2018 106 9 May

$\mathrm{\rho(770)^{0}}$ in pp and Pb–Pb collisions

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

The production of the $\mathrm{\rho(770)^{0}}$ meson has been measured at mid-
rapidity $(|y|<0.5)$ in pp and centrality differential Pb–Pb collisions at
$\sqrt{s_{\mathrm{NN}}}=$ 2.76 TeV with the ALICE detector at the Large Hadron
Collider. The particles have been reconstructed in the
$\mathrm{\rho(770)^{0}}\rightarrow\pi^{+}\pi^{-}$ decay channel in the
transverse momentum ($p_{\mathrm{T}}$) range $0.5-11$
$\mathrm{GeV}\kern-1.79993pt/\kern-0.89996ptc$. A centrality dependent
suppression of the ratio of the integrated yields
$2\mathrm{\rho(770)^{0}}/(\pi^{+}+\pi^{-})$ is observed. The ratio decreases
by $\sim 40\%$ from pp to central Pb–Pb collisions. A study of the
$p_{\mathrm{T}}$-differential $2\mathrm{\rho(770)^{0}}/(\pi^{+}+\pi^{-})$
ratio reveals that the suppression occurs at low transverse momenta,
$p_{\mathrm{T}}<2$ $\mathrm{GeV}\kern-1.79993pt/\kern-0.89996ptc$. At higher
momentum, particle ratios measured in heavy-ion and pp collisions are
consistent. The observed suppression is very similar to that previously
measured for the
$\mathrm{K^{*}\kern-0.89996pt(892)^{0}}\kern-1.79993pt/\mathrm{K}$ ratio and
is consistent with EPOS3 predictions that may imply that rescattering in the
hadronic phase is a dominant mechanism for the observed suppression.

##  1 Introduction

Due to its very short lifetime ($\tau\sim 1.3$ fm/$c$) the
$\mathrm{\rho(770)^{0}}$ meson is well suited to study various properties of
the interaction dynamics in nucleon-nucleon and heavy-ion collisions [1].
Previous measurements at LEP [2, 3, 4, 5] and RHIC [6] showed that properties
of $\mathrm{\rho(770)}$ mesons reconstructed in the two-pion decay channel are
modified in high-energy hadronic interactions and $e^{+}e^{-}$ annihilation.
At low momentum, reconstructed $\mathrm{\rho(770)}$ meson peaks were found to
be significantly distorted from the p-wave Breit-Wigner shape. The observed
modifications in the $\mathrm{\rho(770)^{0}}\rightarrow\pi^{+}\pi^{-}$ channel
were explained by rescattering of pions
($\pi^{+}\pi^{-}\rightarrow\mathrm{\rho(770)^{0}}\rightarrow\pi^{+}\pi^{-}$),
Bose-Einstein correlations between pions from $\mathrm{\rho(770)^{0}}$ decays
and pions in the surrounding matter, and interference between differently
produced $\pi^{+}\pi^{-}$ final states [7, 8, 9]. In general, the masses of
$\mathrm{\rho(770)^{0}}$ mesons produced in hadronic interactions were
measured to be systematically lower than the masses measured in $e^{+}e^{-}$
annihilation and a world-averaged difference of $\sim 10$
$\mathrm{MeV}\kern-1.79993pt/\kern-0.89996ptc^{2}$ was reported in [1]. It is
apparent that these effects depend on the charged pion density in the final
state and should also play an important role in proton-nucleus and nucleus-
nucleus collisions.

In heavy-ion collisions, properties of $\mathrm{\rho(770)^{0}}$ mesons can
additionally be affected by the hot and dense matter produced in such
collisions and by pseudo-elastic or elastic interactions in the late hadron
gas stage occuring between chemical and kinetic freeze out. In-medium
modification of $\mathrm{\rho(770)^{0}}$ mesons was proposed as one of the
signals for chiral symmetry restoration [10, 11, 12]. Dilepton continuum
measurements in heavy-ion collisions at the SPS [13, 14, 15, 16, 17, 18, 19,
20] and RHIC [21, 22, 23] indeed exhibit an excess of low-$p_{\mathrm{T}}$
dilepton pairs below the mass of the $\mathrm{\rho(770)^{0}}$ with respect to
a hadronic cocktail from all known sources. Results at the SPS and RHIC are
well reproduced by models, which assume that $\mathrm{\rho(770)^{0}}$ mesons
are regenerated via $\pi^{+}\pi^{-}$ annihilation throughout the hadron
fireball lifetime and freeze out later than the other, longer-lived hadrons.
The low-mass dilepton excess is thus identified as the thermal radiation
signal from the hadron gas phase, with broadening of the
$\mathrm{\rho(770)^{0}}$ meson spectral function from the scattering off
baryons in the dense hadronic medium and thermal radiation from the QGP. In
heavy-ion collisions, rescattering and regeneration are expected to occur
between chemical and kinetic freeze-out, affecting the final state yields and
peak shapes of short-lived resonances [24, 25, 26]. Rescattering of daughter
particles with the surrounding hadrons changes the kinematics of the decay and
some of the resonances can no longer be reconstructed. However the process of
regeneration, in which pseudo-elastic scattering of hadrons results in the
production of resonances, tends to increase the yields. The cumulative effect
depends on the lifetime of the hadronic phase and that of the resonance, as
well as on particle cross sections and medium density. Previous measurements
at RHIC and the Large Hadron Collider (LHC) showed suppressed production of
$\mathrm{K^{*}\kern-0.89996pt(892)^{0}}$ [27, 28] and $\Lambda$(1520) [29] but
no effect for longer-lived resonances such as the $\upphi(1020)$ [27, 30] and
$\Sigma$(1385)± [29] in central heavy-ion collisions. These results are
qualitatively consistent with expectations from rescattering and regeneration
in the hadronic phase. These measurements allowed for model-dependent
estimates of the hadronic phase lifetime of at least $2-4$ fm/$c$ in central
collisions [27, 29]. With the addition of the very short-lived
$\mathrm{\rho(770)^{0}}$ meson to this study, one can gain additional insight
into processes occurring in the late hadronic phase. A measurement of
$\mathrm{\rho(770)^{0}}$ mesons at high $p_{\mathrm{T}}$ also contributes to
the systematic study of parton energy loss via a measurement of leading hadron
suppression [31, 32, 33].

The measurement of $\mathrm{\rho(770)^{0}}\rightarrow\pi^{+}\pi^{-}$ in heavy-
ion collisions was done only in peripheral Au–Au collisions at
$\sqrt{s_{\mathrm{NN}}}=$ 200 GeV, where the ratio of integrated yields,
$2\mathrm{\rho(770)^{0}}/(\pi^{+}+\pi^{-})$ was found to be consistent with
that in pp collisions and the reconstructed mass of the
$\mathrm{\rho(770)^{0}}$ was shifted to lower values [6]. In this paper,
production of $\mathrm{\rho(770)^{0}}$ mesons is studied in the
$\mathrm{\rho(770)^{0}}\rightarrow\pi^{+}\pi^{-}$ decay channel in pp and
centrality differential Pb–Pb collisions at $\sqrt{s_{\mathrm{NN}}}=$ 2.76
TeV, including in the 0-20% most central Pb–Pb collisions. Measurements in the
hadronic decay channel do not have enough sensitivity for a detailed study of
the reconstructed $\mathrm{\rho(770)^{0}}$ meson peak shape. As a result,
particle yields can be extracted only by using a certain peak model with a
limited number of parameters. At present, there are no measurements for the
$\mathrm{\rho(770)^{0}}$ meson yields or line shapes available in the di-
lepton decay channels at LHC energies. Besides, sensitivity to the in-medium
spectral function of the $\mathrm{\rho(770)^{0}}$ is expected to be different
in the di-lepton and the hadronic decay channels. Measurements in the di-
lepton channels are sensitive to the whole evolution of the system since
leptons leave the fireball mostly unaffected. Measurements in the hadronic
channel, because of rescattering and regeneration, should be more sensitive to
$\mathrm{\rho(770)^{0}}$ mesons, which decay late in the evolution of the
hadron gas, where the medium density is low and the mean free path of the
decay pions is large. Prediction of the $\mathrm{\rho(770)^{0}}$ peak shape in
the hadronic channel should rely on the models that describe the full dynamics
of heavy-ion collisions, including the late hadronic phase. An example of such
studies performed for $\mathrm{K^{*}\kern-0.89996pt(892)^{0}}$ can be found in
[34]. Similar studies are not yet available for $\mathrm{\rho(770)^{0}}$. In
this work, the yields of $\mathrm{\rho(770)^{0}}$ mesons in pp collisions in
different $p_{\mathrm{T}}$ bins were extracted by using a p-wave relativistic
Breit-Wigner function corrected for phase space, a mass dependent
reconstruction efficiency and pion interference as described by the Söding
parameterization [35]. The peak position was kept as a free parameter. Due to
the lack of detailed predictions for the $\mathrm{\rho(770)^{0}}$ meson peak
shape as a function of transverse momentum and centrality in heavy-ion
collisions, the same model was also used in Pb–Pb collisions.

The paper is organized as follows. Details of the data analysis and the peak
model are described in Section 2. Sections 3 and 4 present details on the
normalization and corrections used to obtain the invariant differential yields
of $\mathrm{\rho(770)^{0}}$ mesons in pp and Pb–Pb collisions. Results,
including $\mathrm{\rho(770)^{0}}$ meson yields, reconstructed masses,
particle ratios and nuclear modification factors are presented in Section 5
and compared to model predictions where available. For the remainder of this
paper, the $\mathrm{\rho(770)^{0}}$ will be denoted by the symbol
$\mathrm{\rho^{0}}$ and the half sum of the charged pion yields
$(\pi^{+}+\pi^{-})/2$ as $\pi$.

##  2 Data analysis

###  2.1 Event and track selection

In this work, the production of $\mathrm{\rho^{0}}$ mesons is measured at mid-
rapidity $(|y|<0.5)$ in Pb–Pb and pp collisions at $\sqrt{s_{\mathrm{NN}}}=$
2.76 TeV using the data samples collected by the ALICE experiment at the LHC
during the 2010 and 2011 data taking periods, respectively. The experimental
setup and the event selection criteria for these periods are described in
detail in previous ALICE publications on resonance production [27, 36].

The main detector subsystems used in this analysis are the V0 detectors, the
Inner Tracking System (ITS), the Time Projection Chamber (TPC) and the Time-
of-Flight (TOF) detector [37]. The minimum bias trigger in pp collisions was
configured to obtain high efficiency for hadronic interactions and required at
least one hit in either of the V0 detectors (V0A and V0C) or in the Silicon
Pixel Detector (SPD), which constitutes the two innermost layers of the ITS.
In Pb–Pb collisions, the minimum bias trigger required at least two out of the
following three conditions: (i) two hits in the outer layer of the SPD, (ii) a
signal in V0A, (iii) a signal in V0C [38]. The collision centrality is
determined on the basis of the multiplicity measured in the V0 detectors.
Glauber-model simulations are used to estimate the average number of
participants ($\langle N_{\mathrm{part}}\rangle$) and number of binary
inelastic nucleon-nucleon collisions ($\langle N_{\mathrm{coll}}\rangle$) for
each selected centrality interval [39, 40]. The number of analyzed minimum
bias events is equal to about $6\times 10^{7}$ in pp collisions, corresponding
to an integrated luminosity of
$\mathcal{L}_{int}=N_{\mathrm{MB}}/\sigma_{\mathrm{MB}}=1.1$ nb-1, where
$N_{\mathrm{MB}}$ and $\sigma_{\mathrm{MB}}=(55.4\pm 1.0)$ mb are the number
and cross section of pp collisions passing the minimum bias trigger conditions
[41]. In Pb–Pb collisions the number of analyzed events is $17.5\times
10^{6}$. The TPC is used to reconstruct charged particle tracks with the
requirement that the track has crossed at least 70 read-out rows out of a
maximum 159 [42]. Only high-quality tracks reconstructed with the TPC and ITS
are selected for analysis; tracks are required to be matched to the primary
vertex within 2 cm in the longitudinal direction and within 7$\sigma$ in the
transverse plane, where $\sigma$ is (0.0015 + 0.0050/$p_{\mathrm{T}}^{1.1}$)
cm for pp and (0.0026 + 0.0050/$p_{\mathrm{T}}^{1.01}$) cm for Pb–Pb [27],
with $p_{\mathrm{T}}$ in units of
$\mathrm{GeV}\kern-1.79993pt/\kern-0.89996ptc$. The primary vertex is required
to be within $\pm 10$ cm of the detector center along the beam axis. Tracks
are required to have a minimum transverse momentum of 150
$\mathrm{MeV}\kern-1.79993pt/\kern-0.89996ptc$ in pp collisions and 400
$\mathrm{MeV}\kern-1.79993pt/\kern-0.89996ptc$ in Pb–Pb collisions and a
pseudorapidity of $|\eta|<0.8$. The higher $p_{\mathrm{T}}$ cut in Pb–Pb
collisions was needed to improve the signal-to-background ratio at low and
intermediate momentum. To be identified as charged pions, reconstructed tracks
in pp collisions need to have a specific ionisation energy loss
$\mathrm{d}E\kern-1.79993pt/\kern-0.89996pt\mathrm{d}x$ measured in the TPC
within $2\sigma_{\mathrm{TPC}}$ of the expected value. For Pb–Pb collisions,
particles with a signal in the TOF subsystem are identified by requiring the
time-of-flight and $\mathrm{d}E\kern-1.79993pt/\kern-0.89996pt\mathrm{d}x$ to
be within $2\sigma_{\mathrm{TOF}}$ and $5\sigma_{\mathrm{TPC}}$ of the
expected values, respectively. Particles without a signal in the TOF are
identified in the same way as in pp collisions. The $\sigma_{\mathrm{TPC}}$ is
about 5% for isolated tracks and 6.5% for central Pb–Pb collisions. The
typical value of $\sigma_{\mathrm{TOF}}$ is about 80 ps.

###  2.2 Yield extraction

Yields of $\mathrm{\rho^{0}}$ mesons for each $p_{\mathrm{T}}$ and centrality
interval are measured by calculating invariant mass distributions of
oppositely charged identified pions ($\pi^{+}\pi^{-}$ pairs). The
combinatorial background is estimated using the like-sign method: this
background is $2\sqrt{N^{++}N^{--}}$, where $N^{++}$ and $N^{--}$ are the
numbers of $\pi^{+}\pi^{+}$ and $\pi^{-}\pi^{-}$ pairs within the same event,
respectively. In addition to the uncorrelated combinatorial background, the
like-sign method also partly subtracts the minijet [43] contribution in the
background; this is the main reason why it is preferred to the mixed-event
approach in this analysis. However, production of like-sign and opposite-sign
pairs in jets differ and a perfect background description is not expected.
Examples of invariant mass distributions after subtraction of the like-sign
background in minimum bias pp, 0–20% and 60–80% central Pb–Pb collisions at
$\sqrt{s_{\mathrm{NN}}}=$ 2.76 TeV are shown in Fig. 1.

Figure 1: (Color online) Invariant mass distributions for $\pi^{+}\pi^{-}$
pairs after subtraction of the like-sign background. Plots on the left and
right are for the low and high transverse momentum intervals, respectively.
Examples are shown for minimum bias pp, 0–20% and 60–80% central Pb–Pb
collisions at $\sqrt{s_{\mathrm{NN}}}=$ 2.76 TeV. Solid red curves represent
fits to the function described in the text. Colored dashed curves represent
different components of the fit function, which includes a smooth remaining
background as well as contributions from $\mathrm{K_{S}^{0}}$,
$\mathrm{\rho^{0}}$, $\mathrm{\omega\kern-0.89996pt(782)}$,
$\mathrm{K^{*}\kern-0.89996pt(892)^{0}}$, $\mathrm{f_{0}\kern-0.89996pt(980)}$
and $\mathrm{f_{2}\kern-0.89996pt(1270)}$. See text for details.

After subtraction of the like-sign background, the resulting distributions
contain the remaining correlated background from minijets and pairs from
hadronic decays. The latter has a very complex shape, which depends on
$\pi^{+}\pi^{-}$ pair invariant mass and transverse momentum. The main
contributions to the correlated background are: (i)
$\mathrm{\omega\kern-0.89996pt(782)}\rightarrow\pi^{0}\pi^{+}\pi^{-}$,
$\mathrm{\omega\kern-0.89996pt(782)}\rightarrow\pi^{+}\pi^{-}$,
$\mathrm{f_{0}\kern-0.89996pt(980)}\rightarrow\pi^{+}\pi^{-}$,
$\mathrm{f_{2}\kern-0.89996pt(1270)}\rightarrow\pi^{+}\pi^{-}$ and
$\mathrm{K_{S}^{0}}\rightarrow\pi^{+}\pi^{-}$, (ii)
$\mathrm{K^{*}\kern-0.89996pt(892)^{0}}\rightarrow$$K^{\pm}\pi^{\mp}$, where
the charged kaon in the final state is reconstructed as a pion, and (iii)
$\eta\rightarrow\pi^{0}\pi^{+}\pi^{-}$,
$\eta^{{}^{\prime}}$(958)$\rightarrow\eta\pi^{+}\pi^{-}$ and
$\upphi(1020)\rightarrow\mathrm{K}^{-}\mathrm{K}^{+}$ decays. The first two
contributions overlap with the wide $\mathrm{\rho^{0}}$ meson peak and need to
be correctly accounted for as described in Section 2.1.2. The last
contribution can be neglected if the analysis is limited to a mass range of
$M_{\mathrm{\pi^{+}\pi^{-}}}>0.4$
$\mathrm{GeV}\kern-1.79993pt/\kern-0.89996ptc^{2}$. Contributions from
misreconstructed decays of heavier hadrons do not result in peaked structures
and were estimated to be negligible.

