]}

2022 061 24 March Elliptic Flow Fluctuations at Midrapidity using Spectator
Neutrons ALICE Collaboration††thanks: See Appendix A for the list of
collaboration members ALICE Collaboration

Measurements of the elliptic flow coefficient relative to the collision plane
defined by the spectator neutrons
$v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}$ in collisions of Pb ions
at center-of-mass energy per nucleon–nucleon pair
$\sqrt{s_{\mathrm{NN}}}=$2.76\text{\,}\mathrm{T}\mathrm{e}\mathrm{V}$$ and Xe
ions at $\sqrt{s_{\mathrm{NN}}}=$5.44\text{\,}\mathrm{T}\mathrm{e}\mathrm{V}$$
are reported. The results are presented for charged particles produced at
midrapidity as a function of centrality and transverse momentum for the 5–70%
and $0.26\text{\,}\mathrm{GeV}\text{/}\mathrm{\textit{c}}$ ranges,
respectively. The ratio between
$v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}$ and the elliptic flow
coefficient relative to the participant plane $v_{2}\left\\{4\right\\}$,
estimated using four-particle correlations, deviates by up to 20% from unity
depending on centrality. This observation differs strongly from the magnitude
of the corresponding eccentricity ratios predicted by the TRENTo and the
elliptic power models of initial state fluctuations that are tuned to describe
the participant plane anisotropies. The differences can be interpreted as a
decorrelation of the neutron spectator plane and the reaction plane because of
fragmentation of the remnants from the colliding nuclei, which points to an
incompleteness of current models describing the initial state fluctuations. A
significant transverse momentum dependence of the ratio
$\left.v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}\right/v_{2}\left\\{4\right\\}$
is observed in all but the most central collisions, which may help to
understand whether momentum anisotropies at low and intermediate transverse
momentum have a common origin in initial state fluctuations. The ratios of
$v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}$ and
$v_{2}\left\\{4\right\\}$ to the corresponding initial state eccentricities
for Xe–Xe and Pb–Pb collisions at similar initial entropy density show a
difference of $(7.0\pm 0.9)\%$ with an additional variation of $+1.8\%$ when
including RHIC data in the TRENTo parameter extraction. These observations
provide new experimental constraints for viscous effects in the hydrodynamic
modeling of the expanding quark–gluon plasma produced in heavy-ion collisions
at the LHC.

Determining the properties of deconfined quark–gluon matter, called
quark–gluon plasma (QGP), is the goal of the heavy-ion program at the Large
Hadron Collider (LHC). Previous studies of data collected at the Brookhaven
Relativistic Heavy-Ion Collider (RHIC) and the LHC have shown that the QGP
behaves like a liquid with very small specific shear and bulk viscosities [1,
2]. In heavy-ion collisions, these properties are encoded in the collective
expansion of the strongly interacting QGP. Measurements of this collective
behavior, in particular the anisotropic flow driven by the spatial anisotropy
of the shape of the overlap region of the colliding nuclei, can be used to
infer the QGP transport properties. The anisotropic flow is quantified by the
coefficients $v_{n}$ of a Fourier decomposition of the momentum anisotropy of
emitted particles relative to the collision symmetry planes with angles
$\Psi_{n}$ of the harmonic $n$. The dominant coefficient in off-center
collision of heavy ions is the elliptic flow $v_{2}$. The shape of the initial
energy density distribution in the overlap region of the nuclei (participant
zone) fluctuates from collision to collision due to the motion of nucleons and
the quantum mechanical nature of the nucleus–nucleus interaction, which is
typically modeled by spatial position fluctuations of the interacting
nucleons. This was initially discussed in the context of the elliptic flow
fluctuations [3, 4, 5] and later confirmed by observations [6, 7, 8, 9, 10] of
significant non-zero triangular flow $v_{3}$ and higher flow harmonics. A
detailed picture of fluctuations has already been inferred from the comparison
of initial state models to measurements of flow fluctuations relative to the
participant symmetry planes [11, 12, 13, 8, 14, 15, 16, 17, 18, 19, 20, 21,
22, 23, 24, 25, 26, 27, 28]. Additional information about the pattern of
initial state fluctuations can be obtained from measurements using spectator
nucleons, which decouple very fast from the participant zone.

(a) transverse view

(b) longitudinal view

Figure 1:  (color online) A sketch of the geometry of a non-central heavy-ion
collision in the 1(a) transverse $(x_{\mathrm{RP}},y)$ and 1(b) reaction
$(x_{\mathrm{RP}},z)$ planes. The $x_{\mathrm{RP}}$ axis points along the
direction of the impact parameter given by the distance between the centers of
the colliding nuclei, while the $z$ axis is oriented along the direction of
the colliding nuclei. The full (open) circles represent the protons (neutrons)
from projectile (red) and target (blue) nuclei. The participant nucleons are
shown in purple. In panel 1(a), the arrows indicate the eccentricity vectors
($\epsilon_{n}$ is shown as example) and corresponding reaction
($\Psi_{\mathrm{\mathrm{RP}}}$), projectile/target spectator
($\Psi_{\mathrm{SP}}^{\rm P,T}$), and participant (multiple
$\Psi_{\mathrm{n}}$, $n\geq 1$) plane angles. Panel 1(b) shows the outward
deflection, indicated by curved arrows, of the spectators and fragmentation
products of the projectile ($\eta>0$) and target ($\eta<0$) recoil nuclei,
such as protons ($p$), neutrons ($n$), and nuclei (deuteron, helium, etc).

Figure 1 sketches the geometry of a non-central heavy-ion collision, divided
into the regions of the participant nucleons (i.e. those encountering strong
interactions) and the deflected spectator nucleons of the target (T) and
projectile (P) nuclei. The geometrical reaction plane, denoted by its angle
$\Psi_{\mathrm{\mathrm{RP}}}$ in Fig. 1(a), is spanned by the impact
parameter, pointing in the direction of the $\mathrm{x}_{\mathrm{RP}}$ axis,
and the movement direction of the colliding nuclei, which is indicated by the
z axis. The fluctuating shape of the energy density distribution of the
collision can be characterized by the eccentricities $\varepsilon_{n}$ for
$n>1$

$\varepsilon_{n}e^{in\Psi_{n}}=-\frac{\int
r^{n}e^{in\varphi}\rho(r,\varphi)r\mathrm{d}r\mathrm{d}\varphi}{\int
r^{n}\rho(r,\varphi)r\mathrm{d}r\mathrm{d}\varphi}\ ,$ (1)

where $\rho(r,\varphi)$ is the initial energy or entropy density near
midrapidity and $(r,\varphi)$ are the polar coordinates. Eq. 1 for $n=2$ gives
the standard formula for the ellipticity [29, 30]. In the absence of
fluctuations, the azimuthal symmetry plane of the collision is given by the
reaction plane. In the presence of fluctuations, the collision symmetry is not
described by a single reaction plane, but by multiple participant planes with
angles $\Psi_{n}$ and spectator planes with angles
$\Psi_{\mathrm{\mathrm{SP}}}^{\mathrm{T}}$ and
$\Psi_{\mathrm{\mathrm{SP}}}^{\mathrm{P}}$. The spectator planes are spanned
by the beam direction and the deflection of the spectators, which is
determined by the sum of the momenta of the spectator nucleons and fragments.
For small fluctuations of the spectator deflection, the target and projectile
spectator planes share a common symmetry plane with angle
$\Psi_{\mathrm{\mathrm{SP}}}$. The sketch is oriented along the reaction plane
$x_{\mathrm{RP}}$ (i.e. $\Psi_{\mathrm{\mathrm{RP}}}=0$), while in the
experiment the orientation of the collision relative to the laboratory frame
fluctuates from one collision to another. This causes the reaction plane angle
to be different from zero.

Figure 1(b) illustrates a longitudinal view of the early time of a heavy-ion
collision, in particular the deflection of the spectators. The fragmentation
of the nuclear recoil is a complex process [31] involving the release of
protons, neutrons, and other nuclei, which causes a decorrelation of the
reaction plane and spectator planes. Additionally, a plane defined only by a
subset of the spectator fragments (e.g. only neutrons or protons) can be
different from the overall spectator plane orientation illustrated in Fig.
1(a). This difference depends on the collision centrality due to the balance
between the energy carried by free nucleons and nuclear fragments.

The deflection of the spectators along the spectator planes at LHC collision
energies, as illustrated by the red and blue arrows in Fig. 1(a), was shown to
be outward from the nuclear overlap region, based on the measured directed
flow relative to the neutron spectator plane and hydrodynamic model
calculations [32]. From measurements of the neutron deflection at the LHC, the
transverse momentum exchange between the participants and the spectators has
been estimated to be in the order of
$20\text{\,}\mathrm{MeV}\text{/}\mathrm{\textit{c}}$ per nucleon in midcentral
collisions [33]. This is about an order of magnitude smaller than the width of
the transverse momentum distribution of emitted spectators, which is
proportional [34, 35] to the Fermi momentum of
$265\text{\,}\mathrm{MeV}\text{/}\mathrm{\textit{c}}$ [36] for lead nuclei.

Due to the geometry of the collision, the direction in which the spectators
are deflected is believed to be strongly correlated to the reaction plane. In
collisions with large impact parameters, the smaller number of sources of
particle production (number of participants) results in a stronger
decorrelation of the participant symmetry plane and the reaction plane.
Measurements of the directed flow using the deflection of spectator neutrons
showed a small but non-zero decorrelation between the direction of the neutron
deflection and the reaction plane orientation, in addition to a relative
decorrelation of the neutron spectator planes originating from the projectile
and target nuclei, respectively [33]. A strong correlation between the
participant and spectator planes is expected in midcentral collisions because
of the dominance of the elliptic flow [37]. Together with measurements
relative to the participant planes, a measurement relative to the spectator
deflection provides unique information about spatial orientation of the
participant zone relative to the geometrical orientation of the colliding
nuclei [33].

Hydrodynamic model calculations with small viscosities indicate an
approximately linear response to the initial eccentricities for elliptic and
triangular flow [38]. In ideal hydrodynamics, the elliptic flow $v_{2}$ is
proportional to the initial eccentricity [39]

$v_{2}\propto\kappa_{2}\varepsilon_{2}\ .$ (2)

This has been demonstrated by the comparison of measurements relative to the
participant plane with eccentricities from different initial state model
calculations [25]. The scaling coefficient $\kappa_{2}$ is related to the
initial entropy density. In ideal hydrodynamics, it is estimated from the
final state multiplicity $\mathrm{d}N_{\mathrm{ch}}/\mathrm{d}y$ per unit of
the overlap area $S$ [40, 41, 42]

$\frac{v_{2}}{\varepsilon_{2}}\propto\frac{1}{S}\frac{\mathrm{d}N_{\mathrm{ch}}}{\mathrm{d}y}\
.$ (3)

Following Ref. [25], the area $S$ is defined as
$S=4\pi\sigma_{\mathrm{x}}\sigma_{\mathrm{y}}$, where $\sigma_{\mathrm{x}}$ is
the spatial width of the participant zone along the reaction plane direction
($\mathrm{x_{RP}}$) and $\sigma_{\mathrm{y}}$ is along the transverse
direction (y). This scaling can be tested by comparing different collision
systems and their dependence on centrality or center-of-mass energy. Such a
scaling is broken by viscous effects, which depend on the magnitude of the
temperature-dependent specific shear and bulk viscosities [41]. Even for an
ideal fluid, the scaling can be broken during the final stages of the
evolution before freeze-out [41].

One of the largest uncertainties in the description of heavy-ion collisions is
the pattern of fluctuations in the initial state that results in large
uncertainties of the extracted QGP transport properties [43, 44]. Among the
observables that quantify the effects of initial state fluctuations are the
cumulants [29], which can be used to decompose both the spatial and momentum
anisotropies. The cumulants of the eccentricity distribution describe the
shape of the initial state fluctuations. There are different models describing
this initial state and its fluctuations. One of the simplest analytical
descriptions is the Bessel-Gaussian model (BGM) [45] in which many sources of
entropy production result in a two-dimensional Gaussian shape of fluctuations,
where all higher-order ($m\geq 4$) eccentricity cumulants,
$\varepsilon_{2}\\{m\\}$, are degenerate and equal to the reaction plane
eccentricity

$\varepsilon_{2}\\{2\\}>\varepsilon_{2}\\{4\\}=\varepsilon_{\mathrm{RP}}\ .$
(4)

The BGM is only applicable to small fluctuations. The elliptic-power model
(EPM) is a more general analytical model, which is also applicable for the
description of large fluctuations [11]. In the EPM, the degeneracy of higher-
order cumulants is broken and therefore

$\varepsilon_{2}\\{2\\}>\varepsilon_{2}\\{4\\}>\varepsilon_{\mathrm{RP}}\ .$
(5)

There are a number of Monte Carlo models of the initial state that either
implement a specific physical mechanism of pre-equilibrium entropy production,
for example IP-Glasma [46], or do not assume a specific mechanism, such as
TRENTo [12]. In TRENTo, the entropy production in the participant zone is
parameterized by the transverse density of the participating nucleons, i.e.
the participant thickness. Each of these models is characterized by specific
signatures of the eccentricity cumulants and their relationships. The
importance of subnucleonic degrees of freedom for modeling fluctuations in
central collisions has been highlighted in Ref. [47].

