physical review c102, 055203 (2020)

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PHYSICAL REVIEW C 102, 055203 (2020) Elliptic and triangular flow of (anti)deuterons in Pb-Pb collisions at s NN = 5.02 TeV S. Acharya et al. (ALICE Collaboration) (Received 5 June 2020; accepted 27 October 2020; published 17 November 2020) The measurements of the (anti)deuteron elliptic flow (v 2 ) and the first measurements of triangular flow (v 3 ) in Pb-Pb collisions at a center-of-mass energy per nucleon-nucleon collision s NN = 5.02 TeV are presented. A mass ordering at low transverse momentum ( p T ) is observed when comparing these measurements with those of other identified hadrons, as expected from relativistic hydrodynamics. The measured (anti)deuteron v 2 lies between the predictions from the simple coalescence and blast-wave models, which provide a good description of the data only for more peripheral and for more central collisions, respectively. The mass number scaling, which is violated for v 2 , is approximately valid for the (anti)deuterons v 3 . The measured v 2 and v 3 are also compared with the predictions from a coalescence approach with phase-space distributions of nucleons generated by IEBE- VISHNU with AMPT initial conditions coupled with URQMD, and from a dynamical model based on relativistic hydrodynamics coupled to the hadronic afterburner SMASH. The model predictions are consistent with the data within the uncertainties in midcentral collisions, while a deviation is observed in the most central collisions. DOI: 10.1103/PhysRevC.102.055203 I. INTRODUCTION The production mechanism of light (anti)nuclei in high- energy hadronic collisions is still not fully clear and is under intense debate in the scientific community [15]. The un- derstanding of the production of loosely bound multibaryon states in heavy-ion collisions has additional complications due to the fact that the phase transition is followed by a hadron gas phase with intense rescattering of hadrons. At the Large Hadron Collider (LHC) energies, the lifetime of the hadronic phase between chemical and kinetic freeze-out is in the range 4–7 fm/c [6] and the kinetic freeze-out temperature, when elastic interactions cease, is of the order of 100 MeV [7,8]. The binding energy of multibaryon systems such as light (anti)nuclei typically does not exceed a few MeV, which is almost two orders of magnitude smaller than the temperature of the system. Considering the high density of hadrons in the posthadronization stage and the large dissociation cross sections of light (anti)nuclei, it is not clear how such loosely bound systems can survive under these extreme conditions. Existing phenomenological models provide very differ- ent interpretations for this observation. In the statistical hadronization model [13,9,10], light (anti)nuclei as well as all other hadron species are assumed to be emitted by a source in local thermal and hadrochemical equilibrium. Their abun- dances are fixed at the chemical freeze-out, occurring at a temperature of T chem = 156 ± 4 MeV for Pb-Pb collisions at Full author list given at the end of the article. Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. the LHC [11]. This model provides a good description of the measured hadron yields in central nucleus-nucleus collisions [1]. However, the mechanism of hadron production and the propagation of loosely bound states through the hadron gas phase are not addressed by this model. In the context of the statistical hadronization model, it has been conjectured that such objects could be produced at the phase transition as compact colorless quark clusters with the same quantum numbers of the final-state hadrons. The survival of these states at high temperatures is interpreted as due to the low interaction cross section with the surrounding medium [1]. In the coalescence approach, multibaryon states are as- sumed to be formed by the coalescence of baryons at the kinetic freeze-out. In the simplest versions of this model [12,13], baryons are treated as pointlike particles and the coa- lescence happens instantaneously if the momentum difference between nucleons is smaller than a given threshold, which is typically of the order of 100 MeV/c, while spatial coor- dinates are ignored. In the state-of-the-art implementations of the coalescence approach [4,14], the quantum-mechanical properties of baryons and their bound states are taken into account and the coalescence probability is calculated from the overlap between the wave functions of baryons and the Wigner density of the final-state cluster. All light (anti)nuclei produced at the phase transition are assumed to be destroyed by the interactions in the hadron gas phase and regenerated with the same amount only at the latest stage of the system evolution. To address the open question of the survival of loosely bound multibaryon states in the hadron gas phase with intense rescattering, models based on relativistic hydrodynamics cou- pled to a hadronic afterburner have been recently developed [4,5]. In these models, nucleons and light nuclei are pro- duced at the phase transition using the Cooper-Frye formula [15], which describes the hadron production based on the 2469-9985/2020/102(5)/055203(19) 055203-1 ©2020 CERN, for the ALICE Collaboration

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Page 1: PHYSICAL REVIEW C102, 055203 (2020)

PHYSICAL REVIEW C 102, 055203 (2020)

Elliptic and triangular flow of (anti)deuterons in Pb-Pb collisions at√

sNN = 5.02 TeV

S. Acharya et al.∗(ALICE Collaboration)

(Received 5 June 2020; accepted 27 October 2020; published 17 November 2020)

The measurements of the (anti)deuteron elliptic flow (v2) and the first measurements of triangular flow (v3)in Pb-Pb collisions at a center-of-mass energy per nucleon-nucleon collision

√sNN = 5.02 TeV are presented.

A mass ordering at low transverse momentum (pT) is observed when comparing these measurements with thoseof other identified hadrons, as expected from relativistic hydrodynamics. The measured (anti)deuteron v2 liesbetween the predictions from the simple coalescence and blast-wave models, which provide a good descriptionof the data only for more peripheral and for more central collisions, respectively. The mass number scaling, whichis violated for v2, is approximately valid for the (anti)deuterons v3. The measured v2 and v3 are also comparedwith the predictions from a coalescence approach with phase-space distributions of nucleons generated by IEBE-VISHNU with AMPT initial conditions coupled with URQMD, and from a dynamical model based on relativistichydrodynamics coupled to the hadronic afterburner SMASH. The model predictions are consistent with the datawithin the uncertainties in midcentral collisions, while a deviation is observed in the most central collisions.

DOI: 10.1103/PhysRevC.102.055203

I. INTRODUCTION

The production mechanism of light (anti)nuclei in high-energy hadronic collisions is still not fully clear and is underintense debate in the scientific community [1–5]. The un-derstanding of the production of loosely bound multibaryonstates in heavy-ion collisions has additional complications dueto the fact that the phase transition is followed by a hadrongas phase with intense rescattering of hadrons. At the LargeHadron Collider (LHC) energies, the lifetime of the hadronicphase between chemical and kinetic freeze-out is in the range4–7 fm/c [6] and the kinetic freeze-out temperature, whenelastic interactions cease, is of the order of 100 MeV [7,8].The binding energy of multibaryon systems such as light(anti)nuclei typically does not exceed a few MeV, which isalmost two orders of magnitude smaller than the temperatureof the system. Considering the high density of hadrons inthe posthadronization stage and the large dissociation crosssections of light (anti)nuclei, it is not clear how such looselybound systems can survive under these extreme conditions.

Existing phenomenological models provide very differ-ent interpretations for this observation. In the statisticalhadronization model [1–3,9,10], light (anti)nuclei as well asall other hadron species are assumed to be emitted by a sourcein local thermal and hadrochemical equilibrium. Their abun-dances are fixed at the chemical freeze-out, occurring at atemperature of Tchem = 156 ± 4 MeV for Pb-Pb collisions at

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

Published by the American Physical Society under the terms of theCreative Commons Attribution 4.0 International license. Furtherdistribution of this work must maintain attribution to the author(s)and the published article’s title, journal citation, and DOI.

the LHC [11]. This model provides a good description of themeasured hadron yields in central nucleus-nucleus collisions[1]. However, the mechanism of hadron production and thepropagation of loosely bound states through the hadron gasphase are not addressed by this model. In the context ofthe statistical hadronization model, it has been conjecturedthat such objects could be produced at the phase transitionas compact colorless quark clusters with the same quantumnumbers of the final-state hadrons. The survival of these statesat high temperatures is interpreted as due to the low interactioncross section with the surrounding medium [1].

In the coalescence approach, multibaryon states are as-sumed to be formed by the coalescence of baryons at thekinetic freeze-out. In the simplest versions of this model[12,13], baryons are treated as pointlike particles and the coa-lescence happens instantaneously if the momentum differencebetween nucleons is smaller than a given threshold, whichis typically of the order of 100 MeV/c, while spatial coor-dinates are ignored. In the state-of-the-art implementationsof the coalescence approach [4,14], the quantum-mechanicalproperties of baryons and their bound states are taken intoaccount and the coalescence probability is calculated fromthe overlap between the wave functions of baryons and theWigner density of the final-state cluster. All light (anti)nucleiproduced at the phase transition are assumed to be destroyedby the interactions in the hadron gas phase and regeneratedwith the same amount only at the latest stage of the systemevolution.