In order to extract the $\mathrm{\rho^{0}}$ yields, the invariant mass
distributions after subtraction of the combinatorial like-sign background are
fitted with a function that accounts for all known correlated contributions to
the $\pi^{+}\pi^{-}$ mass distribution. In this section, we discuss the
assumptions used to approximate different components of the background.

####  2.2.1 Background from minijets

The invariant mass distribution of $\pi^{+}\pi^{-}$ pairs has been extensively
studied using full event Monte-Carlo simulations of the experimental setup.
PYTHIA 6 [44] and HIJING [45] are used as event generators for pp and Pb–Pb
collisions, respectively. The produced particles and their decay products are
propagated through the ALICE detector using GEANT 3 [46]. Invariant mass
distributions for pairs of charged pions are accumulated after application of
the same event, track and particle identification cuts as in data. The study
shows that after subtraction of the like-sign background and known
contributions from $\mathrm{K_{S}^{0}}$, $\eta$, $\mathrm{\rho^{0}}$,
$\mathrm{\omega\kern-0.89996pt(782)}$,
$\mathrm{K^{*}\kern-0.89996pt(892)^{0}}$, $\eta^{{}^{\prime}}$(958),
$\mathrm{f_{0}\kern-0.89996pt(980)}$, $\upphi(1020)$ and
$\mathrm{f_{2}\kern-0.89996pt(1270)}$, the remaining background has a smooth
dependence on mass. Based on a dedicated study of PYTHIA simulations, this
remaining contribution is due to minijets. As described in [3, 4, 5], the
remaining background is parameterized with the following function:
$F_{\mathrm{BG}}(M_{\mathrm{\pi\pi}})=(M_{\mathrm{\pi\pi}}-2m_{\mathrm{\pi}})^{n}\cdot\mathrm{exp}(A+B\cdot
M_{\mathrm{\pi\pi}}+C\cdot M_{\mathrm{\pi\pi}}^{2})$, where $m_{\mathrm{\pi}}$
is the mass of the charged pion and $n$, $A$, $B$ and $C$ are fit parameters.
It has been checked that this function describes the remaining background in
Monte-Carlo events for all analyzed $p_{\mathrm{T}}$ and centrality intervals.
A lower order polynomial in the exponential would not provide enough
flexibility for the function to describe the remaining background in a wide
mass range. A higher order polynomial, while not improving the fit quality,
could result in unjustified fluctuations of the background function. When a
polynomial is tried as a fit function, it needs larger number of fit
parameters to describe the background in the same mass range. Parameters of
the background function are not constrained in fits to data.

####  2.2.2 Contributions from $\mathrm{K_{S}^{0}}$,
$\mathrm{\omega\kern-0.89996pt(782)}$ and
$\mathrm{K^{*}\kern-0.89996pt(892)^{0}}$

The production of $\mathrm{K^{*}\kern-0.89996pt(892)^{0}}$ mesons in pp and
Pb–Pb collisions at $\sqrt{s_{\mathrm{NN}}}=$ 2.76 TeV was measured in [27,
36]. The yield of $\mathrm{K_{S}^{0}}$ mesons in pp collisions is estimated as
$(\mathrm{K}^{+}+\mathrm{K}^{-})/2$ using the charged kaon measurements
published in [47]. For Pb–Pb collisions, the production of
$\mathrm{K_{S}^{0}}$ mesons was measured in [48]. The production of
$\mathrm{\omega\kern-0.89996pt(782)}$ mesons has not been measured in the
collision systems under study. However, it has been estimated using procedures
similar to those previously used in calculations of hadronic cocktails in the
dilepton continuum or direct photon measurements [21, 23, 49, 50].

Contributions from $\mathrm{K_{S}^{0}}$, $\mathrm{\omega\kern-0.89996pt(782)}$
and $\mathrm{K^{*}\kern-0.89996pt(892)^{0}}$ are approximated with templates
extracted from Monte-Carlo simulations and normalized to known yields. The
template shapes are simulated by applying the same analysis cuts as in data
and reconstructing the $\mathrm{K_{S}^{0}}$,
$\mathrm{\omega\kern-0.89996pt(782)}$ and
$\mathrm{K^{*}\kern-0.89996pt(892)^{0}}$ mass shapes in the $\pi^{+}\pi^{-}$
channel separately for each $p_{\mathrm{T}}$ and centrality interval used in
the $\mathrm{\rho^{0}}$ analysis. Then the templates are normalized to the
independently measured $\mathrm{K_{S}^{0}}$,
$\mathrm{\omega\kern-0.89996pt(782)}$ and
$\mathrm{K^{*}\kern-0.89996pt(892)^{0}}$ yields in the corresponding
intervals, corrected for the branching ratios and the acceptance times
reconstruction efficiency values ($A\times\varepsilon_{\mathrm{rec}}$,
hereafter “efficiency”) estimated in simulations.

Measurements of the $\mathrm{\omega\kern-0.89996pt(782)}$ meson
$p_{\mathrm{T}}$ spectrum are rare. A summary of the world-wide measurements
of $\mathrm{\omega\kern-0.89996pt(782)}$ mesons in pp collisions at different
energies is given in the left panel of Fig. 2 [51, 52]. The data are presented
in terms of the $\omega/\pi$ ratio. Most of the data come from PHENIX
measurements at $\sqrt{s}=$ 200 GeV. It is important to note that the
$\omega/\pi$ ratio does not depend on the collision energy within
uncertainties in the range $\sqrt{s}=62-200$ GeV. In this analysis, it is
assumed that the $\omega/\pi$ ratio stays constant in the range
$\sqrt{s}=200-2760$ GeV. This assumption is supported by other light-flavor
meson ratios like $K/\pi$, $\eta/\pi$ and $\phi/\pi$, which do not show any
significant energy dependence in pp collisions in the range
$\sqrt{s}=200-7000$ GeV [47, 53, 54, 55, 56, 57]. This assumption is also
confirmed with PYTHIA 6 [44] and PYTHIA 8 [58] calculations, which predict the
$\omega/\pi$ ratios in pp collisions at $\sqrt{s}=200$ GeV and $\sqrt{s}=2.76$
TeV to be consistent within 10%.

Figure 2: (Color online) Left: measured $\omega/\pi$ ratio as a function of
transverse momentum in pp collisions at $\sqrt{s}=62$ and $200$ GeV [51, 52].
The smooth curve shows the estimated $\omega/\pi$ ratio in pp collisions at
$\sqrt{s}=$ 2.76 TeV. Right: estimated $\omega/\pi$ ratio as a function of the
transverse momentum for 0–20% central Pb–Pb collisions at
$\sqrt{s_{\mathrm{NN}}}=$ 2.76 TeV. The shaded regions in the two panels
correspond to a $\pm 20\%$ variation of the ratio, see text for details.

For pp collisions at $\sqrt{s}=$ 2.76 TeV, the shape of the
$\mathrm{\omega\kern-0.89996pt(782)}$ $p_{\mathrm{T}}$ spectrum is
approximated using the fit to $\pi$ spectrum [47] with a
$m_{\mathrm{T}}$-scaling correction [59]. The function, which is fit to the
transverse momentum distribution of pions, is transformed into a production
spectrum of $\mathrm{\omega\kern-0.89996pt(782)}$ in two steps. First,
$p_{\mathrm{T}}^{\pi}$ of charged pions in the function is replaced with
$\sqrt{m_{\mathrm{\omega}}^{2}-m_{\mathrm{\pi}}^{2}+{p_{\mathrm{T}}^{\omega}}^{2}}$,
where $m_{\mathrm{\omega}}$ and $p_{\mathrm{T}}^{\omega}$ are the mass and
transverse momentum of the $\omega$ meson. Second, the resulting function is
scaled to the $\omega/\pi$ ratio measured at high transverse momentum. Based
on the left panel of Fig. 2, the ratio is normalized to $\omega/\pi=0.81$,
which is in agreement with the value of $\omega/\pi=0.81\pm 0.02\pm 0.09$
measured by PHENIX in pp collisions at $\sqrt{s}=200$ GeV [51]. The ratio of
the derived $\mathrm{\omega\kern-0.89996pt(782)}$ spectrum to the measured
$\pi$ spectrum is shown with a curve in the same figure. The shaded region
corresponds to a $\pm 20\%$ variation of the $\omega/\pi$ ratio, which is used
in Section 5 to estimate the systematic uncertainty for measurement of the
$\mathrm{\rho^{0}}$ yields.

For Pb–Pb collisions one has to additionally account for radial flow that
modifies the shapes of particle production spectra at low and intermediate
transverse momenta. The strength of the radial flow for each centrality
interval is estimated by simultaneous fits of the charged pion, kaon and
(anti)proton production spectra [60, 61] with Tsallis Blast-Wave (TBW)
functions [62]. The non-extensivity parameter $q$ is set to be equal for
mesons and baryons, thus keeping all fit parameters the same for all
particles, except for particle masses and normalizations. Pions, kaons and
protons are fit in similar $p_{\mathrm{T}}$ ranges, from the lowest measured
momentum ($0.1$ $\mathrm{GeV}\kern-1.79993pt/\kern-0.89996ptc$, $0.2$
$\mathrm{GeV}\kern-1.79993pt/\kern-0.89996ptc$ and $0.3$
$\mathrm{GeV}\kern-1.79993pt/\kern-0.89996ptc$ for pions, kaons and protons,
respectively) up to $3.5$ $\mathrm{GeV}\kern-1.79993pt/\kern-0.89996ptc$. In
this range, the fits reproduce the measured results within the experimental
uncertainties. Fits performed in different $p_{\mathrm{T}}$ ranges, $0.1-2$
$\mathrm{GeV}\kern-1.79993pt/\kern-0.89996ptc$ and $0.5-3.5$
$\mathrm{GeV}\kern-1.79993pt/\kern-0.89996ptc$ produce very similar results
and therefore lead to negligible systematic ucncertainties in this procedure.
For all fits, it has been checked that the total integrated yields extracted
from the fit curves are consistent with the published values within
uncertainties. The expected $\mathrm{\omega\kern-0.89996pt(782)}$
$p_{\mathrm{T}}$ spectrum is parameterized with a TBW function with the
$\mathrm{\omega\kern-0.89996pt(782)}$ mass [1] and all other fit parameters
set to the values from the combined fit. This function is normalized so that
the ratio of the integrated yields $\omega/\pi=0.1$. This value of the ratio
was previously measured with high precision in pp and $e^{+}e^{-}$ collisions
[3, 63]. Measurements of the ratio in heavy-ion collisions are available only
from STAR in Au–Au collisions at $\sqrt{s_{\mathrm{NN}}}=$ 200 GeV:
$\omega/\pi=0.086\pm 0.019$ [21]. This measurement is in good agreement with
pp results. This is similar to the $K$/$\pi$ and $p$/$\pi$ ratios, which vary
only within $\sim 20\%$ from pp to central heavy-ion collisions for
$\sqrt{s_{\mathrm{NN}}}=200-2760$ GeV [60]. The resulting $\omega/\pi$ ratio
is shown in the right panel of Fig. 2 with a solid red curve. The shaded
region around the curve corresponds to a $\pm 20\%$ variation of the ratio,
which is used to estimate the systematic uncertainty (see Section 5). Up to
$p_{\mathrm{T}}=3.5$ $\mathrm{GeV}\kern-1.79993pt/\kern-0.89996ptc$ the ratio
is determined from TBW fits as described above. It is important to note that
two alternative approaches are also used for estimation of the
$\mathrm{\omega\kern-0.89996pt(782)}$ production spectrum in this
$p_{\mathrm{T}}$ range. In these approaches, only the production spectra for
charged pions and kaons or only the spectra for charged kaons and
(anti)protons are used to fix parameters of the TBW function. Both approaches
result in $\omega/\pi$ ratios which are consistent with the default value
within the shaded region.

At very high transverse momentum it is assumed that the $\omega/\pi$ ratio
returns to the same values measured in pp collisions (a
$m_{\mathrm{T}}$-scaled $\pi^{\pm}$ spectrum), similar to what is observed for
other ratios like $K$/$\pi$ and $p$/$\pi$ [47]. This assumption is also
confirmed by PHENIX in Au–Au collisions at $\sqrt{s_{\mathrm{NN}}}=$ 200 GeV
where the $\omega/\pi$ ratio was measured at high $p_{\mathrm{T}}$ to be
$\omega/\pi=0.82\pm 0.09\pm 0.06$ [51], very close to the value in pp
collisions. The exact $p_{\mathrm{T}}$ value at which the influence of radial
flow becomes negligible for $\mathrm{\omega\kern-0.89996pt(782)}$ mesons is
not known. It is expected to be mass dependent and sit in between
$p_{\mathrm{T}}$ values where the $K$/$\pi$ (Point A) and $p$/$\pi$ (point B)
ratios measured in Pb–Pb collisions merge with those measured in pp
collisions. The dashed lines show how the $\omega/\pi$ ratio would look in the
transition region if the merging point to the $m_{\mathrm{T}}$-scaled curve
was the same as for $K$/$\pi$ or $p$/$\pi$. For the nominal $\omega/\pi$ ratio
we choose the average of the $\omega/\pi$ ratios obtained for these two
extreme cases, shown with a solid line. The merging point for
$\mathrm{\omega\kern-0.89996pt(782)}$ is varied between the merging points for
$K$/$\pi$ and $p$/$\pi$ for a study of systematic uncertainties. One can see
that the two extreme cases for the transition are within the shaded region.

####  2.2.3 Contributions from $\mathrm{\rho^{0}}$,
$\mathrm{f_{0}\kern-0.89996pt(980)}$ and $\mathrm{f_{2}\kern-0.89996pt(1270)}$

Contributions from $\mathrm{\rho^{0}}$, $\mathrm{f_{0}\kern-0.89996pt(980)}$
and $\mathrm{f_{2}\kern-0.89996pt(1270)}$ mesons are described analytically.
The shapes of these resonances are described with a relativistic Breit-Wigner
function (rBW) [64, 65]:

$\mathrm{rBW}(M_{\mathrm{\pi\pi}})=\frac{AM_{\mathrm{\pi\pi}}M_{\mathrm{0}}\Gamma(M_{\mathrm{\pi\pi}})}{(M_{\mathrm{0}}^{2}-M_{\mathrm{\pi\pi}}^{2})^{2}+M_{\mathrm{0}}^{2}\Gamma^{2}(M_{\mathrm{\pi\pi}})},$
(1)

where $M_{\mathrm{0}}$ is the mass of the resonance under study and $A$ is a
normalization constant. For wide resonances one should account for the
dependence of the resonance width on mass:

$\Gamma(M_{\mathrm{\pi\pi}})=\left(\frac{M_{\mathrm{\pi\pi}}^{2}-4m_{\mathrm{\pi}}^{2}}{M_{\mathrm{0}}^{2}-4m_{\mathrm{\pi}}^{2}}\right)^{\mathrm{(2J+1)/2}}\times\Gamma_{\mathrm{0}}\times
M_{\mathrm{0}}/M_{\mathrm{\pi\pi}},$ (2)

where $\Gamma_{\mathrm{0}}$ is the width of the resonance, $m_{\mathrm{\pi}}$
is the charged pion mass and $J$ is equal to 0 for
$\mathrm{f_{0}\kern-0.89996pt(980)}$, 1 for $\mathrm{\rho^{0}}$ and 2 for
$\mathrm{f_{2}\kern-0.89996pt(1270)}$. The masses of $\mathrm{\rho^{0}}$,
$\mathrm{f_{0}\kern-0.89996pt(980)}$ and $\mathrm{f_{2}\kern-0.89996pt(1270)}$
are kept as free parameters. As has been pointed out, measurements of
$\mathrm{\rho^{0}}$ mesons in the hadronic decay channel do not have enough
sensitivity for a detailed study of the resonance peak shape. As a result, the
width of the $\mathrm{\rho^{0}}$ is fixed to $149.3$
$\mathrm{GeV}\kern-1.79993pt/\kern-0.89996ptc^{2}$, which corresponds to the
resonance width in vacuum $147.8\pm 0.9$
$\mathrm{GeV}\kern-1.79993pt/\kern-0.89996ptc^{2}$ [1] convoluted with the
detector mass resolution extracted from simulations. Due to the large width of
the $\mathrm{\rho^{0}}$ peak, its smearing due to the mass resolution results
in a negligible change in the extracted yields. The width of the
$\mathrm{f_{0}\kern-0.89996pt(980)}$ is limited to be within 40-100
$\mathrm{MeV}\kern-1.79993pt/\kern-0.89996ptc^{2}$ and the width of the
$\mathrm{f_{2}\kern-0.89996pt(1270)}$ is fixed to $186.7$
$\mathrm{MeV}\kern-1.79993pt/\kern-0.89996ptc^{2}$ [1].

Since resonances can be produced through $\pi\pi$ scattering in the hadronic
phase, the reconstructed peaks can be affected by the phase space available
for pions. It was suggested in [6, 66, 67, 68] to use a Boltzmann factor to
account for the phase space correction

$PS(M_{\mathrm{\pi\pi}})=\frac{M_{\mathrm{\pi\pi}}}{\sqrt{M_{\mathrm{\pi\pi}}^{2}+p_{\mathrm{T}}^{2}}}\times\mathrm{exp}\negthickspace\left(-\sqrt{M_{\mathrm{\pi\pi}}^{2}+p_{\mathrm{T}}^{2}}/T\right),$
(3)

where $T$ is the kinetic freeze-out temperature, set to $160$ MeV in pp and
$120$ MeV in heavy-ion collisions [60, 69].

