2018 236 28 August

Energy dependence of exclusive $\mathrm{J}/\psi$ photoproduction …

ALICE Collaboration††thanks: See Appendix A for the list of collaboration
members ALICE Collaboration

The ALICE Collaboration has measured the energy dependence of exclusive
photoproduction of $\mathrm{J}/\psi$ vector mesons off proton targets in
ultra–peripheral p–Pb collisions at a centre-of-mass energy per nucleon pair
$\sqrt{s_{\rm NN}}=5.02$ TeV. The e+e- and $\mu^{+}\mu^{-}$ decay channels are
used to measure the cross section as a function of the rapidity of the
$\mathrm{J}/\psi$ in the range $-2.5<y<2.7$, corresponding to an energy in the
$\gamma$p centre-of-mass in the interval $40<W_{\gamma\mathrm{p}}<550$ GeV.
The measurements, which are consistent with a power law dependence of the
exclusive $\mathrm{J}/\psi$ photoproduction cross section, are compared to
previous results from HERA and the LHC and to several theoretical models. They
are found to be compatible with previous measurements.

##  1 Introduction

One of the most interesting aspects of perturbative Quantum Chromodynamics
(pQCD) is the evolution of the structure of hadrons in terms of quarks and
gluons towards the high-energy limit [1]. Very precise measurements at HERA
[2, 3] have shown that the gluon structure function in protons rises rapidly
at small values of the Bjorken $x$ variable, which corresponds to the high-
energy limit of QCD. This rise, interpreted as the growth of the probability
density function for gluons, has to be damped at some high energy to satisfy
unitarity constraints [4]. Although gluon saturation [5] is the most
straightforward mechanism to slow down the growth of the cross section, no
compelling evidence for this effect has been found so far. Gluon saturation
would have important implications in small-$x$ physics and in the early stages
of ultra-relativistic heavy-ion collisions at RHIC and LHC; consequently,
finding evidence for gluon saturation has become a central task for present
experiments and for future projects [6, 7].

The exclusive photoproduction of charmonium off protons
(${\gamma}{\mathrm{p}}\rightarrow\mathrm{J}/\psi p$) is a very clean probe
with which to search for saturation effects, because the cross section for
this process depends, at leading order in pQCD, on the square of the gluon
density in the target [8]. The mass of the charm quark provides a scale large
enough to allow calculations within pQCD. A reduction in the growth rate of
the cross section for this process as the centre-of-mass energy of the photon-
target system increases would signal the onset of gluon saturation effects.

This process has been extensively studied in ep interactions at the HERA
collider. Both ZEUS and H1 measured the energy dependence of exclusive
$\mathrm{J}/\psi$ photoproduction off protons at $\gamma{\rm p}$ centre-of-
mass energies, $W_{\gamma\mathrm{p}}$, from 20 to 305 GeV [9, 10, 11]. H1 has
also measured exclusive $\psi(\mathrm{2S})$ photoproduction off protons with
$W_{\gamma\mathrm{p}}$ between 40 and 150 GeV [12].

The exclusive photoproduction of charmonium can also be studied at hadron
colliders, where one of the incoming hadrons is the source of the photons and
the other the target. CDF measured exclusive $\mathrm{J}/\psi$ production at
mid-rapidities in p$\bar{\rm p}$ collisions at the Tevatron [13], while LHCb
reported measurements of exclusive $\mathrm{J}/\psi$ and $\psi(\mathrm{2S})$
production at forward rapidities in pp collisions at the LHC [14]. In
addition, $\Upsilon$ production has been studied, both at HERA [15, 16, 17]
and in pp collisions at the LHC [18]. In all cases, the experimental signature
is the production of a vector meson in a collision in which there is no other
hadronic activity, apart from the possible emission of a few very forward
neutrons.

In hadron colliders, as the incoming particles can each be both source or
target, there are two possible centre-of-mass energies for the photon-target
system. This ambiguity can be resolved if the contribution of one beam acting
as the source is much stronger than the other. This is the case for p–Pb
collisions, because photon emission grows with the square of the electric
charge and thus emission by the Pb ion is strongly enhanced with respect to
that from the proton. ALICE published the first measurement of exclusive
photoproduction of $\mathrm{J}/\psi$, at forward and backward rapidities, in
p–Pb collisions at the LHC [19].

In this Letter we present the measurements of exclusive $\mathrm{J}/\psi$
photoproduction in collisions of protons with Pb nuclei at a centre-of-mass
energy per nucleon pair $\sqrt{s_{\rm NN}}=5.02$ TeV. The measurements are
performed in the semi-backward ($-2.5<y<-1.2$), mid ($|y|<0.8$) and semi-
forward ($1.2<y<2.7$) rapidity intervals, where the rapidity $y$ of the
$\mathrm{J}/\psi$ is measured in the laboratory frame with respect to the
direction of the proton beam. The value of $W_{\gamma\mathrm{p}}$ is
determined by the rapidity of the $\mathrm{J}/\psi$ according to
$W_{\gamma{\rm p}}^{2}=2E_{\mathrm{p}}M_{\mathrm{J}/\psi}\exp(-y)$, where
$M_{\mathrm{J}/\psi}$ is the $\mathrm{J}/\psi$ mass and $E_{\mathrm{p}}=4$ TeV
is the energy of the proton beam. Thus, the measurements presented here span
the $W_{\gamma\mathrm{p}}$ range from 40 to 550 GeV. Together with the
measurements presented in [19] (for the rapidity ranges $-3.6<y<-2.6$ and
$2.5<y<4$), ALICE data map the $W_{\gamma\mathrm{p}}$ dependence of the cross
section for this process from about 20 to 700 GeV, which, using the standard
definition $x=M^{2}_{\mathrm{J}/\psi}/W^{2}_{\gamma{\rm p}}$, corresponds to
three orders of magnitude, from ${\sim}2\times 10^{-2}$ to ${\sim}2\times
10^{-5}$.

##  2 Experimental set-up

The ALICE detector and its performance are described in detail in [20, 21]. It
consists of two main sections: a central barrel placed in a large solenoid
magnet ($\mathrm{B}=0.5$ $\mathrm{T}$), covering the pseudorapidity region
$|\eta|<0.9$, and a muon spectrometer covering the range $-4.0<\eta<-2.5$. In
addition, the analyses presented here make use of two other detector systems,
V0 and ZDC, which are placed near the beam pipe and cover large
pseudorapidities.

Because the proton and Pb beams had different energies, 4 TeV and 1.58 TeV per
nucleon respectively, the nucleon-nucleon centre-of-mass was shifted, with
respect to the laboratory frame, by $\Delta y_{\rm{NN}}=0.465$ in the
direction of the proton beam. Collisions were performed in two configurations,
denoted by p–Pb and Pb–p below, by reversing the directions of the LHC beams.
According to the naming convention the first named particle (e.g. ‘p’ in p–Pb)
is the one where the beam travels from the interaction region towards the muon
spectrometer. Note that the convention in ALICE is that the pseudorapidity is
negative in the direction of the muon spectrometer. In contrast, the
laboratory rapidity is measured with respect to the direction of the proton
beam and changes sign accordingly for the p–Pb and Pb–p configurations. In the
semi-backward and semi-forward analyses, the negative rapidity points come
from the Pb–p data, and the positive rapidity points from the p–Pb.

The ALICE apparatus consisted of 18 detector systems at the time the data used
in this study were taken. The detectors relevant for the analysis are
described in more detail below.

###  2.1 The ALICE central barrel

The innermost component of the central barrel is the Inner Tracking System
(ITS) [22]. The ITS contains six cylindrical layers of silicon detectors, with
the innermost layer at a radius of 3.9 cm with respect to the beam axis and
the outermost layer at 43 cm. The two rings closest to the beam form the
Silicon Pixel Detector (SPD) and cover the pseudorapidity ranges $|\eta|<2$
and $|\eta|<1.4$, for the inner and outer layers respectively. It is a fine
granularity detector, having about $10^{7}$ pixels. In addition to functioning
as a tracking device, the SPD signals can be used to build triggers. The other
four layers, two employing silicon drift chambers and two silicon microstrips,
are used in this analysis exclusively for tracking.

The Time Projection Chamber (TPC), surrounding the ITS, is a large cylindrical
detector used for tracking and for particle identification [23]. Its active
volume extends from 85 to 247 cm in the radial direction and has a total
length of 500 cm longitudinally, centred on the interaction point. A 100 kV
central electrode separates its two drift volumes, providing an electric field
for electron drift. The two end-plates are instrumented with Multi-Wire-
Proportional-Chambers (MWPCs) with 560 000 readout pads in all, allowing high
precision track measurements in the transverse plane. The $z$ coordinate is
given by the drift time in the TPC electric field. The TPC acceptance covers
the pseudorapidity range $|\eta|<0.9$ for tracks fully traversing it.
Ionization measurements made along track clusters are used for particle
identification.

Beyond the TPC lies the Time-of-Flight detector (TOF) [24]. It is a large
cylindrical barrel of Multigap Resistive Plate Chambers (MRPCs) giving very
high precision timing for tracks traversing it. Its pseudorapidity coverage
matches that of the TPC. It is also capable of delivering signals for
triggering purposes [25].

###  2.2 The ALICE muon spectrometer

The muon spectrometer consists of a 3 Tm dipole magnet, coupled with a
tracking and a triggering system. A ten interaction-length conical front
absorber, made of carbon, concrete and steel, is placed between the
interaction point (IP) and the muon spectrometer tracking system, between 0.9
and 5 m from the IP, to filter out primary hadrons. Muon tracking is performed
by means of five tracking stations, each one made of two planes of Cathode Pad
Chambers. A 7.2 interaction-length iron wall is placed after the tracking
stations. It is followed by the muon trigger system, based on two stations
equipped with Resistive Plate Chambers. The trigger system can provide single-
muon and dimuon triggers with a programmable $p_{\mathrm{T}}$ threshold. The
$p_{\mathrm{T}}$ threshold is an approximate value owing to the coarse grain
of the trigger spatial information. In addition, there is a conical absorber
made of tungsten, lead and steel, that surrounds the beam pipe at small angles
($\theta<2^{\circ}$) and shields the spectrometer from secondary particles
produced in interactions of primary particles in the beam pipe.