One can probe the initial state eccentricities by comparing the ratios of
eccentricity cumulants defined by Eq. 1 to equivalent flow observables, if the
fluid response is linear as given by Eq. 2. These observables can be
constructed through angular correlations of the emitted particles and the
symmetry planes

$\displaystyle v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}{}$
$\displaystyle=\langle\langle\cos
2(\varphi_{1}-\Psi_{\mathrm{\mathrm{SP}}})\rangle\rangle~{},$ (6)
$\displaystyle v_{2}\left\\{2,\left|\Delta\eta\right|\right\\}$
$\displaystyle=\sqrt{\langle\langle\cos
2(\varphi_{1}-\varphi_{2})\rangle\rangle}=\langle
v^{2}_{2}\rangle^{\frac{1}{2}}~{},$ (7) $\displaystyle
v_{2}\left\\{4\right\\}$ $\displaystyle=\left[2\langle\langle\cos
2(\varphi_{1}-\varphi_{2})\rangle\rangle^{2}-\langle\langle\cos
2(\varphi_{1}-\varphi_{2}+\varphi_{3}-\varphi_{4})\rangle\rangle\right]^{\frac{1}{4}}=\left[2\langle
v^{2}_{2}\rangle^{2}-\langle v^{4}_{2}\rangle\right]^{\frac{1}{4}}\ .$ (8)

Here $\varphi_{i}$ ($i=1\dots 4$) are the azimuthal angles of the produced
particles, $\langle\ldots\rangle$ is the average over all collisions, and
$\langle\langle\ldots\rangle\rangle$ is the average over all particles in a
given transverse momentum window in all collisions. The
$v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}$ is the elliptic flow
measured relative to the spectator plane with angle
$\Psi_{\mathrm{\mathrm{SP}}}$, where fluctuations of the spectator symmetry
planes are assumed to be small. The $v_{2}\left\\{2\right\\}$ and
$v_{2}\left\\{4\right\\}$ are estimators of elliptic flow coefficients whose
equations, including $p_{\mathrm{T}}$-dependence, are derived from the two-
and four-particle cumulants [48, 49]. The variable $|\Delta\eta|$ in Eq. 7
refers to the minimum pseudorapidity ($\eta$) separation between the two
correlated particles. The observables
$v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}$,
$v_{2}\left\\{4\right\\}$, and
$v_{2}\left\\{2,\left|\Delta\eta\right|\right\\}$ may deviate from
$v_{2}\\{\Psi_{\mathrm{\mathrm{RP}}}\\}$, which is the unmeasurable momentum
anisotropy relative to the reaction plane. The comparison of ratios of the
measured anisotropic flow coefficients to their respective eccentricities is
instrumental for identifying the most realistic model of the initial state.

The transverse momentum dependence of the flow coefficients $v_{n}$ allows one
to study if there is a common origin of anisotropy at different transverse
momentum scales due to initial state eccentricity fluctuations. The main
source of anisotropy for soft
($p_{\mathrm{T}}<$3\text{\,}\mathrm{GeV}\text{/}\mathrm{\textit{c}}$$)
particle production is the collective expansion of the QGP [38]. At
significantly larger $p_{\mathrm{T}}$, the dominant contribution to $v_{n}$ is
the path length dependent energy loss of the jet propagating through the
azimuthally asymmetric medium oriented along $\Psi_{\mathrm{n}}$ [50]. A
significant transverse momentum dependence of flow fluctuations relative to
the participant planes is observed [50] in central collisions and within large
experimental uncertainties in midcentral collisions. Given that the spectators
only probe the early time evolution of the collision and provide sensitivity
to a different symmetry plane, the transverse momentum dependence of the ratio
$\left.v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}\right/v_{2}\left\\{4\right\\}$
can be used as an additional observable to investigate the origin of flow
fluctuations.

An accurate determination of the flow coefficients relative to the spectator
plane, in particular of the elliptic flow
$v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}$, is also crucial for the
search of the chiral magnetic effect (CME) [51, 52]. Because the magnetic
field orientation is correlated more strongly to the spectator deflection than
to the participant plane orientation, the measurement relative to both planes
allows the separation of the CME signal from the background correlations
coupled to the elliptic flow [53, 54, 55, 56, 57, 52].

In this letter, the charged particle elliptic flow relative to the neutron
spectator deflection, $v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}$, and
to the participant plane, quantified by
$v_{2}\left\\{2,\left|\Delta\eta\right|>1\right\\}$ and
$v_{2}\left\\{4\right\\}$, is reported as a function of centrality and
transverse momentum for collisions of Pb ions at a center-of-mass energy per
nucleon–nucleon pair of
$\sqrt{s_{\mathrm{NN}}}=$2.76\text{\,}\mathrm{T}\mathrm{e}\mathrm{V}$$ and Xe
ions at
$\sqrt{s_{\mathrm{NN}}}=$5.44\text{\,}\mathrm{T}\mathrm{e}\mathrm{V}$$. The
comparison with different initial state models, such as BGM, EPM, and TRENTo,
and the scaling properties of $v_{2}/\varepsilon_{2}$ are also presented.

ALICE is a dedicated heavy-ion experiment at the LHC. A detailed description
of the detector and its performance can be found elsewhere [58, 59]. The
trajectories of the charged particles are reconstructed using the Inner
Tracking System (ITS) and the Time Projection Chamber (TPC) [60, 61]. The
neutron spectator deflection is estimated using the neutron Zero Degree
Calorimeters (ZDC) [62]. The ZDC consist of two detectors with a $2\times 2$
transverse segmentation. During the Pb–Pb (Xe–Xe) data-taking, the ZDC were
placed 114 m (112.5 m) away from the collision point on both sides of the
experiment, named A and C side, covering the pseudorapidity interval
$|\eta|>8.78~{}(8.77)$. The collision centrality is reconstructed using the
energy deposition in the forward V0 scintillator arrays [63].

About 10 (1) million of minimum bias [59] Pb–Pb (Xe–Xe) collisions collected
in the year 2010 (2017) are analyzed. This corresponds to collisions in the
5–70% centrality range and a reconstructed primary collision vertex located
within $\pm$10\text{\,}\mathrm{c}\mathrm{m}$$ along the beam direction from
the nominal interaction point. Outside of this centrality range, the
deflection of the spectators cannot be reliably reconstructed because of the
small number of detected neutron spectators in central collisions and the
large fraction of spectator neutrons that are not detected by the ZDC in
peripheral collisions because they are bound in charged fragments and thus
deflected by the LHC magnets.

The charged particles are selected within the range of pseudorapidity
$|\eta|<0.8$ and transverse momentum
$p_{\mathrm{T}}>$0.2\text{\,}\mathrm{GeV}\text{/}\mathrm{\textit{c}}$$. The
tracks are reconstructed using the combined information from the ITS and the
TPC detectors. A minimum of 70 TPC space points (out of a maximum of 159) and
a minimum of two ITS hits, with at least one in one of the two innermost
layers, are required for all tracks. A reduced $\chi^{2}$ per TPC space point
(ITS hit) in the range 0.1–4 (less than 36) is required. Only tracks with a
distance of closest approach to the primary vertex position smaller than
$3.2\text{\,}\mathrm{c}\mathrm{m}$ in the beam direction and within a radius
of $2.4\text{\,}\mathrm{c}\mathrm{m}$ in the transverse plane are considered.

The observables in Eqs. 6, 7 and 8, are calculated using flow vectors
$q_{n}^{K}$ of harmonic $n$ in each collision as

$q_{n}^{K}=x_{n}^{K}+iy_{n}^{K}=\left.\sum_{j\in
K}(w_{j})^{p}e^{in\varphi_{j}}\right/\sum_{j\in K}(w_{j})^{p}~{},$ (9)

where $K$ denotes either the reconstructed tracks $K=T$ or the two ZDC
subdetectors $K=A,C$.

For the second harmonic flow vector of the reconstructed tracks $q_{2}^{T}$,
the $w_{j}$ and $\varphi_{j}$ are the weight and azimuthal angle of the $j$-th
track, respectively. The weights in the $q_{2}^{T}$ calculation are defined by
the inverse product $w=1/(\epsilon\mathrm{d}N/\mathrm{d}\varphi)$ of the
$p_{\mathrm{T}}$-dependent reconstruction efficiency $\epsilon$ and the
measured non-uniform azimuthal angle distribution
$\mathrm{d}N/\mathrm{d}\varphi$ of the charged particles. The
$\mathrm{d}N/\mathrm{d}\varphi$ is calculated as a function of the
pseudorapidity of the particles and the primary vertex position along the beam
direction. The impact of the correction for the non-uniform azimuthal
acceptance of the tracks is negligible. The reconstruction efficiency
correction is derived from a Monte Carlo simulation using the HIJING [64]
heavy-ion event generator to simulate collisions and GEANT3 [65] to model
particle transport through the ALICE detector material. It is applied to all
measurements of the $p_{\mathrm{T}}$-integrated flow coefficients. The power
$p$ in Eq. 9 corresponds to the correction of the non-uniform azimuthal
acceptance and reconstruction efficiency in the multi-particle cumulant method
[66]. It only differs from unity for $q_{2}^{T}$. The
$v_{2}\left\\{2,\left|\Delta\eta\right|>1\right\\}$ and
$v_{2}\left\\{4\right\\}$ are calculated from flow vectors defined in Eq. 9
using the multi-particle cumulant approach [66]. In the measurement of
$v_{2}\left\\{2,\left|\Delta\eta\right|>1\right\\}$, a pseudorapidity
separation of $|\Delta\eta|>1$ is applied as it largely suppresses few-
particle correlations (so called non-flow), such as those originating from
jets or resonance decays [67].

For the first harmonic flow vectors of the ZDC, $q_{1}^{A}$ and $q_{1}^{C}$,
$\varphi_{j}$ corresponds to the angle of the center of the $j$-th calorimeter
segment and $w_{j}$ to its measured energy deposition. The indices $A$ and $C$
stand for the subdetectors located on either side of the interaction point.
The neutron spectator deflection is estimated with these flow vectors. The
beam configuration can result in an average shift of the spectator neutron
distributions in the transverse plane of the ZDC that are corrected by a data-
driven procedure (re-centering)

$q_{n}^{\prime}=q_{n}-\langle q_{n}\rangle\ .$ (10)

To account for changing beam conditions, the re-centering correction is
calculated as a function of the centrality, and the three dimensional position
of the collision vertex for each data-taking period. The elliptic flow
$v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}$ is calculated from an
average of three independent estimates using the scalar product method with
mixed harmonics [68]

$v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}{}=\frac{2}{3}\left(\frac{\langle
x_{2}^{T}x_{1}^{A}x_{1}^{C}\rangle}{\langle
x_{1}^{A}x_{1}^{C}\rangle}-\frac{\langle
x_{2}^{T}y_{1}^{A}y_{1}^{C}\rangle}{\langle
y_{1}^{A}y_{1}^{C}\rangle}+\sqrt{\frac{\langle
y_{2}^{T}x_{1}^{A}y_{1}^{C}\rangle\langle
y_{2}^{T}y_{1}^{A}x_{1}^{C}\rangle}{\langle x_{1}^{A}x_{1}^{C}\rangle\langle
y_{1}^{A}y_{1}^{C}\rangle}}\right)\ ,$ (11)

which corresponds to a measurement of elliptic flow relative to the common
spectator plane $\Psi_{\mathrm{\mathrm{SP}}}$. The numerical coefficient (2/3)
arises from (1/3) which corresponds to an average of the three independent
terms in Eq.(11) and an additional factor two from an expectation that
correlators in the numerators of individual terms gives
$(1/4)v_{2}\\{\Psi_{\mathrm{SP}}\\}R_{1}^{2}\\{\mathrm{ZDC}\\}$ and in the
denominators $(1/2)R_{1}^{2}\\{\mathrm{ZDC}\\}$, where
$R_{1}\\{\mathrm{ZDC}\\}$ is a convolution of the directed flow of spectators
with the ZDC response.

The systematic uncertainties are evaluated from variations of the analysis
procedure. The total systematic uncertainty is given by the square root of the
sum in quadrature of the differences in the results obtained from each
significant variation. A variation is considered significant, if $\Delta
R/\Delta\sigma>1$ [69], where $\Delta R$ is the difference between results
from a given variation and the default analysis procedure. The variable
$\Delta\sigma$ is the square root of the difference between the corresponding
squared statistical uncertainties.

