2015 252 14 September

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

Transverse momentum dependence of D-meson production in Pb–Pb collisions

The production of prompt charmed mesons ${\rm D^{0}}$, ${\rm D^{+}}$ and ${\rm
D^{*+}}$, and their antiparticles, was measured with the ALICE detector in
Pb–Pb collisions at the centre-of-mass energy per nucleon pair,
$\sqrt{s_{\scriptscriptstyle\rm NN}}$, of $2.76\leavevmode\nobreak\
\mathrm{TeV}$. The production yields for rapidity $|y|<0.5$ are presented as a
function of transverse momentum, $p_{\rm T}$, in the interval 1–36
$\mathrm{GeV}/c$ for the centrality class 0–10% and in the interval 1–16
GeV/$c$ for the centrality class 30–50%. The nuclear modification factor
$R_{\rm AA}$ was computed using a proton–proton reference at
$\sqrt{s}=2.76\leavevmode\nobreak\ \mathrm{TeV}$, based on measurements at
$\sqrt{s}=7\leavevmode\nobreak\ \mathrm{TeV}$ and on theoretical calculations.
A maximum suppression by a factor of 5–6 with respect to binary-scaled pp
yields is observed for the most central collisions at $p_{\rm T}$ of about
$10\leavevmode\nobreak\ \mathrm{GeV}/c$. A suppression by a factor of about
2–3 persists at the highest $p_{\rm T}$ covered by the measurements. At low
$p_{\rm T}$ (1–3 GeV/$c$), the $R_{\rm AA}$ has large uncertainties that span
the range 0.35 (factor of about 3 suppression) to 1 (no suppression). In all
$p_{\rm T}$ intervals, the $R_{\rm AA}$ is larger in the 30–50% centrality
class compared to central collisions. The D-meson $R_{\rm AA}$ is also
compared with that of charged pions and, at large $p_{\rm T}$, charged
hadrons, and with model calculations.

##  1 Introduction

A state of strongly-interacting matter characterised by high energy density
and temperature is predicted to be formed in ultra-relativistic collisions of
heavy nuclei. According to calculations using Quantum Chromodynamics (QCD) on
the lattice, these extreme conditions lead to the formation of a Quark–Gluon
Plasma (QGP) state, in which quarks and gluons are deconfined, and chiral
symmetry is partially restored (see e.g. [1, 2, 3, 4]).

Heavy quarks are produced in the hard scattering processes that occur in the
early stage of the collision between partons of the incoming nuclei. Their
production is characterised by a timescale $\Delta t<1/(2\,m_{\rm c,b})$,
$\sim 0.1$ fm/$c$ for charm and $\sim 0.01$ fm/$c$ for beauty quarks, that is
shorter than the formation time of the QGP medium, about $0.3$ fm/$c$ at Large
Hadron Collider (LHC) energies [5]. They can successively interact with the
constituents of the medium and lose part of their energy, via inelastic
processes (gluon radiation) [6, 7] or elastic scatterings (collisional
processes) [8, 9, 10]. Energy loss can be studied using the nuclear
modification factor $R_{\rm AA}$, which compares the transverse-momentum
($p_{\rm T}$) differential production yields in nucleus–nucleus collisions
(${\rm d}N_{\rm AA}/{\rm d}p_{\rm T}$) with the cross section in proton–proton
collisions (${\rm d}\sigma_{\rm pp}/{\rm d}p_{\rm T}$) scaled by the average
nuclear overlap function ($\left\langle T_{\rm AA}\right\rangle$)

$R_{\rm AA}(p_{\rm T})={1\over\left\langle T_{\rm AA}\right\rangle}\cdot{{\rm
d}N_{\rm AA}/{\rm d}p_{\rm T}\over{\rm d}\sigma_{\rm pp}/{\rm d}p_{\rm T}}\,.$
(1)

The average nuclear overlap function $\left\langle T_{\rm AA}\right\rangle$
over a centrality class is proportional to the number of binary nucleon-
nucleon collisions per A–A collision in that class and it can be estimated via
Glauber model calculations [11, 12].