To address the open question of the survival of looselybound multibaryon states in the hadron gas phase with intenserescattering, models based on relativistic hydrodynamics cou-pled to a hadronic afterburner have been recently developed[4,5]. In these models, nucleons and light nuclei are pro-duced at the phase transition using the Cooper-Frye formula[15], which describes the hadron production based on the

2469-9985/2020/102(5)/055203(19) 055203-1 ©2020 CERN, for the ALICE Collaboration

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S. ACHARYA et al. PHYSICAL REVIEW C 102, 055203 (2020)

local energy density of the fireball, and their yields are fixedto the value predicted by the thermal model at the chem-ical freeze-out temperature. Their propagation through thehadronic medium is simulated based on known interactioncross sections and resonant states using different transportcodes. Existing calculations are based on URQMD [16,17],with light nuclei being produced by nucleon coalescence, andSMASH [5], where (anti)deuterons are assumed to be destroyedand regenerated with equal rates in the hadronic stage. Themodel based on URQMD with nucleon coalescence [4] pro-vides a good description of the elliptic flow of (anti)deuteronsmeasured in Pb-Pb collisions at

√sNN = 2.76 TeV [18]

and of that of (anti)3He measured in Pb-Pb collisions at√sNN = 5.02 TeV [19]. The model is able to describe the low-

pT spectra of deuterons, but overpredicts the deuteron dataabove 2.5 GeV/c and the (anti)3He spectra in the full momen-tum interval. The hybrid model based on SMASH successfullydescribes the measured (anti)deuteron pT spectra and coales-cence parameter B2, defined as the ratio of the invariant yieldof deuterons and that of protons squared, measured in Pb-Pbcollisions at

√sNN = 2.76 TeV [18].

A conceptually similar approach, based on the analogybetween the evolution of the early universe after the BigBang and the space-time evolution of the system created inheavy-ion collisions, has recently been developed [20]. Theproduction of light (anti)(hyper)nuclei in heavy-ion collisionsat the LHC is considered in the framework of the Saha equa-tion assuming that disintegration and regeneration reactionsinvolving light nuclei proceed in relative chemical equilibriumafter the chemical freeze-out of hadrons.

The existing models depict radically different pictures ofthe posthadronization stage for loosely bound states. Consid-ering this scenario, the measurements of radial and anisotropicflow of light (anti)nuclei, i. e., the harmonics (vn) of theFourier decomposition of their azimuthal production distribu-tion with respect to a symmetry plane of the collision, arerelevant to study their propagation through the hadron gasphase and the dynamics of their interactions with other parti-cles. Compared to the elliptic flow, the triangular flow of light(anti)nuclei has a better sensitivity to the fluctuating initialconditions as well as the properties of the created systems.Therefore, tighter constraints on the theoretical model thatdescribe the production mechanism of light (anti)nuclei canbe set.

The elliptic flow of (anti)deuterons was measured as afunction of the transverse momentum (pT) for different cen-trality classes in Pb-Pb collisions at

√sNN = 2.76 TeV [18].

A clear mass ordering is observed at low pT (pT < 3 GeV/c)when this measurement is compared to that of other hadronspecies [21], as expected from relativistic hydrodynamics.The simple coalescence model, based on the assumption thatthe (anti)deuteron invariant yield is proportional to the invari-ant yield of (anti)protons squared, is found to overestimatethe measured v2 in all centrality intervals. The data are betterdescribed by the blast-wave model, a simplified version ofthe relativistic hydrodynamic approach in which the collectiveexpansion is described using a parametrized hydrodynamicflow field. The elliptic flow of (anti)3He was measured inPb-Pb collisions at

√sNN = 5.02 TeV [19]. Also in the case

of (anti)3He, the mass ordering is observed for pT < 3 GeV/cand the measured elliptic flow lies between the predictionsof the blast-wave [22] and the simple coalescence model.A better description of the measurement is provided by amore sophisticated coalescence model where the phase-spacedistributions of protons and neutrons are generated by theIEBE-VISHNU hybrid model with AMPT initial conditions [4].The picture that has emerged so far, regarding the elliptic flowof (anti)nuclei measured at LHC energies, is that the simplecoalescence and blast-wave models represent the upper andlower edges of a region where the data are mostly located.Recent developments in the coalescence approach, which takeinto account momentum-space correlations of nucleons andtheir quantum-mechanical properties, provide a better descrip-tion of the data [4,5].

In this paper, a precision measurement of the (anti)deuteronelliptic flow and the first ever measurement of (anti)deuterontriangular flow for different pT and centrality intervals in Pb-Pb collisions at

√sNN = 5.02 TeV are presented. Thanks to

the large data sample collected at higher energy, the ellipticflow measurement is performed in wider pT and up to a highercentrality interval compared to that in Pb-Pb collisions at√

sNN = 2.76 TeV, allowing for a more differential comparisonwith the theoretical models.

II. THE ALICE DETECTOR

A detailed description of the ALICE detector can be foundin Ref. [23] and references therein. The main subdetectorsused for the present analysis are the V0 detector, the innertracking system (ITS), the time projection chamber (TPC),and the time-of-flight (TOF) detector, which are located insidea solenoidal magnet that provides a uniform field of 0.5 T di-rected along the beam direction. The V0 detector [24] consistsof two arrays of scintillation counters placed around the beamvacuum tube on either side of the interaction point: one cover-ing the pseudorapidity interval 2.8 < η < 5.1 (V0A) and theother one covering −3.7 < η < −1.7 (V0C). Each V0 arrayconsists of four rings in the radial direction, with each ringcomposed of eight cells with the same azimuthal size. Thescintillator arrays have an intrinsic time resolution better than0.5 ns, and their timing information is used in coincidencefor offline rejection of events produced by the interaction ofthe beams with residual gas in the vacuum pipe. The V0scintillators are used to determine the collision centrality fromthe measured charged-particle multiplicity [25–27] and tomeasure the orientation of the symmetry plane of the collision.

The ITS [28], designed to provide high-resolution trackpoints in the vicinity of the nominal vertex position, is com-posed of three subsystems of silicon detectors placed aroundthe interaction region with a cylindrical symmetry. The siliconpixel detector (SPD) is the subsystem closest to the beamvacuum tube and it is made of two layers of pixel detectors.The third and the fourth layers are formed by silicon driftdetectors, while the outermost two layers are equipped withdouble-sided silicon strip detectors. The ITS covers the pseu-dorapidity interval |η| < 0.9.

The same pseudorapidity interval is covered by the TPC,which is the main tracking detector, consisting of a hollow

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ELLIPTIC AND TRIANGULAR FLOW … PHYSICAL REVIEW C 102, 055203 (2020)

cylinder the axis of which coincides with the nominal beamaxis.

The active volume of 90 m3 is filled with a gas mixturecontaining 88% Ar and 12% CO2.

The trajectory of a charged particle is estimated using upto 159 space points. The charged-particle tracks are then builtby combining the hits in the ITS and the reconstructed spacepoints in the TPC. The TPC is also used for particle identifi-cation (PID) by measuring the specific energy loss (dE/dx)in the TPC gas.

The TOF detector [29] covers the full azimuth in thepseudorapidity interval |η| < 0.9. The detector is based onmultigap resistive plate chamber technology and it is located,with cylindrical symmetry, at an average radial distance of380 cm from the beam axis. The TOF allows for PID, basedon the difference between the measured time of flight andits expected value, computed for each mass hypothesis fromthe track momentum and length. The resolution on the mea-surement of the time of flight is about 60 ps in heavy-ioncollisions.

III. DATA SAMPLE AND ANALYSIS TECHNIQUES

A. Event and track selections

The data sample used for the measurements presented inthis paper was recorded by ALICE in 2015 during the LHCPb-Pb run at

√sNN = 5.02 TeV. A minimum bias trigger was

used during the data taking, which required coincident signalsin both V0 detectors. An offline event selection is appliedto remove beam-gas collisions using the timing informationprovided by the V0 detectors and the zero-degree calorimeters[23]. Events with multiple primary vertices identified with theSPD are tagged as pileup and removed from the analysis. Inaddition, events with significantly different charged-particlemultiplicities measured by the V0 detector and by the trackingdetectors at midrapidity, which have different readout times,are rejected. After the offline event selection, the remainingcontribution of beam-gas events is smaller than 0.02% [23]and the fraction of pileup events is found to be negligible.The primary vertex position is determined from tracks recon-structed in the ITS and TPC as described in Ref. [23] and onlyevents with a reconstructed primary vertex position along thebeam axis within 10 cm from the nominal interaction point areselected. The total number of events selected for the analysisfor centrality 0–70% is about 73 × 106.

Deuteron (d) and antideuteron (d) candidates are selectedfrom charged-particle tracks reconstructed in the ITS and TPCin the kinematic range |η| < 0.8 and 0.8 < pT < 6 GeV/c.Only tracks with at least 70 clusters out of a maximum of 159and with a χ2 per degree of freedom for the track fit lowerthan 2 are accepted. In addition, in order to guarantee a track-momentum resolution of 2% in the measured pT range and adE/dx resolution of about 6%, each track is required to bereconstructed from at least 80% of the number of expectedTPC clusters and to have at least one hit in either of the twoinnermost layers of the ITS. The distances of closest approach(DCA) to the primary vertex in the plane perpendicular andparallel to the beam axis for the selected tracks are determined

with a resolution better than 300 μm [23]. To suppress thecontribution of secondary particles, the reconstructed tracksare required to have a longitudinal DCA smaller than 2 cm anda transverse DCA smaller than 0.0105 + 0.0350/p1.1

T cm, withpT in units of GeV/c. The latter corresponds to approximately7σDCA(pT), where σDCA(pT) is the transverse DCA resolutionin the corresponding pT interval.

