Energy dependence and fluctuations of anisotropic flow in Pb-Pb collisions at √sNN = 5.02 and 2.76 TeV

This is a self-archived version of an original article. This version may differ from the original in pagination and typographic details. Author(s): Title: Year: Version: Copyright: Rights: Rights url: Please cite the original version: CC BY 4.0 https://creativecommons.org/licenses/by/4.0/ Energy dependence and fluctuations of anisotropic flow in Pb-Pb collisions at √sNN = 5.02 and 2.76 TeV © The Authors 2018. CERN, for the benefit of the ALICE Collaboration. Article funded by SCOAP3. Published version ALICE Collaboration ALICE Collaboration. (2018). Energy dependence and fluctuations of anisotropic flow in Pb-Pb collisions at √sNN = 5.02 and 2.76 TeV. Journal of High Energy Physics, 2018(7), Article 103. https://doi.org/10.1007/jhep07(2018)103 2018 JHEP07(2018)103 Published for SISSA by Springer Received:May 24, 2018 Accepted:July 1, 2018 Published:July 16, 2018 Energy dependence and fluctuations of anisotropic flow in Pb–Pb collisions at √sNN = 5.02 and 2.76 TeV The ALICE collaboration E-mail: [email protected] Abstract: Measurements of anisotropic flow coefficients with twoand multi-particle cumulants for inclusive charged particles in Pb–Pb collisions at √sNN = 5.02 and 2.76 TeV are reported in the pseudorapidity range |η|<0.8 and transverse momentum 0.2< pT< 50 GeV/c. The full data sample collected by the ALICE detector in 2015 (2010), corresponding to an integrated luminosity of 12.7 (2.0) µb−1in the centrality range 0–80%, is analysed. Flow coefficients up to the sixth flow harmonic (v6) are reported and a detailed comparison among results at the two energies is carried out. The pTdependence of anisotropic flow coefficients and its evolution with respect to centrality and harmonic number nare investigated. An approximate power-law scaling of the form vn(pT)∼pn/3 T is observed for all flow harmonics at low pT(0.2< pT<3 GeV/c). At the same time, the ratios vn/vn/m mare observed to be essentially independent of pTfor most centralities up to about pT= 10 GeV/c. Analysing the differences among higher-order cumulants of elliptic flow (v2), which have different sensitivities to flow fluctuations, a measurement of the standardised skewness of the event-by-event v2distribution P(v2) is reported and constraints on its higher moments are provided. The Elliptic Power distribution is used to parametrise P(v2), extracting its parameters from fits to cumulants. The measurements are compared to different model predictions in order to discriminate among initial-state models and to constrain the temperature dependence of the shear viscosity to entropy-density ratio. Keywords: Heavy Ion Experiments ArXiv ePrint: 1804.02944 Open Access, Copyright CERN, for the benefit of the ALICE Collaboration. Article funded by SCOAP3. https://doi.org/10.1007/JHEP07(2018)103 JHEP07(2018)103 Contents 1 Introduction 1 2 Data sample and analysis methods 3 3 Collision energy, transverse momentum and centrality dependence 6 4 Elliptic flow fluctuations 14 5 Conclusions 21 A Additional figures 24 The ALICE collaboration 32 1 Introduction The primary goal of ultra-relativistic heavy-ion collisions is to study the properties of QCD matter at extremely high temperatures and/or densities and to understand the microscopic dynamics from which these properties arise, especially in the non-perturbative regime. The study of anisotropies in the azimuthal distribution of produced particles, commonly called anisotropic flow, has contributed significantly to the characterization of the system created in heavy-ion collisions [1–5]. According to the current paradigm of bulk particle production, anisotropic flow is determined by the response of the system to its initial spatial anisotropies. Initial-state spatial anisotropies come in turn from both the geometry of the collision and fluctuations in the wave function of the incident nuclei [3–8]. The significant magnitude of anisotropic flow is interpreted as evidence of the formation of a stronglycoupled system, which can effectively be described as a fluid with very low shear viscosity to entropy-density ratio (η/s) [9]. Anisotropic flow is quantified by the coefficients vnof a Fourier series decomposition of the distribution in azimuthal angle ϕof final-state particles [10] dN dϕ∝1+2 +∞ X n=1 vncos [n(ϕ−Ψn)],(1.1) where Ψncorresponds to the symmetry plane angle of order n. The dominant flow coefficient in non-central heavy-ion collisions is the second flow harmonic (v2), called elliptic flow, which is mostly a result of the average ellipsoidal shape of the overlapping area between the colliding nuclei, whereas higher harmonics originate from initial-state fluctuations. For transverse momenta pT.3 GeV/c, anisotropic flow is thought to be quantitatively determined by the whole evolution of the system, including the phase of hadronic rescatterings – 1 – JHEP07(2018)103 that takes place after chemical freeze-out [11]. Flow coefficients have been shown to be sensitive not only to initial-state anisotropies, but also to the transport parameters (such as shear and bulk viscosity [12,13]) and the equation of state of the system, and they have therefore been used to constrain these properties [14,15]. However, given the different heterogeneous phases that the system is believed to undergo, it has not been possible so far to simultaneously constrain the large number of model parameters, although attempts have been made [16,17]. In this regard, the energy dependence of anisotropic flow has been shown to provide additional discriminating power over initial-state models and temperature dependence of transport parameters [18,19]. In fact, some theoretical uncertainties in the determination of anisotropic flow coefficients are expected to partially cancel in the ratios of vncoefficients measured at different collision energies, such as those on the choice of initial-state model or on the absolute value of η/s. These ratios would then effectively constrain the variations with collision energy and, therefore, system temperature of the parameters to which anisotropic flow is most sensitive. It is known that the magnitude of anisotropic flow, being approximately proportional to the initial-state spatial anisotropy [20], fluctuates from collision to collision even for fixed centrality [6,21–24], and that its probability distribution function (p.d.f.) P(vn) is to a first approximation Bessel-Gaussian [1,25], i.e. the product of a modified Bessel function and a Gaussian function. It has been pointed out that small deviations from a Bessel-Gaussian shape are to be expected independently from the details of initial-state fluctuations [26–28]. Evidence of such small deviations has been previously reported [29]. These deviations are due to first order to the flow p.d.f. having a finite skewness. Its quantitative determination would therefore improve the characterization of these deviations. For dimensional reasons, it is convenient to use a standardised skewness (γ1), defined as [30] γ1=h(vn{RP}−hvn{RP}i)3i h(vn{RP}−hvn{RP}i)2i3/2,(1.2) where vn{RP}refers to the anisotropic flow with respect to the reaction plane ΨRP, i.e. the plane spanned by the impact parameter and the beam axis, and the brackets h···i indicate an average over all events. It is worthwhile to note that the symmetry planes Ψndo not generally coincide with ΨRP because of initial-state fluctuations. A robust experimental method to quantify flow fluctuations is to measure vnwith multi-particle cumulants, which have different sensitivities to the moments of the underlying flow p.d.f. P(vn) vn{2}=2 phv2 ni,(1.3) vn{4}=4 p2hv2 ni2−hv4 ni,(1.4) vn{6}=6 phv6 ni−9hv2 nihv4 ni+ 12hv2 ni3,(1.5) vn{8}=8 phv8 ni−16hv2 nihv6 ni−18hv4 ni2+ 144hv2 ni2hv4 ni−144hv2 ni4.(1.6) The number in curly brackets indicates the order of the cumulant. – 2 – JHEP07(2018)103 For elliptic flow, a large difference between v2{2}and v2{4}and approximately equal values of the higher order cumulants (v2{4},v2{6},v2{8}) have been previously observed [29,31], which is indeed consistent with an approximately Bessel-Gaussian flow p.d.f.. However, a fine-splitting of a few percent among the higher order cumulants (v2{4}, v2{6},v2{8}) has also been reported [29], which is thought to be determined by the residual deviations from Bessel-Gaussian shape, in particular a non-zero skewness. A negative value of γ1, which corresponds to P(v2) being left skewed, is expected [27] from the necessary condition on the initial-state eccentricity ε2<1, which acts as a right cutoff on P(v2). The Elliptic Power distribution, proposed in [26,27], was motivated mainly by this observation and it was shown to provide a good description of P(v2) in a wide centrality range [32]. Moreover, γ1has been predicted to increase in absolute value from central to peripheral collisions [30], being roughly proportional to hv2{RP}i and being inversely proportional to the square root of the system size [28]. γ1can be estimated from the fine-splitting among twoand multi-particle cumulants [30] γexp 1=−6√2v2{4}2v2{4}−v2{6} (v2{2}2−v2{4}2)3/2.