According to QCD calculations, quarks are expected to lose less energy than
gluons because their coupling to the medium is smaller [6, 7]. In the energy
regime of the LHC, light-flavour hadrons with $p_{\rm T}$ ranging from 5 to
$20\leavevmode\nobreak\ \mathrm{GeV}/c$ originate predominantly from gluons
produced in hard scattering processes, while for larger $p_{\rm T}$ they
originate mainly from light quarks (see e.g. [13]). Charmed mesons, instead,
provide an experimental tag for a quark parent at all momenta. Therefore, the
comparison of the heavy-flavour hadron $R_{\rm AA}$ with that of pions is
expected to be sensitive to the colour-charge dependence of energy loss.
However, other aspects than the energy loss, like the parton $p_{\rm T}$
spectrum and fragmentation into hadrons, influence the nuclear modification
factor (see e.g. [14, 13]). The effect of the colour-charge dependence of the
energy loss should be then studied via the comparison with model calculations,
that include the description of the aforementioned aspects.

In addition, several mass-dependent effects are predicted to influence the
energy loss for quarks (see [15] for a recent review). The dead-cone effect
should reduce small-angle gluon radiation for quarks that have moderate
energy-over-mass values, i.e. for c and b quarks with momenta up to about 10
and $30\leavevmode\nobreak\ \mathrm{GeV}/c$, respectively [16, 17, 18, 19, 20,
21, 22]. Likewise, collisional energy loss is predicted to be reduced for
heavier quarks, because the spatial diffusion coefficient, which regulates the
momentum transfers with the medium, scales with the inverse of the quark mass
for a given quark momentum [23]. In particular, the study of D mesons from
low-$p_{\rm T}$ to high-$p_{\rm T}$ allows to study the variation of the
energy loss for different charm quark velocity: from a non-relativistic regime
to an highly relativistic one. Low-momentum heavy quarks, including those
shifted to low momentum by parton energy loss, could participate in the
collective expansion of the system as a consequence of multiple interactions
[24, 25]. It was also suggested that low-momentum heavy quarks could hadronise
not only via fragmentation in the vacuum, but also via the mechanism of
recombination with other quarks from the medium [25, 26].

The nuclear modification factor of heavy-flavour production was first studied
at the Relativistic Heavy Ion Collider (RHIC). The PHENIX and STAR
Collaborations reported measurements using heavy-flavour decay electrons and
muons in Au–Au and Cu–Cu collisions at centre-of-mass energy per nucleon pair,
$\sqrt{s_{\scriptscriptstyle\rm NN}}=200$ GeV [27, 28, 29, 30]. A suppression
with respect to binary scaling was observed for $p_{\rm T}$ larger than about
3 GeV/$c$, reaching a minimum $R_{\rm AA}$ of about 0.2–0.3 in the interval
$4<p_{\rm T}<6$ GeV/$c$. The STAR Collaboration recently measured the $R_{\rm
AA}$ of $\rm D^{0}$ mesons in Au–Au collisions for the interval $0<p_{\rm
T}<6$ GeV/$c$ [31]. At $p_{\rm T}$ of about 5–6 GeV/$c$ the $R_{\rm AA}$ value
is similar to that observed for electrons from heavy-flavour decays and the
$R_{\rm AA}$ increases towards low $p_{\rm T}$, reaching a maximum value of
about 1.5 at 1–2 GeV/$c$. This feature is described by heavy-flavour transport
calculations that include radial flow and a contribution due to recombination
in the charm hadronisation process [31].

A first measurement of the production of prompt D mesons at mid-rapidity in
the $p_{\rm T}$ interval 2–16 $\mathrm{GeV}/c$ was published, using the Pb–Pb
data at $\sqrt{s_{\scriptscriptstyle\rm NN}}=2.76\leavevmode\nobreak\
\mathrm{TeV}$ collected in 2010 during LHC Run 1 [32]. A minimum $R_{\rm AA}$
of about 0.2–0.3 was measured at $p_{\rm T}$ of about 10 GeV/$c$ for the 20%
most central collisions. The measurement of D-meson production in p–Pb
collisions at $\sqrt{s_{\scriptscriptstyle\rm NN}}=5.02$ TeV, showing an
$R_{\rm pPb}$ compatible with unity, has provided clear evidence that the
suppression with respect to binary-scaled pp cross sections, observed in Pb–Pb
collisions, cannot be attributed to cold nuclear matter effects for $p_{\rm
T}$ larger than 2 GeV/$c$ and is, thus, caused by final-state interactions in
the hot and dense medium [33].