The description of systematic uncertainties related to measurements of
$v_{2}\left\\{2,\left|\Delta\eta\right|>1\right\\}$ and
$v_{2}\left\\{4\right\\}$ is presented in Ref. [70]. The details of the
systematic uncertainty evaluation for
$v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}$ are described below. The
largest source of systematic uncertainty is due to spurious correlations which
are not corrected by the recentering procedure. These affect the denominators
in Eq. 11, which are determined by the diagonal correlations $\langle
x^{A}_{1}x^{C}_{1}\rangle$ and $\langle y^{A}_{1}y^{C}_{1}\rangle$. The
corresponding relative uncertainty, labeled as ZDC scale uncertainty, is
evaluated from the off-diagonal correlations $\langle
x_{1}^{A}y_{1}^{C}\rangle$ and $\langle y_{1}^{A}x_{1}^{C}\rangle$, which
should not contain physical signal, divided by the diagonal correlations. This
uncertainty is found to be about $4\%$ ($9\%$) in Pb–Pb (Xe–Xe) collisions for
all centrality classes and it is assigned as a fully correlated uncertainty
for $v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}$ results. The observed
negative sign of the diagonal correlations indicates a deflection of the
neutron spectators in, on average, opposite directions [33]. The off-diagonal
correlations may be non-zero because of the specific beam conditions during
the LHC operations that may affect the distribution of neutrons impinging ZDC,
such as the beam divergence at the interaction point.

The second largest contribution to the relative uncertainty comes from the
differences among the three independent estimates of
$v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}$ corresponding to the three
terms in Eq. 11 and amounts to lower than 2%. The uncertainty due to the
implementation of the flow vector re-centering procedure, defined by Eq. 10,
is evaluated by comparing to results from an iterative procedure. In the
latter, each of the four iterations consists of one coarse-binned four-
dimensional re-centering step followed by four fine-grained one-dimensional
steps as a function of the centrality and the three dimensional position of
the collision vertex. The corresponding relative variation is below 1%.
Introducing an additional equalization of the average ZDC signals in the flow
vector calculation in Eq. 9 amounts to a relative uncertainty less than $1\%$.

The systematic uncertainties related to the reconstruction of charged particle
tracks and to the secondary particle contamination are evaluated by varying
the track selection criteria. A relative uncertainty from changing the
selection of the distance to the primary vertex of the collision as a function
of particle $p_{\mathrm{T}}$, the minimum number of TPC clusters and the
reduced $\chi^{2}$ per TPC cluster is about 1.5%. No significant difference
between results for positively and negatively charged particles is observed. A
relative uncertainty of 0.7% on the $p_{\mathrm{T}}$-dependent track
reconstruction efficiency was estimated from the difference between the
results obtained with an efficiency calculation using all primary tracks and
those using only tracks of primary $\pi$, K, p, $\mu$, and e. The uncertainty
due to the non-uniform acceptance correction, estimated from the difference of
results with and without applying the $1/(\mathrm{d}N/\mathrm{d}\varphi)$
weights in Eq. 9, is not significant. An uncertainty due to the centrality
determination reaching up to 2% in the most peripheral collisions is estimated
from the difference of the results obtained when using an alternative
centrality estimator based on the multiplicity of hits in the ITS. The effects
of the TPC misalignment and the beam optics at the interaction point are
estimated to be smaller than 0.5% by comparing results obtained with different
magnetic field polarities of the ALICE solenoid. The impact on the results of
the variation of charged particle acceptance in pseudorapidity within the
fiducial volume of ALICE is probed by reducing the accepted range of the
position of the reconstructed primary vertex of the collisions along the beam
direction from the nominal $\pm$10\text{\,}\mathrm{c}\mathrm{m}$$ to
$\pm$8\text{\,}\mathrm{c}\mathrm{m}$$. It yields no significant change of
$v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}$. For the ratios
$v_{2}\left\\{2,\left|\Delta\eta\right|>1\right\\}/v_{2}\left\\{4\right\\}$
and
$\left.v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}\right/v_{2}\left\\{4\right\\}$
most of the common sources of systematic uncertainties cancel out. In
addition, the bin-to-bin uncorrelated uncertainties cancel in the
$p_{\mathrm{T}}$-dependence of these ratios.

Figure 2:  (color online) (upper panels) Elliptic flow relative to the
spectator plane, $v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}$, and to
the participant plane, $v_{2}\left\\{2,\left|\Delta\eta\right|>1\right\\}$ and
$v_{2}\left\\{4\right\\}$, as a function of centrality in Pb–Pb (left) and
Xe–Xe (right) collisions. (bottom panels) Ratios of the elliptic flow
$v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}$ and
$v_{2}\left\\{2,\left|\Delta\eta\right|>1\right\\}$ to
$v_{2}\left\\{4\right\\}$. The dashed (solid) lines show the eccentricity
ratios of $\varepsilon_{\mathrm{RP}}$ ($\varepsilon_{2}\\{2\\}$) to
$\varepsilon_{2}\\{4\\}$ from the elliptic power model. The corresponding
eccentricity ratios for TRENTo are shown as solid bands. The error bars (open
boxes) indicate statistical (systematic) uncertainties. The bin-to-bin
uncorrelated uncertainties and the correlated ones are combined for
$v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}$ results. For the ratio
$\left.v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}\right/v_{2}\left\\{4\right\\}$,
the ZDC scale uncertainties are shown separately as solid boxes centered at
unity on the right side of the lower panels.

The results for the elliptic flow coefficients relative to the spectator
symmetry plane, $v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}$, and the
participant plane, $v_{2}\left\\{2\right\\}$ and $v_{2}\left\\{4\right\\}$, as
a function of the centrality in Pb–Pb and Xe–Xe collisions are shown in the
upper panels of Fig. 2. In both Pb–Pb and Xe–Xe collisions, the maximum of
$v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}$ is located in the 35–45%
centrality range with a hint of being shifted towards more peripheral
collisions for smaller systems. The difference between
$v_{2}\left\\{2,\left|\Delta\eta\right|>1\right\\}$ and
$v_{2}\left\\{4\right\\}$ is due to fluctuations in the participant zone,
which have been extensively studied [8, 71, 72, 73]. In peripheral collisions,
this difference may also originate from residual few-particle correlations. In
midcentral collisions, $v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}$ and
$v_{2}\left\\{4\right\\}$ are similar as expected from the BGM (see Eq. 4).

To study the differences between the flow observables in detail, the lower
panels of Fig. 2 show the centrality dependence of the ratios of
$v_{2}\left\\{2,\left|\Delta\eta\right|>1\right\\}$ and
$v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}$ to
$v_{2}\left\\{4\right\\}$ as well as the ratios of the respective eccentricity
cumulants calculated from the EPM and the TRENTo models. The width of the
bands, which represent the TRENTo calculations, in Fig. 2 indicate the
differences between two configurations that are tuned to different
experimental data. The model in Ref. [43] uses Pb–Pb collisions at
$\sqrt{s_{\mathrm{NN}}}=$2.76\text{\,}\mathrm{T}\mathrm{e}\mathrm{V}$$ and
$\sqrt{s_{\mathrm{NN}}}=$5.02\text{\,}\mathrm{T}\mathrm{e}\mathrm{V}$$,
whereas Ref. [44] uses data of Au–Au collisions at
$\sqrt{s_{\mathrm{NN}}}=$0.2\text{\,}\mathrm{T}\mathrm{e}\mathrm{V}$$ and
Pb–Pb collisions at
$\sqrt{s_{\mathrm{NN}}}=$2.76\text{\,}\mathrm{T}\mathrm{e}\mathrm{V}$$. The
deformed Woods-Saxon parametrization of Xe nuclei is adopted from Ref. [74].
The considered model calculations do not take into account the subnucleonic
degrees of freedom. It was demonstrated in Ref. [25] based on two-particle
cumulant measurements that at the LHC they only impact very central (0–5%)
Pb–Pb collisions, which is outside of the reported centrality range. The EPM
model parameters, which relies on significant differences between higher order
cumulants, are only accessible with the larger data sample of Pb–Pb collisions
at $\sqrt{s_{\mathrm{NN}}}=$5.02\text{\,}\mathrm{T}\mathrm{e}\mathrm{V}$$
[70].

In both central and peripheral Pb–Pb collisions, the ratio
$\left.v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}\right/v_{2}\left\\{4\right\\}$
strongly deviates from unity, which is the value expected from the BGM for the
eccentricity ratio. In midcentral collisions, the measured ratio is smaller
than in central collisions, but it is significantly larger than the BGM
(unity), EPM and TRENTo model calculations. The later indicates that the
spectator plane becomes decorrelated from the reaction plane and
simultaneously more correlated with the participant plane. Thus
$v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}$ becomes closer to
$v_{2}\left\\{2,\left|\Delta\eta\right|>1\right\\}$, which makes the ratio
$\left.v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}\right/v_{2}\left\\{4\right\\}$
above unity. Similar trends are observed in Xe–Xe collisions, however due to
the limited size of the data sample the deviations from unity are not
significant within the uncertainties except in the most peripheral collisions.
A decorrelation in peripheral collisions is expected due to the small number
of sources of particle production (number of participants), as well as due to
the decreasing fraction of energy carried by the neutrons measured with the
ZDC relative to the unmeasured energy of protons and other charged nuclear
fragments.

In central collisions, despite the largest number of particle-producing
sources, the fluctuations are also large and deviations of the
$\left.v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}\right/v_{2}\left\\{4\right\\}$
ratio from unity are growing, which is in contrast to BGM expectations. The
deviation from unity is also large compared to the EPM calculations, which
yield a value close to unity in central collisions. This can be either due to
(a) a small number of spectators emitted in these collisions which increases
the spectator plane fluctuations (decorrelation) around the reaction plane and
consequently increases the magnitude of
$v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}$, (b) the strengthening of
the correlation between $\Psi_{\mathrm{\mathrm{SP}}}$ and $\Psi_{2}$ angles,
or (c) specific geometry fluctuations and/or correlated local particle
production in individual participating nucleon–nucleon interactions that
reduce $v_{2}\left\\{4\right\\}$. In midcentral and peripheral collisions,
both models predict a small deviation from unity for
$\varepsilon_{\mathrm{RP}}/\varepsilon_{2}\\{4\\}$, which is expected for
small fluctuations given by the second equality of Eq. 4 and due to the small
skewness observed in Ref. [70]. The ratio of
$\varepsilon_{2}\\{2\\}/\varepsilon_{2}\\{4\\}$ from the TRENTo model shows
smaller fluctuations compared to the tuned-on-data EPM calculations and the
measured
$v_{2}\left\\{2,\left|\Delta\eta\right|>1\right\\}/v_{2}\left\\{4\right\\}$.

Figure 3:  (color online) (upper panels) Elliptic flow relative to the
spectator plane, $v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}$, and to
the participant plane, $v_{2}\left\\{4\right\\}$, as a function of transverse
momentum in different centrality classes for Pb–Pb collisions. The linear fits
to the ratio
$\left.v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}\right/v_{2}\left\\{4\right\\}$
are shown as red lines for the individual centrality classes. The error bars
(open boxes) indicate statistical (systematic) uncertainties. The correlated
uncertainties, related to the ZDC, and bin-to-bin uncorrelated ones are
combined for $v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}$ (upper
panels). For the ratio
$\left.v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}\right/v_{2}\left\\{4\right\\}$
(lower panels), the correlated uncertainty is shown by the grey band at unity.

The upper panels of Fig. 3 show the dependence of the elliptic flow
coefficients $v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}$ and
$v_{2}\left\\{4\right\\}$ on transverse momentum for different centrality
classes in Pb–Pb collisions. The lower panels of Fig. 3 show the ratio
$\left.v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}\right/v_{2}\left\\{4\right\\}$
as a function of $p_{\mathrm{T}}$ for different centrality classes. To
quantify the possible dependence of
$\left.v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}\right/v_{2}\left\\{4\right\\}$
on $p_{\mathrm{T}}$, the ratio was fitted with a linear function in the range
$0.26\text{\,}\mathrm{GeV}\text{/}\mathrm{\textit{c}}$. The slopes of the
linear fit in different centrality classes are: $2.31\pm 2.17$ (5–10%),
$1.41\pm 0.48$ (10–20%), $1.48\pm 0.36$ (20–30%), $1.40\pm 0.42$ (30–40%),
$1.74\pm 0.65$ (40–50%), $4.29\pm 1.34$ (50–60%) in units of
$100/(\mathrm{GeV}/c)$. There are indications for a non-flat transverse
momentum dependence of
$\left.v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}\right/v_{2}\left\\{4\right\\}$
with a statistical significance of about 2.5–4$\sigma$ in all centrality
classes except for 5–10% central collisions where it is only 1$\sigma$. These
observations are important for understanding to which extent the momentum
anisotropy at low and intermediate transverse momentum has a common origin
from the fluctuating initial state anisotropy in the coordinate space and
quantifying the effects of momentum-dependent flow magnitude and angle
decorrelation [22, 75].