(1.7) It is denoted as γexp 1to emphasize that it does not exactly match the definition of γ1given in eq. (1.2), although the two have been estimated to coincide within a few percents [30]. The derivation of eq. (1.7) relies on a Taylor expansion of the generating function in powers of the moments, truncated at the order of the skewness. It is experimentally possible to test the validity of this approximation through the universal equality that it implies [30,33] v2{6}−v2{8}=1 11(v2{4}−v2{6}).(1.8) The precision up to which this equality holds depends on the residual contribution of higher central moments of the flow p.d.f., e.g. the kurtosis, to the multi-particle cumulants. At high pT(pT&10 GeV/c) the dominant mechanism that determines azimuthal anisotropies of the produced final-state particles is thought to be path-length dependent energy-loss of highly energetic partons [34–36]. Although several experimental observations, such as jet azimuthal anisotropies [37,38], are consistent with this hypothesis, the details of the process are largely unconstrained and measurements of anisotropic flow of high-pTparticles can help in this regard. Although the mechanism that determines it is fundamentally different, the origin of anisotropic flow at high pTis common to the one at low pT: initial-state geometry and its event-by-event fluctuations. Measurements reported in [39] seem to confirm this interpretation. Recent CMS results on non-Gaussian elliptic flow fluctuations [40] appeared during the writing of this article. Numerical data are not yet available, but the observations seem to be essentially compatible with our measurements and their conclusions agree with those of this article. 2 Data sample and analysis methods The sample of Pb–Pb collisions used for this measurement was recorded with the ALICE detector [41,42] in November and December 2015 (2010), during the Run 2 (Run 1) of the – 3 – JHEP07(2018)103 LHC, at a centre of mass energy per nucleon of √sNN = 5.02 (2.76) TeV. The detectors used in the present analysis are the Inner Tracking System (ITS) and Time Projection Chamber (TPC), for primary vertex determination and charged particle tracking, and the V0 detector, for symmetry plane determination, centrality estimation [43] and trigger. The trigger conditions are described in [41]. About 78.4×106(12.6×106) minimum-bias events in the centrality range 0–80%, corresponding to an integrated luminosity of 12.7 µb−1(2.0 µb−1), with a reconstructed primary vertex position along the beam direction (zvtx) within ±10 cm from the nominal interaction point, passed offline selection criteria [41] for the data sample at √sNN = 5.02 (2.76) TeV. Centrality is determined from the measured amplitude in the V0, which is proportional to the number of charged tracks in the corresponding acceptance (2.8< η < 5.1 for V0A and −3.6< η < −1.7 for V0C). Charged tracks with transverse momentum 0.2< pT<50 GeV/cand pseudorapidity |η|<0.8 are used in the present analysis. These tracks are reconstructed using combined information from the ITS and TPC. A minimum number of TPC space points of 70 (out of 159) is required for all tracks, together with a χ2per TPC space point (χ2 TPC) in the range 0.1< χ2 TPC <4. A minimum number of 2 ITS hits, of which at least one in the two innermost layers, is required, together with a χ2per ITS hit per degree of freedom (χ2 ITS) smaller than 36. Only tracks with a distance of closest approach (DCA) to the primary vertex position less than 3.2 cm in the beam direction and 2.4 cm transverse to it are used. These track selection criteria ensure an optimum rejection of secondary particles and a pT resolution better than 5% in the pTrange used in the present analysis [41]. Anisotropic flow coefficients are measured with the Q-cumulant method [44], using the implementation proposed in [45]. Track weights (w) are used in the construction of the Q-vectors, in order to correct for non-uniform reconstruction efficiency and acceptance Qn,m = M X j=1 wj(pT, η, ϕ, zvtx)meinϕj,(2.1) where Mis the charged track multiplicity, nthe harmonic and man integer exponent of the weights. After applying track weights, the effects due to non-uniformities in azimuthal acceptance, which would introduce a bias in the measured flow coefficients, are observed to be negligible. This is evaluated by measuring the event-averaged values of the real and imaginary part of Qn, which are consistent with zero. Multi-particle cumulants are measured on an event-by-event basis and then, in order to minimise statistical fluctuations, averaged over all events using the corrected charged track multiplicity as a weight, following the procedure proposed in [44]. All observables are computed in small centrality bins (1%) and then integrated, when limited size of the data sample makes it necessary, in wider centrality intervals using the charged particle yield in each 1% centrality bin as weight. This avoids that the event weighting procedure, based on multiplicity, would introduce a bias in the average centrality within a large centrality bin, since multiplicity varies with centrality. For pT-integrated results, the m-particle cumulants are calculated using all tracks within given pTrange, while for pT-differential results one particle at a given pTis correlated with m−1 particles in the full pTrange (0.2< pT<50 GeV/c). In terms of reference – 4 – JHEP07(2018)103 (cn{m}) and differential (dn{m}) cumulants, as defined in [44], the flow coefficients are measured as vn{2}=2 pcn{2},(2.2) vn{4}=4 p−cn{4},(2.3) vn{6}=6 r1 4cn{6},(2.4) vn{8}=8 r−1 33cn{8},(2.5) vn{2}(pT) = dn{2}(pT)/2 pcn{2},(2.6) vn{4}(pT) = −dn{4}(pT)/4 p−cn{4}3.(2.7) For two-particle correlations, a separation in pseudorapidity between the correlated particles (∆η) is applied in order to suppress short-range azimuthal correlations which are not associated to the symmetry planes, usually called ‘non-flow’. These correlations arise from jets, mini-jets and resonance decays. For flow coefficients of higher order (vn{m > 2}), non-flow contribution has been previously found to be negligible in Pb–Pb collisions [24,31]. Results corresponding to |∆η|>1 (denoted with vn{2,|∆η|>1}) are obtained with the two-particle cumulant correlating tracks from opposite sides of the TPC acceptance, −0.8< η < −0.5 and 0.5< η < 0.8. Results corresponding to |∆η|>2 (and reported as vn{2,|∆η|>2}) are obtained with the scalar product method [46], correlating all tracks at mid-rapidity (|η|<0.8) with the n-th harmonic Q-vector QV0A ncalculated from the azimuthal distribution of the energy deposition measured in the V0A detector [2,47] vn{2,|∆η|>2}=hun,0QV0A* ni rhQV0A nQ∗ n,1ihQV0A nQV0C* ni hQn,1QV0C* ni ,(2.8) where un,0=einϕ is the unit flow vector from charged particle tracks at mid-rapidity and Qn,1is computed from the same type of tracks according to eq. (2.1). Both methods have their own limitations and thus are complementary to each other: vn{2,|∆η|>2} can be reliably employed only up to the fourth harmonic, because of the finite azimuthal segmentation of the V0 detectors (8 sectors in 2π), while vn{2,|∆η|>1}suffers from bigger statistical uncertainties, due to the limited acceptance from which tracks are selected, and bigger non-flow contribution for pT>10 GeV/c. The systematic uncertainties are evaluated by varying the track and event selection criteria and comparing the variation in the flow coefficients relative to the default results. The absolute value of the variation itself is assigned as a systematic uncertainty if it is considered significant according to the Barlow criterion [48]. Different track quality variables are varied: number of TPC space points, χ2 TPC and χ2 ITS, fraction of shared TPC space points and number of ITS hits. For each of these, the default values are varied in order to increase the fraction of excluded tracks as much as 5 times. No significant differences are observed in the reported measurements between positively and negatively charged particles. Concerning the event selection criteria, the following are investigated: polarity of the – 5 – JHEP07(2018)103 Centrality (%) 0 10 20 30 40 50 60 70 80 n v 0.05 0.1 0.15 2.76 5.02 TeV |>1}η∆{2,| 2 v {4} 2 v |>1}η∆{2,| 3 v |>1}η∆{2,| 4 v |>1}η∆{2,| 5 v |>1}η∆{2,| 6 v ALICE Pb-Pb c < 3 GeV/ T p0.2 < | < 0.8η| Figure 1. Anisotropic flow coefficients vnof inclusive charged particles as a function of centrality, for the two-particle (denoted with |∆η|>1) and four-particle cumulant methods. Measurements for Pb–Pb collisions at √sNN = 5.02 (2.76) TeV are shown by solid (open) markers. magnetic field, reconstructed primary vertex position along the beam direction (selecting only events with zvtx within ±8 cm from the nominal interaction point), pile-up rejection (imposing stronger or weaker constraints on the consistency of different event multiplicity estimators) and variations in the instantaneous luminosity delivered to the ALICE detector by the LHC. The uncertainty on centrality determination is evaluated using an alternative estimator based on the number of hits in the second ITS layer (|η|<1.4), which is directly proportional to the number of charged particles in the corresponding acceptance. Among the aformentioned sources, for all observables in this article, track quality and centrality determination are the dominant sources. The total systematic uncertainties are evaluated summing in quadrature the systematic uncertainties coming from each of the sources, i.e. considering the different sources to be uncorrelated. 