In Pb–Pb collisions, the nuclear modification factor at low $p_{\rm T}$
results from the interplay of different effects occurring in the initial and
in the final state. The measured D-meson nuclear modification factor in p–Pb
collisions, although consistent with unity, is also described within
uncertainties by calculations that include substantial initial-state effects,
such as parton shadowing or saturation [33], that could manifest as a
reduction of the yields in Pb–Pb (and thus of the $R_{\rm AA}$) by up to 50%
at low $p_{\rm T}$. In addition, the measurement of a significant azimuthal
anisotropy of D-meson production, with respect to the estimated direction of
the reaction plane in non-central Pb–Pb collisions, indicates that charm
quarks participate in the collective expansion of the medium [34, 35].
Therefore, radial flow could play a relevant role as well. In order to
investigate these aspects, it is important to have a precise measurement of
$R_{\rm AA}$ down to low $p_{\rm T}$. In the high-$p_{\rm T}$ region, where
parton energy loss is expected to be dominated by radiative processes, the
extension of the D-meson $R_{\rm AA}$ beyond 20 $\mathrm{GeV}/c$ would provide
the first measurement of identified-hadron $R_{\rm AA}$ at such high $p_{\rm
T}$.

In this article we present the measurement of $p_{\rm T}$-differential yields
and nuclear modification factors of prompt ${\rm D^{0}}$, ${\rm D^{+}}$ and
${\rm D^{*+}}$ mesons (including their antiparticles), reconstructed via their
hadronic decays in Pb–Pb collisions at $\sqrt{s_{\scriptscriptstyle\rm
NN}}=2.76\leavevmode\nobreak\ \mathrm{TeV}$, using the data sample recorded in
2011. For central collisions, the integrated luminosity is larger by a factor
of about 10 than that used for the previously published results [32]. This
allows us to extend the measurement of $R_{\rm AA}$ to lower and higher
$p_{\rm T}$ (from 2–16 $\mathrm{GeV}/c$ to 1–36 $\mathrm{GeV}/c$), to improve
its precision, and to perform the study in a narrower class of the most
central collisions (10% most central instead of 20% most central).

The article is organised as follows: the experimental apparatus is described
in Section 2, together with the data sample. In Section 3, the D-meson decay
reconstruction and all corrections applied to the yields are presented, along
with the procedure used to obtain the pp reference at
$\sqrt{s}=2.76\leavevmode\nobreak\ \mathrm{TeV}$. In Section 4 the systematic
uncertainties are discussed. The results for the 0–10% (central) and 30–50%
(semi-peripheral) centrality classes are presented in Section 5. In the same
Section results obtained in Pb–Pb collisions are compared with the nuclear
modification factor measured in p–Pb collisions at
$\sqrt{s_{\scriptscriptstyle\rm NN}}=5.02\leavevmode\nobreak\ \mathrm{TeV}$. A
comparison with charged pions, charged particles ($ch$) and with theoretical
model predictions is also reported. These comparisons are presented in terms
of the ratio $R_{\rm AA}^{\rm D}/R_{\rm AA}^{\pi,\,ch}$ as well. Conclusions
are drawn in Section 6.

##  2 Experimental apparatus and data sample

The ALICE experimental apparatus [36] is composed of various detectors for
particle reconstruction and identification at mid-rapidity ($|\eta|<0.9$), a
forward muon spectrometer ($-4<\eta<-2.5$) and a set of forward-backward
detectors for triggering and event characterization. The detector performance
for measurements in pp, p–Pb and Pb–Pb collisions from the LHC Run 1 is
presented in [37].

The main detector components used in this analysis are the V0 detector, the
Inner Tracking System (ITS), the Time Projection Chamber (TPC) and the Time Of
Flight (TOF) detector, which are located inside a large solenoidal magnet
providing a uniform magnetic field of 0.5 T parallel to the LHC beam direction
($z$ axis in the ALICE reference system) and the Zero Degree Calorimeter
(ZDC), located at $\pm 114$ m from the interaction point.

Pb–Pb collision data were recorded with a minimum-bias interaction trigger
based on information from the V0 detector, which consists of two scintillator
arrays covering the full azimuth in the pseudorapidity intervals
$-3.7<\eta<-1.7$ and $2.8<\eta<5.1$ [38]. The trigger logic required the
coincidence of signals on both sides of the detector. An online selection
based on the V0 signal amplitudes was used to enhance the sample of central
and mid-central collisions through two separate trigger classes. The
scintillator arrays have an intrinsic time resolution better than 0.5 ns, and
their timing information was used together with that from the ZDCs for offline
rejection of events produced by the interaction of the beams with residual gas
in the vacuum pipe. Only events with a reconstructed interaction point
(primary vertex) within $\pm 10$ cm from the centre of the detector along the
beam line were used in the analysis.