The $\mathrm{\rho^{0}}$, $\mathrm{f_{0}\kern-0.89996pt(980)}$ and
$\mathrm{f_{2}\kern-0.89996pt(1270)}$ resonances have quite large widths.
Efficiencies for these mesons can change with particle masses at a given
transverse momentum, resulting in distortion of the reconstructed peak shapes.
The effect is most prominent at low $p_{\mathrm{T}}$, where the efficiency
$A\times\varepsilon_{\mathrm{rec}}$ rapidly increases with mass and transverse
momentum. Therefore, the peak shapes for $\mathrm{\rho^{0}}$,
$\mathrm{f_{0}\kern-0.89996pt(980)}$ and $\mathrm{f_{2}\kern-0.89996pt(1270)}$
are corrected for the dependence of $A\times\varepsilon_{\mathrm{rec}}$ on the
particle masses. The corresponding corrections are evaluated from Monte-Carlo
simulations.

Previous measurements showed that $\mathrm{\rho^{0}}$ meson peaks
reconstructed in the $\pi^{+}\pi^{-}$ decay channel are distorted: the central
value (mass) was shifted to lower values by tens of
$\mathrm{MeV}\kern-1.79993pt/\kern-0.89996ptc^{2}$. This phenomenon was
studied in detail at LEP [2, 3, 4, 5] and was also observed at RHIC [6]. The
modification of the reconstructed $\mathrm{\rho^{0}}$ meson shape was
explained by Bose-Einstein correlations between identical pions in the final
state (including decay pions from short-lived $\mathrm{\rho^{0}}$ mesons) and
interference between final states which are either two directly produced pions
or two pions from $\mathrm{\rho^{0}}$ decays. Both effects result in a similar
modification of the peak shape, which at LEP was accounted for by including an
interference term parameterized by Söding [35] in the peak model

$f_{\mathrm{i}}(M_{\mathrm{\pi\pi}})=C\left(\frac{M_{\mathrm{0}}^{2}-M_{\mathrm{\pi\pi}}^{2}}{M_{\mathrm{\pi\pi}}\Gamma(M_{\mathrm{\pi\pi}})}\right)f_{\mathrm{s}}(M_{\mathrm{\pi\pi}}),$
(4)

where $f_{\mathrm{s}}(M_{\mathrm{\pi\pi}})$ is the default peak shape as
described above, $f_{\mathrm{i}}(M_{\mathrm{\pi\pi}})$ is the interference
term and $C$ is a free parameter that determines the strength of the
interference. Using this term in the peak model enhances the left side of the
reconstructed peak and suppresses the right side of the peak. If one fits the
distorted peak with the regular rBW function, the reconstructed mass is
shifted towards lower values and the fit quality is poor due to the distorted
tails. We note that RHIC [64] and LHC [65] measurements of photoproduction of
$\mathrm{\rho^{0}}$ mesons in ultra-peripheral heavy-ion collisions were
performed with this Söding correction included in the peak model and the
reconstructed parameters of $\mathrm{\rho^{0}}$ were found to be in agreement
with vacuum values. In this study, the extraction of $\mathrm{\rho^{0}}$ meson
yields is performed using peak models with and without the Söding interference
term. For the hadronic interactions the Söding correction is just empirical.
The peak model with the term somewhat better describes the measured peaks at
low momentum and leads to reconstructed meson masses closer to the accepted
vacuum value [1] and is used by default. The peak model without the
interference term is used in the evaluation of the systematic uncertainties.

In heavy-ion collisions, the shape of the $\mathrm{\rho^{0}}$ meson peak can
also be distorted due to chiral symmetry restoration [10, 11, 12] in the
earlier stages of the collisions and due to rescattering, regeneration,
correlations, and interference in the later stages [24, 25, 26]. The relative
strengths of these effects are not well understood and there are no detailed
predictions for the $p_{\mathrm{T}}$ and centrality dependence of
$\mathrm{\rho^{0}}$ peak modifications that take all of them into account. In
this analysis, we therefore limit our peak model to the effects discussed in
the preceding paragraphs.

In summary, the default $\mathrm{\rho^{0}}$ peak model used in this analysis
is the product of a relativistic Breit-Wigner function (with a mass-dependent
width), a phase-space factor, a mass-dependent efficiency correction, and a
Söding interference term. The same peak model, only without the interference
term, is used to fit the $\mathrm{f_{0}\kern-0.89996pt(980)}$ and
$\mathrm{f_{2}\kern-0.89996pt(1270)}$ peaks.

####  2.2.4 Fit results

The fitting function has eleven free parameters: the masses and yields of
$\mathrm{\rho^{0}}$, $\mathrm{f_{0}\kern-0.89996pt(980)}$ and
$\mathrm{f_{2}\kern-0.89996pt(1270)}$, the strength of the interference term
for $\mathrm{\rho^{0}}$, and four parameters for the smooth background
function $F_{\mathrm{BG}}(M_{\mathrm{\pi\pi}})$). The width of
$\mathrm{f_{0}\kern-0.89996pt(980)}$ is limited to be within 40–100
$\mathrm{MeV}\kern-1.79993pt/\kern-0.89996ptc^{2}$ [1]. Fits are performed in
the mass range $0.45<M_{\pi\pi}<1.7$
$\mathrm{GeV}\kern-1.79993pt/\kern-0.89996ptc^{2}$. The lower limit is
selected to include a contribution from $\mathrm{K_{S}^{0}}$ in the fit but
reject contributions from $\eta$, $\eta^{{}^{\prime}}(958)$ and $\upphi(1020)$
mesons, which are difficult to constrain. The upper limit is set to 1.7
$\mathrm{GeV}\kern-1.79993pt/\kern-0.89996ptc^{2}$ to account for tails from
the $\mathrm{\rho^{0}}$ and $\mathrm{f_{2}\kern-0.89996pt(1270)}$
contributions. Most of the contributions to the fitting function are well
separated in mass, thus reducing the uncertainties of the fit parameters.

Examples of the fits in minimum bias pp and 0–20% and 60–80% central Pb–Pb
collisions are shown in Fig. 1 for two different $p_{\mathrm{T}}$ intervals.
The $\chi^{2}\kern-1.79993pt/\kern-0.89996ptn_{\mathrm{dof}}$ values for the
fits are 1.1 (0.9), 0.8 (1.3) and 1.1 (1.2) for pp, 0-20% and 60-80% Pb–Pb
collisions at low(high) transverse momenta, respectively. The contributions of
the $\mathrm{K_{S}^{0}}$, $\mathrm{\omega\kern-0.89996pt(782)}$ and
$\mathrm{K^{*}\kern-0.89996pt(892)^{0}}$ are fixed to the measured particle
yields corrected for branching ratios and efficiencies. The smooth remaining
background is described with the function
$F_{\mathrm{BG}}(M_{\mathrm{\pi\pi}})$. The remaining contributions from
decays of $\mathrm{\rho^{0}}$, $\mathrm{f_{0}\kern-0.89996pt(980)}$ and
$\mathrm{f_{2}\kern-0.89996pt(1270)}$ mesons are described analytically using
the peak model from Section 2.1.3. All fits in different $p_{\mathrm{T}}$ and
centrality intervals result in very reasonable fit probabilities with
$\chi^{2}\kern-1.79993pt/\kern-0.89996ptn_{\mathrm{dof}}$ values close to
unity. The yields of $\mathrm{\rho^{0}}$ mesons are estimated by integrating
the $\mathrm{\rho^{0}}$ fitting function in the mass range from
$2m_{\mathrm{\pi}}$ to $1.7$
$\mathrm{GeV}\kern-1.79993pt/\kern-0.89996ptc^{2}$.

##  3 Simulations

Monte-Carlo simulations are used to evaluate the efficiencies for
$\mathrm{\rho^{0}}$, $\mathrm{K_{S}^{0}}$,
$\mathrm{\omega\kern-0.89996pt(782)}$ and
$\mathrm{K^{*}\kern-0.89996pt(892)^{0}}$ mesons in the $\pi^{+}\pi^{-}$
channel as well as to estimate the mass-dependent efficiency corrections for
$\mathrm{\rho^{0}}$, $\mathrm{f_{0}\kern-0.89996pt(980)}$ and
$\mathrm{f_{2}\kern-0.89996pt(1270)}$. PYTHIA 6 [44] and PHOJET [70, 71] were
used as event generators for pp collisions, while HIJING [45] was used to
simulate Pb–Pb collisions. Signals from the
$\mathrm{f_{0}\kern-0.89996pt(980)}$ and $\mathrm{f_{2}\kern-0.89996pt(1270)}$
resonances, which are not generated by these codes, were injected into the
simulations. The produced particles and their decay products were traced
through the detector materials using GEANT 3 [46]. For each analyzed
$p_{\mathrm{T}}$ and centrality interval, the efficiencies
$A\times\varepsilon_{\mathrm{rec}}$ are calculated as the ratio
$N_{\mathrm{rec}}/N_{\mathrm{gen}}$, where $N_{\mathrm{rec}}$ is the number of
reconstructed particles in the $\pi^{+}\pi^{-}$ channel after all event and
track selection cuts and $N_{\mathrm{gen}}$ is the number of generated mesons
within $|y|<0.5$ decaying in the
$\mathrm{\rho^{0}},\mathrm{K_{S}^{0}},\mathrm{\omega\kern-0.89996pt(782)},\mathrm{f_{0}\kern-0.89996pt(980)},\mathrm{f_{2}\kern-0.89996pt(1270)}\rightarrow\pi^{+}\pi^{-}$,
$\mathrm{\omega\kern-0.89996pt(782)}\rightarrow\pi^{0}\pi^{+}\pi^{-}$ and
$\mathrm{K^{*}\kern-0.89996pt(892)^{0}}\rightarrow$$K^{\pm}\pi^{\mp}$
channels. In general, the efficiency depends on the shape of the generated
particle $p_{\mathrm{T}}$ spectrum. Therefore, the $p_{\mathrm{T}}$ spectra of
the generated $\mathrm{K_{S}^{0}}$, $\mathrm{\omega\kern-0.89996pt(782)}$ and
$\mathrm{K^{*}\kern-0.89996pt(892)^{0}}$ mesons are re-weighted to their known
or expected shapes. The efficiencies for $\mathrm{\rho^{0}}$ are tuned
iteratively so that the shapes of the generated $p_{\mathrm{T}}$ spectra
approach the measured shapes.

Examples of efficiencies evaluated for $\mathrm{\rho^{0}}$ mesons in pp and
the most central Pb–Pb collisions as a function of transverse momentum are
shown in Fig. 3. The difference in the efficiencies between pp and Pb–Pb
collisions is expected and is due to the different minimum $p_{\mathrm{T}}$
cuts and particle identification strategies for daughter particles. In Pb–Pb
collisions, the efficiencies for $\mathrm{\rho^{0}}$ show mild (within 5%)
dependence on collision centrality with a decreasing trend towards more
central collisions.

Figure 3: (Color online) Acceptance times reconstruction efficiency
($A\times\varepsilon_{\mathrm{rec}}$) evaluated for $\mathrm{\rho^{0}}$ meson
in pp and central Pb–Pb collisions at $\sqrt{s_{\mathrm{NN}}}=$ 2.76 TeV.

##  4 Yield corrections

In pp collisions the differential transverse momentum spectrum is

$\frac{\mathrm{d}^{2}N}{\mathrm{d}p_{\mathrm{T}}\mathrm{d}y}=\frac{1}{N_{\mathrm{MB}}}\frac{\varepsilon_{\mathrm{trig}}}{\varepsilon_{\mathrm{vrtx}}}\frac{1}{A\times\varepsilon_{\mathrm{rec}}}\frac{1}{BR}\frac{N_{\mathrm{\mathrm{\rho^{0}}\rightarrow\pi\pi}}}{\Delta
y\Delta p_{\mathrm{T}}},$ (5)

where $N_{\mathrm{\mathrm{\rho^{0}}\rightarrow\pi\pi}}$ is the
$\mathrm{\rho^{0}}$ meson yield measured in a given rapidity ($\Delta y$) and
transverse momentum ($\Delta p_{\mathrm{T}}$) interval, $N_{\mathrm{MB}}$ is
the number of analyzed minimum bias events, $BR$ and
$A\times\varepsilon_{\mathrm{rec}}$ are the resonance branching ratio and
efficiency in the $\pi^{+}\pi^{-}$ decay channel,
$\varepsilon_{\mathrm{trig}}=(88.1^{+5.9}_{-3.5})\%$ is a trigger efficiency
correction to obtain resonance yields per inelastic pp collision [41] and
$\varepsilon_{\mathrm{vrtx}}=91\pm 2\%$ is a vertex cut efficiency correction
that accounts for the fraction of $\mathrm{\rho^{0}}$ mesons lost after
imposing the $z$-vertex cut of 10 cm at the stage of event selection. For the
trigger configuration used in this analysis, the number of $\mathrm{\rho^{0}}$
mesons in non-triggered events is negligible and no corresponding correction
is needed.

For Pb–Pb collisions the trigger and vertex cut efficiency corrections,
$\varepsilon_{\mathrm{trig}}$ and $\varepsilon_{\mathrm{vrtx}}$, are set to
unity. The number of minimum bias events $N_{\mathrm{MB}}$ is replaced with
the number of events analyzed in a given centrality interval.

##  5 Systematic uncertainties

The total systematic uncertainty is dominated by yield extraction, particle
identification and track selection cuts as well as by the global tracking
efficiency uncertainties as summarized in Table 1.

Source | pp | Pb–Pb
---|---|---
Yield extraction | 4–13 | 7–13
Particle identification | 4 | 5
Tracking and analysis cuts | 8–9 | 10
Total | 10–16 | 14–17
Table 1: Relative systematic uncertainties (in %) for $\mathrm{\rho^{0}}$
meson yields in pp and Pb–Pb collisions at $\sqrt{s_{\mathrm{NN}}}=$ 2.76 TeV.
The single valued uncertainties are $p_{\mathrm{T}}$ and centrality
independent. Values given in ranges correspond to minimum and maximum
uncertainties.

The yield extraction uncertainty is estimated by varying the
$\mathrm{\rho^{0}}$ meson peak shape, smooth background function, fitting
range, temperature parameter in the phase space correction and the relative
contributions of $\mathrm{K_{S}^{0}}$, $\mathrm{\omega\kern-0.89996pt(782)}$
and $\mathrm{K^{*}\kern-0.89996pt(892)^{0}}$ in the hadronic cocktail. Two
peak models, with or without the interference term, are used to extract the
$\mathrm{\rho^{0}}$ meson parameters from the invariant mass distributions.
Fits without the interference term result in lower but still acceptable fit
probabilities as well as in systematically lower yields and smaller
reconstructed masses. This is the only source of asymmetric systematic
uncertainties and it dominates the total uncertainties at low momentum. The
difference in the extracted yields is $\sim 10\%$ at low momentum and
decreases to $\sim 1\%$ for $4-6$
$\mathrm{GeV}\kern-1.79993pt/\kern-0.89996ptc$. For the smooth background
function, a fifth order polynomial has been used instead of the
$F_{\mathrm{BG}}(M_{\mathrm{\pi\pi}})$ function described in Section 2.1.1.
This polynomial has a larger number of fit parameters and could provide an
alternative description of the remaining background. The fitting range cannot
be varied at its lower edge: it is difficult to control the contributions from
$\eta$, $\eta^{{}^{\prime}}$(958) and $\phi$(1020) at invariant mass below
$0.45$ $\mathrm{GeV}\kern-1.79993pt/\kern-0.89996ptc^{2}$, but it is necessary
to account for $\mathrm{K_{S}^{0}}$ decays resulting in a peak at $0.5$
$\mathrm{GeV}\kern-1.79993pt/\kern-0.89996ptc^{2}$. Instead, the upper limit
of the fitting range is varied from $1.7$ to $1.1$
$\mathrm{GeV}\kern-1.79993pt/\kern-0.89996ptc^{2}$, thus excluding the
$\mathrm{f_{2}\kern-0.89996pt(1270)}$ from the fit and allowing the background
function to be more flexible in the narrower fitting range. The temperature
parameter in the phase space correction is varied by $\pm 25$ MeV to cover the
variation of the kinetic freeze-out temperature with multiplicity [60, 69].
The normalizations of the $\mathrm{K_{S}^{0}}$,
$\mathrm{\omega\kern-0.89996pt(782)}$ and
$\mathrm{K^{*}\kern-0.89996pt(892)^{0}}$ templates in the cocktail are
independently increased and decreased by the uncertainties of the particle
yields and efficiencies estimated to be $\pm 30\%$, $\pm 20\%$ and $\pm 25\%$,
respectively. The larger variation for $\mathrm{K_{S}^{0}}$ is due to the
statistical uncertainties of the efficiency, which is only 0.5% on average.
This results in negligible variation of the extracted $\mathrm{\rho^{0}}$
meson parameters. The large variation for
$\mathrm{\omega\kern-0.89996pt(782)}$ is dominated by uncertainties in the
determination of the $\omega/\pi$ ratio as described in Section 2.1.2. The
total yield extraction uncertainty varies from 13(10–13)% at low momentum to
4(8)% at intermediate momentum and to 6(7–8)% at high transverse momentum in
pp (Pb–Pb) collisions, with rather weak centrality dependence.

The particle identification uncertainty is estimated by varying the selection
criteria used in analysis. By default, in order to be identified,
reconstructed tracks are required to be within $2\sigma$ of the
$\mathrm{d}E\kern-1.79993pt/\kern-0.89996pt\mathrm{d}x$ or time-of-flight
values expected for charged pions in the TPC or TOF subsystems. The
corresponding uncertainty is defined as the difference between the default
value and the values obtained with ($-1.5\sigma_{\mathrm{TPC}}$,
$1.5\sigma_{\mathrm{TOF}}$) and ($-2.0\sigma_{\mathrm{TPC}}$,
$1.0\sigma_{\mathrm{TOF}}$) particle identification cuts. The latter cut is
included to provide maximum separation between pions and kaons, keeping the
efficiency for pions as high as possible. The resulting uncertainty for the
yields is estimated to be 4% in pp and 5% in Pb–Pb collisions with no
centrality dependence.