3 Collision energy, transverse momentum and centrality dependence Figure 2shows the ratio of vn{2,|∆η|>1}(n= 2,3,4) and v2{4}between √sNN = 5.02 and 2.76 TeV, i.e. the relative variation of these flow coefficients between those two energies. Since the systematic uncertainties of the measurements at different energies are partially – 6 – JHEP07(2018)103 η/s = 0.2η/s(T) param1 1 v2{2,|∆η|>1}0.712 0.645 0.477 v2{4}0.467 0.357 0.028 v3{2,|∆η|>1}0.053 0.003 0.001 v4{2,|∆η|>1}0.484 0.468 0.022 Table 1.p-values for the comparison among ratios of vn{2,|∆η|>1}(n= 2,3,4) and v2{4} between √sNN = 5.02 and 2.76 TeV and model calculations using different parametrisations of η/s(T) [18], shown in figure 2, and unity, in the centrality range 5-50%. correlated, the resulting systematic uncertainty on the ratio is reduced. All harmonics are observed to increase with energy, between about 2 and 10%. A hint of a centrality dependence is observed only for v2, with the increase growing slightly from mid-central towards more peripheral collisions. No significant difference is observed in the increase of v2measured with twoor four-particle correlations. Since the difference between v2{2,|∆η|>1} and v2{4}is directly related to flow fluctuations, this observation suggests that the fluctuations of elliptic flow do not vary significantly between the two energies, within experimental uncertainties. The ratios are compared to hydrodynamical calculations with EKRT initial conditions [51] and different parametrisations of the temperature dependence of η/s [18]. The p-values for the comparison between data and models are also shown in Tab. 1. Among the two parametrisations that provide the best description of RHIC and LHC data [52], both are consistent with the measurements, except for v3{2,|∆η|>1}, albeit the one with constant η/s = 0.2 agrees slightly better. These comparisons take into account the correlation between systematic uncertainties of data points in different centrality intervals. This observation might indicate little or no temperature dependence of η/s within the temperature range at which anisotropic flow develops at the two center of mass energies. As a reference, the p-values for the comparison between data and unity in the same centrality range (5–50%) are also reported in table 1. Looking at the pTdependence in more detail, the flow harmonics are found to follow an approximate power-law scaling up to around the maximum, with exponents being proportional to the harmonic number n,vn(pT)∼pn/3 T, as shown by the dashed fitted lines in figure 3. In ideal hydrodynamics, the pTdependence of anisotropic flow for massive particles should follow a power-law function vn(pT)∼pn Tin the region of pT/M up to order one, where Mis the particle’s mass, and at higher momenta it has been predicted to be linear in pTfor all n, vn(pT)∼pT[53,54]. This pTdependence is notably different from the one observed in the data. At very low pTthis is presumably because the relevant momentum region for inclusive particles, mostly pions, is below the range of our measurements, and at higher pTideal hydro is not expected to hold because of momentum dependent viscous corrections at freeze out [55] and/or non-linear mode mixing for n⩾4 [20,56]. The power-law dependence for n= 2 was noticed before and it was attributed to a novel energy loss mechanism [57], which however cannot explain the scaling observed for n > 2. The emergence of this simple power-law dependence remains unexpected and surprising. – 7 – JHEP07(2018)103 n/m m v/ n v 0.4 1 2 3 10 20 30 0-5%0-5%0-5% n/m m v/ n v 0.4 1 2 3 4 10 20-30%20-30%20-30% )c (GeV/ T p 1 10 n/m m v/ n v 0.4 1 2 3 4 10 50-60%50-60%50-60% 0.4 1 2 3 10 20 30 5-10%5-10%5-10% 0.4 1 2 3 4 10 30-40%30-40%30-40% )c (GeV/ T p 1 10 0.4 1 2 3 4 10 60-70%60-70%60-70% 0.4 1 2 3 10 20 30 10-20%10-20%10-20% 0.4 1 2 3 4 10 40-50%40-50%40-50% ALICE Pb-Pb 5.02 TeV |>2}η∆{2,| n v|<0.8, η| 3/2 2 v/ 3 v 4/2 2 v/ 4 v 4/3 3 v/ 4 v iEBE-VISHNU AMPT-IC + Figure 8. Ratios vn(pT)/vm(pT)n/m, n = 3,4, m = 2,3 of inclusive charged particles for Pb–Pb collisions at √sNN = 5.02, in different centrality classes, measured with the scalar product method with respect to the V0A Q-vector. Dashed lines represent averages in 0.2< pT<3 GeV/c. The ratios are also shown for one hydrodynamic model [62] in the four most central centrality intervals; it is qualitatively similar in the other centrality intervals and for the other models. 4 Elliptic flow fluctuations Figure 9shows the integrated v2in the pTrange 0.2< pT<3 GeV/cas a function of centrality, measured with two-, four-, sixand eight-particle cumulants at √sNN = 5.02 and 2.76 TeV. The corresponding cumulants (c2{2,4,6,8}) are reported in figure 10. The centrality dependence is similar for all multi-particle cumulants and similar to what is shown in figure 1. The differences between v2{2}(shown in figure 9) and v2{2,|∆η|>1} (shown in figure 1), which range from about 4% in mid-central collisions to about 20% in peripheral ones, are mostly attributed to non-flow contributions, which are suppressed in the case of results with a pseudorapidity gap. The possible differences arising from the decorrelation of event planes at different pseudorapidities are expected to be less than 1%, as previously argued. A fine-splitting of less than 1% is observed among v2{4},v2{6}and v2{8}, as it can be seen from their ratios, shown in figure 11 for both collision energies. The ratios v2{6}/v2{4} and v2{8}/v2{4}at √sNN = 5.02 TeV show a significant centrality dependence: the deviations of the ratios from unity is about 0.2% in central and increases up to about 1% for midcentral collisions. A further increase seems to be observed for more peripheral collisions, up to about 2% for centralities above 50%. The systematic uncertainties on these ratios are greately reduced with respect to those on v2{m}(m= 2,4,6,8), since the dominant – 14 – JHEP07(2018)103 Centrality (%) 0 10 20 30 40 50 60 70 {m} 2 v 0 0.05 0.1 ALICE Pb-Pb c < 3 GeV/ T p0.2 < | < 0.8η| 2.76 5.02 TeV {2} 2 v {4} 2 v {6} 2 v {8} 2 v Figure 9. Elliptic flow coefficient v2of inclusive charged particles as a function of centrality, measured with the twoand multi-particle cumulant methods. Measurements for Pb–Pb collisions at √sNN = 5.02 (2.76) TeV are shown by solid (open) markers. sources of systematic uncertainty (track quality variables and centrality determination) among the twoand multi-particle cumulants are highly correlated. This fine-splitting is consistent with non-Bessel-Gaussian behaviour of event-by-event flow fluctuations, as previously explained. These ratios are found to be independent of the choice of pTrange within 0.2< pT<3 GeV/c, indicating that the characterization of flow fluctuations at low pT does not depend on pT, even for such fine-splitting. Results at √sNN = 2.76 TeV are found to be compatible, indicating that these ratios do not change significantly across collision energies. Compared to calculations [30] employing MC-Glauber initial conditions [80] and viscous hydrodynamics (v-USPhydro) for Pb–Pb collisions at √sNN = 2.76 TeV, the ratios v2{6}/v2{4}and v2{8}/v2{4}are found to be compatible. A good agreement is found between the results at √sNN = 2.76 TeV and corresponding ATLAS results on elliptic flow p.d.f. obtained via the unfolding technique [29], as shown in figure 12. Figure 13 shows the ratio between v2{8}and v2{6}at √sNN = 5.02 TeV. A hint of a further fine-splitting between these two, of the order of 0.05%, is observed. The results suggest little or no centrality dependence within centrality 10–50%. This difference is also consistent with non-Bessel-Gaussian elliptic flow fluctuations, and can be attributed to different contributions of the skewness to these higher-order cumulants [30]. Corresponding results at √sNN = 2.76 TeV, here and in the following, are not shown because of the large statistical uncertainties. Figure 14 shows v2{6} − v2{8}and (v2{4} − v2{6})/11 at – 15 – JHEP07(2018)103 Centrality (%) 0 10 20 30 40 50 60 70 {2} 2 c 5 10 3− 10× ALICE Pb-Pb c < 3 GeV/ T p0.2 < | < 0.8η| 2.76 5.02 TeV {m} 2 c Centrality (%) 0 10 20 30 40 50 60 70 {4} 2 c 40− 20− 0 6− 10× Centrality (%) 0 10 20 30 40 50 60 70 {6} 2 c 0 0.5 1 1.5 6− 10× Centrality (%) 0 10 20 30 40 50 60 70 {8} 2 c 0.1− 0.05− 0 6− 10× Figure 10. Cumulants c2of elliptic flow of inclusive charged particles as a function of centrality, for the two-particle and multi-particle cumulant methods. Measurements for Pb–Pb collisions at √sNN = 5.02 (2.76) TeV are shown by solid (open) markers. √sNN = 5.02 TeV: these two are observed to be in agreement, which demonstrates the validity of eq. (1.8). This observation sets an upper limit of 4 ×10−4at 95% confidence level for possible contributions to multi-particle cumulants from higher moments of the flow p.d.f. (kurtosis and beyond) in the centrality range 10–50%. This estimate is obtained assuming gaussian systematic uncertainties and summing them in quadrature with the statistical ones. Figure 15 shows the measurement of the standardised skewness (γexp 1) at √sNN = 5.02 TeV as a function of centrality. To suppress non-flow contributions, the values of v2{2,|∆η|>1}from figure 1are used for v2{2}in eq. (1.7). A negative value of the skewness, with a strong centrality dependence, is observed: γexp 1decreases from zero in central to about −0.4 in peripheral collisions. Compared to model calculations [30] for Pb–Pb