Collisions were divided into centrality classes, determined from the sum of
the V0 signal amplitudes and defined in terms of percentiles of the total
hadronic Pb–Pb cross section. In order to relate the centrality classes to the
collision geometry, the distribution of the V0 summed amplitudes was fitted
with a function based on the Glauber model [11, 12] combined with a two-
component model for particle production [39]. The centrality classes used in
the analysis are reported in Tab. 1, together with the average of the nuclear
overlap function $T_{\rm AA}$, the number of events in each class ($N_{\rm
events}$) and the integrated luminosity.

Centrality class |  $\left\langle T_{\rm AA}\right\rangle$ (mb-1) | $N_{\rm events}$ |  $L_{\rm int}$ ($\rm\mathrm{\mu b}^{-1})$
---|---|---|---
$\phantom{0}0$–10$\%$ | $23.44\pm 0.76$ | $16.4\times 10^{6}$ | $21.3\pm 0.7$
30–50$\%$ | $\phantom{0}3.87\pm 0.18$ | $\phantom{0}9.0\times 10^{6}$ | $\phantom{0}5.8\pm 0.2$
Table 1: Average of the nuclear overlap function, number of events and
integrated luminosity for the two centrality classes used in the analysis. The
uncertainty on the integrated luminosity stems from the uncertainty of the
hadronic Pb–Pb cross section from the Glauber model [39].

The charged-particle tracks used to reconstruct the decay of D mesons were
measured in the TPC and ITS. The tracking algorithm, based on a Kalman filter
[40], starts from three-dimensional space points in the TPC, a large
cylindrical drift detector with both total length and diameter of about 5 m,
covering the pseudorapidity range $\rm|\eta|<$ 0.9 with full azimuthal
acceptance [41]. Tracks are reconstructed in the TPC with up to 159 space
points and with a measurement of the specific ionisation energy loss d$E$/d$x$
with a resolution of about 6%.

Hits in the ITS are associated to the prolongation of the TPC tracks, forming
the global tracks. The ITS consists of six cylindrical layers of silicon
detectors [42]. The two innermost layers, placed at 3.9 and 7.6 cm from the
beam line, consist of Silicon Pixel Detectors (SPD). The third and fourth
layers use Silicon Drift Detectors (SDD) and the two outermost layers contain
double-sided Silicon Strip Detectors (SSD). The effective spatial resolutions,
including the intrinsic detector resolutions and residual mis-alignments, are
about 14, 40 and 25 $\mathrm{\mu m}$, for SPD, SDD and SSD, respectively,
along the most precise direction ($r\varphi$) [42].

Global tracks are used to reconstruct the primary interaction vertex and the
secondary vertices of D-meson decays. The transverse momentum resolution for
global tracks ranges from about 1% at $p_{\rm T}=1\leavevmode\nobreak\
\mathrm{GeV}/c$ to about 2% at $10\leavevmode\nobreak\ \mathrm{GeV}/c$, both
in pp and Pb–Pb collisions. The spatial precision of global tracks is
quantified by the resolution on the impact parameter $d_{0}$, which is the
signed distance of closest approach between the track and the primary vertex
in the $xy$-plane transverse to the beam direction. In Pb–Pb collisions, the
$d_{0}$ resolution is better than $65\leavevmode\nobreak\ \mathrm{\mu m}$ for
tracks with a transverse momentum larger than $1\leavevmode\nobreak\
\mathrm{GeV}/c$ and reaches $20\leavevmode\nobreak\ \mathrm{\mu m}$ for
$p_{\rm T}>20\leavevmode\nobreak\ \mathrm{GeV}/c$ [37].

The TOF detector is an array of Multi-Gap Resistive Plate Chambers positioned
at a distance of about 370 cm from the beam line and covering the full azimuth
over the pseudorapidity interval $|\eta|<0.9$. TOF particle identification is
based on the difference between the particle arrival time at the TOF detector
and a start time determined using the arrival time of all particles of the
event with a $\chi^{2}$ minimization [43]. The resolution ($\sigma$) of the
time-of-flight measurement is about 80 ps for pions at $p_{\rm
T}=1\leavevmode\nobreak\ \mathrm{GeV}/c$ in the Pb–Pb collision centrality
intervals used in this analysis. TOF provides charged-particle identification
in the intermediate momentum range, with a 3$\sigma$ separation up to about
$2.5\leavevmode\nobreak\ \mathrm{GeV}/c$ for pions and kaons, and up to about
$4\leavevmode\nobreak\ \mathrm{GeV}/c$ for kaons and protons [37].