###  2.3 The V0 and the ZDC systems

Two sets of hadronic Zero Degree Calorimeters (ZDC) are located at 112.5 m on
either side of the interaction point. Each station consists of two detectors,
one to detect protons and the other neutrons. The neutron ZDCs detect neutrons
emitted in the very forward region ($|\eta|>8.7$). The calorimeters detect the
Cherenkov light produced in quartz fibers by the hadronic showers. Each
detector is read out by five photomultipliers. Their timing and energy
resolution allow one to select events with neutrons produced at very forward
rapidity, as could be the case in events with proton dissociation.

The V0 counters [26] consist of two arrays of 32 scintillator cells each,
covering the range 2.8 $<$ $\eta$ $<$ 5.1 (V0A on the side opposite to the
muon spectrometer) and –3.7 $<$ $\eta$ $<$ –1.7 (V0C, on the same side as the
muon spectrometer) and positioned respectively at $z$ = 340 cm and $z$ = –90
cm from the interaction point. The raw signals are used in the trigger, but
are refined offline for use in the final data selections. For example, these
detectors provide timing information with a resolution better than 1 ns, which
can be used to distinguish two different timing windows, one corresponding to
the passage of particles coming from collisions, and the other to particles
coming from upstream interactions with residual gas molecules, termed “beam-
gas” interactions.

###  2.4 Triggers

Two different signatures have been used in the analyses described below. In
one case, the mid-rapidity analysis, the $\mathrm{J}/\psi$ candidate decays
into a pair of leptons (either $e^{+}e^{-}$ or $\mu^{+}\mu^{-}$), both of
which are detected with the central barrel detectors. The second case, the
semi-forward (or semi-backward) analysis, corresponds to a $\mathrm{J}/\psi$
candidate decaying into a pair of muons where one of them is measured with the
muon spectrometer and the other with the central barrel detectors.

The trigger for the mid-rapidity analysis required at least two, and at most
six, fired pad-OR in the TOF detector [24], such that at least two of the
signals came from modules separated by more than 150 degrees in azimuth, since
the $\mathrm{J}/\psi$ decay products are predominantly produced back-to-back
in azimuth. The trigger also required no signal in V0A and no signal in V0C,
to ensure that there is very little extra hadronic activity in the event, and
at most six fired pixel chips in the outer layer of the SPD. In addition there
were required to be two inner-outer pairs of these pixels having a back-to-
back topology.

Three triggers were used for the semi-backward and semi-forward analyses. The
first was active during the p–Pb data taking period. It required a muon
candidate in the muon spectrometer trigger system with a transverse momentum
above 0.5 GeV/$c$ (as assessed in the trigger system electronics), at most 4
cells with signal in the V0C and no activity in the V0A. The SPD requirement
was to have at least 1 pixel hit in either the inner or the outer layer and
less than 7 pixels fired in the outer layer. Two different triggers were
active during the Pb–p period. For the first one, in addition to the previous
conditions, it was also required that at least one cell of the V0C had a
signal. The second one had the same requirements as the first, but in addition
vetoed signals from V0A compatible with beam-gas timing. These tighter
conditions were required owing to an increased background trigger rate.

The integrated luminosity $\mathcal{L}_{\mathrm{int}}$ was corrected for the
probability that the exclusivity requirements could be spoilt by multiple
interactions in the same bunch crossing. This pile-up correction is on average
5%. The total luminosity of the sample used for the mid-rapidity analysis is
2.1 nb-1 (4.8 nb-1) in the p–Pb (Pb–p) period, while for the semi-forward
(semi-backward) analysis it is 3.1 nb-1 (3.7 nb-1) in the p–Pb (Pb–p) period.
Note that in the mid-rapidity case, the p–Pb and Pb–p data samples have been
analysed together, taking into account the inversion of the rapidity sign, to
increase the size of the central rapidity data sample.

##  3 Data samples

###  3.1 Event and track selection for the mid-rapidity analysis

The events used in the mid-rapidity analysis fulfilled the following criteria.

  1. 1.

They fired the corresponding trigger.

  2. 2.

There were exactly two tracks reconstructed with the TPC and the ITS.

  3. 3.

The primary vertex had at least two tracks defining it.

  4. 4.

Each track had at least 50 TPC space points out of a maximum of 159, a
TPC-$\chi^{2}/\mathrm{dof}<4$, at least one SPD point and pseudorapidity
$|\eta|<0.9$.

  5. 5.

The distance of closest approach of each track to the (nominal) primary vertex
(DCA) was less than 2 cm in the longitudinal direction and less than
$0.0182+0.035/p_{\mathrm{T}}^{1.01}$ cm, with $p_{\mathrm{T}}$ in GeV/$c$, in
the transverse direction[21].

  6. 6.

Neither track was associated with a kink candidate.

  7. 7.

The coordinate of the primary vertex of the interaction along the beam-line
direction was within 15 cm of the nominal interaction point.

  8. 8.

The two tracks had opposite electric charge.

To build dilepton candidates the tracks were separated into electrons and
muons using the energy loss measured by the TPC, such that:

  1. 1.

the quadratic sum of the normalised deviation from the corresponding Bethe-
Bloch expectation for the positive and negative track had to be less than 16;

  2. 2.

the rapidity, measured in the laboratory frame, of the dilepton candidate,
formed by the 4-vector sum of the two tracks with the corresponding mass
hypothesis, had to be in the range $|y|<0.8$.

In addition, the events had to

  1. 3.

have no signal in V0 as determined by the offline decision, and

  2. 4.

no signal in either of the neutron ZDCs.

###  3.2 Event and track selection for the semi-backward and semi-forward
analyses

The events used in the semi-backward and semi-forward analyses fulfilled the
following criteria.

  1. 1.

They fired the corresponding trigger.

  2. 2.

There was exactly one track reconstructed with the TPC and the ITS.

  3. 3.

This track fulfilled similar requirements to those for the central analysis
tracks, with two modifications: it had to be compatible with a muon (within
$4\sigma$) according to the energy-loss measurement, and the acceptance was
enlarged to $|\eta|<1.1$.

  4. 4.

Furthermore, the distance of closest approach of this track to the nominal
interaction point had to be less than 15 cm in the direction along the beam-
line.

  5. 5.

The event also had to have exactly one track in the muon spectrometer such
that:

    1. (a)

the track is matched to a trigger track above the $p_{\mathrm{T}}$ threshold;

    2. (b)

the radial coordinate of the track at the end of the front absorber ($R_{\rm
abs}$) was required to be in the range 17.5 cm $<R_{\rm abs}<$ 89.5 cm;

    3. (c)

it had a pseudorapidity in the range $-4.0<\eta<-2.5$ ($-3.7<\eta<-2.5$) in
the p–Pb (Pb–p) period and fulfilled the so called $p\times$DCA requirement.

The $p\times$DCA requirement uses the difference in the distributions for
signal and beam-induced background in the ($p$, DCA) plane, where $p$ is the
track momentum and DCA is the distance between the interaction vertex and the
track extrapolated to the vertex transverse plane. If in a given event no
interaction vertex was found, the point (0, 0, 0) was used to calculate the
distance of closest approach. The pseudorapidity ranges are different in p–Pb
and Pb–p owing to the additional V0C trigger requirement (see section 2.4).

  6. 6.

The two tracks had to have opposite electric charge.

  7. 7.

The rapidity, measured in the laboratory frame, of the dimuon candidate,
formed by the 4-vector sum of the two tracks with the muon-mass hypothesis,
had to be in the range $1.2<y<2.7$ for the p–Pb and $-2.5<y<-1.2$ for the Pb–p
sample, respectively.

  8. 8.

In addition, the events had to have no signal in V0A, at most one cell with a
signal in V0C, (in both cases as determined by the offline reconstruction), no
signal in either of the neutron ZDCs and at most one tracklet in the SPD
layers.

###  3.3 Selection of background samples

Several background samples, one for each analysis, were selected. The events
in these samples satisfy the conditions listed in the previous sections, and
in addition there is required to be a signal, compatible with the presence of
a neutron, in the ZDC placed in the proton direction. Both like-sign and
opposite-sign dilepton candidates are accepted.

These samples are highly efficient to tag dissociative processes (where the
target proton breaks up) and other hadronic collisions and were used to build
templates to subtract the remaining background in the real data samples as
explained below. As the trigger suppresses events with higher $p_{\mathrm{T}}$
dileptons ($p_{\mathrm{T}}\geq 0.5$ GeV/$c$), due to the condition on
azimuthal separation, the number of events in this $p_{\mathrm{T}}$ range is
limited. Therefore, each background spectrum was used to generate a high
statistics sample, which was smoothed to produce the final template. This is
referred to as “non-exclusive background” in the analysis of the
$p_{\mathrm{T}}$ spectrum. The selections and smoothing algorithms were varied
to estimate the systematic uncertainties, and the background $p_{\mathrm{T}}$
distribution was verified independently by selecting hadronic activity in V0C
instead of the ZDC.

###  3.4 Monte Carlo samples

The STARLIGHT Monte Carlo generator [27, 28] was used to generate large
samples for the following processes: exclusive $\mathrm{J}/\psi$
photoproduction off proton
($\gamma{\mathrm{p}}\rightarrow\mathrm{J}/\psi\mathrm{p}$) and Pb
($\gamma{\mathrm{Pb}}\rightarrow\mathrm{J}/\psi\mathrm{Pb}$) targets,
exclusive photoproduction of $\psi(\mathrm{2S})$ decaying into
$\mathrm{J}/\psi+X$, and continuum dilepton production
$\gamma\gamma\rightarrow l^{+}l^{-}$. The physics models used by STARLIGHT are
described in [28, 29, 30]. All generated events were passed through a full
simulation of the detector based on GEANT 3 transport code [31] and subjected
to the same analysis chain as real data. The Monte Carlo took into account the
changing status of the detectors during data-taking, and their residual
misalignment.

In all cases the polarization of the photoproduced charmonium was taken as
transverse, as expected for photoproduction of vector mesons. For the
$\psi(\mathrm{2S})$ sample three cases were studied, corresponding to an
assumption of longitudinal, transverse and no polarisation of the
$\mathrm{J}/\psi$ produced by the decay of the $\psi(\mathrm{2S})$.