B. (Anti)deuterons identification

The (anti)deuteron identification technique used in thisanalysis is similar to that used in the previous measurementin Pb-Pb collisions at

√sNN = 2.76 TeV [18]. For transverse

momenta up to 1.4 GeV/c (anti)deuterons are identified us-ing only the TPC information by requiring that the averagedE/dx is within 3σ from the expected average value for the(anti)deuteron mass hypothesis. For pT > 1.4 GeV/c the 3σ

TPC identification is complemented by the signal providedby the TOF detector. The number of (anti)deuterons in eachpT interval is extracted from a fit of the �M = mTOF − mdpdg ,where mTOF is the particle mass calculated using the time offlight measured by the TOF and mdpdg is the nominal mass ofdeuterons taken from [30]. In the left panel of Fig. 1 the �Mdistribution for (anti)deuterons with 2.2 � pT <2.4 GeV/cin the centrality interval 20–30% is shown. The d + d signalis fitted using a Gaussian with an exponential tail, while thebackground, originating from TOF hits incorrectly associatedto tracks extrapolated from the TPC, is modeled with anexponential function.

Deuterons and antideuterons are summed together (d + d)in all the centrality intervals and for pT larger than 1.4 GeV/c.This is possible since the v2 and v3 measured for v2 and v3

for d and d are consistent within the statistical uncertainties.At lower pT, deuterons produced by spallation in interactionsbetween particles and the detector material or in the beamvacuum tube constitute a significant background. For thisreason, for pT < 1.4 GeV/c only antideuterons, which arenot affected by this background, are used in the analysis.Since no difference is expected for the v2 and v3 of d andd , hereafter deuterons will denote results for antideuteronsfor pT < 1.4 GeV/c and the sum of d and d elsewhere. Thecontribution of secondary deuterons produced in weak decaysof hypertritons is negligible considering that the productionrate of (hyper)nuclei with mass number A = 3 is suppressedcompared to that of A = 2 by a factor of approximately 300in Pb-Pb collisions at

√sNN = 2.76 TeV [31]. A similar sup-

pression is expected in Pb-Pb collisions at√

sNN = 5.02 TeV.

C. Flow analysis techniques

The particle azimuthal distribution of charged particleswith respect to the nth-order flow symmetry plane �n [32–35]can be expressed as a Fourier series:

Ed3N

d p3= 1

d2N

pTd pTdy

(1 +

∞∑n=1

2vn cos [n(ϕ − �n)]

),

(1)

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S. ACHARYA et al. PHYSICAL REVIEW C 102, 055203 (2020)

0.4− 0.2− 0 0.2 0.4)2c (GeV/MΔ

0

5

10

15

310×)2 cC

ount

s/(2

0 M

eV/

c < 2.4 GeV/T

p ≤2.2 = 5.02 TeVNNsPb −ALICE Pb

30%−20

dd + Signal + BackgroundBackground

0.4− 0.2− 0 0.2 0.4)2c (GeV/MΔ

0

0.1

0.2

0.3| > 2

Δ{S

P, |

Tot

2v

c < 2.4 GeV/T

p ≤2.2

= 5.02 TeVNNsPb −ALICE Pb

30%−20

dd + Fit

0.4− 0.2− 0 0.2 0.4)2c (GeV/MΔ

0

0.05

0.1

0.15

| > 2

Δ{S

P, |

Tot

3v

c < 2.4 GeV/T

p ≤2.0

= 5.02 TeVNNsPb −ALICE Pb

30%−20

dd + Fit

FIG. 1. Raw yield (left), v2 (middle), and v3 (right) of d + d candidates as a function of �M for 2.2 � pT <

2.4 GeV/c (2.0 � pT <2.4 GeV/c for v3) and in the centrality interval 20–30%. The data points represent the measurements. The curveon the left panel is the total fit (signal plus background) as described in the text. The curves in the middle and right panel are the fits performedusing Eq. (5). Vertical bars represent the statistical uncertainties.

where E is the energy of the particle, p is the momentum, ϕ isthe azimuthal angle, y is the rapidity, and

vn = 〈cos [n(ϕ − �n)]〉. (2)

The second coefficient of the Fourier series (v2) is calledelliptic flow and is related to the initial geometrical anisotropyof the overlap region of the colliding nuclei. The third-orderflow coefficient (v3), called triangular flow, is generated byfluctuations in the initial distribution of nucleons and gluonsin the overlap region [34,36,37]. The same fluctuations areresponsible for the v2 measured in most central collisions(centrality < 5%) [38]. The vn coefficients are measured usingthe scalar product (SP) method [32,39]. This is a two-particlecorrelation technique based on the scalar product of the unitflow vector of the particle of interest, k, and the Q vector. Theunit flow vector is denoted by un,k = exp(inϕk ), where ϕk isthe azimuthal angle of the particle k.

The Q-vector is computed from a set of reference flowparticles and is defined as

Qn =∑

wieinϕi (3)

where, in general, ϕi is the azimuthal angle for the ith refer-ence flow particle, n is the order of the harmonic, and wi is aweight applied to correct for reference flow.

The vn flow coefficients are calculated as

vn{SP} = 〈〈un,kQ∗n〉〉√

〈QnQA∗n 〉〈QnQB∗

n 〉〈QA

n QB∗n 〉

. (4)

Single brackets 〈...〉 denote an average over all events,while double brackets 〈〈...〉〉 indicate an average over allparticles in all events, and the asterisk denotes the com-plex conjugate. The denominator is a correction factor thatis introduced to take into account the resolution of the Qn

vector. In this analysis, the Qn vector is calculated from theazimuthal distribution of the energy deposition measured inthe V0A, while the QA

n and QBn vectors are determined from

the azimuthal distribution of the energy deposited in the V0Cand the azimuthal distribution of tracks reconstructed in theTPC, respectively. Using these detectors, a pseudorapidity gap

|�η| > 2 between the particle of interest and the referenceflow particles is introduced. Such a pseudorapidity gap re-duces nonflow effects, which are correlations not arising fromthe collective expansion of the system (e. g., resonance decaysand jets).

The purity of the sample of deuterons identified using theTPC in the 0.8 < pT < 1.4 GeV/c interval is around 100%. Inthis transverse momentum interval the v2 and v3 coefficientswere evaluated on a track-by-track basis and then averagedin each pT interval. For higher pT, the vn coefficients arecalculated in different ranges of �M. vn(�M) contains contri-butions from the signal (vsig

n ) and from the background (vbkgn ):

vn(�M ) = vsign

N sig

N tot(�M ) + vbkg

n (�M )Nbkg

N tot(�M ), (5)

where N sig is the number of deuterons, Nbkg is the numberof background particles, and N tot is their sum. The signal vn

is extracted from a fit to the observed vn as a function of�M, in which v

bkgn is described using a first-order polynomial

function, and vsign is a free fit parameter. N sig and Nbkg are

obtained from the fit to the �M distribution using a Gaussianwith an exponential tail for the signal and an exponential forthe background. The signal extraction procedure is illustratedin Fig. 1 for 2.2 � pT < 2.4 GeV/c (2.0 � pT < 2.4 GeV/cfor v3) in the centrality interval 20–30%.

The elliptic and triangular flows of deuterons are measuredin centrality intervals of 5% width and then the results in widercentrality intervals are obtained as weighted averages of thesemeasurements using the number of deuteron candidates, in thesame centrality interval of 5% width as a weight, similarly towhat was performed in Ref. [19].

D. Systematic uncertainties

The sources of systematic uncertainties for the elliptic andtriangular flow of deuterons are related to event selection,tracking, (anti-)deuteron identification, and the technique usedfor the signal extraction. The contribution related to the eventselection is estimated by taking into account the differences

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ELLIPTIC AND TRIANGULAR FLOW … PHYSICAL REVIEW C 102, 055203 (2020)

TABLE I. Summary of the systematic uncertainties for thedeuterons v2 and v3. The maximum deviation of the systematicuncertainty is reported.

Value

Source v2 v3

Event selections 1.5% 1.5%Tracking and particle identification 1–3% 1–2%Signal extraction 1–4% 2–6%Total 2–7% 3–7%

in the v2 and v3 measurements obtained using different event-selection criteria. In particular, the fiducial region for thevertex position along the beam axis is varied from the range[−10, 10] to [−7, 7] cm to probe the magnitude of potentialedge effects. To investigate possible effects due to chargeasymmetries during tracking and geometrical asymmetries inthe detector, the differences between the results obtained byusing opposite magnetic-field polarities are included. Anal-ogously, the default centrality estimator is changed to thatbased on the number of hits in the first or second layer of theITS. Finally, the effect related to pileup rejection is tested byrequiring a stronger correlation between the V0 and centralbarrel multiplicities. These contributions are assumed to beindependent and added in quadrature. The total systematicuncertainty due to event selection is found to be around 1.5%for both v2 and v3.

To estimate the systematic uncertainties due to reconstruc-tion and identification of deuterons, the track selection and theTPC PID criteria are varied with respect to the default choiceand the vn measurements are repeated for each of these differ-ent settings. The rms of the distribution of vn measurementsin each pT interval is considered as systematic uncertainty.To minimize the effect of statistical fluctuations, all variations

smaller than 2√

|σ 20 − σ 2

i | are not included in the estimate ofthe systematic uncertainties [40], where σ0 is the statistical

uncertainty of the default value while σi is that correspondingto the ith selection criterion. The probability distribution forthe variations of data points due to systematic effects related totracking and PID is assumed to be uniform in each pT intervaland the difference between the maximum and minimum valuedivided by

√12 is assigned as systematic uncertainty. This

contribution ranges from 1 and 3% depending on pT andcentrality.