The global tracking efficiency uncertainty is defined by mismatches between
the measured data and Monte Carlo in the probabilities for TPC tracks to be
matched to signals in the ITS [27, 36]. The uncertainty for single tracks is
doubled to account for $\mathrm{\rho^{0}}$ mesons, which are reconstructed in
a decay channel with two charged tracks in the final state. The global
tracking uncertainty partially cancels out when ratios of integrated yields,
$\rho/\pi$, are calculated. The track selection cuts are varied to estimate
the corresponding changes in the fully corrected yields. It is found that the
results are sensitive to variation of the number of crossed rows in the TPC
and the primary vertex proximity cuts in the transverse plane for
reconstructed tracks. The combined systematic uncertainty for the differential
yields is estimated to be 8–9 (10)% in pp (Pb–Pb) collisions, with practically
no $p_{\mathrm{T}}$ or centrality dependence.

Uncertainties in the determination of centrality percentiles result in
normalization uncertainties for the measured $\mathrm{\rho^{0}}$ yields. The
corresponding uncertainties are estimated to be 0.6%, 1.5%, 2.95% and 5.85% in
0–20%, 20–40%, 40–60% and 60–80% central Pb–Pb collisions using the numbers
reported in [60].

The total systematic uncertainties are calculated as the sum in quadrature of
the different contributions and are summarized in Table 1.

##  6 Results and discussion

###  6.1 Particle masses

The dependence of the reconstructed $\mathrm{\rho^{0}}$ meson mass on
transverse momentum in minimum bias pp, 0–20% and 60–80% Pb–Pb collisions at
$\sqrt{s_{\mathrm{NN}}}=$ 2.76 TeV is shown in Fig. 4. The measurements for
the 20–40% and 40–60% centrality intervals are not shown here, but are similar
to the plotted results; these are available in the High Energy Physics Data
Repository. The systematic uncertainties, shown with boxes, account for mass
variations from all sources considered in Section 5. The asymmetric part of
the systematic uncertainties is from the systematically smaller masses
extracted for $\mathrm{\rho^{0}}$ mesons using the peak model without the
interference term. Two dashed horizontal lines in Fig. 4 correspond to the
$\mathrm{\rho^{0}}$ masses quoted in [1] for mesons produced in $e^{+}e^{-}$
annihilation and hadronic interactions. The difference between the values of
the masses can be explained by pion scattering as described in [72]. For pp
collisions, the reconstructed mass is consistent with the hadroproduced
$\mathrm{\rho^{0}}$-meson mass within uncertainties. In Pb–Pb collisions,
central values of the reconstructed masses are lower by up to $30$
$\mathrm{MeV}\kern-1.79993pt/\kern-0.89996ptc^{2}$ with no strong dependence
on collision centrality. However, rather large uncertainties prevent any
strong conclusions on the mass shift. The STAR data (not shown) also show a
tendency for lower masses for $\mathrm{\rho^{0}}$ mesons in 40–80% central
Au–Au collisions at $\sqrt{s_{\mathrm{NN}}}=$ 200 GeV [6].

Figure 4: Reconstructed masses of $\mathrm{\rho^{0}}$ mesons as a function of
transverse momentum in minimum bias pp, 0–20% and 60–80% Pb–Pb collisions at
$\sqrt{s_{\mathrm{NN}}}=$ 2.76 TeV. The statistical and systematic
uncertainties are shown as bars and boxes, respectively. The width of the
boxes is varied for visibility. The dashed lines show the $\mathrm{\rho^{0}}$
masses as given in [1].

###  6.2 Transverse momentum spectra

The differential yields measured for $\mathrm{\rho^{0}}$ mesons as a function
of transverse momentum in inelastic pp and centrality differential Pb–Pb
collisions at $\sqrt{s_{\mathrm{NN}}}=$ 2.76 TeV are shown in Figs. 5 and 6,
respectively. The measurements span a wide $p_{\mathrm{T}}$ range from $0.5$
to $11$ $\mathrm{GeV}\kern-1.79993pt/\kern-0.89996ptc$.

In Fig. 5, the $p_{\mathrm{T}}$ spectrum in pp collisions is compared to model
calculations from PYTHIA 8.14 (Monash 2013 tune) [58, 73], PHOJET [70, 71] and
PYTHIA 6 (Perugia 2011 tune) [74]. PYTHIA and PHOJET are event generators,
which simulate hadronization using the Lund String fragmentation model [75].
The lower panel of the figure shows the model-to-data ratios as lines and the
total uncertainty of the $\mathrm{\rho^{0}}$ measurement with a grey band. In
general, these models tend to overestimate $\mathrm{\rho^{0}}$-meson
production at low momentum, $p_{\mathrm{T}}<1$
$\mathrm{GeV}\kern-1.79993pt/\kern-0.89996ptc$. PHOJET underestimates
$\mathrm{\rho^{0}}$-meson production at intermediate momentum, the best
agreement with data is provided by PYTHIA 6 Perugia 2011.

Figure 5: (Color online) Differential yields of $\mathrm{\rho^{0}}$ as a
function of transverse momentum in inelastic pp collisions at $\sqrt{s}=$ 2.76
TeV. The statistical and systematic uncertainties are shown as bars and boxes,
respectively. The results are compared with model calculations from PYTHIA 6
(Perugia 2011 tune) [74], PYTHIA 8.14 (Monash 2013 tune) [58] and PHOJET [70,
71]. The lower panel shows the model-to-data ratios and the the gray shaded
region represents the sum in quadrature of the systematic and statistical
uncertainties associated with the data.

In Fig. 6 the production spectra of $\mathrm{\rho^{0}}$ in pp and Pb–Pb
collisions are shown. The spectra are fit with a Lévy-Tsallis function [76] in
the transverse momentum range $p_{\mathrm{T}}<7$
$\mathrm{GeV}\kern-1.79993pt/\kern-0.89996ptc$ to estimate the meson yields
outside of the measured range ($p_{\mathrm{T}}<0.5$
$\mathrm{GeV}\kern-1.79993pt/\kern-0.89996ptc$). The fits are used to
calculate the integrated yields
($\mathrm{d}N\kern-1.79993pt/\kern-0.89996pt\mathrm{d}y$) and mean transverse
momenta ($\langle p_{\mathrm{T}}\rangle$) following a procedure described in
[27, 36]. The $\mathrm{d}N\kern-1.79993pt/\kern-0.89996pt\mathrm{d}y$ and
$\langle p_{\mathrm{T}}\rangle$ values are evaluated using the data in the
measured range and the fit function at lower momentum. The fraction of the
total integrated yield in the extrapolated region varies from 30% in pp
collisions to 20 (25)% in central (peripheral) Pb–Pb interactions. Alternative
fitting functions, such as Boltzmann-Gibbs blast-wave [77],
$m_{\mathrm{T}}$-exponential and power-law functions, are used to fit the
measured spectra in different $p_{\mathrm{T}}$ ranges and evaluate systematic
uncertainties for $\mathrm{d}N\kern-1.79993pt/\kern-0.89996pt\mathrm{d}y$ and
$\langle p_{\mathrm{T}}\rangle$ from the extrapolation. The resulting values
of $\mathrm{d}N\kern-1.79993pt/\kern-0.89996pt\mathrm{d}y$ and $\langle
p_{\mathrm{T}}\rangle$ are summarized in Table 2 along with their statistical
and systematic uncertainties.

Figure 6:  (Color online) Differential yields of $\mathrm{\rho^{0}}$ in pp and 0–20%, 20–40%, 40–60%, 60–80% central Pb–Pb collisions at $\sqrt{s_{\mathrm{NN}}}=$ 2.76 TeV. The statistical and systematic uncertainties are shown as bars and boxes, respectively.  Collision system | $\mathrm{d}N\kern-1.79993pt/\kern-0.89996pt\mathrm{d}y$ |  $\langle p_{\mathrm{T}}\rangle$ ($\mathrm{GeV}\kern-1.79993pt/\kern-0.89996ptc$) | $\mathrm{\rho^{0}}/\pi$
---|---|---|---
Inelastic pp | $0.235\pm 0.003^{+0.032}_{-0.041}$ | $0.901\pm 0.006^{+0.039}_{-0.045}$ | $0.126\pm 0.002^{+0.015}_{-0.020}$
Pb–Pb, 0–20% | $42.90\pm 2.59^{+6.04}_{-6.91}\pm 0.26$ | $1.191\pm 0.031^{+0.095}_{-0.096}$ | $0.076\pm 0.005^{+0.009}_{-0.011}$
Pb–Pb, 20–40% | $21.01\pm 0.91^{+2.90}_{-3.40}\pm 0.32$ | $1.162\pm 0.023^{+0.064}_{-0.067}$ | $0.083\pm 0.004^{+0.009}_{-0.012}$
Pb–Pb, 40–60% | $8.67\pm 0.45^{+1.26}_{-1.44}\pm 0.26$ | $1.143\pm 0.028^{+0.064}_{-0.067}$ | $0.089\pm 0.005^{+0.011}_{-0.013}$
Pb–Pb, 60–80% | $2.74\pm 0.13^{+0.41}_{-0.46}\pm 0.16$ | $1.083\pm 0.024^{+0.070}_{-0.072}$ | $0.101\pm 0.005^{+0.012}_{-0.015}$
Table 2: Integrated yields
($\mathrm{d}N\kern-1.79993pt/\kern-0.89996pt\mathrm{d}y$), mean transverse
momenta ($\langle p_{\mathrm{T}}\rangle$) and $\mathrm{\rho^{0}}/\pi$ ratios
in pp and centrality differential Pb–Pb collisions at
$\sqrt{s_{\mathrm{NN}}}=$ 2.76 TeV. For each value the first uncertainty is
statistical. For yields the second uncertainty is systematic, but it does not
include the normalization uncertainty associated with the centrality selection
in Pb–Pb collisions. The normalization uncertainty in Pb–Pb is reported as the
third uncertainty for the yields. For $\rho/\pi$ and $\langle
p_{\mathrm{T}}\rangle$ the second uncertainty is the total systematic
uncertainty. The asymmetric part of the systematic uncertainties comes from
the use of the Söding interference term in the fitting function and is
correlated between collision systems.

###  6.3 $p_{\mathrm{T}}$-integrated particle ratios

The collision energy dependence of the $\mathrm{\rho^{0}}/\pi$ ratio is
presented in Fig. 7 [6]. The ALICE result in pp collisions at $\sqrt{s}=$ 2.76
TeV obtained using charged pion yields from [47] is in good agreement with
lower energy measurements and with thermal model predictions for pp collisions
at $\sqrt{s}=$ 200 GeV [78], $\sqrt{s}=$ 2.76 TeV [79] and $\sqrt{s}=$ 7 TeV
[80].

Figure 7:  (Color online) Compilation of
$2\mathrm{\rho^{0}}/(\pi^{+}+\pi^{-})$ and $\mathrm{\rho^{0}}/\pi^{-}$
measurements at different energies. The ratios are from measurements in
$e^{+}e^{-}$ collisions at $\sqrt{s}=10.45$ GeV [81], $29$ GeV [82] and $91$
GeV [83]; pp collisions at $6.8$ GeV [84], $19.7$ GeV [85], $27.5$ GeV [86],
$52.5$ GeV [87] and $200$ GeV [6]; $K^{+}$p collisions at $7.82$ GeV [88] and
$\pi^{-}$p collisions at $19.6$ GeV [89]. The ALICE measurement in pp
collisions at $\sqrt{s}=$ 2.76 TeV is shown with a red marker. The total
uncertainties are shown as bars.

The left panel of Fig. 8 shows the $\mathrm{\rho^{0}}/\pi$ ratio measured as a
function of
$\langle\mathrm{d}N_{\mathrm{ch}}\kern-0.59998pt/\kern-1.30005pt\mathrm{d}\eta\rangle^{1/3}$
at mid-rapidity [39] in pp and Pb–Pb collisions at $\sqrt{s_{\mathrm{NN}}}=$
2.76 TeV. In Pb–Pb collisions
$\langle\mathrm{d}N_{\mathrm{ch}}\kern-0.59998pt/\kern-1.30005pt\mathrm{d}\eta\rangle^{1/3}$
is used as a proxy for the system size [90]. The charged pion yields are taken
from [60]. The bars represent the statistical uncertainties and the total
systematic uncertainties are shown with open boxes. The part of the systematic
uncertainties related to the interference term in the
$\mathrm{\rho^{0}}$-meson peak model is correlated between points and addition
of this term shifts the points in a similar way in pp and Pb–Pb collisions.
The uncorrelated systematic uncertainties are shown with shaded boxes.

Figure 8:  (Color online) $\mathrm{\rho^{0}}/\pi$ ratio (left) and $\langle
p_{\mathrm{T}}\rangle$ (right) at mid-rapidity ($|y|<0.5$) in pp and 0–20%,
20–40%, 40–60%, 60–80% central Pb–Pb collisions at $\sqrt{s_{\mathrm{NN}}}=$
2.76 TeV as a function of
$\langle\mathrm{d}N_{\mathrm{ch}}\kern-0.59998pt/\kern-1.30005pt\mathrm{d}\eta\rangle^{1/3}$.
Statistical uncertainties are shown as bars. The total and uncorrelated
systematic uncertainties are shown with open and shaded boxes, respectively.
The widths of the boxes are fixed to arbitrary values for better visibility.
The measurements are compared to EPOS3 [26] calculations. The
$\mathrm{\rho^{0}}/\pi$ ratio is also compared to grand canonical thermal
model [91] prediction shown with the red horizontal line.

The measured $\mathrm{\rho^{0}}/\pi$ ratio in Pb–Pb collisions is compared to
predictions from a grand-canonical thermal model with a chemical freeze-out
temperature of $156$ MeV [91]. The model is consistent with data only in
peripheral collisions. The $\mathrm{\rho^{0}}/\pi$ ratio shows a suppression
from pp to peripheral Pb–Pb and then to central Pb–Pb collisions by about 40%.
An analogous suppression was previously observed for short-lived
$\mathrm{K^{*}\kern-0.89996pt(892)^{0}}$ mesons ($\tau\sim 4.2$ fm/$c$)
measured in the
$\mathrm{K^{*}\kern-0.89996pt(892)^{0}}\rightarrow$$K^{\pm}\pi^{\mp}$ decay
channel at RHIC and the LHC: the $K^{*0}/K$ ratio was similarly suppressed in
central heavy-ion collisions with respect to its value in pp collisions [27,
28]. The suppression was explained by rescattering of the
$\mathrm{K^{*}\kern-0.89996pt(892)^{0}}$ daughter particles in the dense
hadron gas phase between chemical and kinetic freeze-out. A similar
explanation may apply for $\mathrm{\rho^{0}}$ mesons, which have a lifetime
three times shorter than $\mathrm{K^{*}\kern-0.89996pt(892)^{0}}$ and a higher
probability to decay before kinetic freeze out.

The measured results are also compared with EPOS3 [26] calculations. EPOS3
models the evolution of heavy-ion collisions, with initial conditions
described by the Gribov-Regge multiple-scattering framework. The high-density
core of the collision is simulated using 3+1 dimensional viscous hydrodynamics
and is surrounded by a corona in which decaying strings hadronize. After the
core hadronizes, the evolution of the full system is simulated using UrQMD
[92, 93], which includes rescattering and regeneration effects. Calculations
were performed with and without a hadronic cascade modeled with UrQMD. Without
UrQMD, no significant system size dependence is predicted for the ratio. When
UrQMD is enabled, the measured evolution of the $\mathrm{\rho^{0}}/\pi$ ratio
with multiplicity is well reproduced in Pb–Pb collisions (cf. Fig. 8, left
panel). This suggests that the observed suppression of the $\mathrm{\rho^{0}}$
indeed originates from rescattering of its daughter particles in the hadronic
phase. EPOS3 was also successful in description of $K^{*0}/K$ ratio in Pb–Pb
collision [36, 26]. Under assumption that all suppression for
$\mathrm{\rho^{0}}$ is from hadronic phase effects, the same lifetime of the
hadronic phase is needed to suppress $K^{*0}$ and $\mathrm{\rho^{0}}$.

In the right panel of Fig. 8 the obtained values of mean $\langle
p_{\mathrm{T}}\rangle$ in pp and Pb–Pb collisions are reported as a function
of the multiplicity. The $\langle p_{\mathrm{T}}\rangle$ values estimated for
$\mathrm{\rho^{0}}$ by EPOS3 in Pb–Pb collisions show an increase as a
function of the multiplicity. The calculation with UrQMD reproduces the
measured values in Pb–Pb collisions reasonably well, while the calculation
without UrQMD significantly underestimates the data.

###  6.4 $p_{\mathrm{T}}$-differential particle ratios

The $\mathrm{\rho^{0}}/\pi$ ratios measured in pp and Pb–Pb collisions (in the
0–20%, 60–80% centrality intervals) at $\sqrt{s_{\mathrm{NN}}}=$ 2.76 TeV as a
function of transverse momentum are shown in Figs. 9 and 10, respectively. The
$p_{\mathrm{T}}$ spectra for pions are obtained from [60, 61].