The dependence of exclusive photoproduction on the momentum transferred in the
target vertex is modelled in STARLIGHT using an exponential distribution
$F(Q^{2})=e^{-bQ^{2}}$, with the slope $b$ taking the default value of 4
GeV-2[32]. HERA measurements have shown that the value of this parameter
depends on $W_{\gamma\mathrm{p}}$ [10]. This effect is particularly important
for the mid-rapidity and the semi-backward samples, where
$W_{\gamma\mathrm{p}}$ is larger. To take this into account additional samples
of exclusive $\mathrm{J}/\psi$ were produced using STARLIGHT with a value of
$b$ given by the H1 parameterisation from [10].

##  4 Data analysis

###  4.1 Signal extraction

The mass distributions for the dilepton candidates that passed the selection
described in the previous section are shown in Fig. 1. In all cases a clear
$\mathrm{J}/\psi$ signal is observed over a small background. The data can be
satisfactorily described in all cases by a combination of a Crystal-Ball
function (CB) [33] and an exponential distribution, which represent the signal
and the background from continuum dilepton production, respectively. The tail
parameters of the CB distribution have been fixed to the values obtained by
fitting simulated events.

Figure 2 shows the distribution of transverse momentum for dilepton pairs
having mass ($m_{\mathrm{l^{+}l^{-}}}$) in the range
$2.9<m_{\mathrm{l^{+}l^{-}}}<3.2$ GeV/$c^{2}$ for all the samples, except for
the dimuon case in the mid-rapidity analysis where the lower bound was raised
to 3.0 GeV/$c^{2}$ to make use of the better mass resolution of this channel.
In all cases the transverse momenta populate the region below about 1 GeV/$c$,
as expected from exclusive photoproduction off protons. These distributions
are used to extract the number of exclusive $\mathrm{J}/\psi$, within the
stipulated mass range, in each of the measured rapidity intervals. An extended
binned likelihood method is used in fits of data to a sum of templates for
signal and background obtained from data (see Section 3.3) and from Monte
Carlo (see Section 3.4) samples. These templates are also shown in the figure.

The number of candidates from the continuum dilepton template, which is a free
parameter in the fit, was found always to be less than what is obtained, in
the given mass range, from the exponential part of the fit to the mass
distribution. This exponential distribution includes both the exclusive and
the dissociative dilepton production, while the template describes only the
exclusive component. The number of candidates for coherent $\mathrm{J}/\psi$
production off lead has been estimated using STARLIGHT. The STARLIGHT
predictions were rescaled so as to be compatible, within the uncertainties,
with ALICE measurements in Pb–Pb collisions [34, 35]. The normalisation of the
exclusive $\mathrm{J}/\psi$ and non-exclusive background templates have been
left free. Note that the non-exclusive background is lower at higher energies
of the photon-target system, as has already been observed at HERA [10, 11],
and also by ALICE [19].

The number of candidates obtained from the fitted template for exclusive
$\mathrm{J}/\psi$ production has been corrected for the feed-down from
exclusive production of $\psi(\mathrm{2S})$ decaying into $\mathrm{J}/\psi+X$
[35]. This correction amounts to about 2% (4%) for the semi-backward and semi-
forward (mid-rapidity) analyses. The correction factor to take into account
the acceptance and efficiency ($\epsilon\times\mathrm{A}$) of the detector was
computed using simulated events, as described in section 3.4. This factor
depends on the rapidity of the $\mathrm{J}/\psi$ and varies from around 3% to
almost 9%. For the semi-backward sample the $\epsilon\times\mathrm{A}$
includes the efficiency of the V0C (around 60%) to detect the passing muon
(because it is included in the trigger). The values for the number of
exclusive $\mathrm{J}/\psi$ extracted in the different data samples, as well
as the corresponding $\epsilon\times\mathrm{A}$ factors and available
luminosity, are summarised in Table 1. Note that, in order to make best use of
the available statistics, both the central and the semi-forward (but not the
semi-backward) samples have been sub-divided into two rapidity bins.

Rapidity | $N_{\mathrm{J}/\psi}$ | $\epsilon\times\mathrm{A}$ |  $\mathcal{L}_{\mathrm{int}}$ (nb-1)
---|---|---|---
(1.9,2.7) | 73$\pm$15 | 0.071 | 3.147
(1.2,1.9) | 98$\pm$17 | 0.086 | 3.147
(0.0,0.8) |  |  |
dielectron | 106$\pm$16 | 0.029 | 6.915
dimuon | 196$\pm$17 | 0.057 | 6.915
(-0.8,0.0) |  |  |
dielectron | 117$\pm$13 | 0.033 | 6.915
dimuon | 199$\pm$20 | 0.063 | 6.915
(-2.5,-1.2) | 76$\pm$11 | 0.037 | 3.743
Table 1: Number of measured exclusive $\mathrm{J}/\psi$, value of the
efficiency and acceptance correction factor, as well as integrated luminosity
for each rapidity interval. These values are used in Eq. 1 to compute the
measured cross sections.

$\begin{array}[]{cc}\includegraphics[width=203.80193pt]{mass_el_pub}&\includegraphics[width=203.80193pt]{mass_mu_pub}\\\
\includegraphics[width=203.80193pt]{mass_pPb_pub}&\includegraphics[width=203.80193pt]{mass_Pbp_pub}\end{array}$

Figure 1: Mass distributions of selected dileptons for the dielectron (upper
left) and dimuon (upper right) samples for the central analysis and dimuon
samples for the semi-forward (lower left) and semi-backward (lower right)
analyses. In all cases the data are represented by points with error bars. The
solid blue line is a fit to a Crystal-Ball function plus an exponential
distribution, where this last contribution is shown by a dotted red line.

$\begin{array}[]{cc}\includegraphics[width=208.13574pt]{pT_el_pub}&\includegraphics[width=208.13574pt]{pT_mu_pub}\\\
\includegraphics[width=208.13574pt]{pT_pPb_pub}&\includegraphics[width=208.13574pt]{pT_Pbp_pub}\end{array}$

Figure 2:  Transverse momentum distributions of dileptons around the
$\mathrm{J}/\psi$ mass for the dielectron (upper left) and dimuon (upper
right) samples for the central analysis and dimuon samples for the semi-
forward (lower left) and semi-backward (lower right) analyses. In all cases
the data are represented by points with error bars. The blue, magenta (dash)
and green (dash-dot-dot) lines correspond to Monte Carlo templates for
$\mathrm{J}/\psi$ coming from exclusive photoproduction off protons or off
lead and continuous dilepton production respectively. The red (dash-dot) line
is a template for dissociative and hadronic background obtained from data. The
solid black line is the sum of all contributions.

###  4.2 Estimation of systematic uncertainties

Several sources of systematic uncertainty have been studied. They are
discussed below, while their contribution to the uncertainty on the measured
cross sections are summarised in Table 2.

The uncertainty on the tracking efficiency in the TPC was estimated repeating
the analyses using different track selections. Four different values for the
minimal number of points and three values for the minimum number of TPC pads
crossed by the track were used. The systematic uncertainty related to the
selection of tracks at mid-rapidity was estimated from the spread of the
variations with respect to the standard selection. It varies from 0.8% to
5.7%.

The uncertainty related to the identification of electrons and muons using
their energy deposition in TPC has been obtained using an alternative
selection based directly on the energy loss [36]. The difference between the
two methods was used as an estimate of the systematic uncertainty, and was at
most 1.3%. Cross contamination from muon pairs in the electron sample and vice
versa was found to be negligible.

The uncertainty on the single muon tracking efficiency in the muon
spectrometer was obtained by comparing the results of measurements performed
on simulations with those from real data [35] and amounts to 2% (3%) for the
p–Pb (Pb–p) period. There is also a 0.5% contribution from variations on the
conditions required to match the trigger and the tracking information of a
given muon.

The uncertainties related to triggering in the muon spectrometer have been
evaluated as in [36]. The efficiency maps of the trigger chambers have been
obtained using data. The statistical uncertainty on this procedure has been
used to vary the efficiency in simulations, which was then used to estimate a
systematic uncertainty of 1%. There is also a small discrepancy between the
efficiency in data and in simulations around the trigger threshold. This gives
a contribution of 1.7% (1.3%) for the p–Pb (Pb–p) period. The addition in
quadrature of these two effects yields the uncertainty on muon triggering.

The two main contributions to the uncertainty on the trigger efficiency for
the mid-rapidity analysis come from the back-to-back topology condition in the
SPD and TOF detectors. The first one was estimated using a data sample
obtained using a zero-bias trigger (all bunch crossings taken). It amounts to
4.5%. The second one was taken from the analysis of [35]. It amounts to (–9%,
+3.8)%, using a zero bias trigger to compute the efficiency and comparing the
result with the efficiency from simulated events.

The efficiency of the V0C to detect one muon from the $\mathrm{J}/\psi$ decay,
which is needed in the semi-backward analysis, was estimated using events from
the p–Pb period, whose trigger did not include this V0C requirement. The
procedure was cross checked using the forward dimuon sample used for the
analysis described in [19]. The efficiency depends slightly on the mass range
used to compute it. The addition in quadrature of the statistical uncertainty
(2.7%) and the mass dependence (2.0%) yields an uncertainty of 3.4%. The veto
efficiency of the V0 detector can also be estimated offline using a more
complex algorithm than that used in the online trigger. To estimate the
uncertainty on the use of V0 to veto extra activity, the analyses were
compared using the online V0 decision only and requiring (standard selection)
in addition the offline decision, with the difference giving the systematic
uncertainty. The uncertainty varies from 1.2% to 3.5%.

The trigger conditions associated with the upper limits in the activity in
TOF, SPD and V0C have a negligible effect on the systematic uncertainty,
because the limits are set well above the levels of activity produced by the
signal in our sample.

The systematic uncertainty on the yield was obtained by varying the range of
fit to the transverse momentum template, the width of the binning and the
selections and smoothing algorithms used to determine the non-exclusive
template. (See section 3.3.) Furthermore, the value of the $b$ parameter used
in the production of the exclusive $\mathrm{J}/\psi$ template was varied,
taking into account the uncertainties reported by H1 [10]. The uncertainty
varies from 1.9% to 3.6%. (See “signal extraction” in Table 2.)

The polarization of the $\mathrm{J}/\psi$ coming from $\psi(\mathrm{2S})$
feed-down is not known. The uncertainty on the amount of feed-down has been
estimated by assuming that the $\mathrm{J}/\psi$ was either not polarised or
that it was fully transversely or fully longitudinally polarised. This
uncertainty is asymmetric and varies from $+1.0\%$ to $-1.4\%$. (See “feed-
down” in Table 2.)