To estimate the contribution to the systematic uncertaintiesdue to the signal extraction, the function used to describethe v

bkgn is changed. In addition to a first-order polyno-

mial, a constant function and a second-order polynomial arealso used, and the maximum difference with respect to thedefault measurement is considered as systematic uncertainty.A contribution up to 5% is observed for central collisions andfor pT < 2 GeV/c. Moreover, different functions and fittingranges are used to describe the signal and the background ofEq. (5). More specifically, besides a Gaussian function with anexponential tail, a Gaussian is also used for the signal, whilesingle and double exponentials and linear functions are alsoused for the background. This contribution is relevant onlyfor pT > 1.4 GeV/c, where the TOF is used to extract thesignal, and is found to vary from 1 to 6% depending on pT

and centrality. Table I shows the summary of the differentcontributions to the systematic uncertainties for the v2 and v3

of deuterons. The total uncertainties are given by their sum inquadrature, assuming that all contributions are independent.

IV. RESULTS AND DISCUSSION

The v2 and v3 of deuterons measured in Pb-Pb collisionsat

√sNN = 5.02 TeV are shown in Fig. 2 as a function of pT

for different centrality intervals. In the measured pT interval,an increasing trend is observed with increasing pT and goingfrom central to more peripheral Pb-Pb collisions, as expectedbased on the relativistic hydrodynamic description of the col-lective expansion of a hot and dense medium [41]. Initial-state

0 1 2 3 4 5 6)c (GeV/

Tp

0

0.2

0.4

0.6| > 2

}η Δ

{S

P, |

2v

5%−0

10%−5

20%−10

30%−20

40%−30

50%−40

60%−50

70%−60

= 5.02 TeVNNsPb −ALICE Pb

dd +

0 1 2 3 4 5 6)c (GeV/

Tp

0

0.1

0.2

0.3

| > 2

}η Δ

{S

P, |

3v

20%−0

40%−20

60%−40

= 5.02 TeVNNsPb −ALICE Pb

dd +

FIG. 2. Elliptic (v2, left) and triangular (v3, right) flow of deuterons as a function of pT for different centrality intervals measured in Pb-Pbcollisions at

√sNN = 5.02 TeV. The horizontal line at zero is to guide the eye. Vertical bars and boxes represent the statistical and systematic

uncertainties, respectively.

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0 1 2 3 4 5 6)c (GeV/

Tp

0

0.1

0.2

0.3

0.4

0.5

2v

ALICE Pb−Pb

20%−10

dd +

0 1 2 3 4 5 6)c (GeV/

Tp

50%−40

2.76 TeV

5.02 TeV

FIG. 3. Deuterons v2 measured in Pb-Pb collisions at√

sNN = 5.02 TeV (red square) compared to that measured at√

sNN = 2.76 TeV [18](light blue circles) for two centrality intervals (10–20 and 40–50%). Both protons and deuteron elliptic flow were measured for pseudorapiditygap between the particle of interest and the reference flow particle |�η| > 0.9. Vertical bars and boxes represent the statistical and systematicuncertainties, respectively.

fluctuations of the energy density distribution of partons in thecolliding nuclei imply a nonzero v3 [37].

The measurement presented in this paper shows that theseinitial-state effects, already observed for other hadron speciesat LHC energies [42,43], are also visible for deuterons.

The measurement of the deuterons v2 in Pb-Pb collisionsat

√sNN = 5.02 TeV is compared to that in Pb-Pb colli-

sions at√

sNN = 2.76 TeV [18] in Fig. 3 for two centralityintervals. The observed v2 and their trend are similar at thetwo center-of-mass energies, but a decrease of the observedelliptic flow for a given pT is observed with increasing center-of-mass energy. This effect is more pronounced in peripheralrather than in central collisions. A similar effect was observedfor the proton v2 measurements [43] and is interpreted as

partially due to the increasing radial flow with increasingcollision energy, which produces a shift of the v2 towardshigher pT.

The effect due to radial flow is assessed quantitatively bycomparing the ratio of the deuteron and proton v2 as a functionof pT at the two energies. The ratio between the deuteron v2

in Pb-Pb collisions at√

sNN = 5.02 TeV to that measuredat

√sNN = 2.76 TeV, with v2 and pT scaled by the mass

number A = 2, is shown in Fig. 4 for two centrality intervalsin comparison with the same ratio for protons. As indicatedby these ratios, the radial flow effects are quantitatively verysimilar for protons and deuterons. It has to be noted that amass scaling would lead to the same conclusion since thebinding energy of deuterons is 2.2 MeV, i. e., the deuteron

0 1 2 3 4 5 6)c (GeV/A/

Tp

0.5

1

1.52.76

TeV

5.02

TeV

: A/ 2

v

ALICE Pb−Pb

20%−10

0 1 2 3 4 5 6)c (GeV/A/

Tp

50%−40

pp + dd +

FIG. 4. Ratio of the v2 of deuterons measured in Pb-Pb collisions at√

sNN = 5.02 TeV to that measured at√

sNN = 2.76 TeV (red circles)compared with the same ratio obtained for protons (blue squares) for two centrality intervals (10–20% on the left panel and 40–50% on theright panel). For a direct comparison of protons and deuterons, the measured v2 and pT were divided by A. Vertical bars and boxes representthe statistical and systematic uncertainties, respectively.

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0 1 2 3 4 5 6) c (GeV/

Tp

0

0.1

0.2

0.3

0.4

0.5

0.62v

d d + He3He + 3

±π ± K

p p +

ALICE

20%− = 5.02 TeV, 0NNsPb, −Pb

0 1 2 3 4 5 6) c (GeV/

Tp

40%−20

0 1 2 3 4 5 6) c (GeV/

Tp

60%−40

FIG. 5. Comparison of the elliptic flow of pions, kaons, protons, deuterons, and (anti)3He in different centrality intervals for Pb-Pbcollisions at

√sNN = 5.02 TeV. (Anti)3He v2 is measured using the event plane method [19]. Vertical bars and boxes represent the statistical

and systematic uncertainties, respectively.

mass is approximately equal to 2mp, where mp is the protonmass.

The elliptic flow of deuterons is compared to that of pions,kaons, protons, and (anti)3He measured at the same center-of-mass energy [19,43] in Fig. 5. Since the (anti)3He ellipticflow is measured in centrality intervals of 20% width due to itsrarer production compared to that of lighter hadrons, the v2 ofpions, kaons, protons, and deuterons are recalculated to matchthe same centrality intervals. This is achieved by averagingthe v2 measurements of these particles in narrower centralityintervals weighted by the corresponding pT spectra [8,44]. Aclear mass ordering of v2 is observed at low pT, as expectedfor a system expansion driven by the pressure gradient asdescribed by relativistic hydrodynamics [41,45,46].

In Fig. 6, the deuteron v3 is compared to that of pions,kaons, and protons at the same center-of-mass energy [43]for the centrality intervals 0–20% (left) and 20–40% (right).Also for v3, a clear mass ordering is observed for pT � 2.5and 3 GeV/c for the centrality intervals 0–20 and 20–40%,respectively.

A. Comparison with the blast-wave model predictions

The elliptic flow of deuterons is compared with the expec-tations of the blast-wave model [22,47,48], which is basedon the assumption that the system produced in heavy-ioncollisions is locally thermalized and expands collectively witha common velocity field. The system is assumed to undergo aninstantaneous kinetic freeze-out at the temperature Tkin and tobe characterized by a common transverse radial flow velocityat the freeze-out surface. A simultaneous fit of the v2 andthe pT spectra of pions, kaons, and protons [8,43] with theblast-wave model is performed in the transverse-momentumranges 0.5 � pπ

T < 1 GeV/c, 0.7 � pKT < 2 GeV/c, and 0.7 �

ppT < 2.5 GeV/c. The four free parameters of the blast-wave

function are the kinetic freeze-out temperature (Tkin), the vari-ation in the azimuthal density of the source (s2), the meantransverse expansion rapidity (ρ0), and the amplitude of itsazimuthal variation (ρa), as described in Ref. [47]. The valuesof these parameters extracted from the fits are reported inTable II for each centrality interval. These values are em-ployed to predict the elliptic flow of deuterons under the

0 1 2 3 4 5 6)c (GeV/

Tp

0.05−

0

0.05

0.1

0.15

0.2

0.25| > 2

Δ{S

P, |

3v

20%−0

±π±K

pp + dd +

0 1 2 3 4 5 6)c (GeV/

Tp

40%−20

= 5.02 TeVNNsPb −ALICE Pb

FIG. 6. Triangular flow (v3) of deuterons, pions, kaons, and protons [43] as a function of pT for the centrality intervals 0–20 and 20–40%.Vertical bars and boxes represent the statistical and systematic uncertainties, respectively.

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TABLE II. Blast-wave parameters extracted from the simulta-neous fits of the pT spectra and v2 of pions, kaons, and protonsmeasured at

√sNN = 5.02 TeV. See text for details. The error as-

signed to each parameter is shown only with one significant digit.

Fit parameters

Centrality Tkin (MeV) s2 (10−2) ρ0 (10−1) ρa (10−2)

0–5% 104 ± 1 2.63 ± 0.01 8.57 ± 0.01 0.83 ± 0.015–10% 106 ± 1 4.15 ± 0.01 8.85 ± 0.01 1.47 ± 0.0110–20% 107 ± 1 6.09 ± 0.01 9.12 ± 0.01 2.17 ± 0.0120–30% 109 ± 1 8.25 ± 0.01 9.02 ± 0.01 2.85 ± 0.0130–40% 111 ± 1 10.1 ± 0.01 8.61 ± 0.01 3.25 ± 0.0140–50% 116 ± 1 12.3 ± 0.01 7.73 ± 0.01 3.30 ± 0.0150–60% 121 ± 1 14.5 ± 0.01 6.93 ± 0.01 2.85 ± 0.0160–70% 129 ± 1 17.4 ± 0.01 5.95 ± 0.01 1.74 ± 0.01

assumption that the same kinetic freeze-out conditions applyfor all particles produced in the collision. The deuteron massis taken from [30].