collisions at √sNN = 2.76 TeV, the results are found to be compatible for the – 16 – JHEP07(2018)103 Centrality (%) 0 10 20 30 40 50 60 70 {m} 2 v/{n} 2 v 0.96 0.98 1 1.02 2.76 5.02 TeV {4} 2 v/{6} 2 v {4} 2 v/{8} 2 v ALICE Pb-Pb c < 3 GeV/ T p0.2 < | < 0.8η| Figure 11. Ratios of elliptic flow coefficients v2of inclusive charged particles between measurements with different multi-particle cumulant methods, as a function of centrality. Measurements at √sNN = 5.02 (2.76) TeV are shown by solid (open) markers. Centrality (%) 0 10 20 30 40 50 60 70 {m} 2 v/{n} 2 v 0.96 0.98 1 1.02 Pb-Pb 2.76 TeV {4} 2 v/{6} 2 vALICE {4} 2 v/{8} 2 vALICE {4} 2 v/{6} 2 vATLAS EbyE {4} 2 v/{8} 2 vATLAS EbyE Glauber+v-USPhydro c < 3 GeV/ T p0.2 < | < 0.8η| Figure 12. Ratios of elliptic flow coefficients v2of inclusive charged particles between measurements with different multi-particle cumulant methods, as a function of centrality, at √sNN = 2.76 TeV. Hydrodynamic calculations [30] and ATLAS measurements [29] are shown for comparison. – 17 – JHEP07(2018)103 Centrality (%) 5 10 15 20 25 30 35 40 45 50 {6} 2 v/{8} 2 v 0.998 1 1.002 ALICE Pb-Pb 5.02 TeV c < 3 GeV/ T p0.2 < | < 0.8η| Figure 13. Ratio of elliptic flow coefficients v2{8}/v2{6}of inclusive charged particles as a function of centrality. Centrality (%) 0 10 20 30 40 50 60 70 {m} 2 v-{n} 2 v 0.2− 0 0.2 0.4 3− 10× {8} 2 v-{6} 2 v )/11{6} 2 v-{4} 2 v( ALICE Pb-Pb 5.02 TeV c < 3 GeV/ T p0.2 < | < 0.8η| Figure 14. Differences of elliptic flow coefficients v2of inclusive charged particles between measurements with different multi-particle cumulant methods, as a function of centrality. – 18 – JHEP07(2018)103 Centrality (%) 0 10 20 30 40 50 60 70 exp 1 γ 0.6− 0.4− 0.2− 0 0.2 ALICE 5.02 TeV Glauber+v-USPhydro 2.76 TeV Pb-Pb c < 3 GeV/ T p0.2 < | < 0.8η| Figure 15. Skewness of elliptic flow γexp 1of inclusive charged particles as a function of centrality, for Pb–Pb collisions at √sNN = 5.02 TeV. Hydrodynamic calculations [30] for Pb–Pb collisions at √sNN = 2.76 TeV are shown for comparison. entire centrality range. This observation is consistent with the elliptic flow p.d.f. being progressively more left-skewed going from central to peripheral collisions. We attribute this feature to the combination of an increase in hε2iand the geometrical constrain ε2<1, as previously argued. In order to report the full p.d.f. of elliptic flow P(v2), which can be compared to previous experimental results and theoretical predictions, it is parametrised with the Elliptic Power distribution [26,27] P(v2) = dε2 dv2 P(ε2) = 1 k2 Pv2 k2=2αv2 πk2 2 (1 −ε2 0)α+1/2Zπ 0 (1 −v2 2/k2 2)α−1 (1 −v2ε0cos ϕ/k2)2α+1 dϕ, (4.1) and its three free parameters (α,ε0and k2) are extracted from fits to the elliptic flow cumulants c2{2,|∆η|>1}and c2{m}(m= 4,6,8) at √sNN = 5.02 TeV. The parameter αquantifies the magnitude of elliptic flow fluctuations, ε0the mean eccentricity in the reaction plane and k2is the proportionality coefficient between initial-state eccentricity and v2coefficient: v2=k2ε2. The relation between cumulants and Elliptic Power parameters is given by [27] c2{2}=k2 2(1 −f1),(4.2) c2{4}=−k4 21−2f1+ 2 f2 1−f2,(4.3) c2{6}=k6 24 + 18 f2 1−12 f3 1+ 12f1(3f2−1) −6f2−f3,(4.4) c2{8}=−k8 2(33 −288 f3 1+ 144 f4 1−66 f2+ 18 f2 2−24 f2 1(−11 + 6 f2) −12 f3+ 4 f1(−33 + 42 f2+ 4 f3)−f4) (4.5) – 19 – JHEP07(2018)103 Centrality (%) 0 10 20 30 40 50 60 2 k 0.1 0.2 0.3 0.4 ALICE Pb-Pb 5.02 TeV c < 3 GeV/ T p0.2 < | < 0.8η| Centrality (%) 0 10 20 30 40 50 60 α 0 100 200 300 Centrality (%) 0 10 20 30 40 50 60 0 ε 0 0.1 0.2 0.3 Figure 16. Elliptic power parameters k2,αand ε0as a function of centrality, for Pb–Pb collisions at √sNN = 5.02 TeV, extracted from measurements of v2of inclusive charged particles with twoparticle and multi-particle cumulant methods. where fk≡ h(1 −ε2 n)ki=α α+k(1 −ε2 0)k2F1k+1 2, k;α+k+ 1, ε2 0(4.6) and 2F1is the hypergeometric function. The results are shown in figure 16. The systematic uncertainties are assigned varying the fit ranges and initial values of the parameters and shifting the data points according to the corresponding systematic uncertainties. An additional source of uncertainty, which is investigated, is a possible cubic response coefficient k0 2, defined as v2=k2ε2+k0 2ε3 2. This coefficient is introduced to quantify the possible increase of flow fluctuations that the hydrodynamic expansion of the medium introduces with respect to geometrical fluctuations in the initial state and was argued to be non-zero in mid-central and peripheral collisions due to general properties of the hydrodynamic phase [81]. In particular, k0 2is expected to be ≤0.15 in the centrality range 0–60% [81]. The residual differences in α,ε0and k2when including k0 2as an additional free parameter are considered in the systematic uncertainties. The statistical uncertainties are evaluated using the subsampling method: the analysed dataset is divided into 10 sub-samples and v2{m}is measured in each of them. The Elliptic Power parameters are then extracted in each subsample and their dispersion is used to estimate the statistical uncertainties. The resulting p.d.f., constructed using the Elliptic Power distribution (eq. (4.1)) with the parameters shown in figure 16 and scaled by its mean (hv2i), is reported in figure 17, for centralities 5–10%, 25–30% and 45–50%. The systematic uncertainties take into account the correlation of the uncertainties of the Elliptic Power parameters. Other centrality ranges that are not shown here are reported in the appendix A. Scaling by hv2iallows a comparison of our data with results by the ATLAS collaboration [70] obtained in different pTranges. The observed agreement is also consistent, as previously noted, with elliptic flow fluctuations at low pTnot depending on pTand not changing significantly between collision energies, except for the trivial increase in pT-integrated v2due to the change in hpTi. Comparison with iEBE-VISHNU model calculations with AMPT and TRENTo initial conditions [62] indicates that TRENTo initial conditions are better at describing the experimental data. The data are found to be in agreement also with predictions from – 20 – JHEP07(2018)103 0 0.5 1 1.5 2 2.5 〉 2 v〈)* 2 P(v 3− 10 1 0 0.5 1 1.5 2 2.5 〉 2 v〈)* 2 P(v 3− 10 1 |<0.8ηPb-Pb 5.02 TeV, | <3 GeV/c T ALICE: 0.2<p 〉 2 v〈/ 2 v 0 0.5 1 1.5 2 2.5 〉 2 v〈)* 2 P(v 3− 10 1 Pb-Pb 5.02 TeV IP-Glasma + MUSIC AMPT-IC + iEBE-VISHNU TRENTo-IC + iEBE-VISHNU 0 0.5 1 1.5 2 2.5 1 5-10% 0 0.5 1 1.5 2 2.5 1 25-30% 〉 2 v〈/ 2 v 0 0.5 1 1.5 2 2.5 1 |<2.5ηPb-Pb 2.76 TeV, | <1 GeV/c T ATLAS: 0.5<p >0.5 GeV/c T ATLAS: p 45-50% Figure 17. Elliptic flow p.d.f. P(v2) rescaled by the mean v2(hv2i) of inclusive charged particles for Pb–Pb collisions at √sNN = 5.02 TeV, in different centrality classes. Several hydrodynamic calculations [61,62] and previous measurements from ATLAS [70] at lower energies are shown for comparison. the IP-Glasma+MUSIC model [61] (with initial conditions very similar to the TRENTo ones), although the uncertainties on the theoretical predictions do not allow to draw firm conclusions. 5 Conclusions Anisotropic flow coefficients are measured up to the sixth harmonic for inclusive charged particles at mid-rapidity (|η|<0.8), in a wide centrality (0–80%) and pT(0.2< pT< 50 GeV/c) ranges, for Pb–Pb collisions at √sNN = 5.02 and 2.76 TeV. Comparing the results at √sNN = 5.02 and 2.76 TeV the energy dependence of anisotropic flow at the LHC is – 21 – JHEP07(2018)103 investigated. Comparison with different model calculations demonstrates that these measurements have the potential to constrain initial-state fluctuations, transport parameters of the medium and path-length dependence of energy loss of high-pTpartons. The evolution of vn(pT) with respect to centrality and harmonic number nis also investigated. Flow coefficient of all harmonics are observed to follow an approximate power-law scaling of the form vn(pT)∼pn/3 Tin the pTrange 0.2< pT<3 GeV/c. The ratios vn/vn/m mn= 3,4 and m= 2,3 are also observed to be independent of pTwithin the same pTrange and show deviations of about 10% for 3 < pT<10 GeV/c. The fluctuations of elliptic flow are investigated through the fine-splitting of the higherorder multi-particle cumulants (v2{4},v2{6},v2{8}), from which the standardised skewness (γexp 1) of the flow p.d.f. is extracted. Results are found to be compatible both with predictions from hydrodynamical models and with previous ATLAS results at lower energies. It is concluded that the characterization of elliptic flow fluctuations at low pTdoes not depend on the pTrange and on the collision energy, except for the increase in pT-integrated v2due to the change in hpTi. Direct constraints on the contribution of higher moments to the multi-particle cumulants are also reported. Finally, the full elliptic flow p.d.f., parametrised with the Elliptic Power distribution, is reported in the centrality ranges 0– 60%. These results are also found to be in agreement with previous experimental results. Overall, calculations including initial conditions matching the IP-Glasma description are observed to better reproduce the elliptic flow p.d.f. while failing to describe the pTdependence of anisotropic flow coefficients, whereas the opposite situation is observed for calculations that employ AMPT initial conditions. Acknowledgments 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: A. I. Alikhanyan National Science Laboratory (Yerevan Physics Institute) Foundation (ANSL), State Committee of Science and World Federation of Scientists (WFS), Armenia; Austrian Academy of Sciences and Nationalstiftung f¨ur Forschung, Technologie und Entwicklung, Austria; Ministry of Communications and High Technologies, National Nuclear Research Center, Azerbaijan; Conselho Nacional de Desenvolvimento Cient´ıfico e Tecnol´ogico (CNPq), Universidade Federal do Rio Grande do Sul (UFRGS), Financiadora de Estudos e Projetos (Finep) and Funda¸c˜ao de Amparo `a Pesquisa do Estado de S˜ao Paulo (FAPESP), Brazil; Ministry of Science & Technology of China (MSTC), National Natural Science Foundation of China (NSFC) and Ministry of Education of China (MOEC) , China; Ministry of Science and Education, Croatia; Ministry of Education, Youth and Sports of the Czech Republic, Czech Republic; The Danish Council for Independent Research — Natural Sciences, the Carlsberg Foundation and Dan- – 22 – JHEP07(2018)103 ish National Research Foundation (DNRF), Denmark; Helsinki Institute of Physics (HIP), Finland; Commissariat `a l’Energie Atomique (CEA) and Institut National de Physique Nucl´eaire et de Physique des Particules (IN2P3) and Centre National de la Recherche Scientifique (CNRS), France; Bundesministerium f¨ur Bildung, Wissenschaft, Forschung und Technologie (BMBF) and GSI Helmholtzzentrum f¨ur Schwerionenforschung GmbH, Germany; General Secretariat for Research and Technology, Ministry of Education, Research and Religions, Greece; National Research, Development and Innovation Office, Hungary; Department of Atomic Energy Government of India (DAE), Department of Science and Technology, Government of India (DST), University Grants Commission, Government of India (UGC) and Council of Scientific and Industrial Research (CSIR), India; Indonesian Institute of Science, Indonesia; Centro Fermi — Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi and Istituto Nazionale di Fisica Nucleare (INFN), Italy; Institute for Innovative Science and Technology, Nagasaki Institute of Applied Science (IIST), Japan Society for the Promotion of Science (JSPS) KAKENHI and Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan; Consejo Nacional de Ciencia (CONACYT) y Tecnolog´ıa, through Fondo de Cooperaci´on Internacional en Ciencia y Tecnolog´ıa (FONCICYT) and Direcci´on General de Asuntos del Personal Academico (DGAPA), Mexico; Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO), Netherlands; The Research Council of Norway, Norway; Commission on Science and Technology for Sustainable Development in the South (COMSATS), Pakistan; Pontificia Universidad Cat´olica del Per´u, Peru; Ministry of Science and Higher Education and National Science Centre, Poland; Korea Institute of Science and Technology Information and National Research Foundation of Korea (NRF), Republic of Korea; Ministry of Education and Scientific Research, Institute of Atomic Physics and Romanian National Agency for Science, Technology and Innovation, Romania; Joint Institute for Nuclear Research (JINR), Ministry of Education and Science of the Russian Federation and National Research Centre Kurchatov Institute, Russia; Ministry of Education, Science, Research and Sport of the Slovak Republic, Slovakia; National Research Foundation of South Africa, South Africa; Centro de Aplicaciones Tecnol´ogicas y Desarrollo Nuclear (CEADEN), Cubaenerg´ıa, Cuba and Centro de Investigaciones Energ´eticas, Medioambientales y Tecnol´ogicas (CIEMAT), Spain; Swedish Research Council (VR) and Knut & Alice Wallenberg Foundation (KAW), Sweden; European Organization for Nuclear Research, Switzerland; National Science and Technology Development Agency (NSDTA), Suranaree University of Technology (SUT) and Office of the Higher Education Commission under NRU project of Thailand, Thailand; Turkish Atomic Energy Agency (TAEK), Turkey; National Academy of Sciences of Ukraine, Ukraine; Science and Technology Facilities Council (STFC), United Kingdom; National Science Foundation of the United States of America (NSF) and United States Department of Energy, Office of Nuclear Physics (DOE NP), United States of America. – 23 – JHEP07(2018)103 [48] R. Barlow, Systematic errors: Facts and fictions, in the proceedings of the Conference on Statistical Techniques in Particle Physics, March 18–22, Durhamm, U.K. (2002), hep-ex/0207026 [INSPIRE]. [49] ALICE collaboration, Anisotropic flow of charged particles in Pb-Pb collisions at √sNN = 5.02 TeV,Phys. Rev. Lett. 116 (2016) 132302 [arXiv:1602.01119] [INSPIRE]. [50] STAR collaboration, K.H. Ackermann et al., Elliptic flow in Au + Au collisions at √sNN = 130 GeV,Phys. Rev. Lett. 86 (2001) 402 [nucl-ex/0009011] [INSPIRE]. [51] K.J. Eskola, K. Kajantie, P.V. Ruuskanen and K. Tuominen, Scaling of transverse energies and multiplicities with atomic number and energy in ultrarelativistic nuclear collisions,Nucl. Phys. B 570 (2000) 379 [hep-ph/9909456] [INSPIRE]. [52] H. Niemi, K.J. Eskola and R. Paatelainen, Event-by-event fluctuations in a perturbative QCD + saturation + hydrodynamics model: Determining QCD matter shear viscosity in ultrarelativistic heavy-ion collisions,Phys. Rev. C 93 (2016) 024907 [arXiv:1505.02677] [INSPIRE]. [53] N. Borghini and J.-Y. Ollitrault, Momentum spectra, anisotropic flow and ideal fluids,Phys. Lett. B 642 (2006) 227 [nucl-th/0506045] [INSPIRE]. [54] B.H. Alver, C. Gombeaud, M. Luzum and J.-Y. Ollitrault, Triangular flow in hydrodynamics and transport theory,Phys. Rev. C 82 (2010) 034913 [arXiv:1007.5469] [INSPIRE]. [55] D. Teaney, The effects of viscosity on spectra, elliptic flow and HBT radii,Phys. Rev. C 68 (2003) 034913 [nucl-th/0301099] [INSPIRE]. [56] Z. Qiu and U.W. Heinz, Event-by-event shape and flow fluctuations of relativistic heavy-ion collision fireballs,Phys. Rev. C 84 (2011) 024911 [arXiv:1104.0650] [INSPIRE]. [57] C. Andr´es, M. Braun and C. Pajares, Energy loss as the origin of a universal scaling law of the elliptic flow,Eur. Phys. J. A 53 (2017) 41 [arXiv:1609.03927] [INSPIRE]. [58] F.G. Gardim, F. Grassi, M. Luzum and J.-Y. Ollitrault, Breaking of factorization of two-particle correlations in hydrodynamics,Phys. Rev. C 87 (2013) 031901 [arXiv:1211.0989] [INSPIRE]. [59] CMS collaboration, Evidence for transverse momentum and pseudorapidity dependent event plane fluctuations in PbPb and pPb collisions,Phys. Rev. C 92 (2015) 034911 [arXiv:1503.01692] [INSPIRE]. [60] J. Bartels, K.J. Golec-Biernat and H. Kowalski, A modification of the saturation model: DGLAP evolution,Phys. Rev. D 66 (2002) 014001 [hep-ph/0203258] [INSPIRE]. [61] S. McDonald et al., Phys. Rev. C 95 (2017) 064913 [arXiv:1609.02958] [INSPIRE]. [62] W. Zhao, H.-j. Xu and H. Song, Collective flow in 2.76 A TeV and 5.02 A TeV Pb+Pb collisions,Eur. Phys. J. C 77 (2017) 645 [arXiv:1703.10792] [INSPIRE]. [63] Z.-W. Lin et al., A Multi-phase transport model for relativistic heavy ion collisions,Phys. Rev. C 72 (2005) 064901 [nucl-th/0411110] [INSPIRE]. [64] J.S. Moreland, J.E. Bernhard and S.A. Bass, Alternative ansatz to wounded nucleon and binary collision scaling in high-energy nuclear collisions,Phys. Rev. C 92 (2015) 011901 [arXiv:1412.4708] [INSPIRE]. [65] S.A. Bass et al., Microscopic models for ultrarelativistic heavy ion collisions,Prog. Part. Nucl. Phys. 41 (1998) 255 [nucl-th/9803035] [INSPIRE]. – 30 – JHEP07(2018)103 [66] B. Betz et al., Cumulants and nonlinear response of high pTharmonic flow at √sNN = 5.02 TeV,Phys. Rev. C 95 (2017) 044901 [arXiv:1609.05171] [INSPIRE]. [67] J. Noronha-Hostler et al., Bulk viscosity effects in event-by-event relativistic hydrodynamics, Phys. Rev. C 88 (2013) 044916 [arXiv:1305.1981] [INSPIRE]. [68] B. Betz, M. Gyulassy and G. Torrieri, Fourier harmonics of high-pTparticles probing the fluctuating intitial condition geometries in heavy-ion collisions,Phys. Rev. C 84 (2011) 024913 [arXiv:1102.5416] [INSPIRE]. [69] R.J. Fries, V. Greco, and P. Sorensen, Coalescence models for hadron formation from quark gluon plasma,Ann. Rev. Nucl. Part. Sci. 58 (2008) 177 [arXiv:0807.4939]. [70] ATLAS collaboration, Measurement of the distributions of event-by-event flow harmonics in lead-lead collisions at = 2.76 TeV with the ATLAS detector at the LHC,JHEP 11 (2013) 183 [arXiv:1305.2942] [INSPIRE]. [71] ALICE collaboration, Event shape engineering for inclusive spectra and elliptic flow in Pb-Pb collisions at √sNN = 2.76 TeV,Phys. Rev. C 93 (2016) 034916 [arXiv:1507.06194] [INSPIRE]. [72] J. Schukraft, A. Timmins and S.A. Voloshin, Ultra-relativistic nuclear collisions: event shape engineering,Phys. Lett. B 719 (2013) 394 [arXiv:1208.4563] [INSPIRE]. [73] ALICE collaboration, Anisotropic flow of charged hadrons, pions and (anti-)protons measured at high transverse momentum in Pb-Pb collisions at √sNN = 2.76 TeV,Phys. Lett. B 719 (2013) 18 [arXiv:1205.5761] [INSPIRE]. [74] STAR collaboration, J. Adams et al., Azimuthal anisotropy at RHIC: the first and fourth harmonics,Phys. Rev. Lett. 92 (2004) 062301 [nucl-ex/0310029] [INSPIRE]. [75] PHENIX collaboration, A. Adare et al., Elliptic and hexadecapole flow of charged hadrons in Au+Au collisions at √sNN = 200 GeV,Phys. Rev. Lett. 105 (2010) 062301 [arXiv:1003.5586] [INSPIRE]. [76] C. Gombeaud and J.-Y. Ollitrault, Effects of flow fluctuations and partial thermalization on v(4), Phys. Rev. C 81 (2010) 014901 [arXiv:0907.4664] [INSPIRE]. [77] P.F. Kolb, L.