The uncertainty on the measurement of the luminosity has a contribution of
1.6%, which is correlated between the p–Pb and Pb–p data-taking periods and,
in addition, an uncorrelated part of 3.3% (3.0%) in the p–Pb (Pb–p)
configuration [37]. For the mid-rapidity analysis, which has data from both
p–Pb and Pb–p, the uncorrelated part of the uncertainty on the luminosity
amounts to 2.3%.

Furthermore, the uncertainties on the TPC selection, particle identification,
offline V0 veto efficiency and signal extraction are uncorrelated across
rapidity. The uncertainty on the $\psi(\mathrm{2S})$ feed-down is correlated
for all rapidities. The uncertainties on muon tracking, matching and trigger
efficiencies are mostly uncorrelated across rapidity, and for the purposes of
this analysis we treat the uncertainties as fully uncorrelated. (This includes
also the measurements from [19].) The trigger efficiency at mid-rapidity is
correlated between the (0.0,0.8) and (-0.8,0.0) rapidity intervals.

The mid-rapidity analysis offers two other possibilities to cross check the
consistency of the results. One can compare the results of the cross section
in the p–Pb and Pb–p periods, and one can compare the results of the electron
and the muon decay channels. The cross sections agreed in all cases within the
statistical uncertainties. As a cross-check, the possible contribution from
incoherent production of $\mathrm{J}/\psi$ off the Pb nucleus was
investigated, and found to be negligible. In addition, the effect on the
$\epsilon\times\mathrm{A}$ correction of varying the slope parameter b within
the HERA limits was also found to be negligible.

Systematic effects related to noise or pileup events in the ZDC are estimated
using randomly triggered events and are also found to be negligible.

| (1.9,2.7) | (1.2,1.9) | (0.0,0.8) | (–0.8,0.0) | (–2.5,–1.2)
---|---|---|---|---|---
TPC track selection | 5.7 | 1.2 | 0.9 | 0.8 | 3.3
Particle identification | - | - | 1.3 | 0.6 | -
Muon tracking efficiency | 2.0 | 2.0 | - | - | 3.0
Muon matching efficiency | 0.5 | 0.5 | - | - | 0.5
Trigger efficiency | 2.0 | 2.0 | ${}^{+5.9}_{-10.1}$ | ${}^{+5.9}_{-10.1}$ | 1.6
V0C Trigger efficiency | - | - | - | - | 3.4
Offline V0 veto efficiency | 2.7 | 3.5 | 2.1 | 2.1 | 1.2
Signal extraction | 3.6 | 2.2 | 2.1 | 1.9 | 3.0
Feed-down | ${}^{+0.0}_{-1.3}$ | 1.0 | ${}^{+0.6}_{-1.0}$ | ${}^{+1.0}_{-0.6}$ | ${}^{+0.0}_{-1.4}$
Luminosity uncorrelated | 3.3 | 3.3 | 2.3 | 2.3 | 3.0
Luminosity correlated | 1.6 | 1.6 | 1.6 | 1.6 | 1.6
Branching ratio [38] | 0.6 | 0.6 | 0.4 | 0.4 | 0.6
Total | 8.7 | 6.4 | 11.1 | 11.0 | 7.7
Table 2: Summary of the contributions to the systematic uncertainty, in
percent, for the $\mathrm{J}/\psi$ cross section in the different rapidity
intervals.

##  5 Results

###  5.1 Cross sections for exclusive production of $\mathrm{J}/\psi$ in p–Pb
collisions

The measured cross section for the exclusive production of $\mathrm{J}/\psi$
in collisions of protons with lead nuclei is computed according to

$\frac{{\rm d}\sigma}{{\rm
d}y}=\frac{N_{\mathrm{J}/\psi}}{\epsilon\times\mathrm{A}\cdot\mathrm{BR}(\mathrm{J}/\psi\to
l^{+}l^{-})\cdot\mathcal{L}_{\mathrm{int}}\cdot\Delta y}\,$ (1)

where $\Delta y$ represents the width of the rapidity region where the
measurement is performed and the branching ratios are
$\mathrm{BR}(\mathrm{J}/\psi\to\mathrm{e}^{+}\mathrm{e}^{-})=(5.97\pm 0.03$)%
and $\mathrm{BR}(\mathrm{J}/\psi\to\mu^{+}\mu^{-})=(5.96\pm 0.03)$% according
to [38]. The values that go into this equation are listed in Table 1, while
the measured cross sections are given in Table 3.

For the mid-rapidity analysis the measurements in the muon and electron
channels are computed independently. The cross sections in the rapidity range
$-0.8<y<0$ ($0<y<0.8$) are 10.7$\pm$1.3 (11.1$\pm$1.8) $\mu$b for the electron
channel and 9.6$\pm$1.0 (10.4$\pm$1.0) $\mu$b for the muon channel, where the
errors represent the statistical uncertainty. These measurements have been
averaged, weighting each cross section with its statistical uncertainty.

###  5.2 Cross sections for exclusive photoproduction of $\mathrm{J}/\psi$ off
protons

The relation between ${\rm d}\sigma/{\rm d}y$ and the cross section for the
photoproduction of $\mathrm{J}/\psi$ off protons, $\sigma(\gamma+{\rm
p}\rightarrow\mathrm{J}/\psi+{\rm p})$, is given by

$\frac{{\rm d}\sigma}{{\rm
d}y}=k\frac{\mathrm{d}n}{\mathrm{d}k}\sigma(\gamma+{\rm
p}\rightarrow\mathrm{J}/\psi+{\rm p})\,$ (2)

where $k=0.5{\times}M_{\mathrm{J}/\psi}\exp{(-y)}$ is the photon energy in the
laboratory frame and $k\mathrm{d}n/\mathrm{d}k$ the flux of photons with
energy $k$ emitted by the lead nucleus. Using STARLIGHT, the flux has been
computed in impact parameter space and convoluted with the probability of no
hadronic interaction. The uncertainty in the flux is obtained varying the
radius of the lead nucleus, used in the nuclear form factor, by $\pm 0.5$ fm,
which corresponds to the nuclear skin thickness.

The measured cross sections are given in Table 3, and also include the value
of the centre-of mass energy of the photon-proton system, $\langle
W_{\gamma{\rm p}}\rangle$, computed as the average of $W_{\gamma{\rm p}}$ over
the rapidity interval weighted by the photoproduction cross section predicted
by STARLIGHT.

Rapidity |  $\frac{{\rm d}\sigma}{{\rm d}y}$ ($\mu$b) | $k\frac{\mathrm{d}n}{\mathrm{d}k}$ |  $W_{\gamma{\rm p}}$ (GeV) |  $\langle W_{\gamma{\rm p}}\rangle$ (GeV) | $\sigma(\gamma+{\rm p}\rightarrow\mathrm{J}/\psi+{\rm p})(\mathrm{nb})$
---|---|---|---|---|---
(1.9, 2.7) |  6.9 $\pm$ 1.4 $\pm$ 0.6 |  163.6$\pm$1.5 | (40.8, 60.9) | 50.4 |  42 $\pm$ 9 $\pm$ 4 $\pm$ 1
(1.2, 1.9) |  8.7 $\pm$ 1.5 $\pm$ 0.6 |  140.2$\pm$1.5 | (60.9, 86.4) | 73.1 |  62 $\pm$ 11 $\pm$ 4 $\pm$ 1
(0.0, 0.8) |  10.6 $\pm$ 0.8 $\pm$ 1.2 |  104.3$\pm$1.5 | (105.5, 157.4) | 129.9 |  101 $\pm$ 8 $\pm$ 11 $\pm$ 1
(–0.8, 0.0) |  10.0 $\pm$ 0.8 $\pm$ 1.1 |  79.4$\pm$1.5 | (157.4, 234.9) | 193.3 |  126 $\pm$ 10 $\pm$ 14 $\pm$ 2
(–2.5, –1.2) |  7.1 $\pm$ 1.0 $\pm$ 0.5 |  36.5$\pm$1.4 | (286.9, 549.5) | 391.2 |  194 $\pm$ 27 $\pm$ 15 $\pm$ 7
Table 3: Measured differential cross sections ${\rm d}\sigma/{\rm d}y$ for
exclusive $\mathrm{J}/\psi$ photoproduction off protons in ultra-peripheral
p–Pb (positive rapidity values) and Pb–p (negative rapidity values) collisions
at $\sqrt{s_{\rm NN}}=5.02$ TeV in the different rapidity intervals. Values of
the photon flux $k\mathrm{d}n/\mathrm{d}k$, the interval in
$W_{\gamma\mathrm{p}}$ corresponding to the rapidity, the average
$W_{\gamma\mathrm{p}}$ ($\langle W_{\gamma{\rm p}}\rangle$) and the extracted
cross section $\sigma(\gamma+{\rm p}\rightarrow\mathrm{J}/\psi+{\rm p})$. The
first uncertainty in the cross sections is statistical, the second is
systematic and the third comes from the uncertainty in the photon flux.

$\begin{array}[]{c}\includegraphics[width=424.94574pt]{fig3_ratio07042018}\end{array}$

Figure 3: (Upper panel) ALICE data (red symbols) on exclusive photoproduction
of $\mathrm{J}/\psi$ off protons as a function of the centre-of-mass energy of
the photon–proton system $W_{\gamma\mathrm{p}}$, obtained in collisions of
protons and lead nuclei at $\sqrt{s_{\mathrm{\scriptscriptstyle NN}}}=5.02$
TeV, including results from [19], compared to a power-law fit, to data from
HERA[9, 11], to the solutions from LHCb[39] and to theoretical models (see
text). The uncertainties are the quadratic sum of the statistical and
systematic uncertainties. (Lower panel) Ratio of the models shown in the upper
panel to the power law fit through the ALICE data points. The Bjorken x value
corresponding to $W_{\gamma\mathrm{p}}$ is also displayed on the top of the
Figure, see text for details.

###  5.3 Energy dependence of the exclusive photoproduction of
$\mathrm{J}/\psi$ off protons

Figure 3 shows all ALICE measurements, including those from [19], for the
exclusive photoproduction of $\mathrm{J}/\psi$ off protons as a function of
$W_{\gamma\mathrm{p}}$. The data cover the $W_{\gamma\mathrm{p}}$ range from
24 to 706 GeV, which corresponds roughly to three orders of magnitude in $x$,
from $\sim 2\times 10^{-2}$ to $\sim 2\times 10^{-5}$. The error bars are the
quadratic sum of the statistical and the total systematic uncertainties.