The blast-wave fits to the v2 of pions, kaons, and protonsand the predictions for the deuterons v2 are reported in Fig. 7for the centrality intervals 10–20 and 40–50%. In the lowerpanels, the data-to-fit ratios for pions, kaons, and protonsand the ratios of the deuterons v2 to the model are shown.Because of the finite size of the pT intervals, the average of

the blast-wave function within the interval, weighted by the pT

spectrum of the corresponding particle species, is consideredin the calculation of these ratios.

The predictions of the blast-wave model underestimate thedeuteron elliptic flow experimental values in semiperipheralcollisions for pT > 1.4 GeV/c, while they are close to themeasurements for central events in the measured pT interval.This is better observed in Fig. 8, which shows the centralityevolution of the data-to-model ratios.

B. Test of the coalescence hypothesis

The deuterons v2 and v3 are compared to the expectationsof a coalescence approach based on mass number scaling andisospin symmetry, for which the proton and neutron v2 (v3)are identical. In particular, the v2 (v3) measured for protons[43] was used to predict the v2 (v3) of deuterons using thefollowing relation [49]:

v2(3),d (pT) = 2v2(3),p(pT/2)

1 + 2v22(3),p(pT/2)

. (6)

The results of this calculation for different centrality inter-vals for v2 are shown in the left panel of Fig. 9. The measuredelliptic flow in 10–20 and 40–50% centrality intervals ofdeuterons is compared with coalescence model predictionsfrom Eq. (6) using the measured vn of protons. Similarly,the right panel of Fig. 9 shows a comparison between the

FIG. 7. Blast-wave fits to the v2 (pT) of pions, kaons, and protons [43] and predictions of the deuterons v2 (pT) for the centrality intervals10–20% (left) and 40–50% (right). In the lower panels, the data-to-fit ratios are shown for pions, kaons, and protons as well as the ratio ofthe deuterons v2 to the blast-wave predictions. Vertical bars and boxes represent the statistical and systematic uncertainties, respectively. Thedashed line is to guide the eye.

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0 1 2 3 4 5 6)c (GeV/

Tp

0.5

1

1.5

Dat

a/B

last

-wav

e

40%−30

dd +

0.5

1

1.5

Dat

a/B

last

-wav

e

5%−0

0 1 2 3 4 5 6)c (GeV/

Tp

50%−40

10%−5

0 1 2 3 4 5 6)c (GeV/

Tp

60%−50

20%−10

0 1 2 3 4 5 6)c (GeV/

Tp

70%−60

ALICE = 5.02 TeVNNsPb −Pb

30%−20

FIG. 8. Data-to-model ratios of the deuterons v2 to the blast-wave predictions as a function of pT for different centrality intervals asindicated in each pad. Vertical bars and boxes represent the statistical and systematic uncertainties, respectively.

calculated and measured v3 in the 0–20 and 20–40% centralityintervals.

The coalescence model overestimates the deuteron v2 byabout 20 to 30% in central collisions and is close to thedata for semiperipheral collisions, as illustrated in Fig. 10,which shows the centrality evolution of the data-to-modelratio. The coalescence approach seems to have a slightly betteragreement with deuterons v3; however, the large statistical un-certainties on the v3 measurements do not allow for conclusivestatements.

C. Comparison with IEBE-VISHNU and coalescence calculations

In Fig. 11, the deuterons v2 and v3 are compared toa model [4] implementing light nuclei formation via co-alescence of nucleons originating from a hydrodynamicalevolution of the fireball coupled to a URQMD simulation ofthe hadronic cascade [16,17]. In this model, the coalescenceprobability is calculated as the superposition of the wavefunctions of protons and neutrons and the Wigner func-tion of the deuterons. The coalescence happens in a flowing

0

0.1

0.2

0.3

0.4

0.5| > 2

Δ{S

P, |

2v

ALICE

= 5.02 TeVNNsPb −Pb

20%−10

0 1 2 3 4 5 6)c (GeV/

Tp

0.5

1.0

)co

al2

v)/

(d 2

v(

Coalescencedd +

50%−40

0 1 2 3 4 5 6)c (GeV/

Tp

0

0.1

0.2

0.3

0.4| > 2

Δ{S

P, |

3v

ALICE

= 5.02 TeVNNsPb −Pb

20%−0

0 1 2 3 4 5 6)c (GeV/

Tp

0.5

1.0

)co

al3

v)/

(d 3

v(

Coalescencedd +

40%−20

0 1 2 3 4 5 6)c (GeV/

Tp

FIG. 9. Measured deuterons v2 and v3 (red circles) compared with the expectations from simple coalescence [Eq. (6) (blue shaded bands)]for two centrality intervals. In the left panel, the v2 measurements in the 10–20 and 40–50% centrality intervals are shown. The right paneldisplays the results of v3 in the 0–20 and 20–40% centrality intervals. The bottom panels show the ratio between the measured v2 (v3) andthe expectations from the coalescence model. In each panel, vertical bars and boxes represent the statistical and systematic uncertainties,respectively. The line is to guide the eye.

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0 1 2 3 4 5 6)c (GeV/

Tp

0.5

1

1.5)co

al2

v)/

(d 2

v(

40%−30Coalescence

dd +

0.5

1

1.5)co

al2

v)/

(d 2

v(

5%−0

0 1 2 3 4 5 6)c (GeV/

Tp

50%−40

10%−5

0 1 2 3 4 5 6)c (GeV/

Tp

60%−50

20%−10

0 1 2 3 4 5 6)c (GeV/

Tp

70%−60

ALICE = 5.02 TeVNNsPb −Pb

30%−20

FIG. 10. Centrality evolution of the deuterons v2 compared with the expectations from the simple coalescence model [Eq. (6)]. Verticalbars and boxes represent the statistical and systematic uncertainties, respectively.

medium introducing position-momentum correlations, whichare absent in the simple coalescence approach. The phase-space distributions of protons and neutrons are generatedfrom the IEBE-VISHNU hybrid model with AMPT [50] initialconditions. This model provides a good description of theproton spectra up to 3 GeV/c and of the deuterons v2 mea-sured in Pb-Pb collisions at

√sNN = 2.76 TeV [4]. The

predictions are consistent with the measured deuterons v2

for events with centrality larger than 20% and for mea-sured v3 within the statistical and systematical uncertainties,while some discrepancy at the level of 2σ (taking into ac-count statistical and systematical uncertainties in quadrature)is observed for the centrality interval 10–20% as shown inFig. 11.

0

0.1

0.2

0.3

0.4

0.5| > 2

}η Δ

{SP

, |2

v

dd + 20%− Data 1030%− Data 2040%− Data 30

iEBE-VISHNU + Coalescence

20%−10

30%−20

40%−30

ALICE = 5.02 TeVNNsPb −Pb

0 1 2 3 4 5 6)c (GeV/

Tp

0.04−0.02−0.000.020.04

Mod

el−

Dat

a

0

0.05

0.1

0.15

0.2

0.25| > 2

}η Δ

{SP

, |3

v

dd +

20%− Data 0

40%− Data 20

iEBE-VISHNU + Coalescence

20%−0

40%−20

ALICE = 5.02 TeVNNsPb −Pb

0 1 2 3 4 5 6)c (GeV/

Tp

0.04−0.02−0.00

0.02

0.04

Mod

el−

Dat

a

FIG. 11. Elliptic (left) and triangular (right) flow of deuterons compared to the predictions of the IEBE-VISHNU hybrid model with AMPT

initial conditions [4]. The predictions are shown as bands the widths of which represent the statistical uncertainties associated with the model.The data-to-model differences are shown in the lower panels. Vertical bars and boxes represent the statistical and systematic uncertainties,respectively.

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0

0.1

0.2

0.3

0.4

0.5| > 2

}η Δ

{SP

, |2

vdd +

20%− Data 1030%− Data 2040%− Data 30

JETSCAPE 1.0 sims

20%−10

30%−20

40%−30

ALICE

= 5.02 TeVNNsPb −Pb

0 1 2 3 4 5 6)c (GeV/

Tp

0.04−0.02−0.00

0.02

0.04

Mod

el−

Dat

a

FIG. 12. Measured deuterons v2 compared to the predictionsfrom a microscopic model [5] based on the JETSCAPE generator [52].The model predictions, based on the SMASH afterburner and whichused TRENTo [51] initial conditions, are shown as bands. The widthof the band represents the statistical uncertainty associated with themodel. In the lower panel the data-to-model differences are shown.Vertical bars and boxes represent the statistical and systematic uncer-tainties, respectively.