The ratio in pp collisions is compared to the same model calculations as in
Fig. 5. As for the $p_{\mathrm{T}}$ spectra, the models overestimate
$\mathrm{\rho^{0}}/\pi$ ratio at low momenta, $p_{\mathrm{T}}<1$
$\mathrm{GeV}\kern-1.79993pt/\kern-0.89996ptc$. At higher momentum, the
predictions of the event generators differ by tens of percent, with PYTHIA
8.14 Monash 2013 [58] and PHOJET [70, 71] providing the best description of
the data. The $m_{\mathrm{T}}$-scaling curve shown in the figure is obtained
in the same way as in Fig. 2. It is normalized to $\mathrm{\rho^{0}}/\pi=0.88$
at high momentum, which is obtained from the fit to data points at
$p_{\mathrm{T}}>4$ $\mathrm{GeV}\kern-1.79993pt/\kern-0.89996ptc$. The curve
very well reproduces the measurement results in the whole range of
measurements. We also note that the $\mathrm{\rho^{0}}/\pi$ ratio measured in
pp collisions at $\sqrt{s}=$ 2.76 TeV is very close to the $\omega/\pi$ ratio
measured at lower energies and presented in Fig. 2. This is consistent with
PYTHIA, which predicts very weak energy dependence of the
$\mathrm{\rho^{0}}/\pi$ and $\omega/\pi$ ratios, with
$\mathrm{\rho^{0}}/\omega\sim 1.05$ in the measured $p_{\mathrm{T}}$ range.

Figure 9:  (Color online) $\mathrm{\rho^{0}}/\pi$ ratio in pp collisions at
$\sqrt{s}=$ 2.76 TeV as a function of transverse momentum. The statistical and
systematic uncertainties are shown as bars and boxes, respectively. The
results are compared with model calculations from PYTHIA Perugia 2011 [74],
PYTHIA 8.14 Monash 2013 [58] and PHOJET [70, 71].

The $\mathrm{\rho^{0}}/\pi$ ratio measured in peripheral Pb–Pb collisions is
very similar to that in pp collisions, as can be seen by comparing Fig. 9 and
the right panel of Fig. 10. However, in central Pb–Pb collisions the ratio is
significantly suppressed at low momentum ($p_{\mathrm{T}}<2$
$\mathrm{GeV}\kern-1.79993pt/\kern-0.89996ptc$). This means that the
suppression of the $p_{\mathrm{T}}$-integrated $\mathrm{\rho^{0}}/\pi$ ratio
reported earlier is due to the suppression of low-$p_{\mathrm{T}}$ particle
production in central Pb–Pb collisions. It is important to note that the
$p_{\mathrm{T}}$-dependent suppression of the $\mathrm{\rho^{0}}/\pi$ ratio is
reproduced by EPOS3 calculations when the hadronic cascade simulated with
UrQMD is taken into account. For $p_{\mathrm{T}}<2$
$\mathrm{GeV}\kern-1.79993pt/\kern-0.89996ptc$, EPOS3 without UrQMD
overestimates the ratio by 30–40%. This may serve as another indication that
$\mathrm{\rho^{0}}$-meson suppression is due to daughter particle rescattering
in the hadronic phase.

Figure 10:  (Color online) $\mathrm{\rho^{0}}/\pi$ ratio in 0–20% (left panel)
and 60–80% (right panel) central Pb–Pb collisions at $\sqrt{s_{\mathrm{NN}}}=$
2.76 TeV. The statistical and systematic uncertainties are shown as bars and
boxes, respectively. The measurements are compared to EPOS3 [26] calculations
performed with and without a hadronic cascade modeled with UrQMD [92, 93]. In
the lower panels, the model to data ratio is reported. Bars indicate
statistical uncertainty of calculations whereas the gray shaded boxes
represent the square root of sum of squares of statistical and systematic
uncertainties associated with data.

###  6.5 Nuclear modification factors

The nuclear modification factor $R_{\mathrm{AA}}$ is used to study medium-
induced effects in heavy-ion collisions. The $R_{\mathrm{AA}}$ is the ratio of
the yield of a particle in nucleus-nucleus collisions to its yield in pp
collisions. This ratio is scaled by the number of binary nucleon-nucleon
collisions in each centrality class, which is estimated from Glauber model
calculations [94, 95]. For each $p_{\mathrm{T}}$ bin,

$R_{\mathrm{AA}}=\frac{1}{\langle
N_{\mathrm{coll}}\rangle}\cdot\frac{\mathrm{d}N_{\mathrm{AA}}/\mathrm{d}p_{\mathrm{T}}}{\mathrm{d}N_{\mathrm{pp}}/\mathrm{d}p_{\mathrm{T}}}.$
(6)

The nuclear modification factors measured in 0–20% and 60–80% central Pb–Pb
collisions at $\sqrt{s_{\mathrm{NN}}}=$ 2.76 TeV for charged pions, charged
kaons, (anti)protons [61] and $\mathrm{\rho^{0}}$ mesons are reported in Fig.
11. ($R_{\mathrm{AA}}$ values for the other centrality classes are available
in the High Energy Physics Data Repository.) One can see that in Pb–Pb
collisions, production of all hadrons is suppressed by a similar amount at
high transverse momenta of
$p_{\mathrm{T}}>8~{}\mathrm{GeV}\kern-1.79993pt/\kern-0.89996ptc$ and there is
no dependence of the suppression on particle mass or quark content within
uncertainties. This observation, also confirmed by measurements for
$\mathrm{K^{*}\kern-0.89996pt(892)^{0}}$ and $\upphi(1020)$ mesons [36], rules
out models that predict a species-dependent suppression of light hadrons and
puts additional constraints on parton energy loss and fragmentation models
[96, 97, 98]. There is a clear species dependence of $R_{\mathrm{AA}}$ at
intermediate transverse momentum, which is likely to be a result of an
interplay between different effects such as radial flow, low-$p_{\mathrm{T}}$
suppression, species dependent $p_{\mathrm{T}}$ shapes of the pp reference
spectra [27, 36].

Figure 11:  (Color online) Nuclear modification factors $R_{\mathrm{AA}}$
measured for charged pions, charged kaons, (anti)protons [61] and
$\mathrm{\rho^{0}}$ mesons in 0–20% (left panel) and 60–80% (right panel)
central Pb–Pb collisions at $\sqrt{s_{\mathrm{NN}}}=$ 2.76 TeV. The
statistical and systematic uncertainties are shown as bars and boxes,
respectively. The boxes at unity correspond to scaling uncertainties.

##  7 Conclusions

We have measured the production of $\mathrm{\rho^{0}}$ mesons in minimum bias
pp and centrality differential Pb–Pb collisions at $\sqrt{s_{\mathrm{NN}}}=$
2.76 TeV. These measurements were performed in a wide $p_{\mathrm{T}}$ range
from $0.5$ to $11$ $\mathrm{GeV}\kern-1.79993pt/\kern-0.89996ptc$ in the
hadronic decay channel $\mathrm{\rho^{0}}\rightarrow\pi^{+}\pi^{-}$. The
invariant mass distributions are well described by a hadronic cocktail,
assuming the same $\mathrm{\rho^{0}}$-meson peak shape in pp and central
heavy-ion collisions. However, alternative peak models for $\mathrm{\rho^{0}}$
mesons are not ruled out by data. The reconstructed masses of
$\mathrm{\rho^{0}}$ mesons are consistent with the hadroproduced mass of
$\mathrm{\rho^{0}}$ within uncertainties. In pp collisions, the transverse
momentum spectrum for $p_{\mathrm{T}}>1$
$\mathrm{GeV}\kern-1.79993pt/\kern-0.89996ptc$ is rather well reproduced by
PYTHIA 8.14 Monash 2013 and PYTHIA 6 Perugia 2011, while a better agreement is
observed for PYTHIA 8.14 Monash 2013 and PHOJET for the
$p_{\mathrm{T}}$-differential $\mathrm{\rho^{0}}/\pi$ ratio. In Pb–Pb
collisions, the measured yields for the $\mathrm{\rho^{0}}$ meson are
suppressed at low momentum ($p_{\mathrm{T}}<2$
$\mathrm{GeV}\kern-1.79993pt/\kern-0.89996ptc$). The ratio of integrated
yields, $\mathrm{\rho^{0}}/\pi$, decreases by $\sim 40\%$ from pp to central
Pb–Pb collisions, similar to what was previously observed for the
$\mathrm{K^{*0}}\kern-1.79993pt/\mathrm{K}^{-}$ ratio and explained by
rescattering of the daughter particles in the hadron-gas phase. The relative
suppression of the $p_{\mathrm{T}}$-integrated and
$p_{\mathrm{T}}$-differential $\mathrm{\rho^{0}}/\pi$ ratios is well
reproduced by EPOS3 calculations, provided that the hadronic cascade is
modeled with UrQMD. This suggests that the observed centrality-dependent
suppression of $\mathrm{\rho^{0}}$ production occurs due to rescattering of
daughter pions in the hadronic phase between chemical and kinetic freeze-out,
with the rescattering being most important at low $p_{\mathrm{T}}$. However,
suppression of $\mathrm{\rho^{0}}$-meson production may also occur due to
significant line shape modifications not accounted for in the peak model used
in this analysis. The development of a realistic model of the
$\mathrm{\rho^{0}}$-meson peak shape in heavy-ion collisions would be an
important subject for theoretical studies. Once available, the model
predictions can be compared to the ’vacuum shape’ results for
$\mathrm{\rho^{0}}$ reported in this paper and implications for the measured
yields due to possible line shape modifications can be inferred and discussed.

## 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; 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; Centro de
Aplicaciones Tecnológicas y Desarrollo Nuclear (CEADEN), Cubaenergía, Cuba and
Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas
(CIEMAT), Spain; Swedish Research Council (VR) and Knut & Alice Wallenberg
Foundation (KAW), Sweden; European Organization for Nuclear Research,
Switzerland; National Science and Technology Development Agency (NSDTA),
Suranaree University of Technology (SUT) and Office of the Higher Education
Commission under NRU project of Thailand, Thailand; Turkish Atomic Energy
Agency (TAEK), Turkey; National Academy of Sciences of Ukraine, Ukraine;
Science and Technology Facilities Council (STFC), United Kingdom; National
Science Foundation of the United States of America (NSF) and United States
Department of Energy, Office of Nuclear Physics (DOE NP), United States of
America.