-W. Chen, V. Greco and C.M. Ko, Momentum anisotropies in the quark coalescence model,Phys. Rev. C 69 (2004) 051901 [nucl-th/0402049] [INSPIRE]. [78] P. Liu and R.A. Lacey, Acoustic scaling of linear and mode-coupled anisotropic flow; implications for precision extraction of the specific shear viscosity,arXiv:1802.06595 [INSPIRE]. [79] R.A. Lacey, A. Taranenko, N.N. Ajitanand and J.M. Alexander, Scaling of the higher-order flow harmonics: implications for initial-eccentricity models and the ‘viscous horizon’, arXiv:1105.3782 [INSPIRE]. [80] B. Alver, M. Baker, C. Loizides and P. Steinberg, The PHOBOS glauber Monte Carlo, arXiv:0805.4411 [INSPIRE]. [81] J. Noronha-Hostler, L. Yan, F.G. Gardim and J.-Y. Ollitrault, Linear and cubic response to the initial eccentricity in heavy-ion collisions,Phys. Rev. C 93 (2016) 014909 [arXiv:1511.03896] [INSPIRE]. – 31 – JHEP07(2018)103 The ALICE collaboration S. Acharya138 , F.T.-. Acosta22 , D. Adamov´a93 , J. Adolfsson80 , M.M. Aggarwal97 , G. Aglieri Rinella36 , M. Agnello33 , N. Agrawal48 , Z. Ahammed138 , S.U. Ahn76 , S. Aiola143 , A. Akindinov64 , M. Al-Turany103 , S.N. Alam138 , D.S.D. Albuquerque119 , D. Aleksandrov87 , B. Alessandro58 , R. Alfaro Molina72 , Y. Ali16 , A. Alici11 ,53 ,29 , A. Alkin3, J. Alme24 , T. Alt69 , L. Altenkamper24 , I. Altsybeev137 , C. Andrei47 , D. Andreou36 , H.A. Andrews107 , A. Andronic103 , M. Angeletti36 , V. Anguelov101 , C. Anson17 , T. Antiˇci´c104 , F. Antinori56 , P. Antonioli53 , R. Anwar123 , N. Apadula79 , L. Aphecetche111 , H. Appelsh¨auser69 , S. Arcelli29 , R. Arnaldi58 , O.W. Arnold102 ,114 , I.C. Arsene23 , M. Arslandok101 , B. Audurier111 , A. Augustinus36 , R. Averbeck103 , M.D. Azmi18 , A. Badal`a55 , Y.W. Baek60 ,41 , S. Bagnasco58 , R. Bailhache69 , R. Bala98 , A. Baldisseri134 , M. Ball43 , R.C. Baral85 , A.M. Barbano28 , R. Barbera30 , F. Barile52 , L. Barioglio28 , G.G. Barnaf¨oldi142 , L.S. Barnby92 , V. Barret131 , P. Bartalini7, K. Barth36 , E. Bartsch69 , N. Bastid131 , S. Basu140 , G. Batigne111 , B. Batyunya75 , P.C. Batzing23 , J.L. Bazo Alba108 , I.G. Bearden88 , H. Beck101 , C. Bedda63 , N.K. Behera60 , I. Belikov133 , F. Bellini29 ,36 , H. Bello Martinez2, R. Bellwied123 , L.G.E. Beltran117 , V. Belyaev91 , G. Bencedi142 , S. Beole28 , A. Bercuci47 , Y. Berdnikov95 , D. Berenyi142 , R.A. Bertens127 , D. Berzano36 ,58 , L. Betev36 , P.P. Bhaduri138 , A. Bhasin98 , I.R. Bhat98 , H. Bhatt48 , B. Bhattacharjee42 , J. Bhom115 , A. Bianchi28 , L. Bianchi123 , N. Bianchi51 , J. Bielˇc´ık38 , J. Bielˇc´ıkov´a93 , A. Bilandzic102 ,114 , G. Biro142 , R. Biswas4, S. Biswas4, J.T. Blair116 , D. Blau87 , C. Blume69 , G. Boca135 , F. Bock36 , A. Bogdanov91 , L. Boldizs´ar142 , M. Bombara39 , G. Bonomi136 , M. Bonora36 , H. Borel134 , A. Borissov141 ,20 , M. Borri125 , E. Botta28 , C. Bourjau88 , L. Bratrud69 , P. Braun-Munzinger103 , M. Bregant118 , T.A. Broker69 , M. Broz38 , E.J. Brucken44 , E. Bruna58 , G.E. Bruno36 ,35 , D. Budnikov105 , H. Buesching69 , S. Bufalino33 , P. Buhler110 , P. Buncic36 , O. Busch130 , Z. Buthelezi73 , J.B. Butt16 , J.T. Buxton19 , J. Cabala113 , D. Caffarri89 , H. Caines143 , A. Caliva103 , E. Calvo Villar108 , R.S. Camacho2, P. Camerini27 , A.A. Capon110 , F. Carena36 , W. Carena36 , F. Carnesecchi29 ,11 , J. Castillo Castellanos134 , A.J. Castro127 , E.A.R. Casula54 , C. Ceballos Sanchez9, S. Chandra138 , B. Chang124 , W. Chang7, S. Chapeland36 , M. Chartier125 , S. Chattopadhyay138 , S. Chattopadhyay106 , A. Chauvin114 ,102 , C. Cheshkov132 , B. Cheynis132 , V. Chibante Barroso36 , D.D. Chinellato119 , S. Cho60 , P. Chochula36 , T. Chowdhury131 , P. Christakoglou89 , C.H. Christensen88 , P. Christiansen80 , T. Chujo130 , S.U. Chung20 , C. Cicalo54 , L. Cifarelli11 ,29 , F. Cindolo53 , J. Cleymans122 , F. Colamaria52 , D. Colella65 ,52 ,36 , A. Collu79 , M. Colocci29 , M. Concas58 ,i, G. Conesa Balbastre78 , Z. Conesa del Valle61 , J.G. Contreras38 , T.M. Cormier94 , Y. Corrales Morales58 , P. Cortese34 , M.R. Cosentino120 , F. Costa36 , S. Costanza135 , J. Crkovsk´a61 , P. Crochet131 , E. Cuautle70 , L. Cunqueiro94 ,141 , T. Dahms102 ,114 , A. Dainese56 , M.C. Danisch101 , A. Danu68 , D. Das106 , I. Das106 , S. Das4, A. Dash85 , S. Dash48 , S. De49 , A. De Caro32 , G. de Cataldo52 , C. de Conti118 , J. de Cuveland40 , A. De Falco26 , D. De Gruttola11 ,32 , N. De Marco58 , S. De Pasquale32 , R.D. De Souza119 , H.F. Degenhardt118 , A. Deisting103 ,101 , A. Deloff84 , S. Delsanto28 , C. Deplano89 , P. Dhankher48 , D. Di Bari35 , A. Di Mauro36 , B. Di Ruzza56 , R.A. Diaz9, T. Dietel122 , P. Dillenseger69 , Y. Ding7, R. Divi`a36 , Ø. Djuvsland24 , A. Dobrin36 , D. Domenicis Gimenez118 , B. D¨onigus69 , O. Dordic23 , L.V.R. Doremalen63 , A.K. Dubey138 , A. Dubla103 , L. Ducroux132 , S. Dudi97 , A.K. Duggal97 , M. Dukhishyam85 , P. Dupieux131 , R.J. Ehlers143 , D. Elia52 , E. Endress108 , H. Engel74 , E. Epple143 , B. Erazmus111 , F. Erhardt96 , M.R. Ersdal24 , B. Espagnon61 , G. Eulisse36 , J. Eum20 , D. Evans107 , S. Evdokimov90 , L. Fabbietti102 ,114 , M. Faggin31 , J. Faivre78 , A. Fantoni51 , M. Fasel94 , L. Feldkamp141 , A. Feliciello58 , G. Feofilov137 , A. Fern´andez T´ellez2, A. Ferretti28 , – 32 – JHEP07(2018)103 A. Festanti31 ,36 , V.J.G. Feuillard134 ,131 , J. Figiel115 , M.A.S. Figueredo118 , S. Filchagin105 , D. Finogeev62 , F.M. Fionda24 , G. Fiorenza52 , M. Floris36 , S. Foertsch73 , P. Foka103 , S. Fokin87 , E. Fragiacomo59 , A. Francescon36 , A. Francisco111 , U. Frankenfeld103 , G.G. Fronze28 , U. Fuchs36 , C. Furget78 , A. Furs62 , M. Fusco Girard32 , J.J. Gaardhøje88 , M. Gagliardi28 , A.M. Gago108 , K. Gajdosova88 , M. Gallio28 , C.D. Galvan117 , P. Ganoti83 , C. Garabatos103 , E. Garcia-Solis12 , K. Garg30 , C. Gargiulo36 , P. Gasik102 ,114 , E.F. Gauger116 , M.B. Gay Ducati71 , M. Germain111 , J. Ghosh106 , P. Ghosh138 , S.K. Ghosh4, P. Gianotti51 , P. Giubellino58 ,103 , P. Giubilato31 , P. Gl¨assel101 , D.M. Gom´ez Coral72 , A. Gomez Ramirez74 , V. Gonzalez103 , P. Gonz´alez-Zamora2, S. Gorbunov40 , L. G¨orlich115 , S. Gotovac126 , V. Grabski72 , L.K. Graczykowski139 , K.L. Graham107 , L. Greiner79 , A. Grelli63 , C. Grigoras36 , V. Grigoriev91 , A. Grigoryan1, S. Grigoryan75 , J.M. Gronefeld103 , F. Grosa33 , J.F. Grosse-Oetringhaus36 , R. Grosso103 , R. Guernane78 , B. Guerzoni29 , M. Guittiere111 , K. Gulbrandsen88 , T. Gunji129 , A. Gupta98 , R. Gupta98 , I.B. Guzman2, R. Haake36 , M.K. Habib103 , C. Hadjidakis61 , H. Hamagaki81 , G. Hamar142 , J.C. Hamon133 , M.R. Haque63 , J.W. Harris143 , A. Harton12 , H. Hassan78 , D. Hatzifotiadou53 ,11 , S. Hayashi129 , S.T. Heckel69 , E. Hellb¨ar69 , H. Helstrup37 , A. Herghelegiu47 , E.G. Hernandez2, G. Herrera Corral10 , F. Herrmann141 , K.F. Hetland37 , T.E. Hilden44 , H. Hillemanns36 , C. Hills125 , B. Hippolyte133 , B. Hohlweger102 , D. Horak38 , S. Hornung103 , R. Hosokawa130 ,78 , P. Hristov36 , C. Hughes127 , P. Huhn69 , T.J. Humanic19 , H. Hushnud106 , N. Hussain42 , T. Hussain18 , D. Hutter40 , D.S. Hwang21 , J.P. Iddon125 , S.A. Iga Buitron70 , R. Ilkaev105 , M. Inaba130 , M. Ippolitov87 , M.S. Islam106 , M. Ivanov103 , V. Ivanov95 , V. Izucheev90 , B. Jacak79 , N. Jacazio29 , P.M. Jacobs79 , M.B. Jadhav48 , S. Jadlovska113 , J. Jadlovsky113 , S. Jaelani63 , C. Jahnke118 ,114 , M.J. Jakubowska139 , M.A. Janik139 , C. Jena85 , M. Jercic96 , R.T. Jimenez Bustamante103 , M. Jin123 , P.G. Jones107 , A. Jusko107 , P. Kalinak65 , A. Kalweit36 , J.H. Kang144 , V. Kaplin91 , S. Kar7, A. Karasu Uysal77 , O. Karavichev62 , T. Karavicheva62 , P. Karczmarczyk36 , E. Karpechev62 , U. Kebschull74 , R. Keidel46 , D.L.D. Keijdener63 , M. Keil36 , B. Ketzer43 , Z. Khabanova89 , S. Khan18 , S.A. Khan138 , A. Khanzadeev95 , Y. Kharlov90 , A. Khatun18 , A. Khuntia49 , M.M. Kielbowicz115 , B. Kileng37 , B. Kim130 , D. Kim144 , D.J. Kim124 , E.J. Kim14 , H. Kim144 , J.S. Kim41 , J. Kim101 , M. Kim60 ,101 , S. Kim21 , T. Kim144 , T. Kim144 , S. Kirsch40 , I. Kisel40 , S. Kiselev64 , A. Kisiel139 , J.L. Klay6, C. Klein69 , J. Klein36 ,58 , C. Klein-B¨osing141 , S. Klewin101 , A. Kluge36 , M.L. Knichel36 ,101 , A.G. Knospe123 , C. Kobdaj112 , M. Kofarago142 , M.K. K¨ohler101 , T. Kollegger103 , N. Kondratyeva91 , E. Kondratyuk90 , A. Konevskikh62 , M. Konyushikhin140 , O. Kovalenko84 , V. Kovalenko137 , M. Kowalski115 , I. Kr´alik65 , A. Kravˇc´akov´a39 , L. Kreis103 , M. Krivda107 ,65 , F. Krizek93 , M. Kr¨uger69 , E. Kryshen95 , M. Krzewicki40 , A.M. Kubera19 , V. Kuˇcera60 ,93 , C. Kuhn133 , P.G. Kuijer89 , J. Kumar48 , L. Kumar97 , S. Kumar48 , S. Kundu85 , P. Kurashvili84 , A. Kurepin62 , A.B. Kurepin62 , A. Kuryakin105 , S. Kushpil93 , M.J. Kweon60 , Y. Kwon144 , S.L. La Pointe40 , P. La Rocca30 , Y.S. Lai79 , I. Lakomov36 , R. Langoy121 , K. Lapidus143 , C. Lara74 , A. Lardeux23 , P. Larionov51 , A. Lattuca28 , E. Laudi36 , R. Lavicka38 , R. Lea27 , L. Leardini101 , S. Lee144 , F. Lehas89 , S. Lehner110 , J. Lehrbach40 , R.C. Lemmon92 , E. Leogrande63 , I. Le´on Monz´on117 , P. L´evai142 , X. Li13 , X.L. Li7, J. Lien121 , R. Lietava107 , B. Lim20 , S. Lindal23 , V. Lindenstruth40 , S.W. Lindsay125 , C. Lippmann103 , M.A. Lisa19 , V. Litichevskyi44 , A. Liu79 , H.M. Ljunggren80 , W.J. Llope140 , D.F. Lodato63 , V. Loginov91 , C. Loizides79 ,94 , P. Loncar126 , X. Lopez131 , E. L´opez Torres9, A. Lowe142 , P. Luettig69 , J.R. Luhder141 , M. Lunardon31 , G. Luparello59 , M. Lupi36 , A. Maevskaya62 , M. Mager36 , S.M. Mahmood23 , A. Maire133 , R.D. Majka143 , M. Malaev95 , L. Malinina75 ,ii, D. Mal’Kevich64 , P. Malzacher103 , A. Mamonov105 , V. Manko87 , F. Manso131 , V. Manzari52 , Y. Mao7, M. Marchisone132 ,128 ,73 , J. Mareˇs67 , – 33 – JHEP07(2018)103 G.V. Margagliotti27 , A. Margotti53 , J. Margutti63 , A. Mar´ın103 , C. Markert116 , M. Marquard69 , N.A. Martin103 , P. Martinengo36 , M.I. Mart´ınez2, G. Mart´ınez Garc´ıa111 , M. Martinez Pedreira36 , S. Masciocchi103 , M. Masera28 , A. Masoni54 , L. Massacrier61 , E. Masson111 , A. Mastroserio52 , A.M. Mathis102 ,114 , P.F.T. Matuoka118 , A. Matyja115 ,127 , C. Mayer115 , M. Mazzilli35 , M.A. Mazzoni57 , F. Meddi25 , Y. Melikyan91 , A. Menchaca-Rocha72 , E. Meninno32 , J. Mercado P´erez101 , M. Meres15 , C.S. Meza108 , S. Mhlanga122 , Y. Miake130 , L. Micheletti28 , M.M. Mieskolainen44 , D.L. Mihaylov102 , K. Mikhaylov64 ,75 , A. Mischke63 , A.N. Mishra70 , D. Mi´skowiec103 , J. Mitra138 , C.M. Mitu68 , N. Mohammadi36 ,63 , A.P. Mohanty63 , B. Mohanty85 , M. Mohisin Khan18 ,iii, D.A. Moreira De Godoy141 , L.A.P. Moreno2, S. Moretto31 , A. Morreale111 , A. Morsch36 , V. Muccifora51 , E. Mudnic126 , D. M¨uhlheim141 , S. Muhuri138 , M. Mukherjee4, J.D. Mulligan143 , M.G. Munhoz118 , K. M¨unning43 , M.I.A. Munoz79 , R.H. Munzer69 , H. Murakami129 , S. Murray73 , L. Musa36 , J. Musinsky65 , C.J. Myers123 , J.W. Myrcha139 , B. Naik48 , R. Nair84 , B.K. Nandi48 , R. Nania53 ,11 , E. Nappi52 , A. Narayan48 , M.U. Naru16 , H. Natal da Luz118 , C. Nattrass127 , S.R. Navarro2, K. Nayak85 , R. Nayak48 , T.K. Nayak138 , S. Nazarenko105 , R.A. Negrao De Oliveira69 ,36 , L. Nellen70 , S.V. Nesbo37 , G. Neskovic40 , F. Ng123 , M. Nicassio103 , J. Niedziela139 ,36 , B.S. Nielsen88 , S. Nikolaev87 , S. Nikulin87 , V. Nikulin95 , F. Noferini11 ,53 , P. Nomokonov75 , G. Nooren63 , J.C.C. Noris2, J. Norman78 ,125 , A. Nyanin87 , J. Nystrand24 , H. Oh144 , A. Ohlson101 , J. Oleniacz139 , A.C. Oliveira Da Silva118 , M.H. Oliver143 , J. Onderwaater103 , C. Oppedisano58 , R. Orava44 , M. Oravec113 , A. Ortiz Velasquez70 , A. Oskarsson80 , J. Otwinowski115 , K. Oyama81 , Y. Pachmayer101 , V. Pacik88 , D. Pagano136 , G. Pai´c70 , P. Palni7, J. Pan140 , A.K. Pandey48 , S. Panebianco134 , V. Papikyan1, P. Pareek49 , J. Park60 , J.E. Parkkila124 , S. Parmar97 , A. Passfeld141 , S.P. Pathak123 , R.N. Patra138 , B. Paul58 , H. Pei7, T. Peitzmann63 , X. Peng7, L.G. Pereira71 , H. Pereira Da Costa134 , D. Peresunko87 , E. Perez Lezama69 , V. Peskov69 , Y. Pestov5, V. Petr´aˇcek38 , M. Petrovici47 , C. Petta30 , R.P. Pezzi71 , S. Piano59 , M. Pikna15 , P. Pillot111 , L.O.D.L. Pimentel88 , O. Pinazza53 ,36 , L. Pinsky123 , S. Pisano51 , D.B. Piyarathna123 , M. P losko´n79 , M. Planinic96 , F. Pliquett69 , J. Pluta139 , S. Pochybova142 , P.L.M. Podesta-Lerma117 , M.G. Poghosyan94 , B. Polichtchouk90 , N. Poljak96 , W. Poonsawat112 , A. Pop47 , H. Poppenborg141 , S. Porteboeuf-Houssais131 , V. Pozdniakov75 , S.K. Prasad4, R. Preghenella53 , F. Prino58 , C.A. Pruneau140 , I. Pshenichnov62 , M. Puccio28 , V. Punin105 , J. Putschke140 , S. Raha4, S. Rajput98 , J. Rak124 , A. Rakotozafindrabe134 , L. Ramello34 , F. Rami133 , R. Raniwala99 , S. Raniwala99 , S.S. R¨as¨anen44 , B.T. Rascanu69 , V. Ratza43 , I. Ravasenga33 , K.F. Read127 ,94 , K. Redlich84 ,iv, A. Rehman24 , P. Reichelt69 , F. Reidt36 , X. Ren7, R. Renfordt69 , A. Reshetin62 , J.-P. Revol11 , K. Reygers101 , V. Riabov95 , T. Richert63 ,80 , M. Richter23 , P. Riedler36 , W. Riegler36 , F. Riggi30 , C. Ristea68 , M. Rodr´ıguez Cahuantzi2, K. Røed23 , R. Rogalev90 , E. Rogochaya75 , D. Rohr36 , D. R¨ohrich24 , P.S. Rokita139 , F. Ronchetti51 , E.D. Rosas70 , K. Roslon139 , P. Rosnet131 , A. Rossi56 ,31 , A. Rotondi135 , F. Roukoutakis83 , C. Roy133 , P. Roy106 , O.V. Rueda70 , R. Rui27 , B. Rumyantsev75 , A. Rustamov86 , E. Ryabinkin87 , Y. Ryabov95 , A. Rybicki115 , S. Saarinen44 , S. Sadhu138 , S. Sadovsky90 , K. ˇ Safaˇr´ık36 , S.K. Saha138 , B. Sahoo48 , P. Sahoo49 , R. Sahoo49 , S. Sahoo66 , P.K. Sahu66 , J. Saini138 , S. Sakai130 , M.A. Saleh140 , S. Sambyal98 , V. Samsonov95 ,91 , A. Sandoval72 , A. Sarkar73 , D. Sarkar138 , N. Sarkar138 , P. Sarma42 , M.H.P. Sas63 , E. Scapparone53 , F. Scarlassara31 , B. Schaefer94 , H.S. Scheid69 , C. Schiaua47 , R. Schicker101 , C. Schmidt103 , H.R. Schmidt100 , M.O. Schmidt101 , M. Schmidt100 , N.V. Schmidt94 ,69 , J. Schukraft36 , Y. Schutz36 ,133 , K. Schwarz103 , K. Schweda103 , G. Scioli29 , E. Scomparin58 , M. ˇ Sefˇc´ık39 , J.E. Seger17 , Y. Sekiguchi129 , D. Sekihata45 , I. Selyuzhenkov91 ,103 , K. Senosi73 , S. Senyukov133 , E. Serradilla72 , P. Sett48 , A. Sevcenco68 , – 34 – JHEP07(2018)103 A. Shabanov62 , A. Shabetai111 , R. Shahoyan36 , W. Shaikh106 , A. Shangaraev90 , A. Sharma97 , A. Sharma98 , N. Sharma97 , A.I. Sheikh138 , K. Shigaki45 , M. Shimomura82 , S. Shirinkin64 , Q. Shou7,109 , K. Shtejer28 , Y. Sibiriak87 , S. Siddhanta54 , K.M. Sielewicz36 , T. Siemiarczuk84 , D. Silvermyr80 , G. Simatovic89 , G. Simonetti102 ,36 , R. Singaraju138 , R. Singh85 , V. Singhal138 , T. Sinha106 , B. Sitar15 , M. Sitta34 , T.B. Skaali23 , M. Slupecki124 , N. Smirnov143 , R.J.M. Snellings63 , T.W. Snellman124 , J. Song20 , F. Soramel31 , S. Sorensen127 , F. Sozzi103 , I. Sputowska115 , J. Stachel101 , I. Stan68 , P. Stankus94 , E. Stenlund80 , D. Stocco111 , M.M. Storetvedt37 , P. Strmen15 , A.A.P. Suaide118 , T. Sugitate45 , C. Suire61 , M. Suleymanov16 , M. Suljic36 ,27 , R. Sultanov64 , M. ˇ Sumbera93 , S. Sumowidagdo50 , K. Suzuki110 , S. Swain66 , A. Szabo15 , I. Szarka15 , U. Tabassam16 , J. Takahashi119 , G.J. Tambave24 , N. Tanaka130 , M. Tarhini61 ,111 , M. Tariq18 , M.G. Tarzila47 , A. Tauro36 , G. Tejeda Mu˜noz2, A. Telesca36 , C. Terrevoli31 , B. Teyssier132 , D. Thakur49 , S. Thakur138 , D. Thomas116 , F. Thoresen88 , R. Tieulent132 , A. Tikhonov62 , A.R. Timmins123 , A. Toia69 , N. Topilskaya62 , M. Toppi51 , S.R. Torres117 , S. Tripathy49 , S. Trogolo28 , G. Trombetta35 , L. Tropp39 , V. Trubnikov3, W.H. Trzaska124 , T.P. Trzcinski139 , B.A. Trzeciak63 , T. Tsuji129 , A. Tumkin105 , R. Turrisi56 , T.S. Tveter23 , K. Ullaland24 , E.N. Umaka123 , A. Uras132 , G.L. Usai26 , A. Utrobicic96 , M. Vala113 , J.W. Van Hoorne36 , M. van Leeuwen63 , P. Vande Vyvre36 , D. Varga142 , A. Vargas2, M. Vargyas124 , R. Varma48 , M. Vasileiou83 , A. Vasiliev87 , A. Vauthier78 , O. V´azquez Doce102 ,114 , V. Vechernin137 , A.M. Veen63 , A. Velure24 , E. Vercellin28 , S. Vergara Lim´on2, L. Vermunt63 , R. Vernet8, R. V´ertesi142 , L. Vickovic126 , J. Viinikainen124 , Z. Vilakazi128 , O. Villalobos Baillie107 , A. Villatoro Tello2, A. Vinogradov87 , T. Virgili32 , V. Vislavicius80 , A. Vodopyanov75 , M.A. V¨olkl100 , K. Voloshin64 , S.A. Voloshin140 , G. Volpe35 , B. von Haller36 , I. Vorobyev114 ,102 , D. Voscek113 , D. Vranic103 ,36 , J. Vrl´akov´a39 , B. Wagner24 , H. Wang63 , M. Wang7, Y. Watanabe130 ,129 , M. Weber110 , S.G. Weber103 , A. Wegrzynek36 , D.F. Weiser101 , S.C. Wenzel36 , J.P. Wessels141 , U. Westerhoff141 , A.M. Whitehead122 , J. Wiechula69 , J. Wikne23 , G. Wilk84 , J. Wilkinson53 , G.A. Willems141 ,36 , M.C.S. Williams53 , E. Willsher107 , B. Windelband101 , W.E. Witt127 , R. Xu7, S. Yalcin77 , K. Yamakawa45 , S. Yano45 , Z. Yin7, H. Yokoyama130 ,78 , I.-K. Yoo20 , J.H. Yoon60 , V. Yurchenko3, V. Zaccolo58 , A. Zaman16 , C. Zampolli36 , H.J.C. Zanoli118 , N. Zardoshti107 , A. Zarochentsev137 , P. Z´avada67 , N. Zaviyalov105 , H. Zbroszczyk139 , M. Zhalov95 , X. Zhang7, Y. Zhang7, Z. Zhang131 ,7, C. Zhao23 , V. Zherebchevskii137 , N. Zhigareva64 , D. Zhou7, Y. Zhou88 , Z. Zhou24 , H. Zhu7, J. Zhu7, Y. Zhu7, A. Zichichi29 ,11 , M.B. Zimmermann36 , G. Zinovjev3, J. Zmeskal110 , S. Zou7, iDipartimento DET del Politecnico di Torino, Turin, Italy ii M.V. Lomonosov Moscow State University, D.V. Skobeltsyn Institute of Nuclear, Physics, Moscow, Russia iii Department of Applied Physics, Aligarh Muslim University, Aligarh, India iv Institute of Theoretical Physics, University of Wroclaw, Poland 1A.I. Alikhanyan National Science Laboratory (Yerevan Physics Institute) Foundation, Yerevan, Armenia 2Benem´erita Universidad Aut´onoma de Puebla, Puebla, Mexico 3Bogolyubov Institute for Theoretical Physics, National Academy of Sciences of Ukraine, Kiev, Ukraine 4Bose Institute, Department of Physics and Centre for Astroparticle Physics and Space Science (CAPSS), Kolkata, India 5Budker Institute for Nuclear Physics, Novosibirsk, Russia – 35 – JHEP07(2018)103 6California Polytechnic State University, San Luis Obispo, California, United States 7Central China Normal University, Wuhan, China 8Centre de Calcul de l’IN2P3, Villeurbanne, Lyon, France 9Centro de Aplicaciones Tecnol´ogicas y Desarrollo Nuclear (CEADEN), Havana, Cuba 10 Centro de Investigaci´on y de Estudios Avanzados (CINVESTAV), Mexico City and M´erida, Mexico 11 Centro Fermi - Museo Storico della Fisica e Centro Studi e Ricerche “Enrico Fermi’, Rome, Italy 12 Chicago State University, Chicago, Illinois, United States 13 China Institute of Atomic Energy, Beijing, China 14 Chonbuk National University, Jeonju, Republic of Korea 15 Comenius University Bratislava, Faculty of Mathematics, Physics and Informatics, Bratislava, Slovakia 16 COMSATS Institute of