D. Comparison with hybrid (hydrodynamics plus transport)approach expectations

The deuterons v2 measured in the centrality intervals 10–20, 20–30, and 30–40% are compared in Fig. 12 with thepredictions from a hybrid model based on relativistic viscoushydrodynamics, with fluctuating initial conditions generatedby TRENTO [51], coupled to the hadronic afterburner SMASH

[5]. The simulations are obtained by using the JETSCAPE 1.0event generator [52]. The parameters of this model, includingthe shear and bulk viscosities, are tuned to the measurementsof pT spectra and azimuthal flow of pions, kaons, and protonsobtained by ALICE in Pb-Pb collisions at

√sNN = 2.76 TeV

[7,21] and by PHENIX and STAR in Au-Au collisions at√sNN = 200 GeV [53–55]. The interactions of deuterons with

other hadrons in the hadron gas phase are simulated usingSMASH in which all known resonances and the experimentallyknown cross sections, most importantly πd → πnp and itsinverse reaction, are included.

In this model, the number of deuterons at the kineticfreeze-out is independent from their primordial abundance atthe Cooper-Frye hypersurface. It was found that even whentheir initial number is set to zero the number of deuteronsregenerated in the hadronic phase converges towards the equi-librium value, which is the same as that predicted by thestatistical hadronization model. Considering that in this modelonly ≈1% of the primordial deuterons survive the hadronic

stage, the elliptic flow of deuterons observed after the kineticfreeze-out is almost identical to that of the regenerated ones.For this reason, deuterons are not sampled at the Cooper-Fryehypersurface for these predictions.

The model predictions are consistent with the measuredv2 within the uncertainties in the centrality intervals 20–30and 30–40% for 0.8< pT < 4 GeV/c, while the data areoverestimated by up to 30% in the centrality interval 10–20%for pT > 2 GeV/c.

V. SUMMARY

The measurements of the deuterons v2 and the first mea-surement of v3 in Pb-Pb collisions at

√sNN = 5.02 TeV are

presented. The observed centrality and pT dependence areconsistent with the expectations from relativistic hydrody-namics. A mass ordering is observed for pT < 3 GeV/c whencomparing these results with the measured v2 and v3 of pions,kaons, and protons. The shift of the deuterons v2 towardshigher pT with respect to the measurement in Pb-Pb collisionsat

√sNN = 2.76 TeV, mainly due to a stronger radial flow at

higher center-of-mass energy, is consistent with that observedfor the proton v2 measurement.

The results of this measurement are compared with theexpectations from the simple coalescence approach, in whichthe deuteron v2 is obtained from that of protons assuming thatthe deuteron invariant yield is proportional to that of protonssquared, and with the predictions of the blast-wave model.The deuteron v2 is overestimated by a simple coalescence ap-proach, which describes the data only in peripheral (centrality>50%) collisions. On the other hand, the blast-wave modelunderestimates the peripheral measurements and it is closeto the data in central collisions. These results are consistentwith the scenario previously seen for deuterons and 3He el-liptic flow: these simplified models bracket a region wherethe light nucleus v2 is located and describe reasonably thedata in different multiplicity regimes, indicating that neither ofthese two models is able to describe the deuteron productionmeasurement from low to high multiplicity environments.

Similar considerations are valid for the deuterons v3 withsome limitations due to the rather large statistical uncertain-ties. This specific aspect will be addressed with the larger datasample that will be collected in run 3 following the ALICEupgrade, where a significant improvement of the statisticalprecision is expected. This measurement will be crucial tobetter constrain models that describe the production of lightnuclei in heavy-ion collisions.

A more advanced coalescence model coupled to hydro-dynamics and the hadronic afterburner URQMD, which takesinto account the quantum-mechanical properties of nucleonsand nuclei and space-momentum correlations of nucleons,provides a good description of the deuterons v2 and v3 forpT > 2.5 GeV/c. The model predictions deviate from the dataat lower pT, in particular for the centrality interval 10–20%.The same model provides a good description of the deuteronv2 measured in Pb-Pb collisions at

√sNN = 2.76 TeV and that

of 3He at√

sNN = 5.02 TeV. The deuteron v2 is also comparedto the predictions from a hybrid model based on relativistichydrodynamics coupled to the hadronic afterburner SMASH.

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The model predictions are consistent with the data within theuncertainties in the centrality intervals 20–30 and 30–40%,while a deviation of up to 30% is observed in the centralityinterval 10–20% for 2 < pT < 3 GeV/c.

In general, the state-of-the-art implementations of coa-lescence and the hybrid approach based on hydrodynamicscoupled to hadronic afterburners provide better descriptions ofthe data compared to the simple coalescence and blast-wavemodels. Further efforts, on both the experimental and thetheoretical side, are needed to have a more comprehensiveunderstanding of dynamics and production of light nuclei.

ACKNOWLEDGMENTS

The ALICE Collaboration would like to thank all its en-gineers and technicians for their invaluable contributions tothe construction of the experiment and the CERN accel-erator teams for the outstanding performance of the LHCcomplex. The ALICE Collaboration gratefully acknowledgesthe resources and support provided by all Grid centers andthe Worldwide LHC Computing Grid collaboration. TheALICE Collaboration acknowledges the following fundingagencies for their support in building and running the AL-ICE detector: A. I. Alikhanyan National Science Laboratory(Yerevan Physics Institute) Foundation, State Committee ofScience and World Federation of Scientists, Armenia; Aus-trian Academy of Sciences, Austrian Science Fund (Grant No.M 2467-N36) and Nationalstiftung für Forschung, Technolo-gie und Entwicklung, Austria; Ministry of Communicationsand High Technologies, National Nuclear Research Cen-ter, Azerbaijan; Conselho Nacional de DesenvolvimentoCientífico e Tecnológico, Financiadora de Estudos e Pro-jetos, Fundação de Amparo à Pesquisa do Estado de SãoPaulo, and Universidade Federal do Rio Grande do Sul,Brazil; Ministry of Education of China, Ministry of Sci-ence and Technology of China, and National Natural ScienceFoundation of China, China; Ministry of Science and Ed-ucation and Croatian Science Foundation, Croatia; Centrode Aplicaciones Tecnológicas y Desarrollo Nuclear, Cubaen-ergía, Cuba; Ministry of Education, Youth, and Sports ofthe Czech Republic, Czech Republic; The Danish Councilfor Independent Research—Natural Sciences, the VILLUMFONDEN, and Danish National Research Foundation, Den-mark; Helsinki Institute of Physics, Finland; Commissariatà l’Energie Atomique, Institut National de Physique Nu-cléaire et de Physique des Particules, and Centre National

de la Recherche Scientifique, France; Bundesministerium fürBildung und Forschung and GSI Helmholtzzentrum für Schw-erionenforschung GmbH, Germany; General Secretariat forResearch and Technology, Ministry of Education, Research,and Religions, Greece; National Research, Development, andInnovation Office, Hungary; Department of Atomic EnergyGovernment of India, Department of Science and Technol-ogy, Government of India, University Grants Commission,Government of India, and Council of Scientific and IndustrialResearch, India; Indonesian Institute of Science, Indonesia;Centro Fermi—Museo Storico della Fisica e Centro Studie Ricerche Enrico Fermi and Istituto Nazionale di FisicaNucleare, Italy; Institute for Innovative Science and Technol-ogy, Nagasaki Institute of Applied Science, Japanese Ministryof Education, Culture, Sports, Science, and Technology,and Japan Society for the Promotion of Science KAK-ENHI, Japan; Consejo Nacional de Ciencia y Tecnología,through Fondo de Cooperación Internacional en Ciencia yTecnología and Dirección General de Asuntos del PersonalAcademico, Mexico; Nederlandse Organisatie voor Weten-schappelijk Onderzoek, Netherlands; The Research Councilof Norway, Norway; Commission on Science and Technologyfor Sustainable Development in the South, Pakistan; Pontifi-cia Universidad Católica del Perú, Peru; Ministry of Scienceand Higher Education, National Science Centre and WUTID-UB, Poland; Korea Institute of Science and TechnologyInformation and National Research Foundation of Korea,Republic of Korea; Ministry of Education and Scientific Re-search, Institute of Atomic Physics and Ministry of Researchand Innovation and Institute of Atomic Physics, Romania;Joint Institute for Nuclear Research, Ministry of Educationand Science of the Russian Federation, National ResearchCentre Kurchatov Institute, Russian Science Foundation, andRussian Foundation for Basic Research, Russia; Ministry ofEducation, Science, Research, and Sport of the Slovak Repub-lic, Slovakia; National Research Foundation of South Africa,South Africa; Swedish Research Council and Knut and Al-ice Wallenberg Foundation, Sweden; European Organizationfor Nuclear Research, Switzerland; Suranaree University ofTechnology, National Science and Technology DevelopmentAgency, and Office of the Higher Education Commissionunder NRU project of Thailand, Thailand; Turkish AtomicEnergy Agency, Turkey; National Academy of Sciences ofUkraine, Ukraine; Science and Technology Facilities Coun-cil, United Kingdom; National Science Foundation and USDepartment of Energy, Office of Nuclear Physics.