## References

  * [1] Particle Data Group Collaboration, C. Patrignani et al., “Review of particle physics,” Chin. Phys. C40 no. 10, (2016) 100001.
  * [2] OPAL Collaboration, P. D. Acton et al., “Inclusive neutral vector meson production in hadronic $Z^{0}$ decays,” Z. Phys. C56 (1992) 521–536.
  * [3] OPAL Collaboration, K. Ackerstaff et al., “Photon and light meson production in hadronic $Z^{0}$ decays,” Eur. Phys. J. C5 (1998) 411–437, arXiv:hep-ex/9805011 [hep-ex].
  * [4] DELPHI Collaboration, P. Abreu et al., “Production characteristics of $K^{0}$ and light meson resonances in hadronic decays of the $Z^{0}$,” Z. Phys. C65 (1995) 587–602.
  * [5] A. Beddall, A. Beddall, and A. Bingül, “Inclusive production of the $\rho(770)^{\pm}$ meson in hadronic decays of the $Z$ boson,” Phys. Lett. B670 (2009) 300–306.
  * [6] STAR Collaboration, J. Adams et al., “$\rho^{0}$ production and possible modification in Au+Au and p+p collisions at $\sqrt{s_{\rm NN}}=200$ GeV,” Phys. Rev. Lett. 92 (2004) 092301, arXiv:nucl-ex/0307023 [nucl-ex].
  * [7] DELPHI Collaboration, P. Abreu et al., “Invariant mass dependence of particle correlations in hadronic final states from the decay of the $Z^{0}$,” Z. Phys. C63 (1994) 17–28.
  * [8] G. D. Lafferty, “Residual Bose-Einstein correlations in inclusive $\pi^{+}\pi^{-}$ systems and the $\rho(770)^{0}$ line shape in multi-hadronic $Z^{0}$ decay,” Z. Phys. C60 (1993) 659–666.
  * [9] A. Beddall, A. Beddall, and A. Bingül, “Residual Bose-Einstein correlations and the Söding model,” Acta Phys. Polon. B39 (2008) 173–180.
  * [10] P. Petreczky, “Lattice QCD at non-zero temperature,” J. Phys. G39 (2012) 093002, arXiv:1203.5320 [hep-lat].
  * [11] C. A. Dominguez, M. Loewe, and Y. Zhang, “Chiral symmetry restoration and deconfinement in QCD at finite temperature,” Phys. Rev. D86 no. 3, (2012) 034030, arXiv:1205.3361 [hep-ph]. [Erratum: Phys. Rev.D90,no.3,039903(2014)].
  * [12] R. Rapp and J. Wambach, “Chiral symmetry restoration and dileptons in relativistic heavy ion collisions,” Adv. Nucl. Phys. 25 (2000) 1, arXiv:hep-ph/9909229 [hep-ph].
  * [13] CERES Collaboration, G. Agakichiev et al., “Enhanced production of low mass electron pairs in 200-GeV/u S-Au collisions at the CERN SPS,” Phys. Rev. Lett. 75 (1995) 1272–1275.
  * [14] CERES/NA45 Collaboration, G. Agakishiev et al., “Low mass $e^{+}e^{-}$ pair production in 158/A-GeV Pb-Au collisions at the CERN SPS, its dependence on multiplicity and transverse momentum,” Phys. Lett. B422 (1998) 405–412, arXiv:nucl-ex/9712008 [nucl-ex].
  * [15] D. Adamova et al., “Modification of the $\rho$-meson detected by low-mass electron-positron pairs in central Pb-Au collisions at 158-A-GeV/c,” Phys. Lett. B666 (2008) 425–429, arXiv:nucl-ex/0611022 [nucl-ex].
  * [16] CERES/NA45 Collaboration, D. Adamova et al., “Enhanced production of low mass electron pairs in 40-AGeV Pb-Au collisions at the CERN SPS,” Phys. Rev. Lett. 91 (2003) 042301, arXiv:nucl-ex/0209024 [nucl-ex].
  * [17] NA60 Collaboration, R. Arnaldi et al., “First measurement of the $\rho$ spectral function in high-energy nuclear collisions,” Phys. Rev. Lett. 96 (2006) 162302, arXiv:nucl-ex/0605007 [nucl-ex].
  * [18] NA60 Collaboration, R. Arnaldi et al., “Evidence for radial flow of thermal dileptons in high-energy nuclear collisions,” Phys. Rev. Lett. 100 (2008) 022302, arXiv:0711.1816 [nucl-ex].
  * [19] NA60 Collaboration, R. Arnaldi et al., “Evidence for the production of thermal-like muon pairs with masses above 1-GeV/$\textit{c}^{2}$ in 158-A-GeV Indium-Indium Collisions,” Eur. Phys. J. C59 (2009) 607–623, arXiv:0810.3204 [nucl-ex].
  * [20] NA60 Collaboration, R. Arnaldi et al., “NA60 results on thermal dimuons,” Eur. Phys. J. C61 (2009) 711–720, arXiv:0812.3053 [nucl-ex].
  * [21] STAR Collaboration, L. Adamczyk et al., “Measurements of dielectron production in Au+Au collisions at $\sqrt{s_{\rm NN}}=200$ GeV from the STAR experiment,” Phys. Rev. C92 no. 2, (2015) 024912, arXiv:1504.01317 [hep-ex].
  * [22] STAR Collaboration, B. Huang, “Dielectron production in p+p and Au+Au collisions at $\sqrt{s_{\rm NN}}=200$ GeV from STAR,” Acta Phys. Polon. Supp. 5 (2012) 471–476.
  * [23] PHENIX Collaboration, A. Adare et al., “Dielectron production in Au+Au collisions at $\sqrt{s_{\rm NN}}=200$ GeV,” Phys. Rev. C93 no. 1, (2016) 014904, arXiv:1509.04667 [nucl-ex].
  * [24] M. Bleicher and H. Stoecker, “Dynamics and freezeout of hadron resonances at RHIC,” J. Phys. G30 (2004) S111–S118, arXiv:hep-ph/0312278 [hep-ph].
  * [25] M. Bleicher and J. Aichelin, “Strange resonance production: Probing chemical and thermal freezeout in relativistic heavy ion collisions,” Phys. Lett. B530 (2002) 81–87, arXiv:hep-ph/0201123 [hep-ph].
  * [26] A. G. Knospe, C. Markert, K. Werner, J. Steinheimer, and M. Bleicher, “Hadronic resonance production and interaction in partonic and hadronic matter in the EPOS3 model with and without the hadronic afterburner UrQMD,” Phys. Rev. C93 no. 1, (2016) 014911, arXiv:1509.07895 [nucl-th].
  * [27] ALICE Collaboration, B. B. Abelev et al., “$K^{*}(892)^{0}$ and $\phi(1020)$ production in Pb-Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV,” Phys. Rev. C91 (2015) 024609, arXiv:1404.0495 [nucl-ex].
  * [28] STAR Collaboration, J. Adams et al., “$K^{*}(892)^{0}$ resonance production in Au+Au and p+p collisions at $\sqrt{s_{\rm NN}}=200$ GeV at STAR,” Phys. Rev. C71 (2005) 064902, arXiv:nucl-ex/0412019 [nucl-ex].
  * [29] STAR Collaboration, B. I. Abelev et al., “Strange baryon resonance production in $\sqrt{s_{\rm NN}}=200$ GeV p+p and Au+Au collisions,” Phys. Rev. Lett. 97 (2006) 132301, arXiv:nucl-ex/0604019 [nucl-ex].
  * [30] STAR Collaboration, J. Adams et al., “$\phi$ meson production in Au+Au and p+p collisions at $\sqrt{s_{\rm NN}}=200$ GeV,” Phys. Lett. B612 (2005) 181–189, arXiv:nucl-ex/0406003 [nucl-ex].
  * [31] J. D. Bjorken, “Energy Loss of Energetic Partons in Quark - Gluon Plasma: Possible Extinction of High p(t) Jets in Hadron - Hadron Collisions,” 1982, FERMILAB-PUB-82-059-THY, FERMILAB-PUB-82-059-T.
  * [32] M. Gyulassy and M. Plumer, “Jet Quenching in Dense Matter,” Phys. Lett. B243 (1990) 432–438.
  * [33] R. Baier, Y. L. Dokshitzer, S. Peigne, and D. Schiff, “Induced gluon radiation in a QCD medium,” Phys. Lett. B345 (1995) 277–286, arXiv:hep-ph/9411409 [hep-ph].
  * [34] A. Ilner, J. Blair, D. Cabrera, C. Markert, and E. Bratkovskaya, “Probing the hot and dense nuclear matter with $K^{*},\bar{K}^{*}$ vector mesons,” arXiv:1707.00060 [hep-ph].
  * [35] P. Söding, “On the Apparent shift of the $\rho$ meson mass in photoproduction,” Phys. Lett. 19 (1966) 702–704.
  * [36] ALICE Collaboration, J. Adam et al., “K${}^{*}(892)^{0}$ and $\phi(1020)$ meson production at high transverse momentum in pp and Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV,” Phys. Rev. C95 no. 6, (2017) 064606, arXiv:1702.00555 [nucl-ex].
  * [37] ALICE Collaboration, K. Aamodt et al., “The ALICE experiment at the CERN LHC,” JINST 3 (2008) S08002.
  * [38] ALICE Collaboration, E. Abbas et al., “Performance of the ALICE VZERO system,” JINST 8 (2013) P10016, arXiv:1306.3130 [nucl-ex].
  * [39] ALICE Collaboration, K. Aamodt et al., “Centrality dependence of the charged-particle multiplicity density at mid-rapidity in Pb-Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV,” Phys. Rev. Lett. 106 (2011) 032301, arXiv:1012.1657 [nucl-ex].
  * [40] ALICE Collaboration, B. Abelev et al., “Centrality determination of Pb-Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV with ALICE,” Phys. Rev. C88 no. 4, (2013) 044909, arXiv:1301.4361 [nucl-ex].
  * [41] ALICE Collaboration, B. Abelev et al., “Measurement of inelastic, single- and double-diffraction cross sections in proton–proton collisions at the LHC with ALICE,” Eur. Phys. J. C73 no. 6, (2013) 2456, arXiv:1208.4968 [hep-ex].
  * [42] ALICE Collaboration, B. B. Abelev et al., “Performance of the ALICE Experiment at the CERN LHC,” Int. J. Mod. Phys. A29 (2014) 1430044, arXiv:1402.4476 [nucl-ex].
  * [43] T. Sjostrand and M. van Zijl, “A Multiple Interaction Model for the Event Structure in Hadron Collisions,” Phys. Rev. D36 (1987) 2019.
  * [44] T. Sjöstrand, S. Mrenna, and P. Z. Skands, “PYTHIA 6.4 Physics and Manual,” JHEP 05 (2006) 026, arXiv:hep-ph/0603175 [hep-ph].
  * [45] X.-N. Wang and M. Gyulassy, “HIJING: A Monte Carlo model for multiple jet production in pp, pA and AA collisions,” Phys. Rev. D44 (1991) 3501–3516.
  * [46] R. Brun, F. Carminati, and S. Giani, GEANT – Detector Description and Simulation Tool, CERN Program Library Long Writeup W5013.  CERN, Geneva, 1994.
  * [47] ALICE Collaboration, B. B. Abelev et al., “Production of charged pions, kaons and protons at large transverse momenta in pp and Pb-Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV,” Phys. Lett. B736 (2014) 196–207, arXiv:1401.1250 [nucl-ex].
  * [48] ALICE Collaboration, B. B. Abelev et al., “$K^{0}_{S}$ and $\Lambda$ production in Pb-Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV,” Phys. Rev. Lett. 111 (2013) 222301, arXiv:1307.5530 [nucl-ex].
  * [49] PHENIX Collaboration, S. S. Adler et al., “Centrality dependence of direct photon production in $\sqrt{s_{\rm NN}}=200$ GeV Au+Au collisions,” Phys. Rev. Lett. 94 (2005) 232301, arXiv:nucl-ex/0503003 [nucl-ex].
  * [50] ALICE Collaboration, J. Adam et al., “Direct photon production in Pb-Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV,” Phys. Lett. B754 (2016) 235–248, arXiv:1509.07324 [nucl-ex].
  * [51] PHENIX Collaboration, A. Adare et al., “Production of $\omega$ mesons in p+p, d+Au, Cu+Cu, and Au+Au collisions at $\sqrt{s_{\rm NN}}=200$ GeV,” Phys. Rev. C84 (2011) 044902, arXiv:1105.3467 [nucl-ex].
  * [52] M. Diakonou et al., “Inclusive high-$p_{\mathrm{T}}$ $\omega$ and $\eta^{\prime}$ production at the ISR,” Phys. Lett. B89 (1980) 432–436.
  * [53] PHENIX Collaboration, A. Adare et al., “Spectra and ratios of identified particles in Au+Au and d+Au collisions at $\sqrt{s_{\rm NN}}=200$ GeV,” Phys. Rev. C88 no. 2, (2013) 024906, arXiv:1304.3410 [nucl-ex].
  * [54] ALICE Collaboration, B. Abelev et al., “Production of $K^{*}(892)^{0}$ and $\phi(1020)$ in pp collisions at $\sqrt{s}=7$ TeV,” Eur. Phys. J. C72 (2012) 2183, arXiv:1208.5717 [hep-ex].
  * [55] ALICE Collaboration, K. Aamodt et al., “Production of pions, kaons and protons in pp collisions at $\sqrt{s}=900$ GeV with ALICE at the LHC,” Eur. Phys. J. C71 (2011) 1655, arXiv:1101.4110 [hep-ex].
  * [56] ALICE Collaboration, B. Abelev et al., “Neutral pion and $\eta$ meson production in proton-proton collisions at $\sqrt{s}=0.9$ TeV and $\sqrt{s}=7$ TeV,” Phys. Lett. B717 (2012) 162–172, arXiv:1205.5724 [hep-ex].
  * [57] PHENIX Collaboration, S. S. Adler et al., “High transverse momentum $\eta$ meson production in p+p, d+Au and Au+Au collisions at $\sqrt{s_{\rm NN}}=200$ GeV ,” Phys. Rev. C75 (2007) 024909, arXiv:nucl-ex/0611006 [nucl-ex].
  * [58] T. Sjöstrand, S. Mrenna, and P. Z. Skands, “A brief introduction to PYTHIA 8.1,” Comput. Phys. Commun. 178 (2008) 852–867, arXiv:0710.3820 [hep-ph].
  * [59] L. Altenk mper, F. Bock, C. Loizides, and N. Schmidt, “Applicability of transverse mass scaling in hadronic collisions at energies available at the CERN Large Hadron Collider,” Phys. Rev. C96 no. 6, (2017) 064907, arXiv:1710.01933 [hep-ph].
  * [60] ALICE Collaboration, B. Abelev et al., “Centrality dependence of $\pi$, K, p production in Pb-Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV,” Phys. Rev. C88 (2013) 044910, arXiv:1303.0737 [hep-ex].
  * [61] ALICE Collaboration, J. Adam et al., “Centrality dependence of the nuclear modification factor of charged pions, kaons, and protons in Pb-Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV,” Phys. Rev. C93 no. 3, (2016) 034913, arXiv:1506.07287 [nucl-ex].
  * [62] Z. Tang, Y. Xu, L. Ruan, G. van Buren, F. Wang, and Z. Xu, “Spectra and radial flow at RHIC with Tsallis statistics in a Blast-Wave description,” Phys. Rev. C79 (2009) 051901, arXiv:0812.1609 [nucl-ex].
  * [63] PHENIX Collaboration, A. Adare et al., “Measurement of neutral mesons in p+p collisions at $\sqrt{s}=200$ GeV and scaling properties of hadron production,” Phys. Rev. D83 (2011) 052004, arXiv:1005.3674 [hep-ex].
  * [64] STAR Collaboration, C. Adler et al., “Coherent $\rho^{0}$ production in ultraperipheral heavy ion collisions,” Phys. Rev. Lett. 89 (2002) 272302, arXiv:nucl-ex/0206004 [nucl-ex].
  * [65] ALICE Collaboration, J. Adam et al., “Coherent $\rho^{0}$ photoproduction in ultra-peripheral Pb-Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV,” JHEP 09 (2015) 095, arXiv:1503.09177 [nucl-ex].
  * [66] R. Rapp, “$\pi^{+}\pi^{-}$-emission in high-energy nuclear collisions,” Nucl. Phys. A725 (2003) 254–268, arXiv:hep-ph/0305011 [hep-ph].
  * [67] P. F. Kolb and M. Prakash, “Spectroscopy of resonance decays in high-energy heavy ion experiments,” Phys. Rev. C67 (2003) 044902, arXiv:nucl-th/0301007 [nucl-th].
  * [68] E. V. Shuryak and G. E. Brown, “Matter induced modification of resonances at RHIC freezeout,” Nucl. Phys. A717 (2003) 322–335, arXiv:hep-ph/0211119 [hep-ph].
  * [69] ALICE Collaboration, B. B. Abelev et al., “Multiplicity dependence of pion, kaon, proton and Lambda production in p-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV ,” Phys. Lett. B728 (2014) 25–38, arXiv:1307.6796 [nucl-ex].
  * [70] R. Engel, “Photoproduction within the two component dual parton model. 1. Amplitudes and cross-sections,” Z. Phys. C66 (1995) 203–214.
  * [71] R. Engel and J. Ranft, “Hadronic photon-photon interactions at high-energies,” Phys. Rev. D54 (1996) 4244–4262, arXiv:hep-ph/9509373 [hep-ph].
  * [72] H. W. Barz, G. Bertsch, B. L. Friman, H. Schulz, and S. Boggs, “$\mathrm{\rho^{0}}$ thermometry in hot hadronic matter,” Phys. Lett. B265 (1991) 219–222.
  * [73] P. Skands, S. Carrazza, and J. Rojo, “Tuning PYTHIA 8.1: the Monash 2013 Tune,” Eur. Phys. J. C74 no. 8, (2014) 3024, arXiv:1404.5630 [hep-ph].
  * [74] P. Z. Skands, “Tuning Monte Carlo generators: the Perugia tunes,” Phys. Rev. D82 (2010) 074018, arXiv:1005.3457 [hep-ph].
  * [75] B. Andersson, G. Gustafson, G. Ingelman, and T. Sjöstrand, “Parton fragmentation and string dynamics,” Phys. Rept. 97 (1983) 31–145.
  * [76] C. Tsallis, “Possible generalization of Boltzmann-Gibbs statistics,” J. Statist. Phys. 52 (1988) 479–487.
  * [77] E. Schnedermann, J. Sollfrank, and U. W. Heinz, “Thermal phenomenology of hadrons from 200-A/GeV S+S collisions,” Phys. Rev. C48 (1993) 2462–2475, arXiv:nucl-th/9307020 [nucl-th].
  * [78] F. Becattini, P. Castorina, A. Milov, and H. Satz, “A Comparative analysis of statistical hadron production,” Eur. Phys. J. C66 (2010) 377–386, arXiv:0911.3026 [hep-ph].
  * [79] M. Floris, “Hadron yields and the phase diagram of strongly interacting matter,” Nucl. Phys. A931 (2014) 103–112, arXiv:1408.6403 [nucl-ex].
  * [80] F. Becattini, P. Castorina, A. Milov, and H. Satz, “Predictions of hadron abundances in pp collisions at the LHC,” J. Phys. G38 (2011) 025002, arXiv:0912.2855 [hep-ph].
  * [81] ARGUS Collaboration, H. Albrecht et al., “Inclusive production of $K^{*}(892)$, $\rho(770)^{0}$, and $\omega(783)$ mesons in the $\Upsilon$ energy region,” Z. Phys. C61 (1994) 1–18.
  * [82] M. Derrick et al., “Neutral $K^{*}(890)$ and $\rho^{0}$ meson production in $e^{+}e^{-}$ annihilation at the $\sqrt{s}=29$-GeV,” Phys. Lett. B158 (1985) 519–524.
  * [83] Y.-J. Pei, “A Simple approach to describe hadron production rates in $e^{+}e^{-}$ annihilation,” Z. Phys. C72 (1996) 39–46.
  * [84] Bonn-Hamburg-Munich Collaboration, V. Blobel and et al., “Observation of vector meson production in inclusive pp reactions,” Phys. Lett. 48B (1974) 73–76.
  * [85] R. Singer, T. H. Fields, L. G. Hyman, R. Engelmann, T. Kafka, M. Pratap, L. Voyvodic, R. Walker, and J. Whitmore, “$\rho^{0}$ production in 205-GeV/c pp interactions,” Phys. Lett. B60 (1976) 385–388.
  * [86] M. Aguilar-Benitez et al., “Inclusive particle production in 400-GeV/c pp interactions,” Z. Phys. C50 (1991) 405–426.
  * [87] Annecy(LAPP)-CERN-College de France-Dortmund-Heidelberg-Warsaw Collaboration, D. Drijard et al., “Production of vector and tensor mesons in proton-proton collisions at $\sqrt{s}=52$.5-GeV,” Z. Phys. C9 (1981) 293.
  * [88] Soviet-CERN Collaboration, A. P. Vorobjev et al., “Inclusive production of $\rho^{0}$ and $\phi$ in $K^{+}p$ interactions at 32-GeV/c,” Nucl. Phys. B176 (1980) 303.
  * [89] F. C. Winkelmann et al., “Inclusive $\rho^{0}$ production in $\pi^{-}p$ interactions at 205-GeV/c,” Phys. Lett. B56 (1975) 101–104.
  * [90] ALICE Collaboration, K. Aamodt et al., “Two-pion Bose-Einstein correlations in central Pb-Pb collisions at $\sqrt{{s}_{NN}}=$ 2.76 TeV,” Phys. Lett. B696 (2011) 328–337, arXiv:1012.4035 [nucl-ex].
  * [91] A. Andronic, P. Braun-Munzinger, and J. Stachel, “Thermal hadron production in relativistic nuclear collisions: The Hadron mass spectrum, the horn, and the QCD phase transition,” Phys. Lett. B673 (2009) 142–145, arXiv:0812.1186 [nucl-th]. [Erratum: Phys. Lett.B678,516(2009)].
  * [92] S. A. Bass et al., “Microscopic models for ultrarelativistic heavy ion collisions,” Prog. Part. Nucl. Phys. 41 (1998) 255–369, arXiv:nucl-th/9803035 [nucl-th]. [Prog. Part. Nucl. Phys.41,225(1998)].
  * [93] M. Bleicher et al., “Relativistic hadron hadron collisions in the ultrarelativistic quantum molecular dynamics model,” J. Phys. G25 (1999) 1859–1896, arXiv:hep-ph/9909407 [hep-ph].
  * [94] B. Alver, M. Baker, C. Loizides, and P. Steinberg, “The PHOBOS Glauber Monte Carlo,” arXiv:0805.4411 [nucl-ex].
  * [95] C. Loizides, J. Nagle, and P. Steinberg, “Improved version of the PHOBOS Glauber Monte Carlo,” SoftwareX 1-2 (2015) 13–18, arXiv:1408.2549 [nucl-ex].
  * [96] R. Bellwied and C. Markert, “In-medium hadronization in the deconfined matter at RHIC and LHC,” Phys. Lett. B691 (2010) 208–213, arXiv:1005.5416 [nucl-th].
  * [97] W. Liu and R. J. Fries, “Probing nuclear matter with jet conversions,” Phys. Rev. C77 (2008) 054902, arXiv:0801.0453 [nucl-th].
  * [98] W. Liu, C. M. Ko, and B. W. Zhang, “Jet conversions in a quark-gluon plasma,” Phys. Rev. C75 (2007) 051901, arXiv:nucl-th/0607047 [nucl-th].