Figure 4:  (color online) Ratios of $v_{2}/\varepsilon_{2}$ as a function of
$(1/S)\mathrm{d}N_{\mathrm{ch}}/\mathrm{d}\eta$ in Xe–Xe (top panel) and Pb–Pb
(middle panel) collisions. The Linear fit functions to $v_{2}/\varepsilon_{2}$
in the top and middle panels are shown by lines. The bands show the
uncertainty of the fit. (bottom panel) The ratio of $v_{2}/\varepsilon_{2}$ to
the linear Pb–Pb fits shown in the middle panel. The data points of
$v_{2}\left\\{2,\left|\Delta\eta\right|>1\right\\}$, $v_{2}\left\\{4\right\\}$
are shifted by $-0.1$ and $+0.1$ along
$(1/S)\mathrm{d}N_{\mathrm{ch}}/\mathrm{d}\eta$ for better visibility. The
error bars (open boxes) indicate statistical (systematic) uncertainties. The
ZDC scale uncertainty, due to residual correlations in the determination of
the denominators in Eq. 11, and the bin-to-bin uncorrelated one are combined
for $v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}$ (top and middle
panels). For the ratio of $v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}$
to the Pb–Pb fit (bottom panel), the ZDC scale uncertainty is separated and is
shown by the solid boxes on the left side of the bottom panel. The grey box at
unity in the bottom panel on the left side shows the variation depending on
the TRENTo configuration. The blue horizontal band (bottom panel) represents
the relative uncertainties of the individual linear fits to the Pb–Pb data
from the middle panel. The red horizontal line (bottom panel) shows a combined
fit of a constant function to the Xe–Xe data and its uncertainty.

The scaling behavior of the elliptic flow with the initial state
eccentricities, as suggested by Eq. 3, is shown in Fig. 4. The top and middle
panels present the ratio $v_{2}/\varepsilon_{2}$ as a function of the charged
particle multiplicity density per unit of the nuclei overlap area
$(1/S)\mathrm{d}N_{\mathrm{ch}}/\mathrm{d}\eta$ for the elliptic flow
coefficients $v_{2}\left\\{2,\left|\Delta\eta\right|>1\right\\}$,
$v_{2}\left\\{4\right\\}$, and
$v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}$. The area $S$ and the
corresponding eccentricities are calculated from the TRENTo model using the
configuration from Ref. [43]. The experimental data points for
$\mathrm{d}N_{\mathrm{ch}}/\mathrm{d}\eta$ as a function of centrality are
taken from Ref. [76] for Pb–Pb and from Ref. [74] for Xe–Xe collisions. The
lines represent linear fits to the ratios
$v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}/\varepsilon_{\mathrm{RP}}$,
$v_{2}\left\\{2,\left|\Delta\eta\right|>1\right\\}/\varepsilon_{2}\\{2\\}$,
and $v_{2}\left\\{4\right\\}/\varepsilon_{2}\\{4\\}$.

Deviations from the scaling behavior are quantified in the bottom panel of
Fig. 4, which shows $v_{2}/\varepsilon_{2}$ divided by the respective linear
fits of the Pb–Pb measurement. The small differences between eccentricities
calculated from the two TRENTo configurations are reflected in the height of
the solid gray box on the left side. The splitting between the individual
observables for a given collision system may be sensitive to the chosen
association of eccentricities to flow coefficients. A relative deviation of
$(7.0\pm 0.9)\%$ from the scaling given by Eq. 3 between the two collision
systems is extracted from a constant line fit to the Xe–Xe data and by
propagating uncertainties of the Pb–Pb data. An additional variation of
$+1.8\%$ is estimated from the difference between the two TRENTo
configurations. It is similar for the different flow coefficients and only
weakly depends on the multiplicity density or collision centrality. This
collision system dependence may be sensitive to the details of the initial
state models [77, 25] and to viscous effects in the expansion of the QGP [41].
Together with the results on the centrality and transverse momentum
dependence, shown in Figs. 2, LABEL: and 3, the scaling presented in Fig. 4
provides new experimental constraints to both the initial conditions and the
transport coefficients of the QGP produced in heavy-ion collisions.

In summary, the elliptic flow of charged particles at midrapidity
($|\eta|<0.8$) relative to the neutron spectator plane
$v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}$ is measured in Pb–Pb at
$\sqrt{s_{\mathrm{NN}}}=$2.76\text{\,}\mathrm{T}\mathrm{e}\mathrm{V}$$ and
Xe–Xe at
$\sqrt{s_{\mathrm{NN}}}=$5.44\text{\,}\mathrm{T}\mathrm{e}\mathrm{V}$$
collisions as a function of the centrality and as a function of the transverse
momentum in different centrality classes. The measurements are compared to
results of elliptic flow relative to the participant plane obtained from two
and four-particle correlations. Both in central and peripheral collisions, the
ratio
$\left.v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}\right/v_{2}\left\\{4\right\\}$
strongly deviates from the respective ratio of the eccentricities,
$\varepsilon_{\mathrm{RP}}/\varepsilon_{2}\\{4\\}$, predicted by the TRENTo
and EPM models of the initial state fluctuations. The observations can be
interpreted as a decorrelation of the neutron spectator plane and the reaction
plane due to the fragmentation of the recoil from the colliding nuclei which
indicates an incomplete description of initial state fluctuations in the
models. A transverse momentum dependence of the ratio
$\left.v_{2}\left\\{\Psi_{\mathrm{\mathrm{SP}}}\right\\}\right/v_{2}\left\\{4\right\\}$
is observed with 2.5–4$\sigma$ significance in all but the most central
collisions. This is an important experimental input for understanding whether
the momentum anisotropies at low and intermediate transverse momentum have a
common origin in the initial state fluctuations. The ratios of elliptic flow
coefficients to the initial state eccentricities for Xe–Xe and Pb–Pb
collisions reveal a relative deviation from the scaling with the initial
entropy density of $(7.0\pm 0.9)\%$ with an additional variation of $+1.8\%$
when including RHIC data in the TRENTo parameter extraction. The deviation is
independent of the charged particle multiplicity density, which provides new
experimental constraints for viscous effects in the expansion of the
quark–gluon plasma produced in heavy-ion collisions at the LHC.

## Acknowledgements

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, Austrian Science Fund (FWF): [M 2467-N36] and Nationalstiftung für Forschung, Technologie und Entwicklung, Austria; Ministry of Communications and High Technologies, National Nuclear Research Center, Azerbaijan; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Financiadora de Estudos e Projetos (Finep), Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) and Universidade Federal do Rio Grande do Sul (UFRGS), Brazil; Bulgarian Ministry of Education and Science, within the National Roadmap for Research Infrastructures 2020-2027 (object CERN), Bulgaria; Ministry of Education of China (MOEC) , Ministry of Science & Technology of China (MSTC) and National Natural Science Foundation of China (NSFC), China; Ministry of Science and Education and Croatian Science Foundation, Croatia; Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear (CEADEN), Cubaenergía, Cuba; Ministry of Education, Youth and Sports of the Czech Republic, Czech Republic; The Danish Council for Independent Research | Natural Sciences, the VILLUM FONDEN and Danish National Research Foundation (DNRF), Denmark; Helsinki Institute of Physics (HIP), Finland; Commissariat à l’Energie Atomique (CEA) and Institut National de Physique Nucléaire et de Physique des Particules (IN2P3) and Centre National de la Recherche Scientifique (CNRS), France; Bundesministerium für Bildung und Forschung (BMBF) and GSI Helmholtzzentrum für 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; National Research and Innovation Agency - BRIN, Indonesia; Istituto Nazionale di Fisica Nucleare (INFN), Italy; Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT) and Japan Society for the Promotion of Science (JSPS) KAKENHI, Japan; Consejo Nacional de Ciencia (CONACYT) y Tecnología, through Fondo de Cooperación Internacional en Ciencia y Tecnología (FONCICYT) and Dirección 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 Católica del Perú, Peru; Ministry of Education and Science, National Science Centre and WUT ID-UB, 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, Ministry of Research and Innovation and Institute of Atomic Physics and University Politehnica of Bucharest, Romania; Ministry of Education, Science, Research and Sport of the Slovak Republic, Slovakia; National Research Foundation of South Africa, South Africa; Swedish Research Council (VR) and Knut & Alice Wallenberg Foundation (KAW), Sweden; European Organization for Nuclear Research, Switzerland; Suranaree University of Technology (SUT), National Science and Technology Development Agency (NSTDA), Thailand Science Research and Innovation (TSRI) and National Science, Research and Innovation Fund (NSRF), Thailand; Turkish Energy, Nuclear and Mineral Research Agency (TENMAK), 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. In addition, individual groups or members have received support from: Marie Skłodowska Curie, Strong 2020 - Horizon 2020, European Research Council (grant nos. 824093, 896850, 950692), European Union; Academy of Finland (Center of Excellence in Quark Matter) (grant nos. 346327, 346328), Finland; Programa de Apoyos para la Superación del Personal Académico, UNAM, Mexico.

