty79 ,132 , L. Molnar55 , L. Montaño Zetina11 , E. Montes10 , M. Morando30 , D.A. Moreira De Godoy54 ,113 , S. Moretto30 , A. Morreale113 , A. Morsch36 , V. Muccifora72 , E. Mudnic116 , D. Mühlheim54 , S. Muhuri132 , M. Mukherjee132 , J.D. Mulligan137 , M.G. Munhoz120 , S. Murray65 , L. Musa36 , J. Musinsky59 , B.K. Nandi48 , R. Nania105 , E. Nappi104 , M.U. Naru16 , C. Nattrass125 , K. Nayak79 , T.K. Nayak132 , S. Nazarenko99 , A. Nedosekin58 , L. Nellen63 , F. Ng122 , M. Nicassio97 , M. Niculescu62 ,36 , J. Niedziela36 , B.S. Nielsen80 , S. Nikolaev100 , S. Nikulin100 , V. Nikulin85 , F. Noferini12 ,105 , P. Nomokonov66 , G. Nooren57 , J. Norman124 , A. Nyanin100 , J. Nystrand18 , H. Oeschler93 , S. Oh137 , S.K. Oh67 , A. Ohlson36 , A. Okatan69 , T. Okubo47 , L. Olah136 , J. Oleniacz134 , A.C. Oliveira Da Silva120 , M.H. Oliver137 , J. Onderwaater97 , C. Oppedisano111 , A. Ortiz Velasquez63 , A. Oskarsson34 , J. Otwinowski117 , K. Oyama93 , M. Ozdemir53 , Y. Pachmayer93 , P. Pagano31 , G. Paić63 , C. Pajares17 , S.K. Pal132 , J. Pan135 , A.K. Pandey48 , D. Pant48 , P. Papcun115 , V. Papikyan1 , G.S. Pappalardo107 , P. Pareek49 , W.J. Park97 , S. Parmar87 , A. Passfeld54 , V. Paticchio104 , R.N. Patra132 , B. Paul101 , T. Peitzmann57 , H. Pereira Da Costa15 , E. Pereira De Oliveira Filho120 , D. Peresunko76 ,100 , C.E. Pérez Lara81 , V. Peskov53 , Y. Pestov5 , V. Petráček40 , V. Petrov112 , M. Petrovici78 , C. Petta29 , S. Piano110 , M. Pikna39 , P. Pillot113 , O. Pinazza105 ,36 , L. Pinsky122 , D.B. Piyarathna122 , M. Ploskoń74 , M. Planinic129 , J. Pluta134 , S. Pochybova136 , P.L.M. Podesta-Lerma119 , M.G. Poghosyan86 , B. Polichtchouk112 , N. Poljak129 , W. Poonsawat114 , A. Pop78 , S. Porteboeuf-Houssais70 , J. Porter74 , J. Pospisil83 , S.K. Prasad4 , R. Preghenella105 ,36 , F. Prino111 , C.A. Pruneau135 , I. Pshenichnov56 , M. Puccio111 , G. Puddu25 , P. Pujahari135 , V. Punin99 , J. Putschke135 , H. Qvigstad22 , A. Rachevski110 , S. Raha4 , S. Rajput90 , J. Rak123 , A. Rakotozafindrabe15 , L. Ramello32 , R. Raniwala91 , S. Raniwala91 , S.S. Räsänen46 , B.T. Rascanu53 , D. Rathee87 , K.F. Read125 , J.S. Real71 , K. Redlich77 , R.J. Reed135 , A. Rehman18 , P. Reichelt53 , F. Reidt93 ,36 , X. Ren7 , R. Renfordt53 , A.R. Reolon72 , A. Reshetin56 , F. Rettig43 , J.-P. Revol12 , K. Reygers93 , V. Riabov85 , R.A. Ricci73 , T. Richert34 , M. Richter22 , P. Riedler36 , W. Riegler36 , F. Riggi29 , C. Ristea62 , A. Rivetti111 , E. Rocco57 , M. Rodrı́guez Cahuantzi2 , A. Rodriguez Manso81 , K. Røed22 , E. Rogochaya66 , D. Rohr43 , D. Röhrich18 , R. Romita124 , F. Ronchetti72 , L. Ronflette113 , P. Rosnet70 , A. Rossi36 ,30 , F. Roukoutakis88 , A. Roy49 , C. Roy55 , P. Roy101 , A.J. Rubio Montero10 , R. Rui26 , R. Russo27 , E. Ryabinkin100 , Y. Ryabov85 , A. Rybicki117 , S. Sadovsky112 , K. Šafařı́k36 , B. Sahlmuller53 , P. Sahoo49 , R. Sahoo49 , S. Sahoo61 , P.K. Sahu61 , J. Saini132 , S. Sakai72 , M.A. Saleh135 , C.A. Salgado17 , J. Salzwedel20 , S. Sambyal90 , V. Samsonov85 , X. Sanchez Castro55 , L. Šándor59 , A. Sandoval64 , M. Sano128 , G. Santagati29 , D. Sarkar132 , E. Scapparone105 , F. Scarlassara30 , R.P. Scharenberg95 , C. Schiaua78 , R. Schicker93 , C. Schmidt97 , H.R. Schmidt35 , S. Schuchmann53 , J. Schukraft36 , M. Schulc40 , T. Schuster137 , Y. Schutz113 ,36 , K. Schwarz97 , K. Schweda97 , G. Scioli28 , E. Scomparin111 , R. Scott125 , K.S. Seeder120 , J.E. Seger86 , Y. Sekiguchi127 , D. Sekihata47 , I. Selyuzhenkov97 , K. Senosi65 , J. Seo96 ,67 , E. Serradilla64 ,10 , A. Sevcenco62 , A. Shabanov56 , A. Shabetai113 , O. Shadura3 , R. Shahoyan36 , A. Shangaraev112 , A. Sharma90 , N. Sharma61 ,125 , K. Shigaki47 , K. Shtejer9 ,27 , Y. Sibiriak100 , S. Siddhanta106 , K.M. Sielewicz36 , T. Siemiarczuk77 , D. Silvermyr84 ,34 , C. Silvestre71 , G. Simatovic129 , G. Simonetti36 , R. Singaraju132 , R. Singh79 , S. Singha79 ,132 , V. Singhal132 , B.C. Sinha132 , T. Sinha101 , B. Sitar39 , M. Sitta32 , T.B. Skaali22 , M. Slupecki123 , N. Smirnov137 , R.J.M. Snellings57 , T.W. Snellman123 , C. Søgaard34 , R. Soltz75 , J. Song96 , M. Song138 , i ii 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Deceased Also at: University of Kansas, Lawrence, Kansas, United States A.I. Alikhanyan National Science Laboratory (Yerevan Physics Institute) Foundation, Yerevan, Armenia Benemérita Universidad Autónoma 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 Tecnológicas y Desarrollo Nuclear (CEADEN), Havana, Cuba Centro de Investigaciones Energéticas Medioambientales y Tecnológicas (CIEMAT), Madrid, Spain Centro de Investigación y de Estudios Avanzados (CINVESTAV), Mexico City and Mérida, 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 – 29 – JHEP07(2015)051 Z. Song7 , F. Soramel30 , S. Sorensen125 , M. Spacek40 , E. Spiriti72 , I. Sputowska117 , M. Spyropoulou-Stassinaki88 , B.K. Srivastava95 , J. Stachel93 , I. Stan62 , G. Stefanek77 , M. Steinpreis20 , E. Stenlund34 , G. Steyn65 , J.H. Stiller93 , D. Stocco113 , P. Strmen39 , A.A.P. Suaide120 , T. Sugitate47 , C. Suire51 , M. Suleymanov16 , R. Sultanov58 , M. Šumbera83 , T.J.M. Symons74 , A. Szabo39 , A. Szanto de Toledo120 , i , I. Szarka39 , A. Szczepankiewicz36 , M. Szymanski134 , J. Takahashi121 , N. Tanaka128 , M.A. Tangaro33 , J.D. Tapia Takaki, ii,51 , A. Tarantola Peloni53 , M. Tarhini51 , M. Tariq19 , M.G. Tarzila78 , A. Tauro36 , G. Tejeda Muñoz2 , A. Telesca36 , K. Terasaki127 , C. Terrevoli30 ,25 , B. Teyssier130 , J. Thäder74 ,97 , D. Thomas118 , R. Tieulent130 , A.R. Timmins122 , A. Toia53 , S. Trogolo111 , V. Trubnikov3 , W.H. Trzaska123 , T. Tsuji127 , A. Tumkin99 , R. Turrisi108 , T.S. Tveter22 , K. Ullaland18 , A. Uras130 , G.L. Usai25 , A. Utrobicic129 , M. Vajzer83 , M. Vala59 , L. Valencia Palomo70 , S. Vallero27 , J. Van Der Maarel57 , J.W. Van Hoorne36 , M. van Leeuwen57 , T. Vanat83 , P. Vande Vyvre36 , D. Varga136 , A. Vargas2 , M. Vargyas123 , R. Varma48 , M. Vasileiou88 , A. Vasiliev100 , A. Vauthier71 , V. Vechernin131 , A.M. Veen57 , M. Veldhoen57 , A. Velure18 , M. Venaruzzo73 , E. Vercellin27 , S. Vergara Limón2 , R. Vernet8 , M. Verweij135 , L. Vickovic116 , G. Viesti30 , i , J. Viinikainen123 , Z. Vilakazi126 , O. Villalobos Baillie102 , A. Vinogradov100 , L. Vinogradov131 , Y. Vinogradov99 , T. Virgili31 , V. Vislavicius34 , Y.P. Viyogi132 , A. Vodopyanov66 , M.A. Völkl93 , K. Voloshin58 , S.A. Voloshin135 , G. Volpe136 ,36 , B. von Haller36 , I. Vorobyev92 ,37 , D. Vranic97 ,36 , J. Vrláková41 , B. Vulpescu70 , A. Vyushin99 , B. Wagner18 , J. Wagner97 , H. Wang57 , M. Wang7 ,113 , Y. Wang93 , D. Watanabe128 , Y. Watanabe127 , M. Weber36 , S.G. Weber97 , J.P. Wessels54 , U. Westerhoff54 , J. Wiechula35 , J. Wikne22 , M. Wilde54 , G. Wilk77 , J. Wilkinson93 , M.C.S. Williams105 , B. Windelband93 , M. Winn93 , C.G. Yaldo135 , H. Yang57 , P. Yang7 , S. Yano47 , Z. Yin7 , H. Yokoyama128 , I.-K. Yoo96 , V. Yurchenko3 , I. Yushmanov100 , A. Zaborowska134 , V. Zaccolo80 , A. Zaman16 , C. Zampolli105 , H.J.C. Zanoli120 , S. Zaporozhets66 , N. Zardoshti102 , A. Zarochentsev131 , P. Závada60 , N. Zaviyalov99 , H. Zbroszczyk134 , I.S. Zgura62 , M. Zhalov85 , H. Zhang18 ,7 , X. Zhang74 , Y. Zhang7 , C. Zhao22 , N. Zhigareva58 , D. Zhou7 , Y. Zhou80 ,57 , Z. Zhou18 , H. Zhu18 ,7 , J. Zhu113 ,7 , X. Zhu7 , A. Zichichi12 ,28 , A. Zimmermann93 , M.B. Zimmermann54 ,36 , G. Zinovjev3 , M. Zyzak43 15 16 17 18 19 20 21 22 23 24 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 – 30 – JHEP07(2015)051 25 Commissariat à l’Energie Atomique, IRFU, Saclay, France COMSATS Institute of Information Technology (CIIT), Islamabad, Pakistan Departamento de Fı́sica de Partı́culas and IGFAE, Universidad de Santiago de Compostela, Santiago de Compostela, 