The same figure shows the result of a $\chi^{2}$-fit of a power law
$N(W_{\gamma\mathrm{p}}/W_{0})^{\delta}$ to the full set of ALICE data, with
$W_{0}=90.0$ GeV as was done before in HERA analyses [40]. The fit takes into
account the statistical and systematic uncertainties, according to the
technique used by H1 in [41]. The parameters found by the fit are $N=71.8\pm
4.1$ nb and $\delta=0.70\pm 0.05$ with a correlation of $-0.06$ between both
parameters. The quality of the fit is $\chi^{2}=1.21$ for 7 degrees of
freedom. The value of the exponent is compatible to that found using previous
ALICE data [19], as well as with that found by HERA experiments [9, 11].

The comparison of ALICE measurements to data from other experiments as well as
to the results from different models is also shown in Fig. 3. HERA [9, 11] and
ALICE data are compatible within uncertainties. LHCb measured the exclusive
production of $\mathrm{J}/\psi$ in pp collisions, where the photon source can
not be identified. Thus the extraction of the photoproduction cross section is
not possible without further assumptions. For each measurement they reported
two solutions [14] which also agree with ALICE measurements.

ALICE measurements are also compared to theory in Fig. 3. The JMRT group [42]
has two computations, one is based on the leading-order (LO) result from [8]
with the addition of some corrections to the cross section, while the second
includes also the main contributions expected from a next-to-leading order
(NLO) result. The parameters of both models have been obtained by a fit to the
same data and their energy dependence is rather similar, so only the NLO
version is shown. Recently, three new studies have appeared, describing the
$W({\gamma}p)$ dependence of the exclusive $\mathrm{J}/\psi$ cross section in
terms of a colour dipole model [43] (CGC) or of the BFKL evolution of HERA
values (HERA Fit 2) with a photoproduction scale $M^{2}=2.39$
$\mathrm{GeV}^{2}$ [44] (NLO(BFKL)). These are shown as bands in the figure. A
third model, based on the colour dipole approach, and incorporating the energy
dependence of geometrical fluctuations of the proton structure in the impact
parameter plane [45] is also shown (CCT). The models are in reasonable
agreement with our data. Finally the STARLIGHT parameterisation relies on a
power-law fit to fixed-target and HERA data. This model also agrees with our
measurement.

##  6 Summary

The ALICE Collaboration has measured the photoproduction of $\mathrm{J}/\psi$
mesons off protons in p–Pb interactions. New measurements, summarised in Table
3, at central, semi-backward and semi-forward rapidities are added to those
previously given at forward and backward rapidities. Each rapidity interval
corresponds to a given energy for exclusive photoproduction in photon–proton
interactions. The data agree with the previous ALICE measurements at forward
and backward rapidities, with the LHCb results in pp interactions and with
previous HERA measurements over a smaller energy range. The ALICE measurements
are consistent with a power law dependence $\sigma(\gamma
p\rightarrow\mathrm{J}/\psi p)\sim W_{\gamma p}^{\delta}$, with
$\delta=0.70\pm 0.05.$ Several models, based on different physics assumptions,
reproduced this behaviour within the current experimental uncertainties. The
model predictions around and above 1 TeV are not very precise although all
tend to go below the extrapolation of the fit, as shown in the lower panel of
Fig. 3. This energy range will be reachable with the new LHC data from Run 2
and the data to be collected in Run 3 and Run 4. The data presented here,
augmented with the results from future measurements, will be a powerful tool
to better understand the role of saturation at the highest energies.

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## 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 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), Universidade Federal do
Rio Grande do Sul (UFRGS), Financiadora de Estudos e Projetos (Finep) and
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), Brazil;
Ministry of Science & Technology of China (MSTC), National Natural Science
Foundation of China (NSFC) and Ministry of Education of China (MOEC) , China;
Ministry of Science and Education, Croatia; 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 Carlsberg Foundation
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, Wissenschaft, Forschung und Technologie (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; Indonesian Institute of Science, Indonesia; Centro Fermi -
Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi and Istituto
Nazionale di Fisica Nucleare (INFN), Italy; Institute for Innovative Science
and Technology , Nagasaki Institute of Applied Science (IIST), Japan Society
for the Promotion of Science (JSPS) KAKENHI and Japanese Ministry of
Education, Culture, Sports, Science and Technology (MEXT), Japan; Consejo
Nacional de Ciencia (CONACYT) y 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 Science and Higher Education and National Science Centre, Poland;
Korea Institute of Science and Technology Information and National Research
Foundation of Korea (NRF), Republic of Korea; Ministry of Education and
Scientific Research, Institute of Atomic Physics and Romanian National Agency
for Science, Technology and Innovation, Romania; Joint Institute for Nuclear
Research (JINR), Ministry of Education and Science of the Russian Federation
and National Research Centre Kurchatov Institute, Russia; Ministry of
Education, Science, Research and Sport of the Slovak Republic, Slovakia;
National Research Foundation of South Africa, South Africa; Swedish Research
Council (VR) and Knut & Alice Wallenberg Foundation (KAW), Sweden; European
Organization for Nuclear Research, Switzerland; National Science and
Technology Development Agency (NSDTA), Suranaree University of Technology
(SUT) and Office of the Higher Education Commission under NRU project of
Thailand, Thailand; Turkish Atomic Energy Agency (TAEK), Turkey; National
Academy of Sciences of Ukraine, Ukraine; Science and Technology Facilities
Council (STFC), United Kingdom; National Science Foundation of the United
States of America (NSF) and United States Department of Energy, Office of
Nuclear Physics (DOE NP), United States of America.