## References

  * [1] S. Ryu, J. F. Paquet, C. Shen, G. S. Denicol, B. Schenke, S. Jeon, and C. Gale, “Importance of the bulk viscosity of QCD in ultrarelativistic heavy-ion collisions”, Phys. Rev. Lett. 115 (2015) 132301, arXiv:1502.01675 [nucl-th].
  * [2] B. Schenke, S. Jeon, and C. Gale, “Elliptic and triangular flow in event-by-event (3+1)D viscous hydrodynamics”, Phys. Rev. Lett. 106 (2011) 042301, arXiv:1009.3244 [hep-ph].
  * [3] M. Miller and R. Snellings, “Eccentricity fluctuations and its possible effect on elliptic flow measurements”, arXiv:nucl-ex/0312008.
  * [4] PHOBOS Collaboration, B. Alver et al., “The eccentricities of flow: Elliptic flow fluctuations and evidence for transverse localization in the initial state of the matter in relativistic heavy ion collisions”, in International Workshop on Hadron Physics and Property of High Baryon Density Matter.  2, 2007.  arXiv:nucl-ex/0702029.
  * [5] STAR Collaboration, P. Sorensen, “Elliptic flow fluctuations in Au + Au collisions at $\sqrt{s_{\mathrm{NN}}}=200~{}\mathrm{GeV}$”, J. Phys. G 35 (2008) 104102, arXiv:0808.0356 [nucl-ex].
  * [6] B. Alver and G. Roland, “Collision geometry fluctuations and triangular flow in heavy-ion collisions”, Phys. Rev. C 81 (2010) 054905, arXiv:1003.0194 [nucl-th]. [Erratum: Phys.Rev.C 82, 039903 (2010)].
  * [7] PHENIX Collaboration, A. Adare et al., “Measurements of higher-order flow harmonics in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=200~{}\mathrm{GeV}$”, Phys. Rev. Lett. 107 (2011) 252301, arXiv:1105.3928 [nucl-ex].
  * [8] ALICE Collaboration, K. Aamodt et al., “Higher harmonic anisotropic flow measurements of charged particles in Pb–Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76~{}\mathrm{TeV}$”, Phys. Rev. Lett. 107 (2011) 032301, arXiv:1105.3865 [nucl-ex].
  * [9] STAR Collaboration, L. Adamczyk et al., “Third harmonic flow of charged particles in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=200~{}\mathrm{GeV}$”, Phys. Rev. C 88 (2013) 014904, arXiv:1301.2187 [nucl-ex].
  * [10] STAR Collaboration, L. Adamczyk et al., “Beam energy dependence of the third harmonic of azimuthal correlations in Au+Au collisions at RHIC”, Phys. Rev. Lett. 116 (2016) 112302, arXiv:1601.01999 [nucl-ex].
  * [11] L. Yan, J.-Y. Ollitrault, and A. M. Poskanzer, “Eccentricity distributions in nucleus-nucleus collisions”, Phys. Rev. C 90 (2014) 024903, arXiv:1405.6595 [nucl-th].
  * [12] 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 [nucl-th].
  * [13] ALICE Collaboration, S. Acharya et al., “Characterizing the initial conditions of heavy-ion collisions at the LHC with mean transverse momentum and anisotropic flow correlations”, Phys. Lett. B 834 (2022) 137393, arXiv:2111.06106 [nucl-ex].
  * [14] ATLAS Collaboration, G. Aad et al., “Measurement of the azimuthal anisotropy for charged particle production in $\sqrt{s_{\mathrm{NN}}}=2.76~{}\mathrm{TeV}$ lead-lead collisions with the ATLAS detector”, Phys. Rev. C 86 (2012) 014907, arXiv:1203.3087 [hep-ex].
  * [15] CMS Collaboration, S. Chatrchyan et al., “Measurement of higher-order harmonic azimuthal anisotropy in PbPb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76~{}\mathrm{TeV}$”, Phys. Rev. C 89 (2014) 044906, arXiv:1310.8651 [nucl-ex].
  * [16] ATLAS Collaboration, G. Aad et al., “Measurement of the distributions of event-by-event flow harmonics in lead-lead collisions at $\sqrt{s_{\rm NN}}=2.76~{}\mathrm{TeV}$ with the ATLAS detector at the LHC”, JHEP 11 (2013) 183, arXiv:1305.2942 [hep-ex].
  * [17] ATLAS Collaboration, G. Aad et al., “Measurement of event-plane correlations in $\sqrt{s_{\mathrm{NN}}}=2.76~{}\mathrm{TeV}$ lead-lead collisions with the ATLAS detector”, Phys. Rev. C 90 (2014) 024905, arXiv:1403.0489 [hep-ex].
  * [18] ATLAS Collaboration, G. Aad et al., “Measurement of the correlation between flow harmonics of different order in lead-lead collisions at $\sqrt{s_{\mathrm{NN}}}=2.76~{}\mathrm{TeV}$ with the ATLAS detector”, Phys. Rev. C 92 (2015) 034903, arXiv:1504.01289 [hep-ex].
  * [19] ALICE Collaboration, J. Adam et al., “Correlated event-by-event fluctuations of flow harmonics in Pb–Pb collisions at $\sqrt{s_{\rm NN}}=2.76~{}\mathrm{TeV}$”, Phys. Rev. Lett. 117 (2016) 182301, arXiv:1604.07663 [nucl-ex].
  * [20] ALICE Collaboration, J. Adam et al., “Anisotropic flow of charged particles in Pb–Pb collisions at $\sqrt{s_{\rm NN}}=5.02~{}\mathrm{TeV}$”, Phys. Rev. Lett. 116 (2016) 132302, arXiv:1602.01119 [nucl-ex].
  * [21] CMS Collaboration, A. M. Sirunyan et al., “Non-gaussian elliptic-flow fluctuations in PbPb collisions at $\sqrt{s_{\rm NN}}=5.02~{}\mathrm{TeV}$”, Phys. Lett. B 789 (2019) 643–665, arXiv:1711.05594 [nucl-ex].
  * [22] ALICE Collaboration, S. Acharya et al., “Searches for transverse momentum dependent flow vector fluctuations in Pb–Pb and p–Pb collisions at the LHC”, JHEP 09 (2017) 032, arXiv:1707.05690 [nucl-ex].
  * [23] ALICE Collaboration, S. Acharya et al., “Linear and non-linear flow modes in Pb–Pb collisions at $\sqrt{s_{\rm NN}}=2.76~{}\mathrm{TeV}$”, Phys. Lett. B 773 (2017) 68–80, arXiv:1705.04377 [nucl-ex].
  * [24] ALICE Collaboration, S. Acharya et al., “Energy dependence and fluctuations of anisotropic flow in Pb–Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ and $2.76~{}\mathrm{TeV}$”, JHEP 07 (2018) 103, arXiv:1804.02944 [nucl-ex].
  * [25] ALICE Collaboration, S. Acharya et al., “Anisotropic flow in Xe–Xe collisions at $\sqrt{s_{\rm{NN}}}=5.44~{}\mathrm{TeV}$”, Phys. Lett. B 784 (2018) 82–95, arXiv:1805.01832 [nucl-ex].
  * [26] ALICE Collaboration, S. Acharya et al., “Non-linear flow modes of identified particles in Pb–Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02~{}\mathrm{TeV}$”, JHEP 06 (2020) 147, arXiv:1912.00740 [nucl-ex].
  * [27] ALICE Collaboration, S. Acharya et al., “Higher harmonic non-linear flow modes of charged hadrons in Pb–Pb collisions at $\sqrt{s_{\rm{NN}}}=5.02~{}\mathrm{TeV}$”, JHEP 05 (2020) 085, arXiv:2002.00633 [nucl-ex].
  * [28] ALICE Collaboration, S. Acharya et al., “Measurements of mixed harmonic cumulants in Pb–Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02~{}\mathrm{TeV}$”, Phys. Lett. B 818 (2021) 136354, arXiv:2102.12180 [nucl-ex].
  * [29] D. Teaney and L. Yan, “Triangularity and dipole asymmetry in heavy ion collisions”, Phys. Rev. C 83 (2011) 064904, arXiv:1010.1876 [nucl-th].
  * [30] L. Yan, “A flow paradigm in heavy-ion collisions”, Chin. Phys. C 42 (2018) 042001, arXiv:1712.04580 [nucl-th].
  * [31] A. Schüttauf et al., “Universality of spectator fragmentation at relativistic bombarding energies”, Nucl. Phys. A 607 (1996) 457–486, arXiv:nucl-ex/9606001.
  * [32] S. A. Voloshin and T. Niida, “Ultrarelativistic nuclear collisions: Direction of spectator flow”, Phys. Rev. C 94 (2016) 021901, arXiv:1604.04597 [nucl-th].
  * [33] ALICE Collaboration, B. Abelev et al., “Directed flow of charged particles at midrapidity relative to the spectator plane in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76~{}\mathrm{TeV}$”, Phys. Rev. Lett. 111 (2013) 232302, arXiv:1306.4145 [nucl-ex].
  * [34] A. S. Goldhaber, “Statistical models of fragmentation processes”, Phys. Lett. B 53 (1974) 306–308.
  * [35] D. J. Morrissey, “Systematics of momentum distributions from reactions with relativistic ions”, Phys. Rev. C 39 (1989) 460–470.
  * [36] E. J. Moniz, I. Sick, R. R. Whitney, J. R. Ficenec, R. D. Kephart, and W. P. Trower, “Nuclear fermi momenta from quasielastic electron scattering”, Phys. Rev. Lett. 26 (1971) 445–448.
  * [37] ALICE Collaboration, K. Aamodt et al., “Harmonic decomposition of two-particle angular correlations in Pb–Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76~{}\mathrm{TeV}$”, Phys. Lett. B 708 (2012) 249–264, arXiv:1109.2501 [nucl-ex].
  * [38] 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 [nucl-th].
  * [39] F. G. Gardim, F. Grassi, M. Luzum, and J.-Y. Ollitrault, “Mapping the hydrodynamic response to the initial geometry in heavy-ion collisions”, Phys. Rev. C 85 (2012) 024908, arXiv:1111.6538 [nucl-th].
  * [40] S. A. Voloshin and A. M. Poskanzer, “The physics of the centrality dependence of elliptic flow”, Phys. Lett. B 474 (2000) 27–32, arXiv:nucl-th/9906075.
  * [41] H. Song and U. W. Heinz, “Multiplicity scaling in ideal and viscous hydrodynamics”, Phys. Rev. C 78 (2008) 024902, arXiv:0805.1756 [nucl-th].
  * [42] U. Heinz and R. Snellings, “Collective flow and viscosity in relativistic heavy-ion collisions”, Ann. Rev. Nucl. Part. Sci. 63 (2013) 123–151, arXiv:1301.2826 [nucl-th].
  * [43] J. E. Bernhard, J. S. Moreland, and S. A. Bass, “Bayesian estimation of the specific shear and bulk viscosity of quark–gluon plasma”, Nature Phys. 15 (2019) 1113–1117.
  * [44] JETSCAPE Collaboration, D. Everett et al., “Multisystem bayesian constraints on the transport coefficients of QCD matter”, Phys. Rev. C 103 (2021) 054904, arXiv:2011.01430 [hep-ph].
  * [45] S. A. Voloshin, A. M. Poskanzer, A. Tang, and G. Wang, “Elliptic flow in the gaussian model of eccentricity fluctuations”, Phys. Lett. B 659 (2008) 537–541, arXiv:0708.0800 [nucl-th].
  * [46] B. Schenke, P. Tribedy, and R. Venugopalan, “Fluctuating glasma initial conditions and flow in heavy ion collisions”, Phys. Rev. Lett. 108 (2012) 252301, arXiv:1202.6646 [nucl-th].
  * [47] H. Song, S. A. Bass, U. Heinz, T. Hirano, and C. Shen, “200 A GeV Au+Au collisions serve a nearly perfect quark-gluon liquid”, Phys. Rev. Lett. 106 (2011) 192301, arXiv:1011.2783 [nucl-th]. [Erratum: Phys.Rev.Lett. 109, 139904 (2012)].
  * [48] N. Borghini, P. M. Dinh, and J.-Y. Ollitrault, “A new method for measuring azimuthal distributions in nucleus-nucleus collisions”, Phys. Rev. C 63 (2001) 054906, arXiv:nucl-th/0007063.
  * [49] A. Bilandzic, R. Snellings, and S. Voloshin, “Flow analysis with cumulants: Direct calculations”, Phys. Rev. C 83 (2011) 044913, arXiv:1010.0233 [nucl-ex].
  * [50] ALICE Collaboration, B. Abelev et al., “Anisotropic flow of charged hadrons, pions and (anti-)protons measured at high transverse momentum in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76~{}\mathrm{TeV}$”, Phys. Lett. B 719 (2013) 18–28, arXiv:1205.5761 [nucl-ex].
  * [51] STAR Collaboration, M. Abdallah et al., “Search for the chiral magnetic effect with isobar collisions at $\sqrt{s_{\mathrm{NN}}}=200~{}\mathrm{GeV}$ by the STAR collaboration at the BNL Relativistic Heavy Ion Collider”, Phys. Rev. C 105 (2022) 014901, arXiv:2109.00131 [nucl-ex].
  * [52] STAR Collaboration, M. Abdallah et al., “Search for the chiral magnetic effect via charge-dependent azimuthal correlations relative to spectator and participant planes in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 gev”, Phys. Rev. Lett. 128 (2022) 092301, arXiv:2106.09243 [nucl-ex].
  * [53] S. A. Voloshin, “Parity violation in hot QCD: How to detect it”, Phys. Rev. C 70 (2004) 057901, arXiv:hep-ph/0406311.
  * [54] F. Wang, “Effects of cluster particle correlations on local parity violation observables”, Phys. Rev. C 81 (2010) 064902, arXiv:0911.1482 [nucl-ex].
  * [55] A. Bzdak, V. Koch, and J. Liao, “Remarks on possible local parity violation in heavy ion collisions”, Phys. Rev. C 81 (2010) 031901, arXiv:0912.5050 [nucl-th].
  * [56] H.-j. Xu, J. Zhao, X. Wang, H. Li, Z.-W. Lin, C. Shen, and F. Wang, “Varying the chiral magnetic effect relative to flow in a single nucleus-nucleus collision”, Chin. Phys. C 42 (2018) 084103, arXiv:1710.07265 [nucl-th].
  * [57] S. A. Voloshin, “Estimate of the signal from the chiral magnetic effect in heavy-ion collisions from measurements relative to the participant and spectator flow planes”, Phys. Rev. C 98 (2018) 054911, arXiv:1805.05300 [nucl-ex].
  * [58] ALICE Collaboration, K. Aamodt et al., “The ALICE experiment at the CERN LHC”, Journal of Instrumentation 3 (Aug, 2008) S08002–S08002. https://doi.org/10.1088/1748-0221/3/08/s08002.
  * [59] ALICE Collaboration, B. B. Abelev et al., “Performance of the ALICE experiment at the CERN LHC”, Int. J. Mod. Phys. A 29 (2014) 1430044, arXiv:1402.4476 [nucl-ex].
  * [60] ALICE Collaboration, G. Dellacasa et al., “ALICE technical design report of the inner tracking system (ITS)”, CERN-LHCC-99-12 (1999) .
  * [61] J. Alme et al., “The ALICE TPC, a large 3-dimensional tracking device with fast readout for ultra-high multiplicity events”, Nucl. Instrum. Meth. A 622 (2010) 316–367, arXiv:1001.1950 [physics.ins-det].
  * [62] ALICE Collaboration, G. Dellacasa et al., “ALICE technical design report of the zero degree calorimeter (ZDC)”, CERN-LHCC-99-05 (1999) .
  * [63] ALICE Collaboration, E. Abbas et al., “Performance of the ALICE VZERO system”, JINST 8 (2013) P10016, arXiv:1306.3130 [nucl-ex].
  * [64] M. Gyulassy and X.-N. Wang, “HIJING 1.0: A monte carlo program for parton and particle production in high-energy hadronic and nuclear collisions”, Comput. Phys. Commun. 83 (1994) 307, arXiv:nucl-th/9502021.
  * [65] R. Brun, F. Bruyant, M. Maire, A. C. McPherson, and P. Zanarini, GEANT 3: user’s guide Geant 3.10, Geant 3.11; rev. version.  CERN, Geneva, 1987.  https://cds.cern.ch/record/1119728.
  * [66] A. Bilandzic, C. H. Christensen, K. Gulbrandsen, A. Hansen, and Y. Zhou, “Generic framework for anisotropic flow analyses with multiparticle azimuthal correlations”, Phys. Rev. C 89 (2014) 064904, arXiv:1312.3572 [nucl-ex].
  * [67] ALICE Collaboration, B. B. Abelev et al., “Multiparticle azimuthal correlations in p–Pb and Pb–Pb collisions at the CERN Large Hadron Collider”, Phys. Rev. C 90 (2014) 054901, arXiv:1406.2474 [nucl-ex].
  * [68] I. Selyuzhenkov and S. Voloshin, “Effects of non-uniform acceptance in anisotropic flow measurement”, Phys. Rev. C 77 (2008) 034904, arXiv:0707.4672 [nucl-th].
  * [69] R. Barlow, “Systematic errors: Facts and fictions”, in Conference on Advanced Statistical Techniques in Particle Physics, pp. 134–144.  7, 2002.  arXiv:hep-ex/0207026.
  * [70] ALICE Collaboration, S. Acharya et al., “Energy dependence and fluctuations of anisotropic flow in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ and $2.76~{}\mathrm{TeV}$”, JHEP 07 (2018) 103, arXiv:1804.02944 [nucl-ex].
  * [71] STAR Collaboration, G. Agakishiev et al., “Energy and system-size dependence of two- and four-particle $v_{2}$ measurements in heavy-ion collisions at RHIC and their implications on flow fluctuations and nonflow”, Phys. Rev. C 86 (2012) 014904, arXiv:1111.5637 [nucl-ex].
  * [72] PHOBOS Collaboration, B. Alver et al., “Non-flow correlations and elliptic flow fluctuations in gold-gold collisions at $\sqrt{s_{\mathrm{NN}}}=200~{}\mathrm{GeV}$”, Phys. Rev. C 81 (2010) 034915, arXiv:1002.0534 [nucl-ex].
  * [73] PHOBOS Collaboration, B. Alver et al., “Event-by-event fluctuations of azimuthal particle anisotropy in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=200~{}\mathrm{GeV}$”, Phys. Rev. Lett. 104 (2010) 142301, arXiv:nucl-ex/0702036.
  * [74] ALICE Collaboration, S. Acharya et al., “Centrality and pseudorapidity dependence of the charged-particle multiplicity density in Xe–Xe collisions at $\sqrt{s_{\rm NN}}=5.44~{}\mathrm{TeV}$”, Phys. Lett. B 790 (2019) 35–48, arXiv:1805.04432 [nucl-ex].
  * [75] CMS Collaboration, V. Khachatryan et al., “Evidence for transverse momentum and pseudorapidity dependent event plane fluctuations in PbPb and pPb collisions”, Phys. Rev. C 92 (2015) 034911, arXiv:1503.01692 [nucl-ex].
  * [76] ALICE Collaboration, K. Aamodt et al., “Centrality dependence of the charged-particle multiplicity density at mid-rapidity in Pb–Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76~{}\mathrm{TeV}$”, Phys. Rev. Lett. 106 (2011) 032301, arXiv:1012.1657 [nucl-ex].
  * [77] STAR Collaboration, S. A. Voloshin, “Energy and system size dependence of charged particle elliptic flow and $v_{2}/\epsilon$ scaling”, J. Phys. G 34 (2007) S883–886, arXiv:nucl-ex/0701038.