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’Università ’La Sapienza’ and Sezione INFN Rome, Italy Dipartimento di Fisica dell’Università and Sezione INFN, Cagliari, Italy Dipartimento di Fisica dell’Università and Sezione INFN, Trieste, Italy Dipartimento di Fisica dell’Università and Sezione INFN, Turin, Italy Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN, Bologna, Italy Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN, Catania, Italy Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN, Padova, Italy Dipartimento di Fisica ‘E.R. Caianiello’ dell’Università and Gruppo Collegato INFN, Salerno, Italy Dipartimento di Scienze e Innovazione Tecnologica dell’Università del Piemonte Orientale and Gruppo Collegato 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 Universität Tübingen, Tübingen, Germany European Organization for Nuclear Research (CERN), Geneva, Switzerland Excellence Cluster Universe, Technische Universität München, Munich, Germany 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. Šafárik University, Košice, Slovakia Faculty of Technology, Buskerud and Vestfold University College, Vestfold, Norway Frankfurt Institute for Advanced Studies, Johann Wolfgang Goethe-Universität 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 Nucléaire d’Orsay (IPNO), Université Paris-Sud, CNRS-IN2P3, Orsay, France Institut für Informatik, Johann Wolfgang Goethe-Universität Frankfurt, Frankfurt, Germany Institut für Kernphysik, Johann Wolfgang Goethe-Universität Frankfurt, Frankfurt, Germany Institut für Kernphysik, Westfälische Wilhelms-Universität Münster, Münster, Germany Institut Pluridisciplinaire Hubert Curien (IPHC), Université 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, Košice, Slovakia Institute of Physics, Academy of Sciences of the Czech Republic, Prague, Czech Republic Institute of Physics, Bhubaneswar, India 62 63 64 65 66 67 68 69 70 71 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 – 31 – JHEP07(2015)051 72 Institute of Space Science (ISS), Bucharest, Romania Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Mexico City, Mexico Instituto de Fı́sica, Universidad Nacional Autónoma de México, 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 Université, Université Blaise Pascal, CNRS–IN2P3, Clermont-Ferrand, France Laboratoire de Physique Subatomique et de Cosmologie, Université 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, Řež 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 Universität München, Munich, Germany Physikalisches Institut, Ruprecht-Karls-Universität 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 für Schwerionenforschung, Darmstadt, Germany Rudjer Bošković 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 Sección Fı́sica, Departamento de Ciencias, Pontificia Universidad Católica del Perú, 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 111 112 113 114 115 116 117 118 119 120 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 – 32 – View publication stats JHEP07(2015)051 121 Sezione INFN, Turin, Italy SSC IHEP of NRC Kurchatov institute, Protvino, Russia SUBATECH, Ecole des Mines de Nantes, Université de Nantes, CNRS-IN2P3, Nantes, France Suranaree University of Technology, Nakhon Ratchasima, Thailand Technical University of Košice, Košice, Slovakia 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 Autónoma de Sinaloa, Culiacán, Mexico Universidade de São Paulo (USP), São Paulo, Brazil Universidade Estadual de Campinas (UNICAMP), Campinas, Brazil University of Houston, Houston, Texas, United States University of Jyväskylä, Jyväskylä, 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 Université de Lyon, Université 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 Vinča 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 Zentrum für Technologietransfer und Telekommunikation (ZTT), Fachhochschule Worms, Worms, Germany