##  Appendix A The ALICE Collaboration

S. Acharya139, F.T.-. Acosta20, J. Adam37, D. Adamová93, A. Adler74, J.
Adolfsson80, M.M. Aggarwal98, G. Aglieri Rinella34, M. Agnello31, N.
Agrawal48, Z. Ahammed139, S.U. Ahn76, S. Aiola144, A. Akindinov64, M. Al-
Turany104, S.N. Alam139, D.S.D. Albuquerque121, D. Aleksandrov87, B.
Alessandro58, H.M. Alfanda6, R. Alfaro Molina72, Y. Ali15, A. Alici10,27,53,
A. Alkin2, J. Alme22, T. Alt69, L. Altenkamper22, I. Altsybeev111, M.N.
Anaam6, C. Andrei47, D. Andreou34, H.A. Andrews108, A. Andronic104,142, M.
Angeletti34, V. Anguelov102, C. Anson16, T. Antičić105, F. Antinori56, P.
Antonioli53, R. Anwar125, N. Apadula79, L. Aphecetche113, H. Appelshäuser69,
S. Arcelli27, R. Arnaldi58, M. Arratia79, I.C. Arsene21, M. Arslandok102, A.
Augustinus34, R. Averbeck104, M.D. Azmi17, A. Badalà55, Y.W. Baek40,60, S.
Bagnasco58, R. Bailhache69, R. Bala99, A. Baldisseri135, M. Ball42, R.C.
Baral85, A.M. Barbano26, R. Barbera28, F. Barile52, L. Barioglio26, G.G.
Barnaföldi143, L.S. Barnby92, V. Barret132, P. Bartalini6, K. Barth34, E.
Bartsch69, N. Bastid132, S. Basu141, G. Batigne113, B. Batyunya75, P.C.
Batzing21, J.L. Bazo Alba109, I.G. Bearden88, H. Beck102, C. Bedda63, N.K.
Behera60, I. Belikov134, F. Bellini34, H. Bello Martinez44, R. Bellwied125,
L.G.E. Beltran119, V. Belyaev91, G. Bencedi143, S. Beole26, A. Bercuci47, Y.
Berdnikov96, D. Berenyi143, R.A. Bertens128, D. Berzano34,58, L. Betev34, P.P.
Bhaduri139, A. Bhasin99, I.R. Bhat99, H. Bhatt48, B. Bhattacharjee41, J.
Bhom117, A. Bianchi26, L. Bianchi26,125, N. Bianchi51, J. Bielčík37, J.
Bielčíková93, A. Bilandzic103,116, G. Biro143, R. Biswas3, S. Biswas3, J.T.
Blair118, D. Blau87, C. Blume69, G. Boca137, F. Bock34, A. Bogdanov91, L.
Boldizsár143, A. Bolozdynya91, M. Bombara38, G. Bonomi138, M. Bonora34, H.
Borel135, A. Borissov102,142, M. Borri127, E. Botta26, C. Bourjau88, L.
Bratrud69, P. Braun-Munzinger104, M. Bregant120, T.A. Broker69, M. Broz37,
E.J. Brucken43, E. Bruna58, G.E. Bruno33,34, D. Budnikov106, H. Buesching69,
S. Bufalino31, P. Buhler112, P. Buncic34, O. BuschI,131, Z. Buthelezi73, J.B.
Butt15, J.T. Buxton95, J. Cabala115, D. Caffarri89, H. Caines144, A.
Caliva104, E. Calvo Villar109, R.S. Camacho44, P. Camerini25, A.A. Capon112,
W. Carena34, F. Carnesecchi10,27, J. Castillo Castellanos135, A.J. Castro128,
E.A.R. Casula54, C. Ceballos Sanchez8, S. Chandra139, B. Chang126, W. Chang6,
S. Chapeland34, M. Chartier127, S. Chattopadhyay139, S. Chattopadhyay107, A.
Chauvin24, C. Cheshkov133, B. Cheynis133, V. Chibante Barroso34, D.D.
Chinellato121, S. Cho60, P. Chochula34, T. Chowdhury132, P. Christakoglou89,
C.H. Christensen88, P. Christiansen80, T. Chujo131, S.U. Chung18, C. Cicalo54,
L. Cifarelli10,27, F. Cindolo53, J. Cleymans124, F. Colamaria52, D. Colella52,
A. Collu79, M. Colocci27, M. ConcasII,58, G. Conesa Balbastre78, Z. Conesa del
Valle61, J.G. Contreras37, T.M. Cormier94, Y. Corrales Morales58, P.
Cortese32, M.R. Cosentino122, F. Costa34, S. Costanza137, J. Crkovská61, P.
Crochet132, E. Cuautle70, L. Cunqueiro94,142, D. Dabrowski140, T.
Dahms103,116, A. Dainese56, F.P.A. Damas113,135, S. Dani66, M.C. Danisch102,
A. Danu68, D. Das107, I. Das107, S. Das3, A. Dash85, S. Dash48, S. De49, A. De
Caro30, G. de Cataldo52, C. de Conti120, J. de Cuveland39, A. De Falco24, D.
De Gruttola10,30, N. De Marco58, S. De Pasquale30, R.D. De Souza121, H.F.
Degenhardt120, A. Deisting102,104, A. Deloff84, S. Delsanto26, C. Deplano89,
P. Dhankher48, D. Di Bari33, A. Di Mauro34, B. Di Ruzza56, R.A. Diaz8, T.
Dietel124, P. Dillenseger69, Y. Ding6, R. Divià34, Ø. Djuvsland22, A.
Dobrin34, D. Domenicis Gimenez120, B. Dönigus69, O. Dordic21, A.K. Dubey139,
A. Dubla104, L. Ducroux133, S. Dudi98, A.K. Duggal98, M. Dukhishyam85, P.
Dupieux132, R.J. Ehlers144, D. Elia52, E. Endress109, H. Engel74, E. Epple144,
B. Erazmus113, F. Erhardt97, A. Erokhin111, M.R. Ersdal22, B. Espagnon61, G.
Eulisse34, J. Eum18, D. Evans108, S. Evdokimov90, L. Fabbietti103,116, M.
Faggin29, J. Faivre78, A. Fantoni51, M. Fasel94, L. Feldkamp142, A.
Feliciello58, G. Feofilov111, A. Fernández Téllez44, A. Ferretti26, A.
Festanti34, V.J.G. Feuillard102, J. Figiel117, M.A.S. Figueredo120, S.
Filchagin106, D. Finogeev62, F.M. Fionda22, G. Fiorenza52, F. Flor125, M.
Floris34, S. Foertsch73, P. Foka104, S. Fokin87, E. Fragiacomo59, A.
Francescon34, A. Francisco113, U. Frankenfeld104, G.G. Fronze26, U. Fuchs34,
C. Furget78, A. Furs62, M. Fusco Girard30, J.J. Gaardhøje88, M. Gagliardi26,
A.M. Gago109, K. Gajdosova88, M. Gallio26, C.D. Galvan119, P. Ganoti83, C.
Garabatos104, E. Garcia-Solis11, K. Garg28, C. Gargiulo34, K. Garner142, P.
Gasik103,116, E.F. Gauger118, M.B. Gay Ducati71, M. Germain113, J. Ghosh107,
P. Ghosh139, S.K. Ghosh3, P. Gianotti51, P. Giubellino58,104, P. Giubilato29,
P. Glässel102, D.M. Goméz Coral72, A. Gomez Ramirez74, V. Gonzalez104, P.
González-Zamora44, S. Gorbunov39, L. Görlich117, S. Gotovac35, V. Grabski72,
L.K. Graczykowski140, K.L. Graham108, L. Greiner79, A. Grelli63, C.
Grigoras34, V. Grigoriev91, A. Grigoryan1, S. Grigoryan75, J.M. Gronefeld104,
F. Grosa31, J.F. Grosse-Oetringhaus34, R. Grosso104, R. Guernane78, B.
Guerzoni27, M. Guittiere113, K. Gulbrandsen88, T. Gunji130, A. Gupta99, R.
Gupta99, I.B. Guzman44, R. Haake34,144, M.K. Habib104, C. Hadjidakis61, H.
Hamagaki81, G. Hamar143, M. Hamid6, J.C. Hamon134, R. Hannigan118, M.R.
Haque63, A. Harlenderova104, J.W. Harris144, A. Harton11, H. Hassan78, D.
Hatzifotiadou10,53, P. Hauer42, S. Hayashi130, S.T. Heckel69, E. Hellbär69, H.
Helstrup36, A. Herghelegiu47, E.G. Hernandez44, G. Herrera Corral9, F.
Herrmann142, K.F. Hetland36, T.E. Hilden43, H. Hillemanns34, C. Hills127, B.
Hippolyte134, B. Hohlweger103, D. Horak37, S. Hornung104, R. Hosokawa78,131,
J. Hota66, P. Hristov34, C. Huang61, C. Hughes128, P. Huhn69, T.J. Humanic95,
H. Hushnud107, N. Hussain41, T. Hussain17, D. Hutter39, D.S. Hwang19, J.P.
Iddon127, R. Ilkaev106, M. Inaba131, M. Ippolitov87, M.S. Islam107, M.
Ivanov104, V. Ivanov96, V. Izucheev90, B. Jacak79, N. Jacazio27, P.M.
Jacobs79, M.B. Jadhav48, S. Jadlovska115, J. Jadlovsky115, S. Jaelani63, C.
Jahnke116,120, M.J. Jakubowska140, M.A. Janik140, C. Jena85, M. Jercic97, O.
Jevons108, R.T. Jimenez Bustamante104, M. Jin125, P.G. Jones108, A. Jusko108,
P. Kalinak65, A. Kalweit34, J.H. Kang145, V. Kaplin91, S. Kar6, A. Karasu
Uysal77, O. Karavichev62, T. Karavicheva62, P. Karczmarczyk34, E. Karpechev62,
U. Kebschull74, R. Keidel46, D.L.D. Keijdener63, M. Keil34, B. Ketzer42, Z.
Khabanova89, A.M. Khan6, S. Khan17, S.A. Khan139, A. Khanzadeev96, Y.
Kharlov90, A. Khatun17, A. Khuntia49, M.M. Kielbowicz117, B. Kileng36, B.
Kim131, D. Kim145, D.J. Kim126, E.J. Kim13, H. Kim145, J.S. Kim40, J. Kim102,
J. Kim13, M. Kim60,102, S. Kim19, T. Kim145, T. Kim145, K. Kindra98, S.
Kirsch39, I. Kisel39, S. Kiselev64, A. Kisiel140, J.L. Klay5, C. Klein69, J.
Klein58, C. Klein-Bösing142, S. Klewin102, A. Kluge34, M.L. Knichel34, A.G.
Knospe125, C. Kobdaj114, M. Kofarago143, M.K. Köhler102, T. Kollegger104, N.
Kondratyeva91, E. Kondratyuk90, A. Konevskikh62, P.J. Konopka34, M.
Konyushikhin141, L. Koska115, O. Kovalenko84, V. Kovalenko111, M. Kowalski117,
I. Králik65, A. Kravčáková38, L. Kreis104, M. Krivda65,108, F. Krizek93, M.
Krüger69, E. Kryshen96, M. Krzewicki39, A.M. Kubera95, V. Kučera60,93, C.
Kuhn134, P.G. Kuijer89, J. Kumar48, L. Kumar98, S. Kumar48, S. Kundu85, P.
Kurashvili84, A. Kurepin62, A.B. Kurepin62, S. Kushpil93, J. Kvapil108, M.J.
Kweon60, Y. Kwon145, S.L. La Pointe39, P. La Rocca28, Y.S. Lai79, I.
Lakomov34, R. Langoy123, K. Lapidus144, A. Lardeux21, P. Larionov51, E.
Laudi34, R. Lavicka37, R. Lea25, L. Leardini102, S. Lee145, F. Lehas89, S.
Lehner112, J. Lehrbach39, R.C. Lemmon92, I. León Monzón119, P. Lévai143, X.