##  Appendix A The ALICE Collaboration

S. Acharya 123,131, D. Adamová 85, A. Adler69, G. Aglieri Rinella 32, M.
Agnello 29, N. Agrawal 50, Z. Ahammed 131, S. Ahmad 15, S.U. Ahn 70, I. Ahuja
37, A. Akindinov 139, M. Al-Turany 97, D. Aleksandrov 139, B. Alessandro 55,
H.M. Alfanda 6, R. Alfaro Molina 66, B. Ali 15, Y. Ali13, A. Alici 25, N.
Alizadehvandchali 112, A. Alkin 32, J. Alme 20, G. Alocco 51, T. Alt 63, I.
Altsybeev 139, M.N. Anaam 6, C. Andrei 45, A. Andronic 134, V. Anguelov 94, F.
Antinori 53, P. Antonioli 50, C. Anuj 15, N. Apadula 73, L. Aphecetche 102, H.
Appelshäuser 63, S. Arcelli 25, R. Arnaldi 55, I.C. Arsene 19, M. Arslandok
136, A. Augustinus 32, R. Averbeck 97, S. Aziz 127, M.D. Azmi 15, A. Badalà
52, Y.W. Baek 40, X. Bai 97, R. Bailhache 63, Y. Bailung 47, R. Bala 90, A.
Balbino 29, A. Baldisseri 126, B. Balis 2, D. Banerjee 4, Z. Banoo 90, R.
Barbera 26, L. Barioglio 95, M. Barlou77, G.G. Barnaföldi 135, L.S. Barnby 84,
V. Barret 123, L. Barreto 108, C. Bartels 115, K. Barth 32, E. Bartsch 63, F.
Baruffaldi 27, N. Bastid 123, S. Basu 74, G. Batigne 102, D. Battistini 95, B.
Batyunya 140, D. Bauri46, J.L. Bazo Alba 100, I.G. Bearden 82, C. Beattie 136,
P. Becht 97, D. Behera 47, I. Belikov 125, A.D.C. Bell Hechavarria 134, F.
Bellini 25, R. Bellwied 112, S. Belokurova 139, V. Belyaev 139, G. Bencedi
135,64, S. Beole 24, A. Bercuci 45, Y. Berdnikov 139, A. Berdnikova 94, L.
Bergmann 94, M.G. Besoiu 62, L. Betev 32, P.P. Bhaduri 131, A. Bhasin 90, I.R.
Bhat90, M.A. Bhat 4, B. Bhattacharjee 41, L. Bianchi 24, N. Bianchi 48, J.
Bielčík 35, J. Bielčíková 85, J. Biernat 105, A. Bilandzic 95, G. Biro 135, S.
Biswas 4, J.T. Blair 106, D. Blau 139, M.B. Blidaru 97, N. Bluhme38, C. Blume
63, G. Boca 21,54, F. Bock 86, T. Bodova 20, A. Bogdanov139, S. Boi 22, J. Bok
57, L. Boldizsár 135, A. Bolozdynya 139, M. Bombara 37, P.M. Bond 32, G.
Bonomi 130,54, H. Borel 126, A. Borissov 139, H. Bossi 136, E. Botta 24, L.
Bratrud 63, P. Braun-Munzinger 97, M. Bregant 108, M. Broz 35, G.E. Bruno
96,31, M.D. Buckland 115, D. Budnikov 139, H. Buesching 63, S. Bufalino 29, O.
Bugnon102, P. Buhler 101, Z. Buthelezi 67,119, J.B. Butt13, A. Bylinkin 114,
S.A. Bysiak105, M. Cai 27,6, H. Caines 136, A. Caliva 97, E. Calvo Villar 100,
J.M.M. Camacho 107, P. Camerini 23, F.D.M. Canedo 108, M. Carabas 122, F.
Carnesecchi 32, R. Caron 124,126, J. Castillo Castellanos 126, F. Catalano 29,
C. Ceballos Sanchez 140, I. Chakaberia 73, P. Chakraborty 46, S. Chandra 131,
S. Chapeland 32, M. Chartier 115, S. Chattopadhyay 131, S. Chattopadhyay 98,
T.G. Chavez 44, T. Cheng 6, C. Cheshkov 124, B. Cheynis 124, V. Chibante
Barroso 32, D.D. Chinellato 109, E.S. Chizzali II,95, J. Cho 57, S. Cho 57, P.
Chochula 32, P. Christakoglou 83, C.H. Christensen 82, P. Christiansen 74, T.
Chujo 121, M. Ciacco 29, C. Cicalo 51, L. Cifarelli 25, F. Cindolo 50, M.R.
Ciupek97, G. ClaiIII,50, F. Colamaria 49, J.S. Colburn99, D. Colella 96,31, A.
Collu73, M. Colocci 32, M. Concas IV,55, G. Conesa Balbastre 72, Z. Conesa del
Valle 127, G. Contin 23, J.G. Contreras 35, M.L. Coquet 126, T.M. CormierI,86,
P. Cortese 129,55, M.R. Cosentino 110, F. Costa 32, S. Costanza 21,54, P.
Crochet 123, R. Cruz-Torres 73, E. Cuautle64, P. Cui 6, L. Cunqueiro86, A.
Dainese 53, M.C. Danisch 94, A. Danu 62, P. Das 79, P. Das 4, S. Das 4, S.
Dash 46, R.M.H. David44, A. De Caro 28, G. de Cataldo 49, L. De Cilladi 24, J.
de Cuveland38, A. De Falco 22, D. De Gruttola 28, N. De Marco 55, C. De Martin
23, S. De Pasquale 28, S. Deb 47, H.F. Degenhardt108, K.R. Deja132, R. Del
Grande 95, L. Dello Stritto 28, W. Deng 6, P. Dhankher 18, D. Di Bari 31, A.
Di Mauro 32, R.A. Diaz 140,7, T. Dietel 111, Y. Ding 124,6, R. Divià 32, D.U.
Dixit 18, Ø. Djuvsland20, U. Dmitrieva 139, A. Dobrin 62, B. Dönigus 63, A.K.
Dubey 131, J.M. Dubinski 132, A. Dubla 97, S. Dudi 89, P. Dupieux 123, M.
Durkac104, N. Dzalaiova12, T.M. Eder 134, R.J. Ehlers 86, V.N. Eikeland20, F.
Eisenhut 63, D. Elia 49, B. Erazmus 102, F. Ercolessi 25, F. Erhardt 88, M.R.
Ersdal20, B. Espagnon 127, G. Eulisse 32, D. Evans 99, S. Evdokimov 139, L.
Fabbietti 95, M. Faggin 27, J. Faivre 72, F. Fan 6, W. Fan 73, A. Fantoni 48,
M. Fasel 86, P. Fecchio29, A. Feliciello 55, G. Feofilov 139, A. Fernández
Téllez 44, M.B. Ferrer 32, A. Ferrero 126, A. Ferretti 24, V.J.G. Feuillard
94, J. Figiel 105, V. Filova 35, D. Finogeev 139, F.M. Fionda 51, G.
Fiorenza96, F. Flor 112, A.N. Flores 106, S. Foertsch 67, I. Fokin 94, S.
Fokin 139, E. Fragiacomo 56, E. Frajna 135, U. Fuchs 32, N. Funicello 28, C.
Furget 72, A. Furs 139, J.J. Gaardhøje 82, M. Gagliardi 24, A.M. Gago 100, A.
Gal125, C.D. Galvan 107, P. Ganoti 77, C. Garabatos 97, J.R.A. Garcia 44, E.
Garcia-Solis 9, K. Garg 102, C. Gargiulo 32, A. Garibli80, K. Garner134, E.F.
Gauger 106, A. Gautam 114, M.B. Gay Ducati 65, M. Germain 102, S.K. Ghosh4, M.
Giacalone 25, P. Gianotti 48, P. Giubellino 97,55, P. Giubilato 27, A.M.C.
Glaenzer 126, P. Glässel 94, E. Glimos 118, D.J.Q. Goh75, V. Gonzalez 133,
L.H. González-Trueba 66, S. Gorbunov38, M. Gorgon 2, L. Görlich 105, S.
Gotovac33, V. Grabski 66, L.K. Graczykowski 132, E. Grecka 85, L. Greiner 73,
A. Grelli 58, C. Grigoras 32, V. Grigoriev 139, S. Grigoryan 140,1, F. Grosa
32, J.F. Grosse-Oetringhaus 32, R. Grosso 97, D. Grund 35, G.G. Guardiano 109,
R. Guernane 72, M. Guilbaud 102, K. Gulbrandsen 82, T. Gunji 120, W. Guo 6, A.
Gupta 90, R. Gupta 90, S.P. Guzman 44, L. Gyulai 135, M.K. Habib97, C.
Hadjidakis 127, H. Hamagaki 75, M. Hamid6, Y. Han 137, R. Hannigan 106, M.R.
Haque 132, A. Harlenderova97, J.W. Harris 136, A. Harton 9, J.A.
Hasenbichler32, H. Hassan 86, D. Hatzifotiadou 50, P. Hauer 42, L.B. Havener
136, S.T. Heckel 95, E. Hellbär 97, H. Helstrup 34, T. Herman 35, G. Herrera
Corral 8, F. Herrmann134, K.F. Hetland 34, B. Heybeck 63, H. Hillemanns 32, C.
Hills 115, B. Hippolyte 125, B. Hofman 58, B. Hohlweger 83, J. Honermann 134,
G.H. Hong 137, D. Horak 35, A. Horzyk 2, R. Hosokawa14, Y. Hou 6, P. Hristov
32, C. Hughes 118, P. Huhn63, L.M. Huhta 113, C.V. Hulse 127, T.J. Humanic 87,
H. Hushnud98, A. Hutson 112, D. Hutter 38, J.P. Iddon 115, R. Ilkaev139, H.
Ilyas 13, M. Inaba 121, G.M. Innocenti 32, M. Ippolitov 139, A. Isakov 85, T.
Isidori 114, M.S. Islam 98, M. Ivanov 97, V. Ivanov 139, V. Izucheev139, M.
Jablonski 2, B. Jacak 73, N. Jacazio 32, P.M. Jacobs 73, S. Jadlovska104, J.
Jadlovsky104, L. Jaffe38, C. Jahnke 109, M.A. Janik 132, T. Janson69, M.
Jercic88, O. Jevons99, A.A.P. Jimenez 64, F. Jonas 86, P.G. Jones99, J.M.
Jowett 32,97, J. Jung 63, M. Jung 63, A. Junique 32, A. Jusko 99, M.J. Kabus
32,132, J. Kaewjai103, P. Kalinak 59, A.S. Kalteyer 97, A. Kalweit 32, V.
Kaplin 139, A. Karasu Uysal 71, D. Karatovic 88, O. Karavichev 139, T.
Karavicheva 139, P. Karczmarczyk 132, E. Karpechev 139, V. Kashyap79, A.
Kazantsev139, U. Kebschull 69, R. Keidel 138, D.L.D. Keijdener58, M. Keil 32,
B. Ketzer 42, A.M. Khan 6, S. Khan 15, A. Khanzadeev 139, Y. Kharlov 139, A.
Khatun 15, A. Khuntia 105, B. Kileng 34, B. Kim 16, C. Kim 16, D.J. Kim 113,
E.J. Kim 68, J. Kim 137, J.S. Kim 40, J. Kim 94, J. Kim 68, M. Kim 94, S. Kim
17, T. Kim 137, S. Kirsch 63, I. Kisel 38, S. Kiselev 139, A. Kisiel 132, J.P.
Kitowski 2, J.L. Klay 5, J. Klein 32, S. Klein 73, C. Klein-Bösing 134, M.
Kleiner 63, T. Klemenz 95, A. Kluge 32, A.G. Knospe 112, C. Kobdaj 103, T.
Kollegger97, A. Kondratyev 140, N. Kondratyeva 139, E. Kondratyuk 139, J.
Konig 63, S.A. Konigstorfer 95, P.J. Konopka 32, G. Kornakov 132, S.D.
Koryciak 2, A. Kotliarov 85, O. Kovalenko 78, V. Kovalenko 139, M. Kowalski
105, I. Králik 59, A. Kravčáková 37, L. Kreis97, M. Krivda 99,59, F. Krizek
85, K. Krizkova Gajdosova 35, M. Kroesen 94, M. Krüger 63, D.M. Krupova 35, E.
Kryshen 139, M. Krzewicki38, V. Kučera 32, C. Kuhn 125, P.G. Kuijer 83, T.
Kumaoka121, D. Kumar131, L. Kumar 89, N. Kumar89, S. Kundu 32, P. Kurashvili
78, A. Kurepin 139, A.B. Kurepin 139, S. Kushpil 85, J. Kvapil 99, M.J. Kweon
57, J.Y. Kwon 57, Y. Kwon 137, S.L. La Pointe 38, P. La Rocca 26, Y.S. Lai73,
A. Lakrathok103, M. Lamanna 32, R. Langoy 117, P. Larionov 48, E. Laudi 32, L.
Lautner 32,95, R. Lavicka 101, T. Lazareva 139, R. Lea 130,54, J. Lehrbach 38,