Information Technology (CIIT), Islamabad, Pakistan 17 Creighton University, Omaha, Nebraska, United States 18 Department of Physics, Aligarh Muslim University, Aligarh, India 19 Department of Physics, Ohio State University, Columbus, Ohio, United States 20 Department of Physics, Pusan National University, Pusan, Republic of Korea 21 Department of Physics, Sejong University, Seoul, Republic of Korea 22 Department of Physics, University of California, Berkeley, California, United States 23 Department of Physics, University of Oslo, Oslo, Norway 24 Department of Physics and Technology, University of Bergen, Bergen, Norway 25 Dipartimento di Fisica dell’Universit`a ‘La Sapienza’ and Sezione INFN, Rome, Italy 26 Dipartimento di Fisica dell’Universit`a and Sezione INFN, Cagliari, Italy 27 Dipartimento di Fisica dell’Universit`a and Sezione INFN, Trieste, Italy 28 Dipartimento di Fisica dell’Universit`a and Sezione INFN, Turin, Italy 29 Dipartimento di Fisica e Astronomia dell’Universit`a and Sezione INFN, Bologna, Italy 30 Dipartimento di Fisica e Astronomia dell’Universit`a and Sezione INFN, Catania, Italy 31 Dipartimento di Fisica e Astronomia dell’Universit`a and Sezione INFN, Padova, Italy 32 Dipartimento di Fisica ‘E.R. Caianiello’ dell’Universit`a and Gruppo Collegato INFN, Salerno, Italy 33 Dipartimento DISAT del Politecnico and Sezione INFN, Turin, Italy 34 Dipartimento di Scienze e Innovazione Tecnologica dell’Universit`a del Piemonte Orientale and INFN Sezione di Torino, Alessandria, Italy 35 Dipartimento Interateneo di Fisica ‘M. Merlin’ and Sezione INFN, Bari, Italy 36 European Organization for Nuclear Research (CERN), Geneva, Switzerland 37 Faculty of Engineering and Science, Western Norway University of Applied Sciences, Bergen, Norway 38 Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, Prague, Czech Republic 39 Faculty of Science, P.J. ˇ Saf´arik University, Koˇsice, Slovakia 40 Frankfurt Institute for Advanced Studies, Johann Wolfgang Goethe-Universit¨at Frankfurt, Frankfurt, Germany 41 Gangneung-Wonju National University, Gangneung, Republic of Korea 42 Gauhati University, Department of Physics, Guwahati, India 43 Helmholtz-Institut f¨ur Strahlenund Kernphysik, Rheinische Friedrich-Wilhelms-Universit¨at Bonn, Bonn, Germany 44 Helsinki Institute of Physics (HIP), Helsinki, Finland 45 Hiroshima University, Hiroshima, Japan 46 Hochschule Worms, Zentrum f¨ur Technologietransfer und Telekommunikation (ZTT), Worms, Germany 47 Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest, Romania 48 Indian Institute of Technology Bombay (IIT), Mumbai, India 49 Indian Institute of Technology Indore, Indore, India 50 Indonesian Institute of Sciences, Jakarta, Indonesia – 36 – JHEP07(2018)103 51 INFN, Laboratori Nazionali di Frascati, Frascati, Italy 52 INFN, Sezione di Bari, Bari, Italy 53 INFN, Sezione di Bologna, Bologna, Italy 54 INFN, Sezione di Cagliari, Cagliari, Italy 55 INFN, Sezione di Catania, Catania, Italy 56 INFN, Sezione di Padova, Padova, Italy 57 INFN, Sezione di Roma, Rome, Italy 58 INFN, Sezione di Torino, Turin, Italy 59 INFN, Sezione di Trieste, Trieste, Italy 60 Inha University, Incheon, Republic of Korea 61 Institut de Physique Nucl´eaire d’Orsay (IPNO), Institut National de Physique Nucl´eaire et de Physique des Particules (IN2P3/CNRS), Universit´e de Paris-Sud, Universit´e Paris-Saclay, Orsay, France 62 Institute for Nuclear Research, Academy of Sciences, Moscow, Russia 63 Institute for Subatomic Physics, Utrecht University/Nikhef, Utrecht, Netherlands 64 Institute for Theoretical and Experimental Physics, Moscow, Russia 65 Institute of Experimental Physics, Slovak Academy of Sciences, Koˇsice, Slovakia 66 Institute of Physics, Bhubaneswar, India 67 Institute of Physics of the Czech Academy of Sciences, Prague, Czech Republic 68 Institute of Space Science (ISS), Bucharest, Romania 69 Institut f¨ur Kernphysik, Johann Wolfgang Goethe-Universit¨at Frankfurt, Frankfurt, Germany 70 Instituto de Ciencias Nucleares, Universidad Nacional Aut´onoma de M´exico, Mexico City, Mexico 71 Instituto de F´ısica, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, Brazil 72 Instituto de F´ısica, Universidad Nacional Aut´onoma de M´exico, Mexico City, Mexico 73 iThemba LABS, National Research Foundation, Somerset West, South Africa 74 Johann-Wolfgang-Goethe Universit¨at Frankfurt Institut f¨ur Informatik, Fachbereich Informatik und Mathematik, Frankfurt, Germany 75 Joint Institute for Nuclear Research (JINR), Dubna, Russia 76 Korea Institute of Science and Technology Information, Daejeon, Republic of Korea 77 KTO Karatay University, Konya, Turkey 78 Laboratoire de Physique Subatomique et de Cosmologie, Universit´e Grenoble-Alpes, CNRS-IN2P3, Grenoble, France 79 Lawrence Berkeley National Laboratory, Berkeley, California, United States 80 Lund University Department of Physics, Division of Particle Physics, Lund, Sweden 81 Nagasaki Institute of Applied Science, Nagasaki, Japan 82 Nara Women’s University (NWU), Nara, Japan 83 National and Kapodistrian University of Athens, School of Science, Department of Physics , Athens, Greece 84 National Centre for Nuclear Research, Warsaw, Poland 85 National Institute of Science Education and Research, HBNI, Jatni, India 86 National Nuclear Research Center, Baku, Azerbaijan 87 National Research Centre Kurchatov Institute, Moscow, Russia 88 Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark 89 Nikhef, National institute for subatomic physics, Amsterdam, Netherlands 90 NRC ‘Kurchatov Institute’ IHEP, Protvino, Russia 91 NRNU Moscow Engineering Physics Institute, Moscow, Russia 92 Nuclear Physics Group, STFC Daresbury Laboratory, Daresbury, United Kingdom 93 Nuclear Physics Institute of the Czech Academy of Sciences, ˇ Reˇz u Prahy, Czech Republic 94 Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States 95 Petersburg Nuclear Physics Institute, Gatchina, Russia 96 Physics department, Faculty of science, University of Zagreb, Zagreb, Croatia 97 Physics Department, Panjab University, Chandigarh, India – 37 – JHEP07(2018)103 98 Physics Department, University of Jammu, Jammu, India 99 Physics Department, University of Rajasthan, Jaipur, India 100 Physikalisches Institut, Eberhard-Karls-Universit¨at T¨ubingen, T¨ubingen, Germany 101 Physikalisches Institut, Ruprecht-Karls-Universit¨at Heidelberg, Heidelberg, Germany 102 Physik Department, Technische Universit¨at M¨unchen, Munich, Germany 103 Research Division and ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum f¨ur Schwerionenforschung GmbH, Darmstadt, Germany 104 Rudjer Boˇskovi´c Institute, Zagreb, Croatia 105 Russian Federal Nuclear Center (VNIIEF), Sarov, Russia 106 Saha Institute of Nuclear Physics, Kolkata, India 107 School of Physics and Astronomy, University of Birmingham, Birmingham, United Kingdom 108 Secci´on F´ısica, Departamento de Ciencias, Pontificia Universidad Cat´olica del Per´u, Lima, Peru 109 Shanghai Institute of Applied Physics, Shanghai, China 110 Stefan Meyer Institut f¨ur Subatomare Physik (SMI), Vienna, Austria 111 SUBATECH, IMT Atlantique, Universit´e de Nantes, CNRS-IN2P3, Nantes, France 112 Suranaree University of Technology, Nakhon Ratchasima, Thailand 113 Technical University of Koˇsice, Koˇsice, Slovakia 114 Technische Universit¨at M¨unchen, Excellence Cluster ‘Universe’, Munich, Germany 115 The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Cracow, Poland 116 The University of Texas at Austin, Austin, Texas, United States 117 Universidad Aut´onoma de Sinaloa, Culiac´an, Mexico 118 Universidade de S˜ao Paulo (USP), S˜ao Paulo, Brazil 119 Universidade Estadual de Campinas (UNICAMP), Campinas, Brazil 120 Universidade Federal do ABC, Santo Andre, Brazil 121 University College of Southeast Norway, Tonsberg, Norway 122 University of Cape Town, Cape Town, South Africa 123 University of Houston, Houston, Texas, United States 124 University of Jyv¨askyl¨a, Jyv¨askyl¨a, Finland 125 University of Liverpool, Department of Physics Oliver Lodge Laboratory , Liverpool, United Kingdom 126 University of Split, Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture, Split, Croatia 127 University of Tennessee, Knoxville, Tennessee, United States 128 University of the Witwatersrand, Johannesburg, South Africa 129 University of Tokyo, Tokyo, Japan 130 University of Tsukuba, Tsukuba, Japan 131 Universit´e Clermont Auvergne, CNRS/IN2P3, LPC, Clermont-Ferrand, France 132 Universit´e de Lyon, Universit´e Lyon 1, CNRS/IN2P3, IPN-Lyon, Villeurbanne, Lyon, France 133 Universit´e de Strasbourg, CNRS, IPHC UMR 7178, F-67000 Strasbourg, France, Strasbourg, France 134 Universit´e Paris-Saclay Centre d’ ´ Etudes de Saclay (CEA), IRFU, Department de Physique Nucl´eaire (DPhN), Saclay, France 135 Universit`a degli Studi di Pavia, Pavia, Italy 136 Universit`a di Brescia, Brescia, Italy 137 V. Fock Institute for Physics, St. Petersburg State University, St. Petersburg, Russia 138 Variable Energy Cyclotron Centre, Kolkata, India 139 Warsaw University of Technology, Warsaw, Poland 140 Wayne State University, Detroit, Michigan, United States 141 Westf¨alische Wilhelms-Universit¨at M¨unster, Institut f¨ur Kernphysik, M¨unster, Germany 142 Wigner Research Centre for Physics, Hungarian Academy of Sciences, Budapest, Hungary 143 Yale University, New Haven, Connecticut, United States 144 Yonsei University, Seoul, Republic of Korea – 38 –