Li12, X.L. Li6, J. Lien123, R. Lietava108, B. Lim18, S. Lindal21, V.
Lindenstruth39, S.W. Lindsay127, C. Lippmann104, M.A. Lisa95, V.
Litichevskyi43, A. Liu79, H.M. Ljunggren80, W.J. Llope141, D.F. Lodato63, V.
Loginov91, C. Loizides79,94, P. Loncar35, X. Lopez132, E. López Torres8, P.
Luettig69, J.R. Luhder142, M. Lunardon29, G. Luparello59, M. Lupi34, A.
Maevskaya62, M. Mager34, S.M. Mahmood21, A. Maire134, R.D. Majka144, M.
Malaev96, Q.W. Malik21, L. MalininaIII,75, D. Mal’Kevich64, P. Malzacher104,
A. Mamonov106, V. Manko87, F. Manso132, V. Manzari52, Y. Mao6, M.
Marchisone129,133, J. Mareš67, G.V. Margagliotti25, A. Margotti53, J.
Margutti63, A. Marín104, C. Markert118, M. Marquard69, N.A. Martin102,104, P.
Martinengo34, J.L. Martinez125, M.I. Martínez44, G. Martínez García113, M.
Martinez Pedreira34, S. Masciocchi104, M. Masera26, A. Masoni54, L.
Massacrier61, E. Masson113, A. Mastroserio52,136, A.M. Mathis103,116, P.F.T.
Matuoka120, A. Matyja117,128, C. Mayer117, M. Mazzilli33, M.A. Mazzoni57, F.
Meddi23, Y. Melikyan91, A. Menchaca-Rocha72, E. Meninno30, M. Meres14, S.
Mhlanga124, Y. Miake131, L. Micheletti26, M.M. Mieskolainen43, D.L.
Mihaylov103, K. Mikhaylov64,75, A. Mischke63, A.N. Mishra70, D. Miśkowiec104,
J. Mitra139, C.M. Mitu68, N. Mohammadi34, A.P. Mohanty63, B. Mohanty85, M.
Mohisin KhanIV,17, D.A. Moreira De Godoy142, L.A.P. Moreno44, S. Moretto29, A.
Morreale113, A. Morsch34, T. Mrnjavac34, V. Muccifora51, E. Mudnic35, D.
Mühlheim142, S. Muhuri139, M. Mukherjee3, J.D. Mulligan144, M.G. Munhoz120, K.
Münning42, R.H. Munzer69, H. Murakami130, S. Murray73, L. Musa34, J.
Musinsky65, C.J. Myers125, J.W. Myrcha140, B. Naik48, R. Nair84, B.K. Nandi48,
R. Nania10,53, E. Nappi52, A. Narayan48, M.U. Naru15, A.F. Nassirpour80, H.
Natal da Luz120, C. Nattrass128, S.R. Navarro44, K. Nayak85, R. Nayak48, T.K.
Nayak139, S. Nazarenko106, R.A. Negrao De Oliveira34,69, L. Nellen70, S.V.
Nesbo36, G. Neskovic39, F. Ng125, M. Nicassio104, J. Niedziela34,140, B.S.
Nielsen88, S. Nikolaev87, S. Nikulin87, V. Nikulin96, F. Noferini10,53, P.
Nomokonov75, G. Nooren63, J.C.C. Noris44, J. Norman78, A. Nyanin87, J.
Nystrand22, M. Ogino81, H. Oh145, A. Ohlson102, J. Oleniacz140, A.C. Oliveira
Da Silva120, M.H. Oliver144, J. Onderwaater104, C. Oppedisano58, R. Orava43,
M. Oravec115, A. Ortiz Velasquez70, A. Oskarsson80, J. Otwinowski117, K.
Oyama81, Y. Pachmayer102, V. Pacik88, D. Pagano138, G. Paić70, P. Palni6, J.
Pan141, A.K. Pandey48, S. Panebianco135, V. Papikyan1, P. Pareek49, J. Park60,
J.E. Parkkila126, S. Parmar98, A. Passfeld142, S.P. Pathak125, R.N. Patra139,
B. Paul58, H. Pei6, T. Peitzmann63, X. Peng6, L.G. Pereira71, H. Pereira Da
Costa135, D. Peresunko87, E. Perez Lezama69, V. Peskov69, Y. Pestov4, V.
Petráček37, M. Petrovici47, C. Petta28, R.P. Pezzi71, S. Piano59, M. Pikna14,
P. Pillot113, L.O.D.L. Pimentel88, O. Pinazza34,53, L. Pinsky125, S. Pisano51,
D.B. Piyarathna125, M. Płoskoń79, M. Planinic97, F. Pliquett69, J. Pluta140,
S. Pochybova143, P.L.M. Podesta-Lerma119, M.G. Poghosyan94, B. Polichtchouk90,
N. Poljak97, W. Poonsawat114, A. Pop47, H. Poppenborg142, S. Porteboeuf-
Houssais132, V. Pozdniakov75, S.K. Prasad3, R. Preghenella53, F. Prino58, C.A.
Pruneau141, I. Pshenichnov62, M. Puccio26, V. Punin106, K. Puranapanda139, J.
Putschke141, S. Raha3, S. Rajput99, J. Rak126, A. Rakotozafindrabe135, L.
Ramello32, F. Rami134, R. Raniwala100, S. Raniwala100, S.S. Räsänen43, B.T.
Rascanu69, R. Rath49, V. Ratza42, I. Ravasenga31, K.F. Read94,128, K.
RedlichV,84, A. Rehman22, P. Reichelt69, F. Reidt34, X. Ren6, R. Renfordt69,
A. Reshetin62, J.-P. Revol10, K. Reygers102, V. Riabov96, T. Richert63,80,88,
M. Richter21, P. Riedler34, W. Riegler34, F. Riggi28, C. Ristea68, S.P.
Rode49, M. Rodríguez Cahuantzi44, K. Røed21, R. Rogalev90, E. Rogochaya75, D.
Rohr34, D. Röhrich22, P.S. Rokita140, F. Ronchetti51, E.D. Rosas70, K.
Roslon140, P. Rosnet132, A. Rossi29,56, A. Rotondi137, F. Roukoutakis83, C.
Roy134, P. Roy107, O.V. Rueda70, R. Rui25, B. Rumyantsev75, A. Rustamov86, E.
Ryabinkin87, Y. Ryabov96, A. Rybicki117, S. Saarinen43, S. Sadhu139, S.
Sadovsky90, K. Šafařík34, S.K. Saha139, B. Sahoo48, P. Sahoo49, R. Sahoo49, S.
Sahoo66, P.K. Sahu66, J. Saini139, S. Sakai131, M.A. Saleh141, S. Sambyal99,
V. Samsonov91,96, A. Sandoval72, A. Sarkar73, D. Sarkar139, N. Sarkar139, P.
Sarma41, M.H.P. Sas63, E. Scapparone53, F. Scarlassara29, B. Schaefer94, H.S.
Scheid69, C. Schiaua47, R. Schicker102, C. Schmidt104, H.R. Schmidt101, M.O.
Schmidt102, M. Schmidt101, N.V. Schmidt69,94, J. Schukraft34, Y. Schutz34,134,
K. Schwarz104, K. Schweda104, G. Scioli27, E. Scomparin58, M. Šefčík38, J.E.
Seger16, Y. Sekiguchi130, D. Sekihata45, I. Selyuzhenkov91,104, S.
Senyukov134, E. Serradilla72, P. Sett48, A. Sevcenco68, A. Shabanov62, A.
Shabetai113, R. Shahoyan34, W. Shaikh107, A. Shangaraev90, A. Sharma98, A.
Sharma99, M. Sharma99, N. Sharma98, A.I. Sheikh139, K. Shigaki45, M.
Shimomura82, S. Shirinkin64, Q. Shou6,110, Y. Sibiriak87, S. Siddhanta54, K.M.
Sielewicz34, T. Siemiarczuk84, D. Silvermyr80, G. Simatovic89, G.
Simonetti34,103, R. Singaraju139, R. Singh85, R. Singh99, V. Singhal139, T.
Sinha107, B. Sitar14, M. Sitta32, T.B. Skaali21, M. Slupecki126, N.
Smirnov144, R.J.M. Snellings63, T.W. Snellman126, J. Sochan115, C. Soncco109,
J. Song18,60, A. Songmoolnak114, F. Soramel29, S. Sorensen128, F. Sozzi104, I.
Sputowska117, J. Stachel102, I. Stan68, P. Stankus94, E. Stenlund80, D.
Stocco113, M.M. Storetvedt36, P. Strmen14, A.A.P. Suaide120, T. Sugitate45, C.
Suire61, M. Suleymanov15, M. Suljic34, R. Sultanov64, M. Šumbera93, S.
Sumowidagdo50, K. Suzuki112, S. Swain66, A. Szabo14, I. Szarka14, U.
Tabassam15, J. Takahashi121, G.J. Tambave22, N. Tanaka131, M. Tarhini113, M.G.
Tarzila47, D.J. Tapia Takaki61 A. Tauro34, G. Tejeda Muñoz44, A. Telesca34, C.
Terrevoli29, B. Teyssier133, D. Thakur49, S. Thakur139, D. Thomas118, F.
Thoresen88, R. Tieulent133, A. Tikhonov62, A.R. Timmins125, A. Toia69, N.
Topilskaya62, M. Toppi51, S.R. Torres119, S. Tripathy49, S. Trogolo26, G.
Trombetta33, L. Tropp38, V. Trubnikov2, W.H. Trzaska126, T.P. Trzcinski140,
B.A. Trzeciak63, T. Tsuji130, A. Tumkin106, R. Turrisi56, T.S. Tveter21, K.
Ullaland22, E.N. Umaka125, A. Uras133, G.L. Usai24, A. Utrobicic97, M.
Vala115, L. Valencia Palomo44, N. Valle137, N. van der Kolk63, L.V.R. van
Doremalen63, J.W. Van Hoorne34, M. van Leeuwen63, P. Vande Vyvre34, D.
Varga143, A. Vargas44, M. Vargyas126, R. Varma48, M. Vasileiou83, A.
Vasiliev87, O. Vázquez Doce103,116, V. Vechernin111, A.M. Veen63, E.
Vercellin26, S. Vergara Limón44, L. Vermunt63, R. Vernet7, R. Vértesi143, L.
Vickovic35, J. Viinikainen126, Z. Vilakazi129, O. Villalobos Baillie108, A.
Villatoro Tello44, A. Vinogradov87, T. Virgili30, V. Vislavicius80,88, A.
Vodopyanov75, M.A. Völkl101, K. Voloshin64, S.A. Voloshin141, G. Volpe33, B.
von Haller34, I. Vorobyev103,116, D. Voscek115, D. Vranic34,104, J.
Vrláková38, B. Wagner22, M. Wang6, Y. Watanabe131, M. Weber112, S.G. Weber104,
A. Wegrzynek34, D.F. Weiser102, S.C. Wenzel34, J.P. Wessels142, U.
Westerhoff142, A.M. Whitehead124, J. Wiechula69, J. Wikne21, G. Wilk84, J.
Wilkinson53, G.A. Willems34,142, M.C.S. Williams53, E. Willsher108, B.
Windelband102, W.E. Witt128, R. Xu6, S. Yalcin77, K. Yamakawa45, S.
Yano45,135, Z. Yin6, H. Yokoyama78,131, I.-K. Yoo18, J.H. Yoon60, S. Yuan22,
V. Yurchenko2, V. Zaccolo58, A. Zaman15, C. Zampolli34, H.J.C. Zanoli120, N.
Zardoshti108, A. Zarochentsev111, P. Závada67, N. Zaviyalov106, H.
Zbroszczyk140, M. Zhalov96, X. Zhang6, Y. Zhang6, Z. Zhang6,132, C. Zhao21, V.
Zherebchevskii111, N. Zhigareva64, D. Zhou6, Y. Zhou88, Z. Zhou22, H. Zhu6, J.
Zhu6, Y. Zhu6, A. Zichichi10,27, M.B. Zimmermann34, G. Zinovjev2, J.
Zmeskal112