##  Appendix A The ALICE Collaboration

S. Acharyaorg138&F.T.-. Acostaorg22&D. Adamováorg94&J. Adolfssonorg81&M.M.
Aggarwalorg98&G. Aglieri Rinellaorg36&M. Agnelloorg33&N. Agrawalorg49&Z.
Ahammedorg138&S.U. Ahnorg77&S. Aiolaorg143&A. Akindinovorg65&M. Al-
Turanyorg104&S.N. Alamorg138&D.S.D. Albuquerqueorg120&D. Aleksandrovorg88&B.
Alessandroorg59&R. Alfaro Molinaorg73&Y. Aliorg16&A. Aliciorg11,org54,org29&A.
Alkinorg3&J. Almeorg24&T. Altorg70&L. Altenkamperorg24&I. Altsybeevorg137&C.
Andreiorg48&D. Andreouorg36&H.A. Andrewsorg108&A. Andronicorg141,org104&M.
Angelettiorg36&V. Anguelovorg102&C. Ansonorg17&T. Antičićorg105&F.
Antinoriorg57&P. Antonioliorg54&R. Anwarorg124&N. Apadulaorg80&L.
Aphecetcheorg112&H. Appelshäuserorg70&S. Arcelliorg29&R. Arnaldiorg59&O.W.
Arnoldorg103,org115&I.C. Arseneorg23&M. Arslandokorg102&B. Audurierorg112&A.
Augustinusorg36&R. Averbeckorg104&M.D. Azmiorg18&A. Badalàorg56&Y.W.
Baekorg61,org42&S. Bagnascoorg59&R. Bailhacheorg70&R. Balaorg99&A.
Baldisseriorg134&M. Ballorg44&R.C. Baralorg86&A.M. Barbanoorg28&R.
Barberaorg30&F. Barileorg53&L. Barioglioorg28&G.G. Barnaföldiorg142&L.S.
Barnbyorg93&V. Barretorg131&P. Bartaliniorg7&K. Barthorg36&E. Bartschorg70&N.
Bastidorg131&S. Basuorg140&G. Batigneorg112&B. Batyunyaorg76&P.C.
Batzingorg23&J.L. Bazo Albaorg109&I.G. Beardenorg89&H. Beckorg102&C.
Beddaorg64&N.K. Beheraorg61&I. Belikovorg133&F. Belliniorg29,org36&H. Bello
Martinezorg2&R. Bellwiedorg124&L.G.E. Beltranorg118&V. Belyaevorg92&G.
Bencediorg142&S. Beoleorg28&A. Bercuciorg48&Y. Berdnikovorg96&D.
Berenyiorg142&R.A. Bertensorg127&D. Berzanoorg36,org59&L. Betevorg36&P.P.
Bhaduriorg138&A. Bhasinorg99&I.R. Bhatorg99&H. Bhattorg49&B.
Bhattacharjeeorg43&J. Bhomorg116&A. Bianchiorg28&L. Bianchiorg124&N.
Bianchiorg52&J. Bielčíkorg39&J. Bielčíkováorg94&A. Bilandzicorg115,org103&G.
Biroorg142&R. Biswasorg4&S. Biswasorg4&J.T. Blairorg117&D. Blauorg88&C.
Blumeorg70&G. Bocaorg135&F. Bockorg36&A. Bogdanovorg92&L. Boldizsárorg142&M.
Bombaraorg40&G. Bonomiorg136&M. Bonoraorg36&H. Borelorg134&A.
Borissovorg141,org20&M. Borriorg126&E. Bottaorg28&C. Bourjauorg89&L.
Bratrudorg70&P. Braun-Munzingerorg104&M. Bregantorg119&T.A. Brokerorg70&M.
Brozorg39&E.J. Bruckenorg45&E. Brunaorg59&G.E. Brunoorg36,org35&D.
Budnikovorg106&H. Bueschingorg70&S. Bufalinoorg33&P. Buhlerorg111&P.
Buncicorg36&O. Buschorg130&Z. Butheleziorg74&J.B. Buttorg16&J.T.
Buxtonorg19&J. Cabalaorg114&D. Caffarriorg90&H. Cainesorg143&A.
Calivaorg104&E. Calvo Villarorg109&R.S. Camachoorg2&P. Cameriniorg27&A.A.
Caponorg111&F. Carenaorg36&W. Carenaorg36&F. Carnesecchiorg29,org11&J.
Castillo Castellanosorg134&A.J. Castroorg127&E.A.R. Casulaorg55&C. Ceballos
Sanchezorg9&S. Chandraorg138&B. Changorg125&W. Changorg7&S. Chapelandorg36&M.
Chartierorg126&S. Chattopadhyayorg138&S. Chattopadhyayorg107&A.
Chauvinorg115,org103&C. Cheshkovorg132&B. Cheynisorg132&V. Chibante
Barrosoorg36&D.D. Chinellatoorg120&S. Choorg61&P. Chochulaorg36&T.
Chowdhuryorg131&P. Christakoglouorg90&C.H. Christensenorg89&P.
Christiansenorg81&T. Chujoorg130&S.U. Chungorg20&C. Cicaloorg55&L.
Cifarelliorg11,org29&F. Cindoloorg54&J. Cleymansorg123&F. Colamariaorg53&D.
Colellaorg66,org53,org36&A. Colluorg80&M. Colocciorg29&M. Concasorg59orgI&G.
Conesa Balbastreorg79&Z. Conesa del Valleorg62&J.G. Contrerasorg39&T.M.
Cormierorg95&Y. Corrales Moralesorg59&P. Corteseorg34&M.R. Cosentinoorg121&F.
Costaorg36&S. Costanzaorg135&J. Crkovskáorg62&P. Crochetorg131&E.
Cuautleorg71&L. Cunqueiroorg95,org141&T. Dahmsorg103,org115&A.
Daineseorg57&M.C. Danischorg102&A. Danuorg69&D. Dasorg107&I. Dasorg107&S.
Dasorg4&A. Dashorg86&S. Dashorg49&S. Deorg50&A. De Caroorg32&G. de
Cataldoorg53&C. de Contiorg119&J. de Cuvelandorg41&A. De Falcoorg26&D. De
Gruttolaorg11,org32&N. De Marcoorg59&S. De Pasqualeorg32&R.D. De
Souzaorg120&H.F. Degenhardtorg119&A. Deistingorg104,org102&A. Delofforg85&S.
Delsantoorg28&C. Deplanoorg90&P. Dhankherorg49&D. Di Bariorg35&A. Di
Mauroorg36&B. Di Ruzzaorg57&R.A. Diazorg9&T. Dietelorg123&P.
Dillensegerorg70&Y. Dingorg7&R. Diviàorg36&Ø. Djuvslandorg24&A. Dobrinorg36&D.
Domenicis Gimenezorg119&B. Dönigusorg70&O. Dordicorg23&L.V.R.
Doremalenorg64&A.K. Dubeyorg138&A. Dublaorg104&L. Ducrouxorg132&S.
Dudiorg98&A.K. Duggalorg98&M. Dukhishyamorg86&P. Dupieuxorg131&R.J.
Ehlersorg143&D. Eliaorg53&E. Endressorg109&H. Engelorg75&E. Eppleorg143&B.
Erazmusorg112&F. Erhardtorg97&M.R. Ersdalorg24&B. Espagnonorg62&G.
Eulisseorg36&J. Eumorg20&D. Evansorg108&S. Evdokimovorg91&L.
Fabbiettiorg103,org115&M. Fagginorg31&J. Faivreorg79&A. Fantoniorg52&M.
Faselorg95&L. Feldkamporg141&A. Felicielloorg59&G. Feofilovorg137&A. Fernández
Téllezorg2&A. Ferrettiorg28&A. Festantiorg31,org36&V.J.G.
Feuillardorg131,org102,org134&J. Figielorg116&M.A.S. Figueredoorg119&S.
Filchaginorg106&D. Finogeevorg63&F.M. Fiondaorg24&G. Fiorenzaorg53&M.
Florisorg36&S. Foertschorg74&P. Fokaorg104&S. Fokinorg88&E. Fragiacomoorg60&A.
Francesconorg36&A. Franciscoorg112&U. Frankenfeldorg104&G.G. Fronzeorg28&U.
Fuchsorg36&C. Furgetorg79&A. Fursorg63&M. Fusco Girardorg32&J.J.
Gaardhøjeorg89&M. Gagliardiorg28&A.M. Gagoorg109&K. Gajdosovaorg89&M.
Gallioorg28&C.D. Galvanorg118&P. Ganotiorg84&C. Garabatosorg104&E. Garcia-
Solisorg12&K. Gargorg30&C. Gargiuloorg36&P. Gasikorg115,org103&E.F.
Gaugerorg117&M.B. Gay Ducatiorg72&M. Germainorg112&J. Ghoshorg107&P.
Ghoshorg138&S.K. Ghoshorg4&P. Gianottiorg52&P. Giubellinoorg104,org59&P.
Giubilatoorg31&P. Glässelorg102&D.M. Goméz Coralorg73&A. Gomez Ramirezorg75&V.
Gonzalezorg104&P. González-Zamoraorg2&S. Gorbunovorg41&L. Görlichorg116&S.
Gotovacorg37&V. Grabskiorg73&L.K. Graczykowskiorg139&K.L. Grahamorg108&L.
Greinerorg80&A. Grelliorg64&C. Grigorasorg36&V. Grigorievorg92&A.
Grigoryanorg1&S. Grigoryanorg76&J.M. Gronefeldorg104&F. Grosaorg33&J.F.
Grosse-Oetringhausorg36&R. Grossoorg104&R. Guernaneorg79&B. Guerzoniorg29&M.
Guittiereorg112&K. Gulbrandsenorg89&T. Gunjiorg129&A. Guptaorg99&R.
Guptaorg99&I.B. Guzmanorg2&R. Haakeorg36&M.K. Habiborg104&C.
Hadjidakisorg62&H. Hamagakiorg82&G. Hamarorg142&J.C. Hamonorg133&R.
Hanniganorg117&M.R. Haqueorg64&J.W. Harrisorg143&A. Hartonorg12&H.
Hassanorg79&D. Hatzifotiadouorg54,org11&S. Hayashiorg129&S.T. Heckelorg70&E.
Hellbärorg70&H. Helstruporg38&A. Herghelegiuorg48&E.G. Hernandezorg2&G.
Herrera Corralorg10&F. Herrmannorg141&K.F. Hetlandorg38&T.E. Hildenorg45&H.
Hillemannsorg36&C. Hillsorg126&B. Hippolyteorg133&B. Hohlwegerorg103&D.
Horakorg39&S. Hornungorg104&R. Hosokawaorg130,org79&P. Hristovorg36&C.
Hughesorg127&P. Huhnorg70&T.J. Humanicorg19&H. Hushnudorg107&N.
Hussainorg43&T. Hussainorg18&D. Hutterorg41&D.S. Hwangorg21&J.P.
Iddonorg126&S.A. Iga Buitronorg71&R. Ilkaevorg106&M. Inabaorg130&M.
Ippolitovorg88&M.S. Islamorg107&M. Ivanovorg104&V. Ivanovorg96&V.
Izucheevorg91&B. Jacakorg80&N. Jacazioorg29&P.M. Jacobsorg80&M.B.
Jadhavorg49&S. Jadlovskaorg114&J. Jadlovskyorg114&S. Jaelaniorg64&C.
Jahnkeorg119,org115&M.J. Jakubowskaorg139&M.A. Janikorg139&C. Jenaorg86&M.
Jercicorg97&R.T. Jimenez Bustamanteorg104&M. Jinorg124&P.G. Jonesorg108&A.
Juskoorg108&P. Kalinakorg66&A. Kalweitorg36&J.H. Kangorg144&V. Kaplinorg92&S.
Karorg7&A. Karasu Uysalorg78&O. Karavichevorg63&T. Karavichevaorg63&P.
Karczmarczykorg36&E. Karpechevorg63&U. Kebschullorg75&R. Keidelorg47&D.L.D.
Keijdenerorg64&M. Keilorg36&B. Ketzerorg44&Z. Khabanovaorg90&S. Khanorg18&S.A.
Khanorg138&A. Khanzadeevorg96&Y. Kharlovorg91&A. Khatunorg18&A.
Khuntiaorg50&M.M. Kielbowiczorg116&B. Kilengorg38&B. Kimorg130&D.
Kimorg144&D.J. Kimorg125&E.J. Kimorg14&H. Kimorg144&J.S. Kimorg42&J.
Kimorg102&M. Kimorg61,org102&S. Kimorg21&T. Kimorg144&T. Kimorg144&S.
Kirschorg41&I. Kiselorg41&S. Kiselevorg65&A. Kisielorg139&J.L. Klayorg6&C.
Kleinorg70&J. Kleinorg36,org59&C. Klein-Bösingorg141&S. Klewinorg102&A.
Klugeorg36&M.L. Knichelorg36,org102&A.G. Knospeorg124&C. Kobdajorg113&M.
Kofaragoorg142&M.K. Köhlerorg102&T. Kolleggerorg104&N. Kondratyevaorg92&E.
Kondratyukorg91&A. Konevskikhorg63&M. Konyushikhinorg140&O. Kovalenkoorg85&V.
Kovalenkoorg137&M. Kowalskiorg116&I. Králikorg66&A. Kravčákováorg40&L.
Kreisorg104&M. Krivdaorg108,org66&F. Krizekorg94&M. Krügerorg70&E.
Kryshenorg96&M. Krzewickiorg41&A.M. Kuberaorg19&V. Kučeraorg94,org61&C.
Kuhnorg133&P.G. Kuijerorg90&J. Kumarorg49&L. Kumarorg98&S. Kumarorg49&S.
Kunduorg86&P. Kurashviliorg85&A. Kurepinorg63&A.B. Kurepinorg63&A.
Kuryakinorg106&S. Kushpilorg94&M.J. Kweonorg61&Y. Kwonorg144&S.L. La
Pointeorg41&P. La Roccaorg30&Y.S. Laiorg80&I. Lakomovorg36&R. Langoyorg122&K.
Lapidusorg143&C. Laraorg75&A. Lardeuxorg23&P. Larionovorg52&A. Lattucaorg28&E.
Laudiorg36&R. Lavickaorg39&R. Leaorg27&L. Leardiniorg102&S. Leeorg144&F.
Lehasorg90&S. Lehnerorg111&J. Lehrbachorg41&R.C. Lemmonorg93&E.
Leograndeorg64&I. León Monzónorg118&P. Lévaiorg142&X. Liorg13&X.L. Liorg7&J.
Lienorg122&R. Lietavaorg108&B. Limorg20&S. Lindalorg23&V.
Lindenstruthorg41&S.W. Lindsayorg126&C. Lippmannorg104&M.A. Lisaorg19&V.
Litichevskyiorg45&A. Liuorg80&H.M. Ljunggrenorg81&W.J. Llopeorg140&D.F.
Lodatoorg64&V. Loginovorg92&C. Loizidesorg80,org95&P. Loncarorg37&X.
Lopezorg131&E. López Torresorg9&A. Loweorg142&P. Luettigorg70&J.R.
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Majkaorg143&M. Malaevorg96&L. Malininaorg76orgII&D. Mal’Kevichorg65&P.
Malzacherorg104&A. Mamonovorg106&V. Mankoorg88&F. Mansoorg131&V.
Manzariorg53&Y. Maoorg7&M. Marchisoneorg74,org128,org132&J. Marešorg68&G.V.
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Markertorg117&M. Marquardorg70&N.A. Martinorg104&P. Martinengoorg36&M.I.
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Masciocchiorg104&M. Maseraorg28&A. Masoniorg55&L. Massacrierorg62&E.
Massonorg112&A. Mastroserioorg53&A.M. Mathisorg103,org115&P.F.T.
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Mhlangaorg123&Y. Miakeorg130&L. Michelettiorg28&M.M. Mieskolainenorg45&D.L.
Mihaylovorg103&K. Mikhaylovorg65,org76&A. Mischkeorg64&A.N. Mishraorg71&D.
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Mohantyorg64&B. Mohantyorg86&M. Mohisin Khanorg18orgIII&D.A. Moreira De
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Morschorg36&V. Mucciforaorg52&E. Mudnicorg37&D. Mühlheimorg141&S.
Muhuriorg138&M. Mukherjeeorg4&J.D. Mulliganorg143&M.G. Munhozorg119&K.
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Murrayorg74&L. Musaorg36&J. Musinskyorg66&C.J. Myersorg124&J.W.
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Nappiorg53&A. Narayanorg49&M.U. Naruorg16&A.F. Nassirpourorg81&H. Natal da
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Nayakorg138&S. Nazarenkoorg106&R.A. Negrao De Oliveiraorg70,org36&L.
Nellenorg71&S.V. Nesboorg38&G. Neskovicorg41&F. Ngorg124&M. Nicassioorg104&J.
Niedzielaorg139,org36&B.S. Nielsenorg89&S. Nikolaevorg88&S. Nikulinorg88&V.
Nikulinorg96&F. Noferiniorg11,org54&P. Nomokonovorg76&G. Noorenorg64&J.C.C.
Norisorg2&J. Normanorg79,org126&A. Nyaninorg88&J. Nystrandorg24&H. Ohorg144&A.
Ohlsonorg102&J. Oleniaczorg139&A.C. Oliveira Da Silvaorg119&M.H.
Oliverorg143&J. Onderwaaterorg104&C. Oppedisanoorg59&R. Oravaorg45&M.
Oravecorg114&A. Ortiz Velasquezorg71&A. Oskarssonorg81&J. Otwinowskiorg116&K.
Oyamaorg82&Y. Pachmayerorg102&V. Pacikorg89&D. Paganoorg136&G. Paićorg71&P.
Palniorg7&J. Panorg140&A.K. Pandeyorg49&S. Panebiancoorg134&V. Papikyanorg1&P.
Pareekorg50&J. Parkorg61&J.E. Parkkilaorg125&S. Parmarorg98&A.
Passfeldorg141&S.P. Pathakorg124&R.N. Patraorg138&B. Paulorg59&H. Peiorg7&T.
Peitzmannorg64&X. Pengorg7&L.G. Pereiraorg72&H. Pereira Da Costaorg134&D.
Peresunkoorg88&E. Perez Lezamaorg70&V. Peskovorg70&Y. Pestovorg5&V.
Petráčekorg39&M. Petroviciorg48&C. Pettaorg30&R.P. Pezziorg72&S. Pianoorg60&M.
Piknaorg15&P. Pillotorg112&L.O.D.L. Pimentelorg89&O. Pinazzaorg54,org36&L.
Pinskyorg124&S. Pisanoorg52&D.B. Piyarathnaorg124&M. Płoskońorg80&M.
Planinicorg97&F. Pliquettorg70&J. Plutaorg139&S. Pochybovaorg142&P.L.M.
Podesta-Lermaorg118&M.G. Poghosyanorg95&B. Polichtchoukorg91&N. Poljakorg97&W.
Poonsawatorg113&A. Poporg48&H. Poppenborgorg141&S. Porteboeuf-
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Prinoorg59&C.A. Pruneauorg140&I. Pshenichnovorg63&M. Puccioorg28&V.
Puninorg106&J. Putschkeorg140&S. Rahaorg4&S. Rajputorg99&J. Rakorg125&A.
Rakotozafindrabeorg134&L. Ramelloorg34&F. Ramiorg133&R. Raniwalaorg100&S.
Raniwalaorg100&S.S. Räsänenorg45&B.T. Rascanuorg70&V. Ratzaorg44&I.
Ravasengaorg33&K.F. Readorg127,org95&K. Redlichorg85orgIV&A. Rehmanorg24&P.
Reicheltorg70&F. Reidtorg36&X. Renorg7&R. Renfordtorg70&A. Reshetinorg63&J.-P.
Revolorg11&K. Reygersorg102&V. Riabovorg96&T. Richertorg64,org81&M.
Richterorg23&P. Riedlerorg36&W. Rieglerorg36&F. Riggiorg30&C. Risteaorg69&S.P.
Rodeorg50&M. Rodríguez Cahuantziorg2&K. Røedorg23&R. Rogalevorg91&E.
Rogochayaorg76&D. Rohrorg36&D. Röhrichorg24&P.S. Rokitaorg139&F.
Ronchettiorg52&E.D. Rosasorg71&K. Roslonorg139&P. Rosnetorg131&A.
Rossiorg57,org31&A. Rotondiorg135&F. Roukoutakisorg84&C. Royorg133&P.
Royorg107&O.V. Ruedaorg71&R. Ruiorg27&B. Rumyantsevorg76&A. Rustamovorg87&E.
Ryabinkinorg88&Y. Ryabovorg96&A. Rybickiorg116&S. Saarinenorg45&S.
Sadhuorg138&S. Sadovskyorg91&K. Šafaříkorg36&S.K. Sahaorg138&B. Sahooorg49&P.
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Sandovalorg73&A. Sarkarorg74&D. Sarkarorg138&N. Sarkarorg138&P.
Sarmaorg43&M.H.P. Sasorg64&E. Scapparoneorg54&F. Scarlassaraorg31&B.
Schaeferorg95&H.S. Scheidorg70&C. Schiauaorg48&R. Schickerorg102&C.
Schmidtorg104&H.R. Schmidtorg101&M.O. Schmidtorg102&M. Schmidtorg101&N.V.
Schmidtorg70,org95&J. Schukraftorg36&Y. Schutzorg36,org133&K. Schwarzorg104&K.
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Segerorg17&Y. Sekiguchiorg129&D. Sekihataorg46&I. Selyuzhenkovorg104,org92&K.
Senosiorg74&S. Senyukovorg133&E. Serradillaorg73&P. Settorg49&A.
Sevcencoorg69&A. Shabanovorg63&A. Shabetaiorg112&R. Shahoyanorg36&W.
Shaikhorg107&A. Shangaraevorg91&A. Sharmaorg98&A. Sharmaorg99&M.
Sharmaorg99&N. Sharmaorg98&A.I. Sheikhorg138&K. Shigakiorg46&M.
Shimomuraorg83&S. Shirinkinorg65&Q. Shouorg110,org7&K. Shtejerorg28&Y.
Sibiriakorg88&S. Siddhantaorg55&K.M. Sielewiczorg36&T. Siemiarczukorg85&D.
Silvermyrorg81&G. Simatovicorg90&G. Simonettiorg103,org36&R.
Singarajuorg138&R. Singhorg86&R. Singhorg99&V. Singhalorg138&T. Sinhaorg107&B.
Sitarorg15&M. Sittaorg34&T.B. Skaaliorg23&M. Slupeckiorg125&N.
Smirnovorg143&R.J.M. Snellingsorg64&T.W. Snellmanorg125&J. Songorg20&F.
Soramelorg31&S. Sorensenorg127&F. Sozziorg104&I. Sputowskaorg116&J.
Stachelorg102&I. Stanorg69&P. Stankusorg95&E. Stenlundorg81&D.
Stoccoorg112&M.M. Storetvedtorg38&P. Strmenorg15&A.A.P. Suaideorg119&T.
Sugitateorg46&C. Suireorg62&M. Suleymanovorg16&M. Suljicorg36,org27&R.
Sultanovorg65&M. Šumberaorg94&S. Sumowidagdoorg51&K. Suzukiorg111&S.
Swainorg67&A. Szaboorg15&I. Szarkaorg15&U. Tabassamorg16&J.
Takahashiorg120&G.J. Tambaveorg24&N. Tanakaorg130&M. Tarhiniorg62,org112&M.
Tariqorg18&M.G. Tarzilaorg48&A. Tauroorg36&G. Tejeda Muñozorg2&A.
Telescaorg36&C. Terrevoliorg31&B. Teyssierorg132&D. Thakurorg50&S.
Thakurorg138&D. Thomasorg117&F. Thoresenorg89&R. Tieulentorg132&A.
Tikhonovorg63&A.R. Timminsorg124&A. Toiaorg70&N. Topilskayaorg63&M.
Toppiorg52&S.R. Torresorg118&S. Tripathyorg50&S. Trogoloorg28&G.
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Turrisiorg57&T.S. Tveterorg23&K. Ullalandorg24&E.N. Umakaorg124&A.
Urasorg132&G.L. Usaiorg26&A. Utrobicicorg97&M. Valaorg114&J.W. Van
Hoorneorg36&M. van Leeuwenorg64&P. Vande Vyvreorg36&D. Vargaorg142&A.
Vargasorg2&M. Vargyasorg125&R. Varmaorg49&M. Vasileiouorg84&A.
Vasilievorg88&A. Vauthierorg79&O. Vázquez Doceorg103,org115&V.
Vecherninorg137&A.M. Veenorg64&A. Velureorg24&E. Vercellinorg28&S. Vergara
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Wilkinsonorg54&G.A. Willemsorg141,org36&M.C.S. Williamsorg54&E.
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Zampolliorg36&H.J.C. Zanoliorg119&N. Zardoshtiorg108&A. Zarochentsevorg137&P.
Závadaorg68&N. Zaviyalovorg106&H. Zbroszczykorg139&M. Zhalovorg96&X.
Zhangorg7&Y. Zhangorg7&Z. Zhangorg131,org7&C. Zhaoorg23&V.
Zherebchevskiiorg137&N. Zhigarevaorg65&D. Zhouorg7&Y. Zhouorg89&Z.
Zhouorg24&H. Zhuorg7&J. Zhuorg7&Y. Zhuorg7&A. Zichichiorg29,org11&M.B.
Zimmermannorg36&G. Zinovjevorg3&J. Zmeskalorg111&S. Zouorg7&