R.C. Lemmon 84, I. León Monzón 107, M.M. Lesch 95, E.D. Lesser 18, M.
Lettrich95, P. Lévai 135, X. Li10, X.L. Li6, J. Lien 117, R. Lietava 99, B.
Lim 16, S.H. Lim 16, V. Lindenstruth 38, A. Lindner45, C. Lippmann 97, A. Liu
18, D.H. Liu 6, J. Liu 115, I.M. Lofnes 20, V. Loginov139, C. Loizides 86, P.
Loncar 33, J.A. Lopez 94, X. Lopez 123, E. López Torres 7, P. Lu 97,116, J.R.
Luhder 134, M. Lunardon 27, G. Luparello 56, Y.G. Ma 39, A. Maevskaya139, M.
Mager 32, T. Mahmoud42, A. Maire 125, M. Malaev 139, N.M. Malik 90, Q.W.
Malik19, S.K. Malik 90, L. Malinina VII,140, D. Mal’Kevich 139, D. Mallick 79,
N. Mallick 47, G. Mandaglio 30,52, V. Manko 139, F. Manso 123, V. Manzari 49,
Y. Mao 6, G.V. Margagliotti 23, A. Margotti 50, A. Marín 97, C. Markert 106,
M. Marquard63, N.A. Martin94, P. Martinengo 32, J.L. Martinez112, M.I.
Martínez 44, G. Martínez García 102, S. Masciocchi 97, M. Masera 24, A. Masoni
51, L. Massacrier 127, A. Mastroserio 128,49, A.M. Mathis 95, O. Matonoha 74,
P.F.T. Matuoka108, A. Matyja 105, C. Mayer 105, A.L. Mazuecos 32, F. Mazzaschi
24, M. Mazzilli 32, J.E. Mdhluli 119, A.F. Mechler63, Y. Melikyan 139, A.
Menchaca-Rocha 66, E. Meninno 101,28, A.S. Menon 112, M. Meres 12, S.
Mhlanga111,67, Y. Miake121, L. Micheletti 55, L.C. Migliorin124, D.L. Mihaylov
95, K. Mikhaylov 140,139, A.N. Mishra 135, D. Miśkowiec 97, A. Modak 4, A.P.
Mohanty 58, B. Mohanty79, M. Mohisin Khan V,15, M.A. Molander 43, Z. Moravcova
82, C. Mordasini 95, D.A. Moreira De Godoy 134, I. Morozov 139, A. Morsch 32,
T. Mrnjavac 32, V. Muccifora 48, E. Mudnic33, S. Muhuri 131, J.D. Mulligan 73,
A. Mulliri22, M.G. Munhoz 108, R.H. Munzer 63, H. Murakami 120, S. Murray 111,
L. Musa 32, J. Musinsky 59, J.W. Myrcha 132, B. Naik 119, R. Nair 78, B.K.
Nandi 46, R. Nania 50, E. Nappi 49, A.F. Nassirpour 74, A. Nath 94, C.
Nattrass 118, A. Neagu19, A. Negru122, L. Nellen 64, S.V. Nesbo34, G. Neskovic
38, D. Nesterov 139, B.S. Nielsen 82, E.G. Nielsen 82, S. Nikolaev 139, S.
Nikulin 139, V. Nikulin 139, F. Noferini 50, S. Noh 11, P. Nomokonov 140, J.
Norman 115, N. Novitzky 121, P. Nowakowski 132, A. Nyanin 139, J. Nystrand 20,
M. Ogino 75, A. Ohlson 74, V.A. Okorokov 139, J. Oleniacz 132, A.C. Oliveira
Da Silva 118, M.H. Oliver 136, A. Onnerstad 113, C. Oppedisano 55, A. Ortiz
Velasquez 64, A. Oskarsson74, J. Otwinowski 105, M. Oya92, K. Oyama 75, Y.
Pachmayer 94, S. Padhan 46, D. Pagano 130,54, G. Paić 64, A. Palasciano 49, S.
Panebianco 126, J. Park 57, J.E. Parkkila 32,113, S.P. Pathak112, R.N.
Patra90, B. Paul 22, H. Pei 6, T. Peitzmann 58, X. Peng 6, L.G. Pereira 65, H.
Pereira Da Costa 126, D. Peresunko 139, G.M. Perez 7, S. Perrin 126, Y.
Pestov139, V. Petráček 35, V. Petrov 139, M. Petrovici 45, R.P. Pezzi 102,65,
S. Piano 56, M. Pikna 12, P. Pillot 102, O. Pinazza 50,32, L. Pinsky112, C.
Pinto 95,26, S. Pisano 48, M. Płoskoń 73, M. Planinic88, F. Pliquett63, M.G.
Poghosyan 86, S. Politano 29, N. Poljak 88, A. Pop 45, S. Porteboeuf-Houssais
123, J. Porter 73, V. Pozdniakov 140, S.K. Prasad 4, S. Prasad 47, R.
Preghenella 50, F. Prino 55, C.A. Pruneau 133, I. Pshenichnov 139, M. Puccio
32, S. Qiu 83, L. Quaglia 24, R.E. Quishpe112, S. Ragoni 99, A.
Rakotozafindrabe 126, L. Ramello 129,55, F. Rami 125, S.A.R. Ramirez 44, T.A.
Rancien72, R. Raniwala 91, S. Raniwala91, S.S. Räsänen 43, R. Rath 47, I.
Ravasenga 83, K.F. Read 86,118, A.R. Redelbach 38, K. Redlich VI,78, A.
Rehman20, P. Reichelt63, F. Reidt 32, H.A. Reme-Ness 34, Z. Rescakova37, K.
Reygers 94, A. Riabov 139, V. Riabov 139, R. Ricci 28, T. Richert74, M.
Richter 19, W. Riegler 32, F. Riggi 26, C. Ristea 62, M. Rodríguez Cahuantzi
44, K. Røed 19, R. Rogalev 139, E. Rogochaya 140, T.S. Rogoschinski 63, D.
Rohr 32, D. Röhrich 20, P.F. Rojas44, S. Rojas Torres 35, P.S. Rokita 132, F.
Ronchetti 48, A. Rosano 30,52, E.D. Rosas64, A. Rossi 53, A. Roy 47, P. Roy98,
S. Roy 46, N. Rubini 25, D. Ruggiano 132, R. Rui 23, B. Rumyantsev140, P.G.
Russek 2, R. Russo 83, A. Rustamov 80, E. Ryabinkin 139, Y. Ryabov 139, A.
Rybicki 105, H. Rytkonen 113, W. Rzesa 132, O.A.M. Saarimaki 43, R. Sadek 102,
S. Sadovsky 139, J. Saetre 20, K. Šafařík 35, S.K. Saha 131, S. Saha 79, B.
Sahoo 46, P. Sahoo46, R. Sahoo 47, S. Sahoo60, D. Sahu 47, P.K. Sahu 60, J.
Saini 131, K. Sajdakova37, S. Sakai 121, M.P. Salvan 97, S. Sambyal 90, T.B.
Saramela108, D. Sarkar 133, N. Sarkar131, P. Sarma 41, V. Sarritzu 22, V.M.
Sarti 95, M.H.P. Sas 136, J. Schambach 86, H.S. Scheid 63, C. Schiaua 45, R.
Schicker 94, A. Schmah94, C. Schmidt 97, H.R. Schmidt93, M.O. Schmidt 32, M.
Schmidt93, N.V. Schmidt 86,63, A.R. Schmier 118, R. Schotter 125, J. Schukraft
32, K. Schwarz97, K. Schweda 97, G. Scioli 25, E. Scomparin 55, J.E. Seger 14,
Y. Sekiguchi120, D. Sekihata 120, I. Selyuzhenkov 97,139, S. Senyukov 125,
J.J. Seo 57, D. Serebryakov 139, L. Šerkšnytė 95, A. Sevcenco 62, T.J. Shaba
67, A. Shabanov139, A. Shabetai 102, R. Shahoyan32, W. Shaikh98, A. Shangaraev
139, A. Sharma89, D. Sharma 46, H. Sharma 105, M. Sharma 90, N. Sharma 89, S.
Sharma 90, U. Sharma 90, A. Shatat 127, O. Sheibani112, K. Shigaki 92, M.
Shimomura76, S. Shirinkin 139, Q. Shou 39, Y. Sibiriak 139, S. Siddhanta 51,
T. Siemiarczuk 78, T.F. Silva 108, D. Silvermyr 74, T. Simantathammakul103, R.
Simeonov 36, G. Simonetti32, B. Singh90, B. Singh 95, R. Singh 79, R. Singh
90, R. Singh 47, V.K. Singh 131, V. Singhal 131, T. Sinha 98, B. Sitar 12, M.
Sitta 129,55, T.B. Skaali19, G. Skorodumovs 94, M. Slupecki 43, N. Smirnov
136, R.J.M. Snellings 58, E.H. Solheim 19, C. Soncco100, J. Song 112, A.
Songmoolnak103, F. Soramel 27, S.P. Sorensen 118, R. Soto Camacho44, R.
Spijkers 83, I. Sputowska 105, J. Staa 74, J. Stachel 94, I. Stan 62, P.J.
Steffanic 118, S.F. Stiefelmaier 94, D. Stocco 102, I. Storehaug 19, M.M.
Storetvedt 34, P. Stratmann 134, S. Strazzi 25, C.P. Stylianidis83, A.A.P.
Suaide 108, C. Suire 127, M. Sukhanov 139, M. Suljic 32, V. Sumberia 90, S.
Sumowidagdo 81, S. Swain60, A. Szabo12, I. Szarka 12, U. Tabassam13, S.F.
Taghavi 95, G. Taillepied 97,123, J. Takahashi 109, G.J. Tambave 20, S. Tang
123,6, Z. Tang 116, J.D. Tapia Takaki 114, N. Tapus122, L.A. Tarasovicova 134,
M.G. Tarzila 45, A. Tauro 32, A. Telesca 32, L. Terlizzi 24, C. Terrevoli 112,
G. Tersimonov3, S. Thakur 131, D. Thomas 106, R. Tieulent 124, A. Tikhonov
139, A.R. Timmins 112, M. Tkacik104, T. Tkacik 104, A. Toia 63, N. Topilskaya
139, M. Toppi 48, F. Torales-Acosta18, T. Tork 127, A.G. Torres Ramos 31, A.
Trifiró 30,52, A.S. Triolo 30,52, S. Tripathy 50, T. Tripathy 46, S. Trogolo
32, V. Trubnikov 3, W.H. Trzaska 113, T.P. Trzcinski 132, R. Turrisi 53, T.S.
Tveter 19, K. Ullaland 20, B. Ulukutlu 95, A. Uras 124, M. Urioni 54,130, G.L.
Usai 22, M. Vala37, N. Valle 21, S. Vallero 55, L.V.R. van Doremalen58, M. van
Leeuwen 83, C.A. van Veen 94, R.J.G. van Weelden 83, P. Vande Vyvre 32, D.
Varga 135, Z. Varga 135, M. Varga-Kofarago 135, M. Vasileiou 77, A. Vasiliev
139, O. Vázquez Doce 95, O. Vazquez Rueda 74, V. Vechernin 139, E. Vercellin
24, S. Vergara Limón44, L. Vermunt 58, R. Vértesi 135, M. Verweij 58, L.
Vickovic33, Z. Vilakazi119, O. Villalobos Baillie 99, G. Vino 49, A.
Vinogradov 139, T. Virgili 28, V. Vislavicius82, A. Vodopyanov 140, B. Volkel
32, M.A. Völkl 94, K. Voloshin139, S.A. Voloshin 133, G. Volpe 31, B. von
Haller 32, I. Vorobyev 95, N. Vozniuk 139, J. Vrláková 37, B. Wagner20, C.
Wang 39, D. Wang39, M. Weber 101, A. Wegrzynek 32, F.T. Weiglhofer38, S.C.
Wenzel 32, J.P. Wessels 134, S.L. Weyhmiller 136, J. Wiechula 63, J. Wikne 19,
G. Wilk 78, J. Wilkinson 97, G.A. Willems 134, B. Windelband 94, M. Winn 126,
J.R. Wright 106, W. Wu39, Y. Wu 116, R. Xu 6, A.K. Yadav 131, S. Yalcin 71, Y.
Yamaguchi 92, K. Yamakawa92, S. Yang20, S. Yano 92, Z. Yin 6, I.-K. Yoo 16,
J.H. Yoon 57, S. Yuan20, A. Yuncu 94, V. Zaccolo 23, C. Zampolli 32, H.J.C.
Zanoli58, F. Zanone 94, N. Zardoshti 32,99, A. Zarochentsev 139, P. Závada 61,
N. Zaviyalov139, M. Zhalov 139, B. Zhang 6, S. Zhang 39, X. Zhang 6, Y.
Zhang116, M. Zhao 10, V. Zherebchevskii 139, Y. Zhi10, N. Zhigareva139, D.
Zhou 6, Y. Zhou 82, J. Zhu 97,6, Y. Zhu6, G. ZinovjevI,3, N. Zurlo 130,54