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J. Pan,143 S. Panebianco,137 P. Pareek,50,141 J. Park,61 J. E. Parkkila,126 S. Parmar,100 S. P. Pathak,125 B. Paul,23 J. Pazzini,140

H. Pei,6 T. Peitzmann,63 X. Peng,6 L. G. Pereira,70 H. Pereira Da Costa,137 D. Peresunko,88 G. M. Perez,8 S. Perrin,137

Y. Pestov,4 V. Petrácek,37 M. Petrovici,48 R. P. Pezzi,70 S. Piano,60 M. Pikna,13 P. Pillot,115 O. Pinazza,34,54 L. Pinsky,125

C. Pinto,27 S. Pisano,10,52 D. Pistone,56 M. Płoskon,80 M. Planinic,99 F. Pliquett,68 M. G. Poghosyan,96 B. Polichtchouk,91

N. Poljak,99 A. Pop,48 S. Porteboeuf-Houssais,134 V. Pozdniakov,75 S. K. Prasad,3 R. Preghenella,54 F. Prino,59

C. A. Pruneau,143 I. Pshenichnov,62 M. Puccio,34 J. Putschke,143 S. Qiu,90 L. Quaglia,25 R. E. Quishpe,125 S. Ragoni,111

S. Raha,3 S. Rajput,101 J. Rak,126 A. Rakotozafindrabe,137 L. Ramello,31 F. Rami,136 S. A. R. Ramirez,45 R. Raniwala,102

S. Raniwala,102 S. S. Räsänen,44 R. Rath,50 V. Ratza,43 I. Ravasenga,90 K. F. Read,96,130 A. R. Redelbach,39 K. Redlich,85,f

A. Rehman,21 P. Reichelt,68 F. Reidt,34 X. Ren,6 R. Renfordt,68 Z. Rescakova,38 K. Reygers,104 A. Riabov,98 V. Riabov,98

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T. Richert,81,89 M. Richter,20 P. Riedler,34 W. Riegler,34 F. Riggi,27 C. Ristea,67 S. P. Rode,50 M. Rodríguez Cahuantzi,45

K. Røed,20 R. Rogalev,91 E. Rogochaya,75 D. Rohr,34 D. Röhrich,21 P. F. Rojas,45 P. S. Rokita,142 F. Ronchetti,52 A. Rosano,56

E. D. Rosas,69 K. Roslon,142 A. Rossi,28,57 A. Rotondi,139 A. Roy,50 P. Roy,110 O. V. Rueda,81 R. Rui,24 B. Rumyantsev,75

A. Rustamov,87 E. Ryabinkin,88 Y. Ryabov,98 A. Rybicki,118 H. Rytkonen,126 O. A. M. Saarimaki,44 R. Sadek,115 S. Sadhu,141

S. Sadovsky,91 K. Šafarík,37 S. K. Saha,141 B. Sahoo,49 P. Sahoo,49 R. Sahoo,50 S. Sahoo,65 P. K. Sahu,65 J. Saini,141

S. Sakai,133 S. Sambyal,101 V. Samsonov,93,98 D. Sarkar,143 N. Sarkar,141 P. Sarma,42 V. M. Sarti,105 M. H. P. Sas,63

E. Scapparone,54 J. Schambach,119 H. S. Scheid,68 C. Schiaua,48 R. Schicker,104 A. Schmah,104 C. Schmidt,107

H. R. Schmidt,103 M. O. Schmidt,104 M. Schmidt,103 N. V. Schmidt,68,96 A. R. Schmier,130 J. Schukraft,89 Y. Schutz,136

K. Schwarz,107 K. Schweda,107 G. Scioli,26 E. Scomparin,59 J. E. Seger,15 Y. Sekiguchi,132 D. Sekihata,132

I. Selyuzhenkov,93,107 S. Senyukov,136 D. Serebryakov,62 A. Sevcenco,67 A. Shabanov,62 A. Shabetai,115 R. Shahoyan,34

W. Shaikh,110 A. Shangaraev,91 A. Sharma,100 A. Sharma,101 H. Sharma,118 M. Sharma,101 N. Sharma,100 S. Sharma,101

O. Sheibani,125 K. Shigaki,46 M. Shimomura,83 S. Shirinkin,92 Q. Shou,40 Y. Sibiriak,88 S. Siddhanta,55 T. Siemiarczuk,85

D. Silvermyr,81 G. Simatovic,90 G. Simonetti,34 B. Singh,105 R. Singh,86 R. Singh,101 R. Singh,50 V. K. Singh,141 V. Singhal,141

T. Sinha,110 B. Sitar,13 M. Sitta,31 T. B. Skaali,20 M. Slupecki,44 N. Smirnov,146 R. J. M. Snellings,63 C. Soncco,112 J. Song,125

A. Songmoolnak,116 F. Soramel,28 S. Sorensen,130 I. Sputowska,118 J. Stachel,104 I. Stan,67 P. J. Steffanic,130 E. Stenlund,81

S. F. Stiefelmaier,104 D. Stocco,115 M. M. Storetvedt,36 L. D. Stritto,29 A. A. P. Suaide,121 T. Sugitate,46 C. Suire,78

M. Suleymanov,14 M. Suljic,34 R. Sultanov,92 M. Šumbera,95 V. Sumberia,101 S. Sumowidagdo,51 S. Swain,65 A. Szabo,13

I. Szarka,13 U. Tabassam,14 S. F. Taghavi,105 G. Taillepied,134 J. Takahashi,122 G. J. Tambave,21 S. Tang,6,134 M. Tarhini,115

M. G. Tarzila,48 A. Tauro,34 G. Tejeda Muñoz,45 A. Telesca,34 L. Terlizzi,25 C. Terrevoli,125 D. Thakur,50 S. Thakur,141

D. Thomas,119 F. Thoresen,89 R. Tieulent,135 A. Tikhonov,62 A. R. Timmins,125 A. Toia,68 N. Topilskaya,62 M. Toppi,52

F. Torales-Acosta,19 S. R. Torres,37 A. Trifiró,32,56 S. Tripathy,50,69 T. Tripathy,49 S. Trogolo,28 G. Trombetta,33 L. Tropp,38

V. Trubnikov,2 W. H. Trzaska,126 T. P. Trzcinski,142 B. A. Trzeciak,37,63 A. Tumkin,109 R. Turrisi,57 T. S. Tveter,20

K. Ullaland,21 E. N. Umaka,125 A. Uras,135 G. L. Usai,23 M. Vala,38 N. Valle,139 S. Vallero,59 N. van der Kolk,63 L. V. R. vanDoremalen,63 M. van Leeuwen,63 P. Vande Vyvre,34 D. Varga,145 Z. Varga,145 M. Varga-Kofarago,145 A. Vargas,45

M. Vasileiou,84 A. Vasiliev,88 O. Vázquez Doce,105 V. Vechernin,113 E. Vercellin,25 S. Vergara Limón,45 L. Vermunt,63

R. Vernet,7 R. Vértesi,145 L. Vickovic,35 Z. Vilakazi,131 O. Villalobos Baillie,111 G. Vino,53 A. Vinogradov,88 T. Virgili,29

V. Vislavicius,89 A. Vodopyanov,75 B. Volkel,34 M. A. Völkl,103 K. Voloshin,92 S. A. Voloshin,143 G. Volpe,33 B. von Haller,34

I. Vorobyev,105 D. Voscek,117 J. Vrláková,38 B. Wagner,21 M. Weber,114 S. G. Weber,144 A. Wegrzynek,34 S. C. Wenzel,34

J. P. Wessels,144 J. Wiechula,68 J. Wikne,20 G. Wilk,85 J. Wilkinson,10 G. A. Willems,144 E. Willsher,111 B. Windelband,104

M. Winn,137 W. E. Witt,130 J. R. Wright,119 Y. Wu,128 R. Xu,6 S. Yalcin,77 Y. Yamaguchi,46 K. Yamakawa,46 S. Yang,21

S. Yano,137 Z. Yin,6 H. Yokoyama,63 I.-K. Yoo,17 J. H. Yoon,61 S. Yuan,21 A. Yuncu,104 V. Yurchenko,2 V. Zaccolo,24

A. Zaman,14 C. Zampolli,34 H. J. C. Zanoli,63 N. Zardoshti,34 A. Zarochentsev,113 P. Závada,66 N. Zaviyalov,109

H. Zbroszczyk,142 M. Zhalov,98 S. Zhang,40 X. Zhang,6 Z. Zhang,6 V. Zherebchevskii,113 Y. Zhi,12 D. Zhou,6 Y. Zhou,89

Z. Zhou,21 J. Zhu,6,107 Y. Zhu,6 A. Zichichi,10,26 G. Zinovjev,2 and N. Zurlo140

(ALICE Collaboration)

1A. I. Alikhanyan National Science Laboratory (Yerevan Physics Institute) Foundation, Yerevan, Armenia2Bogolyubov Institute for Theoretical Physics, National Academy of Sciences of Ukraine, Kiev, Ukraine

3Bose Institute, Department of Physics and Centre for Astroparticle Physics and Space Science (CAPSS), Kolkata, India4Budker Institute for Nuclear Physics, Novosibirsk, Russia

5California Polytechnic State University, San Luis Obispo, California, United States6Central China Normal University, Wuhan, China

7Centre de Calcul de l’IN2P3, Villeurbanne, Lyon, France8Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear (CEADEN), Havana, Cuba

9Centro de Investigación y de Estudios Avanzados (CINVESTAV), Mexico City and Mérida, Mexico10Centro Fermi - Museo Storico della Fisica e Centro Studi e Ricerche “Enrico Fermi’, Rome, Italy

11Chicago State University, Chicago, Illinois, United States12China Institute of Atomic Energy, Beijing, China

13Comenius University Bratislava, Faculty of Mathematics, Physics and Informatics, Bratislava, Slovakia14COMSATS University Islamabad, Islamabad, Pakistan15Creighton University, Omaha, Nebraska, United States

16Department of Physics, Aligarh Muslim University, Aligarh, India17Department of Physics, Pusan National University, Pusan, Republic of Korea