Affiliation Notes

I Deceased

II Also at: Dipartimento DET del Politecnico di Torino, Turin, Italy

III Also at: M.V. Lomonosov Moscow State University, D.V. Skobeltsyn Institute
of Nuclear, Physics, Moscow, Russia

IV Also at: Department of Applied Physics, Aligarh Muslim University, Aligarh,
India

V Also at: Institute of Theoretical Physics, University of Wroclaw, Poland

Collaboration Institutes

1 A.I. Alikhanyan National Science Laboratory (Yerevan Physics Institute)
Foundation, Yerevan, Armenia

2 Bogolyubov Institute for Theoretical Physics, National Academy of Sciences
of Ukraine, Kiev, Ukraine

3 Bose Institute, Department of Physics and Centre for Astroparticle Physics
and Space Science (CAPSS), Kolkata, India

4 Budker Institute for Nuclear Physics, Novosibirsk, Russia

5 California Polytechnic State University, San Luis Obispo, California, United
States

6 Central China Normal University, Wuhan, China

7 Centre de Calcul de l’IN2P3, Villeurbanne, Lyon, France

8 Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear (CEADEN), Havana,
Cuba

9 Centro de Investigación y de Estudios Avanzados (CINVESTAV), Mexico City and
Mérida, Mexico

10 Centro Fermi - Museo Storico della Fisica e Centro Studi e Ricerche “Enrico
Fermi’, Rome, Italy

11 Chicago State University, Chicago, Illinois, United States

12 China Institute of Atomic Energy, Beijing, China

13 Chonbuk National University, Jeonju, Republic of Korea

14 Comenius University Bratislava, Faculty of Mathematics, Physics and
Informatics, Bratislava, Slovakia

15 COMSATS Institute of Information Technology (CIIT), Islamabad, Pakistan

16 Creighton University, Omaha, Nebraska, United States

17 Department of Physics, Aligarh Muslim University, Aligarh, India

18 Department of Physics, Pusan National University, Pusan, Republic of Korea

19 Department of Physics, Sejong University, Seoul, Republic of Korea

20 Department of Physics, University of California, Berkeley, California,
United States

21 Department of Physics, University of Oslo, Oslo, Norway

22 Department of Physics and Technology, University of Bergen, Bergen, Norway

23 Dipartimento di Fisica dell’Università ’La Sapienza’ and Sezione INFN,
Rome, Italy

24 Dipartimento di Fisica dell’Università and Sezione INFN, Cagliari, Italy

25 Dipartimento di Fisica dell’Università and Sezione INFN, Trieste, Italy

26 Dipartimento di Fisica dell’Università and Sezione INFN, Turin, Italy

27 Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN,
Bologna, Italy

28 Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN,
Catania, Italy

29 Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN,
Padova, Italy

30 Dipartimento di Fisica ‘E.R. Caianiello’ dell’Università and Gruppo
Collegato INFN, Salerno, Italy

31 Dipartimento DISAT del Politecnico and Sezione INFN, Turin, Italy

32 Dipartimento di Scienze e Innovazione Tecnologica dell’Università del
Piemonte Orientale and INFN Sezione di Torino, Alessandria, Italy

33 Dipartimento Interateneo di Fisica ‘M. Merlin’ and Sezione INFN, Bari,
Italy

34 European Organization for Nuclear Research (CERN), Geneva, Switzerland

35 Faculty of Electrical Engineering, Mechanical Engineering and Naval
Architecture, University of Split, Split, Croatia

36 Faculty of Engineering and Science, Western Norway University of Applied
Sciences, Bergen, Norway

37 Faculty of Nuclear Sciences and Physical Engineering, Czech Technical
University in Prague, Prague, Czech Republic

38 Faculty of Science, P.J. Šafárik University, Košice, Slovakia

39 Frankfurt Institute for Advanced Studies, Johann Wolfgang Goethe-
Universität Frankfurt, Frankfurt, Germany

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 Hiroshima University, Hiroshima, Japan

46 Hochschule Worms, Zentrum für Technologietransfer und Telekommunikation
(ZTT), Worms, Germany

47 Horia Hulubei National Institute of Physics and Nuclear Engineering,
Bucharest, Romania

48 Indian Institute of Technology Bombay (IIT), Mumbai, India

49 Indian Institute of Technology Indore, Indore, India

50 Indonesian Institute of Sciences, Jakarta, Indonesia

51 INFN, Laboratori Nazionali di Frascati, Frascati, Italy

52 INFN, Sezione di Bari, Bari, Italy

53 INFN, Sezione di Bologna, Bologna, Italy

54 INFN, Sezione di Cagliari, Cagliari, Italy

55 INFN, Sezione di Catania, Catania, Italy

56 INFN, Sezione di Padova, Padova, Italy

57 INFN, Sezione di Roma, Rome, Italy

58 INFN, Sezione di Torino, Turin, Italy

59 INFN, Sezione di Trieste, Trieste, Italy

60 Inha University, Incheon, Republic of Korea

61 Institut de Physique Nucléaire d’Orsay (IPNO), Institut National de
Physique Nucléaire et de Physique des Particules (IN2P3/CNRS), Université de
Paris-Sud, Université Paris-Saclay, Orsay, France

62 Institute for Nuclear Research, Academy of Sciences, Moscow, Russia

63 Institute for Subatomic Physics, Utrecht University/Nikhef, Utrecht,
Netherlands

64 Institute for Theoretical and Experimental Physics, Moscow, Russia

65 Institute of Experimental Physics, Slovak Academy of Sciences, Košice,
Slovakia

66 Institute of Physics, Homi Bhabha National Institute, Bhubaneswar, India

67 Institute of Physics of the Czech Academy of Sciences, Prague, Czech
Republic

68 Institute of Space Science (ISS), Bucharest, Romania

69 Institut für Kernphysik, Johann Wolfgang Goethe-Universität Frankfurt,
Frankfurt, Germany

70 Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México,
Mexico City, Mexico

71 Instituto de Física, Universidade Federal do Rio Grande do Sul (UFRGS),
Porto Alegre, Brazil

72 Instituto de Física, Universidad Nacional Autónoma de México, Mexico City,
Mexico

73 iThemba LABS, National Research Foundation, Somerset West, South Africa

74 Johann-Wolfgang-Goethe Universität Frankfurt Institut für Informatik,
Fachbereich Informatik und Mathematik, Frankfurt, Germany

75 Joint Institute for Nuclear Research (JINR), Dubna, Russia

76 Korea Institute of Science and Technology Information, Daejeon, Republic of
Korea

77 KTO Karatay University, Konya, Turkey

78 Laboratoire de Physique Subatomique et de Cosmologie, Université Grenoble-
Alpes, CNRS-IN2P3, Grenoble, France

79 Lawrence Berkeley National Laboratory, Berkeley, California, United States

80 Lund University Department of Physics, Division of Particle Physics, Lund,
Sweden

81 Nagasaki Institute of Applied Science, Nagasaki, Japan

82 Nara Women’s University (NWU), Nara, Japan

83 National and Kapodistrian University of Athens, School of Science,
Department of Physics , Athens, Greece

84 National Centre for Nuclear Research, Warsaw, Poland

85 National Institute of Science Education and Research, Homi Bhabha National
Institute, Jatni, India

86 National Nuclear Research Center, Baku, Azerbaijan

87 National Research Centre Kurchatov Institute, Moscow, Russia

88 Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark

89 Nikhef, National institute for subatomic physics, Amsterdam, Netherlands

90 NRC Kurchatov Institute IHEP, Protvino, Russia

91 NRNU Moscow Engineering Physics Institute, Moscow, Russia

92 Nuclear Physics Group, STFC Daresbury Laboratory, Daresbury, United Kingdom

93 Nuclear Physics Institute of the Czech Academy of Sciences, Řež u Prahy,
Czech Republic

94 Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States

95 Ohio State University, Columbus, Ohio, United States

96 Petersburg Nuclear Physics Institute, Gatchina, Russia

97 Physics department, Faculty of science, University of Zagreb, Zagreb,
Croatia

98 Physics Department, Panjab University, Chandigarh, India

99 Physics Department, University of Jammu, Jammu, India

100 Physics Department, University of Rajasthan, Jaipur, India

101 Physikalisches Institut, Eberhard-Karls-Universität Tübingen, Tübingen,
Germany

102 Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg,
Heidelberg, Germany

103 Physik Department, Technische Universität München, Munich, Germany

104 Research Division and ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum
für Schwerionenforschung GmbH, Darmstadt, Germany

105 Rudjer Bošković Institute, Zagreb, Croatia

106 Russian Federal Nuclear Center (VNIIEF), Sarov, Russia

107 Saha Institute of Nuclear Physics, Homi Bhabha National Institute,
Kolkata, India

108 School of Physics and Astronomy, University of Birmingham, Birmingham,
United Kingdom

109 Sección Física, Departamento de Ciencias, Pontificia Universidad Católica
del Perú, Lima, Peru

110 Shanghai Institute of Applied Physics, Shanghai, China

111 St. Petersburg State University, St. Petersburg, Russia

112 Stefan Meyer Institut für Subatomare Physik (SMI), Vienna, Austria

113 SUBATECH, IMT Atlantique, Université de Nantes, CNRS-IN2P3, Nantes, France

114 Suranaree University of Technology, Nakhon Ratchasima, Thailand

115 Technical University of Košice, Košice, Slovakia

116 Technische Universität München, Excellence Cluster ’Universe’, Munich,
Germany

117 The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of
Sciences, Cracow, Poland

118 The University of Texas at Austin, Austin, Texas, United States

119 Universidad Autónoma de Sinaloa, Culiacán, Mexico

120 Universidade de São Paulo (USP), São Paulo, Brazil

121 Universidade Estadual de Campinas (UNICAMP), Campinas, Brazil

122 Universidade Federal do ABC, Santo Andre, Brazil

123 University College of Southeast Norway, Tonsberg, Norway

124 University of Cape Town, Cape Town, South Africa

125 University of Houston, Houston, Texas, United States

126 University of Jyväskylä, Jyväskylä, Finland

127 University of Liverpool, Liverpool, United Kingdom

128 University of Tennessee, Knoxville, Tennessee, United States

129 University of the Witwatersrand, Johannesburg, South Africa

130 University of Tokyo, Tokyo, Japan

131 University of Tsukuba, Tsukuba, Japan

132 Université Clermont Auvergne, CNRS/IN2P3, LPC, Clermont-Ferrand, France

133 Université de Lyon, Université Lyon 1, CNRS/IN2P3, IPN-Lyon, Villeurbanne,
Lyon, France

134 Université de Strasbourg, CNRS, IPHC UMR 7178, F-67000 Strasbourg, France,
Strasbourg, France

135 Université Paris-Saclay Centre d¿Études de Saclay (CEA), IRFU, Department
de Physique Nucléaire (DPhN), Saclay, France

136 Università degli Studi di Foggia, Foggia, Italy

137 Università degli Studi di Pavia and Sezione INFN, Pavia, Italy

138 Università di Brescia and Sezione INFN, Brescia, Italy

139 Variable Energy Cyclotron Centre, Homi Bhabha National Institute, Kolkata,
India

140 Warsaw University of Technology, Warsaw, Poland

141 Wayne State University, Detroit, Michigan, United States

142 Westfälische Wilhelms-Universität Münster, Institut für Kernphysik,
Münster, Germany

143 Wigner Research Centre for Physics, Hungarian Academy of Sciences,
Budapest, Hungary

144 Yale University, New Haven, Connecticut, United States

145 Yonsei University, Seoul, Republic of Korea