## Affiliation notes

orgIDipartimento DET del Politecnico di Torino, Turin, Italy

orgIIM.V. Lomonosov Moscow State University, D.V. Skobeltsyn Institute of
Nuclear, Physics, Moscow, Russia

orgIIIDepartment of Applied Physics, Aligarh Muslim University, Aligarh, India

orgIVInstitute of Theoretical Physics, University of Wroclaw, Poland

## Collaboration Institutes

org1A.I. Alikhanyan National Science Laboratory (Yerevan Physics Institute)
Foundation, Yerevan, Armenia

org2Benemérita Universidad Autónoma de Puebla, Puebla, Mexico

org3Bogolyubov Institute for Theoretical Physics, National Academy of Sciences
of Ukraine, Kiev, Ukraine

org4Bose Institute, Department of Physics and Centre for Astroparticle Physics
and Space Science (CAPSS), Kolkata, India

org5Budker Institute for Nuclear Physics, Novosibirsk, Russia

org6California Polytechnic State University, San Luis Obispo, California,
United States

org7Central China Normal University, Wuhan, China

org8Centre de Calcul de l’IN2P3, Villeurbanne, Lyon, France

org9Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear (CEADEN), Havana,
Cuba

org10Centro de Investigación y de Estudios Avanzados (CINVESTAV), Mexico City
and Mérida, Mexico

org11Centro Fermi - Museo Storico della Fisica e Centro Studi e Ricerche
“Enrico Fermi’, Rome, Italy

org12Chicago State University, Chicago, Illinois, United States

org13China Institute of Atomic Energy, Beijing, China

org14Chonbuk National University, Jeonju, Republic of Korea

org15Comenius University Bratislava, Faculty of Mathematics, Physics and
Informatics, Bratislava, Slovakia

org16COMSATS Institute of Information Technology (CIIT), Islamabad, Pakistan

org17Creighton University, Omaha, Nebraska, United States

org18Department of Physics, Aligarh Muslim University, Aligarh, India

org19Department of Physics, Ohio State University, Columbus, Ohio, United
States

org20Department of Physics, Pusan National University, Pusan, Republic of
Korea

org21Department of Physics, Sejong University, Seoul, Republic of Korea

org22Department of Physics, University of California, Berkeley, California,
United States

org23Department of Physics, University of Oslo, Oslo, Norway

org24Department of Physics and Technology, University of Bergen, Bergen,
Norway

org25Dipartimento di Fisica dell’Università ’La Sapienza’ and Sezione INFN,
Rome, Italy

org26Dipartimento di Fisica dell’Università and Sezione INFN, Cagliari, Italy

org27Dipartimento di Fisica dell’Università and Sezione INFN, Trieste, Italy

org28Dipartimento di Fisica dell’Università and Sezione INFN, Turin, Italy

org29Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN,
Bologna, Italy

org30Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN,
Catania, Italy

org31Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN,
Padova, Italy

org32Dipartimento di Fisica ‘E.R. Caianiello’ dell’Università and Gruppo
Collegato INFN, Salerno, Italy

org33Dipartimento DISAT del Politecnico and Sezione INFN, Turin, Italy

org34Dipartimento di Scienze e Innovazione Tecnologica dell’Università del
Piemonte Orientale and INFN Sezione di Torino, Alessandria, Italy

org35Dipartimento Interateneo di Fisica ‘M. Merlin’ and Sezione INFN, Bari,
Italy

org36European Organization for Nuclear Research (CERN), Geneva, Switzerland

org37Faculty of Electrical Engineering, Mechanical Engineering and Naval
Architecture, University of Split, Split, Croatia

org38Faculty of Engineering and Science, Western Norway University of Applied
Sciences, Bergen, Norway

org39Faculty of Nuclear Sciences and Physical Engineering, Czech Technical
University in Prague, Prague, Czech Republic

org40Faculty of Science, P.J. Šafárik University, Košice, Slovakia

org41Frankfurt Institute for Advanced Studies, Johann Wolfgang Goethe-
Universität Frankfurt, Frankfurt, Germany

org42Gangneung-Wonju National University, Gangneung, Republic of Korea

org43Gauhati University, Department of Physics, Guwahati, India

org44Helmholtz-Institut für Strahlen- und Kernphysik, Rheinische Friedrich-
Wilhelms-Universität Bonn, Bonn, Germany

org45Helsinki Institute of Physics (HIP), Helsinki, Finland

org46Hiroshima University, Hiroshima, Japan

org47Hochschule Worms, Zentrum für Technologietransfer und Telekommunikation
(ZTT), Worms, Germany

org48Horia Hulubei National Institute of Physics and Nuclear Engineering,
Bucharest, Romania

org49Indian Institute of Technology Bombay (IIT), Mumbai, India

org50Indian Institute of Technology Indore, Indore, India

org51Indonesian Institute of Sciences, Jakarta, Indonesia

org52INFN, Laboratori Nazionali di Frascati, Frascati, Italy

org53INFN, Sezione di Bari, Bari, Italy

org54INFN, Sezione di Bologna, Bologna, Italy

org55INFN, Sezione di Cagliari, Cagliari, Italy

org56INFN, Sezione di Catania, Catania, Italy

org57INFN, Sezione di Padova, Padova, Italy

org58INFN, Sezione di Roma, Rome, Italy

org59INFN, Sezione di Torino, Turin, Italy

org60INFN, Sezione di Trieste, Trieste, Italy

org61Inha University, Incheon, Republic of Korea

org62Institut 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

org63Institute for Nuclear Research, Academy of Sciences, Moscow, Russia

org64Institute for Subatomic Physics, Utrecht University/Nikhef, Utrecht,
Netherlands

org65Institute for Theoretical and Experimental Physics, Moscow, Russia

org66Institute of Experimental Physics, Slovak Academy of Sciences, Košice,
Slovakia

org67Institute of Physics, Bhubaneswar, India

org68Institute of Physics of the Czech Academy of Sciences, Prague, Czech
Republic

org69Institute of Space Science (ISS), Bucharest, Romania

org70Institut für Kernphysik, Johann Wolfgang Goethe-Universität Frankfurt,
Frankfurt, Germany

org71Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México,
Mexico City, Mexico

org72Instituto de Física, Universidade Federal do Rio Grande do Sul (UFRGS),
Porto Alegre, Brazil

org73Instituto de Física, Universidad Nacional Autónoma de México, Mexico
City, Mexico

org74iThemba LABS, National Research Foundation, Somerset West, South Africa

org75Johann-Wolfgang-Goethe Universität Frankfurt Institut für Informatik,
Fachbereich Informatik und Mathematik, Frankfurt, Germany

org76Joint Institute for Nuclear Research (JINR), Dubna, Russia

org77Korea Institute of Science and Technology Information, Daejeon, Republic
of Korea

org78KTO Karatay University, Konya, Turkey

org79Laboratoire de Physique Subatomique et de Cosmologie, Université
Grenoble-Alpes, CNRS-IN2P3, Grenoble, France

org80Lawrence Berkeley National Laboratory, Berkeley, California, United
States

org81Lund University Department of Physics, Division of Particle Physics,
Lund, Sweden

org82Nagasaki Institute of Applied Science, Nagasaki, Japan

org83Nara Women’s University (NWU), Nara, Japan

org84National and Kapodistrian University of Athens, School of Science,
Department of Physics , Athens, Greece

org85National Centre for Nuclear Research, Warsaw, Poland

org86National Institute of Science Education and Research, HBNI, Jatni, India

org87National Nuclear Research Center, Baku, Azerbaijan

org88National Research Centre Kurchatov Institute, Moscow, Russia

org89Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark

org90Nikhef, National institute for subatomic physics, Amsterdam, Netherlands

org91NRC Kurchatov Institute IHEP, Protvino, Russia

org92NRNU Moscow Engineering Physics Institute, Moscow, Russia

org93Nuclear Physics Group, STFC Daresbury Laboratory, Daresbury, United
Kingdom

org94Nuclear Physics Institute of the Czech Academy of Sciences, Řež u Prahy,
Czech Republic

org95Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States

org96Petersburg Nuclear Physics Institute, Gatchina, Russia

org97Physics department, Faculty of science, University of Zagreb, Zagreb,
Croatia

org98Physics Department, Panjab University, Chandigarh, India

org99Physics Department, University of Jammu, Jammu, India

org100Physics Department, University of Rajasthan, Jaipur, India

org101Physikalisches Institut, Eberhard-Karls-Universität Tübingen, Tübingen,
Germany

org102Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg,
Heidelberg, Germany

org103Physik Department, Technische Universität München, Munich, Germany

org104Research Division and ExtreMe Matter Institute EMMI, GSI
Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, Germany

org105Rudjer Bošković Institute, Zagreb, Croatia

org106Russian Federal Nuclear Center (VNIIEF), Sarov, Russia

org107Saha Institute of Nuclear Physics, Kolkata, India

org108School of Physics and Astronomy, University of Birmingham, Birmingham,
United Kingdom

org109Sección Física, Departamento de Ciencias, Pontificia Universidad
Católica del Perú, Lima, Peru

org110Shanghai Institute of Applied Physics, Shanghai, China

org111Stefan Meyer Institut für Subatomare Physik (SMI), Vienna, Austria

org112SUBATECH, IMT Atlantique, Université de Nantes, CNRS-IN2P3, Nantes,
France

org113Suranaree University of Technology, Nakhon Ratchasima, Thailand

org114Technical University of Košice, Košice, Slovakia

org115Technische Universität München, Excellence Cluster ’Universe’, Munich,
Germany

org116The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy
of Sciences, Cracow, Poland

org117The University of Texas at Austin, Austin, Texas, United States

org118Universidad Autónoma de Sinaloa, Culiacán, Mexico

org119Universidade de São Paulo (USP), São Paulo, Brazil

org120Universidade Estadual de Campinas (UNICAMP), Campinas, Brazil

org121Universidade Federal do ABC, Santo Andre, Brazil

org122University College of Southeast Norway, Tonsberg, Norway

org123University of Cape Town, Cape Town, South Africa

org124University of Houston, Houston, Texas, United States

org125University of Jyväskylä, Jyväskylä, Finland

org126University of Liverpool, Department of Physics Oliver Lodge Laboratory ,
Liverpool, United Kingdom

org127University of Tennessee, Knoxville, Tennessee, United States

org128University of the Witwatersrand, Johannesburg, South Africa

org129University of Tokyo, Tokyo, Japan

org130University of Tsukuba, Tsukuba, Japan

org131Université Clermont Auvergne, CNRS/IN2P3, LPC, Clermont-Ferrand, France

org132Université de Lyon, Université Lyon 1, CNRS/IN2P3, IPN-Lyon,
Villeurbanne, Lyon, France

org133Université de Strasbourg, CNRS, IPHC UMR 7178, F-67000 Strasbourg,
France, Strasbourg, France

org134 Université Paris-Saclay Centre d¿Études de Saclay (CEA), IRFU,
Department de Physique Nucléaire (DPhN), Saclay, France

org135Università degli Studi di Pavia, Pavia, Italy

org136Università di Brescia, Brescia, Italy

org137V. Fock Institute for Physics, St. Petersburg State University, St.
Petersburg, Russia

org138Variable Energy Cyclotron Centre, Kolkata, India

org139Warsaw University of Technology, Warsaw, Poland

org140Wayne State University, Detroit, Michigan, United States

org141Westfälische Wilhelms-Universität Münster, Institut für Kernphysik,
Münster, Germany

org142Wigner Research Centre for Physics, Hungarian Academy of Sciences,
Budapest, Hungary

org143Yale University, New Haven, Connecticut, United States

org144Yonsei University, Seoul, Republic of Korea