## Affiliation Notes

I Deceased
II Also at: Max-Planck-Institut für Physik, Munich, Germany
III Also at: Italian National Agency for New Technologies, Energy and
Sustainable Economic Development (ENEA), Bologna, Italy
IV Also at: Dipartimento DET del Politecnico di Torino, Turin, Italy
V Also at: Department of Applied Physics, Aligarh Muslim University, Aligarh,
India
VI Also at: Institute of Theoretical Physics, University of Wroclaw, Poland
VII Also at: An institution covered by a cooperation agreement with CERN

## Collaboration Institutes

1 A.I. Alikhanyan National Science Laboratory (Yerevan Physics Institute)
Foundation, Yerevan, Armenia
2 AGH University of Krakow, Cracow, Poland
3 Bogolyubov Institute for Theoretical Physics, National Academy of Sciences
of Ukraine, Kiev, Ukraine
4 Bose Institute, Department of Physics and Centre for Astroparticle Physics
and Space Science (CAPSS), Kolkata, India
5 California Polytechnic State University, San Luis Obispo, California, United
States
6 Central China Normal University, Wuhan, China
7 Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear (CEADEN), Havana,
Cuba
8 Centro de Investigación y de Estudios Avanzados (CINVESTAV), Mexico City and
Mérida, Mexico
9 Chicago State University, Chicago, Illinois, United States
10 China Institute of Atomic Energy, Beijing, China
11 Chungbuk National University, Cheongju, Republic of Korea
12 Comenius University Bratislava, Faculty of Mathematics, Physics and
Informatics, Bratislava, Slovak Republic
13 COMSATS University Islamabad, Islamabad, Pakistan
14 Creighton University, Omaha, Nebraska, United States
15 Department of Physics, Aligarh Muslim University, Aligarh, India
16 Department of Physics, Pusan National University, Pusan, Republic of Korea
17 Department of Physics, Sejong University, Seoul, Republic of Korea
18 Department of Physics, University of California, Berkeley, California,
United States
19 Department of Physics, University of Oslo, Oslo, Norway
20 Department of Physics and Technology, University of Bergen, Bergen, Norway
21 Dipartimento di Fisica, Università di Pavia, Pavia, Italy
22 Dipartimento di Fisica dell’Università and Sezione INFN, Cagliari, Italy
23 Dipartimento di Fisica dell’Università and Sezione INFN, Trieste, Italy
24 Dipartimento di Fisica dell’Università and Sezione INFN, Turin, Italy
25 Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN,
Bologna, Italy
26 Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN,
Catania, Italy
27 Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN,
Padova, Italy
28 Dipartimento di Fisica ‘E.R. Caianiello’ dell’Università and Gruppo
Collegato INFN, Salerno, Italy
29 Dipartimento DISAT del Politecnico and Sezione INFN, Turin, Italy
30 Dipartimento di Scienze MIFT, Università di Messina, Messina, Italy
31 Dipartimento Interateneo di Fisica ‘M. Merlin’ and Sezione INFN, Bari,
Italy
32 European Organization for Nuclear Research (CERN), Geneva, Switzerland
33 Faculty of Electrical Engineering, Mechanical Engineering and Naval
Architecture, University of Split, Split, Croatia
34 Faculty of Engineering and Science, Western Norway University of Applied
Sciences, Bergen, Norway
35 Faculty of Nuclear Sciences and Physical Engineering, Czech Technical
University in Prague, Prague, Czech Republic
36 Faculty of Physics, Sofia University, Sofia, Bulgaria
37 Faculty of Science, P.J. Šafárik University, Košice, Slovak Republic
38 Frankfurt Institute for Advanced Studies, Johann Wolfgang Goethe-
Universität Frankfurt, Frankfurt, Germany
39 Fudan University, Shanghai, China
40 Gangneung-Wonju National University, Gangneung, Republic of Korea
41 Gauhati University, Department of Physics, Guwahati, India
42 Helmholtz-Institut für Strahlen- und Kernphysik, Rheinische Friedrich-
Wilhelms-Universität Bonn, Bonn, Germany
43 Helsinki Institute of Physics (HIP), Helsinki, Finland
44 High Energy Physics Group, Universidad Autónoma de Puebla, Puebla, Mexico
45 Horia Hulubei National Institute of Physics and Nuclear Engineering,
Bucharest, Romania
46 Indian Institute of Technology Bombay (IIT), Mumbai, India
47 Indian Institute of Technology Indore, Indore, India
48 INFN, Laboratori Nazionali di Frascati, Frascati, Italy
49 INFN, Sezione di Bari, Bari, Italy
50 INFN, Sezione di Bologna, Bologna, Italy
51 INFN, Sezione di Cagliari, Cagliari, Italy
52 INFN, Sezione di Catania, Catania, Italy
53 INFN, Sezione di Padova, Padova, Italy
54 INFN, Sezione di Pavia, Pavia, Italy
55 INFN, Sezione di Torino, Turin, Italy
56 INFN, Sezione di Trieste, Trieste, Italy
57 Inha University, Incheon, Republic of Korea
58 Institute for Gravitational and Subatomic Physics (GRASP), Utrecht
University/Nikhef, Utrecht, Netherlands
59 Institute of Experimental Physics, Slovak Academy of Sciences, Košice,
Slovak Republic
60 Institute of Physics, Homi Bhabha National Institute, Bhubaneswar, India
61 Institute of Physics of the Czech Academy of Sciences, Prague, Czech
Republic
62 Institute of Space Science (ISS), Bucharest, Romania
63 Institut für Kernphysik, Johann Wolfgang Goethe-Universität Frankfurt,
Frankfurt, Germany
64 Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México,
Mexico City, Mexico
65 Instituto de Física, Universidade Federal do Rio Grande do Sul (UFRGS),
Porto Alegre, Brazil
66 Instituto de Física, Universidad Nacional Autónoma de México, Mexico City,
Mexico
67 iThemba LABS, National Research Foundation, Somerset West, South Africa
68 Jeonbuk National University, Jeonju, Republic of Korea
69 Johann-Wolfgang-Goethe Universität Frankfurt Institut für Informatik,
Fachbereich Informatik und Mathematik, Frankfurt, Germany
70 Korea Institute of Science and Technology Information, Daejeon, Republic of
Korea
71 KTO Karatay University, Konya, Turkey
72 Laboratoire de Physique Subatomique et de Cosmologie, Université Grenoble-
Alpes, CNRS-IN2P3, Grenoble, France
73 Lawrence Berkeley National Laboratory, Berkeley, California, United States
74 Lund University Department of Physics, Division of Particle Physics, Lund,
Sweden
75 Nagasaki Institute of Applied Science, Nagasaki, Japan
76 Nara Women’s University (NWU), Nara, Japan
77 National and Kapodistrian University of Athens, School of Science,
Department of Physics , Athens, Greece
78 National Centre for Nuclear Research, Warsaw, Poland
79 National Institute of Science Education and Research, Homi Bhabha National
Institute, Jatni, India
80 National Nuclear Research Center, Baku, Azerbaijan
81 National Research and Innovation Agency - BRIN, Jakarta, Indonesia
82 Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
83 Nikhef, National institute for subatomic physics, Amsterdam, Netherlands
84 Nuclear Physics Group, STFC Daresbury Laboratory, Daresbury, United Kingdom
85 Nuclear Physics Institute of the Czech Academy of Sciences, Husinec-Řež,
Czech Republic
86 Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
87 Ohio State University, Columbus, Ohio, United States
88 Physics department, Faculty of science, University of Zagreb, Zagreb,
Croatia
89 Physics Department, Panjab University, Chandigarh, India
90 Physics Department, University of Jammu, Jammu, India
91 Physics Department, University of Rajasthan, Jaipur, India
92 Physics Program and International Institute for Sustainability with Knotted
Chiral Meta Matter (SKCM2), Hiroshima University, Hiroshima, Japan
93 Physikalisches Institut, Eberhard-Karls-Universität Tübingen, Tübingen,
Germany
94 Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Heidelberg,
Germany
95 Physik Department, Technische Universität München, Munich, Germany
96 Politecnico di Bari and Sezione INFN, Bari, Italy
97 Research Division and ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum
für Schwerionenforschung GmbH, Darmstadt, Germany
98 Saha Institute of Nuclear Physics, Homi Bhabha National Institute, Kolkata,
India
99 School of Physics and Astronomy, University of Birmingham, Birmingham,
United Kingdom
100 Sección Física, Departamento de Ciencias, Pontificia Universidad Católica
del Perú, Lima, Peru
101 Stefan Meyer Institut für Subatomare Physik (SMI), Vienna, Austria
102 SUBATECH, IMT Atlantique, Nantes Université, CNRS-IN2P3, Nantes, France
103 Suranaree University of Technology, Nakhon Ratchasima, Thailand
104 Technical University of Košice, Košice, Slovak Republic
105 The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of
Sciences, Cracow, Poland
106 The University of Texas at Austin, Austin, Texas, United States
107 Universidad Autónoma de Sinaloa, Culiacán, Mexico
108 Universidade de São Paulo (USP), São Paulo, Brazil
109 Universidade Estadual de Campinas (UNICAMP), Campinas, Brazil
110 Universidade Federal do ABC, Santo Andre, Brazil
111 University of Cape Town, Cape Town, South Africa
112 University of Houston, Houston, Texas, United States
113 University of Jyväskylä, Jyväskylä, Finland
114 University of Kansas, Lawrence, Kansas, United States
115 University of Liverpool, Liverpool, United Kingdom
116 University of Science and Technology of China, Hefei, China
117 University of South-Eastern Norway, Kongsberg, Norway
118 University of Tennessee, Knoxville, Tennessee, United States
119 University of the Witwatersrand, Johannesburg, South Africa
120 University of Tokyo, Tokyo, Japan
121 University of Tsukuba, Tsukuba, Japan
122 University Politehnica of Bucharest, Bucharest, Romania
123 Université Clermont Auvergne, CNRS/IN2P3, LPC, Clermont-Ferrand, France
124 Université de Lyon, CNRS/IN2P3, Institut de Physique des 2 Infinis de
Lyon, Lyon, France
125 Université de Strasbourg, CNRS, IPHC UMR 7178, F-67000 Strasbourg, France,
Strasbourg, France
126 Université Paris-Saclay, Centre d’Etudes de Saclay (CEA), IRFU, Départment
de Physique Nucléaire (DPhN), Saclay, France
127 Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
128 Università degli Studi di Foggia, Foggia, Italy
129 Università del Piemonte Orientale, Vercelli, Italy
130 Università di Brescia, Brescia, Italy
131 Variable Energy Cyclotron Centre, Homi Bhabha National Institute, Kolkata,
India
132 Warsaw University of Technology, Warsaw, Poland
133 Wayne State University, Detroit, Michigan, United States
134 Westfälische Wilhelms-Universität Münster, Institut für Kernphysik,
Münster, Germany
135 Wigner Research Centre for Physics, Budapest, Hungary
136 Yale University, New Haven, Connecticut, United States
137 Yonsei University, Seoul, Republic of Korea
138 Zentrum für Technologie und Transfer (ZTT), Worms, Germany
139 Affiliated with an institute covered by a cooperation agreement with CERN
140 Affiliated with an international laboratory covered by a cooperation
agreement with CERN.