18Department of Physics, Sejong University, Seoul, Republic of Korea19Department of Physics, University of California, Berkeley, California, United States

20Department of Physics, University of Oslo, Oslo, Norway21Department of Physics and Technology, University of Bergen, Bergen, Norway

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22Dipartimento di Fisica dell’Università ’La Sapienza’ and Sezione INFN, Rome, Italy23Dipartimento di Fisica dell’Università and Sezione INFN, Cagliari, Italy24Dipartimento di Fisica dell’Università and Sezione INFN, Trieste, Italy25Dipartimento di Fisica dell’Università and Sezione INFN, Turin, Italy

26Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN, Bologna, Italy27Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN, Catania, Italy28Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN, Padova, Italy

29Dipartimento di Fisica ‘E. R. Caianiello’ dell’Università and Gruppo Collegato INFN, Salerno, Italy30Dipartimento DISAT del Politecnico and Sezione INFN, Turin, Italy

31Dipartimento di Scienze e Innovazione Tecnologica dell’Università del Piemonte Orientale and INFN Sezione di Torino, Alessandria, Italy32Dipartimento di Scienze MIFT, Università di Messina, Messina, Italy

33Dipartimento Interateneo di Fisica ‘M. Merlin’ and Sezione INFN, Bari, Italy34European Organization for Nuclear Research (CERN), Geneva, Switzerland

35Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture, University of Split, Split, Croatia36Faculty of Engineering and Science, Western Norway University of Applied Sciences, Bergen, Norway

37Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, Prague, Czech Republic38Faculty of Science, P. J. Šafárik University, Košice, Slovakia

39Frankfurt Institute for Advanced Studies, Johann Wolfgang Goethe-Universität Frankfurt, Frankfurt, Germany40Fudan University, Shanghai, China

41Gangneung-Wonju National University, Gangneung, Republic of Korea42Gauhati University, Department of Physics, Guwahati, India

43Helmholtz-Institut für Strahlen- und Kernphysik, Rheinische Friedrich-Wilhelms-Universität Bonn, Bonn, Germany44Helsinki Institute of Physics (HIP), Helsinki, Finland

45High Energy Physics Group, Universidad Autónoma de Puebla, Puebla, Mexico46Hiroshima University, Hiroshima, Japan

47Hochschule Worms, Zentrum für Technologietransfer und Telekommunikation (ZTT), Worms, Germany48Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest, Romania

49Indian Institute of Technology Bombay (IIT), Mumbai, India50Indian Institute of Technology Indore, Indore, India51Indonesian Institute of Sciences, Jakarta, Indonesia

52INFN, Laboratori Nazionali di Frascati, Frascati, Italy53INFN, Sezione di Bari, Bari, Italy

54INFN, Sezione di Bologna, Bologna, Italy55INFN, Sezione di Cagliari, Cagliari, Italy56INFN, Sezione di Catania, Catania, Italy57INFN, Sezione di Padova, Padova, Italy

58INFN, Sezione di Roma, Rome, Italy59INFN, Sezione di Torino, Turin, Italy

60INFN, Sezione di Trieste, Trieste, Italy61Inha University, Incheon, Republic of Korea

62Institute for Nuclear Research, Academy of Sciences, Moscow, Russia63Institute for Subatomic Physics, Utrecht University/Nikhef, Utrecht, Netherlands64Institute of Experimental Physics, Slovak Academy of Sciences, Košice, Slovakia

65Institute of Physics, Homi Bhabha National Institute, Bhubaneswar, India66Institute of Physics of the Czech Academy of Sciences, Prague, Czech Republic

67Institute of Space Science (ISS), Bucharest, Romania68Institut für Kernphysik, Johann Wolfgang Goethe-Universität Frankfurt, Frankfurt, Germany

69Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Mexico City, Mexico70Instituto de Física, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, Brazil

71Instituto de Física, Universidad Nacional Autónoma de México, Mexico City, Mexico72iThemba LABS, National Research Foundation, Somerset West, South Africa

73Jeonbuk National University, Jeonju, Republic of Korea74Johann-Wolfgang-Goethe Universität Frankfurt Institut für Informatik, Fachbereich Informatik und Mathematik, Frankfurt, Germany

75Joint Institute for Nuclear Research (JINR), Dubna, Russia76Korea Institute of Science and Technology Information, Daejeon, Republic of Korea

77KTO Karatay University, Konya, Turkey78Laboratoire de Physique des 2 Infinis, Irène Joliot-Curie, Orsay, France

79Laboratoire de Physique Subatomique et de Cosmologie, Université Grenoble-Alpes, CNRS-IN2P3, Grenoble, France80Lawrence Berkeley National Laboratory, Berkeley, California, United States

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81Lund University Department of Physics, Division of Particle Physics, Lund, Sweden82Nagasaki Institute of Applied Science, Nagasaki, Japan

83Nara Women’s University (NWU), Nara, Japan84National and Kapodistrian University of Athens, School of Science, Department of Physics, Athens, Greece

85National Centre for Nuclear Research, Warsaw, Poland86National Institute of Science Education and Research, Homi Bhabha National Institute, Jatni, India

87National Nuclear Research Center, Baku, Azerbaijan88National Research Centre Kurchatov Institute, Moscow, Russia

89Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark90Nikhef, National institute for subatomic physics, Amsterdam, Netherlands

91NRC Kurchatov Institute IHEP, Protvino, Russia92NRC «Kurchatov» Institute - ITEP, Moscow, Russia

93NRNU Moscow Engineering Physics Institute, Moscow, Russia94Nuclear Physics Group, STFC Daresbury Laboratory, Daresbury, United Kingdom

95Nuclear Physics Institute of the Czech Academy of Sciences, Rež u Prahy, Czech Republic96Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States

97Ohio State University, Columbus, Ohio, United States98Petersburg Nuclear Physics Institute, Gatchina, Russia

99Physics department, Faculty of science, University of Zagreb, Zagreb, Croatia100Physics Department, Panjab University, Chandigarh, India

101Physics Department, University of Jammu, Jammu, India102Physics Department, University of Rajasthan, Jaipur, India

103Physikalisches Institut, Eberhard-Karls-Universität Tübingen, Tübingen, Germany104Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany

105Physik Department, Technische Universität München, Munich, Germany106Politecnico di Bari, Bari, Italy

107Research Division and ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, Germany108Rudjer Boškovic Institute, Zagreb, Croatia

109Russian Federal Nuclear Center (VNIIEF), Sarov, Russia110Saha Institute of Nuclear Physics, Homi Bhabha National Institute, Kolkata, India

111School of Physics and Astronomy, University of Birmingham, Birmingham, United Kingdom112Sección Física, Departamento de Ciencias, Pontificia Universidad Católica del Perú, Lima, Peru

113St. Petersburg State University, St. Petersburg, Russia114Stefan Meyer Institut für Subatomare Physik (SMI), Vienna, Austria

115SUBATECH, IMT Atlantique, Université de Nantes, CNRS-IN2P3, Nantes, France116Suranaree University of Technology, Nakhon Ratchasima, Thailand

117Technical University of Košice, Košice, Slovakia118The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Cracow, Poland

119The University of Texas at Austin, Austin, Texas, United States120Universidad Autónoma de Sinaloa, Culiacán, Mexico121Universidade de São Paulo (USP), São Paulo, Brazil

122Universidade Estadual de Campinas (UNICAMP), Campinas, Brazil123Universidade Federal do ABC, Santo Andre, Brazil124University of Cape Town, Cape Town, South Africa

125University of Houston, Houston, Texas, United States126University of Jyväskylä, Jyväskylä, Finland

127University of Liverpool, Liverpool, United Kingdom128University of Science and Technology of China, Hefei, China

129University of South-Eastern Norway, Tonsberg, Norway130University of Tennessee, Knoxville, Tennessee, United States131University of the Witwatersrand, Johannesburg, South Africa

132University of Tokyo, Tokyo, Japan133University of Tsukuba, Tsukuba, Japan

134Université Clermont Auvergne, CNRS/IN2P3, LPC, Clermont-Ferrand, France135Université de Lyon, Université Lyon 1, CNRS/IN2P3, IPN-Lyon, Villeurbanne, Lyon, France

136Université de Strasbourg, CNRS, IPHC UMR 7178, F-67000 Strasbourg, France, Strasbourg, France137Université Paris-Saclay Centre d’Etudes de Saclay (CEA), IRFU, Départment de Physique Nucléaire (DPhN), Saclay, France

138Università degli Studi di Foggia, Foggia, Italy139Università degli Studi di Pavia, Pavia, Italy

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140Università di Brescia, Brescia, Italy141Variable Energy Cyclotron Centre, Homi Bhabha National Institute, Kolkata, India

142Warsaw University of Technology, Warsaw, Poland143Wayne State University, Detroit, Michigan, United States

144Westfälische Wilhelms-Universität Münster, Institut für Kernphysik, Münster, Germany145Wigner Research Centre for Physics, Budapest, Hungary146Yale University, New Haven, Connecticut, United States

147Yonsei University, Seoul, Republic of Korea

aItalian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA), Bologna, Italy.bDipartimento DET del Politecnico di Torino, Turin, Italy.cDeceased.dM. V. Lomonosov Moscow State University, D. V. Skobeltsyn Institute of Nuclear, Physics, Moscow, Russia.eDepartment of Applied Physics, Aligarh Muslim University, Aligarh, India.fInstitute of Theoretical Physics, University of Wroclaw, Poland.

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