##  3 Data analysis

###  3.1 D-meson reconstruction

${\rm D^{0}}$, ${\rm D^{+}}$ and ${\rm D^{*+}}$ mesons, and their
antiparticles, were reconstructed via their hadronic decay channels ${\rm
D}^{0}\to{\rm K}^{-}\pi^{+}$ (weak decay with branching ratio, BR, of $3.88\pm
0.05\%$), ${\rm D}^{+}\to{\rm K}^{-}\pi^{+}\pi^{+}$ (weak decay, BR of
$9.13\pm 0.19\%$) and ${\rm D}^{*+}\to{\rm D}^{0}\pi^{+}$ (strong decay, BR of
$67.7\pm 0.05\%$) followed by ${\rm D}^{0}\to{\rm K}^{-}\pi^{+}$ [44]. ${\rm
D^{0}}$ and ${\rm D^{+}}$ mesons have mean proper decay lengths ($c\tau$) of
123 and 312 $\mathrm{\mu m}$, respectively [44]. In the case of the ${\rm
D^{*+}}$, the decay topology of the produced ${\rm D^{0}}$ was exploited. The
transverse momentum of the soft pions produced in the ${\rm D^{*+}}$ decays
typically ranges from 0.1 to 1.5 $\mathrm{GeV}/c$, depending on the ${\rm
D^{*+}}$ $p_{\rm T}$.

${\rm D^{0}}$ and ${\rm D^{+}}$ candidates were formed using pairs and
triplets of tracks with the correct charge-sign combination, requiring
$|\eta|<0.8$, $p_{\rm T}>0.4\leavevmode\nobreak\ \mathrm{GeV}/c$, at least 70
associated space points (out of a maximum of 159) and fit quality
$\chi^{2}/{\rm ndf}<2$ in the TPC, and at least two hits (out of six) in the
ITS, out of which at least one in either of the two SPD layers. ${\rm D^{*+}}$
candidates were formed by combining ${\rm D^{0}}$ candidates with tracks with
$p_{\rm T}>0.1\leavevmode\nobreak\ \mathrm{GeV}/c$ and at least three hits in
the ITS, out of which at least one in the SPD.

The aforementioned track selection limits the D-meson acceptance in rapidity.
The acceptance drops steeply to zero for $|y|>0.5$ at low $p_{\rm T}$ and
$|y|>0.8$ for $p_{\rm T}>5\leavevmode\nobreak\ \mathrm{GeV}/c$. A $p_{\rm
T}$-dependent fiducial acceptance cut, $|y_{\rm D}|<y_{\rm fid}(p_{\rm T})$,
was therefore applied to the D-meson rapidity. The cut value, $y_{\rm
fid}(p_{\rm T})$, increases from 0.5 to 0.8 in the range $0<p_{\rm
T}<5\leavevmode\nobreak\ \mathrm{GeV}/c$ according to a second-order
polynomial function and with a constant value of 0.8 for $p_{\rm
T}>5\leavevmode\nobreak\ \mathrm{GeV}/c$.

The selection of the decay topology was based on the displacement of the decay
tracks from the interaction vertex (via their impact parameter, $d_{0}$), the
separation between the secondary and primary vertices (decay length, $L$) and
the pointing angle of the reconstructed D-meson momentum to the primary
vertex. This pointing condition was applied via a selection on the angle
$\theta_{\rm pointing}$ between the direction of the reconstructed momentum of
the candidate and the straight line connecting the primary and secondary
vertices. The projections of the pointing angle and of the decay length onto
the transverse plane ($\theta^{xy}_{\rm pointing}$ and $L^{xy}$) were also
used. The selection requirements were tuned to provide a large statistical
significance for the signal and to keep the selection efficiency as high as
possible. The chosen selection values depend on the $p_{\rm T}$ of the D meson
and become tighter from peripheral to central collisions. A detailed
description of the selection criteria was reported in [32, 35].

In order to further reduce the combinatorial background, pions and kaons were
identified using the TPC and TOF detectors. A 3$\sigma$ compatibility cut was
applied to the difference between the measured and expected signals (for pions
and kaons) for the TPC d$E$/d$x$ and TOF time-of-flight. Tracks that are not
matched with a hit in the TOF detector were identified using only the TPC
information. Particle identification (PID) was not applied to the pion track
from the ${\rm D^{*+}}$ decay. This PID selection provides a reduction of the
background by a factor of 2–3 at low $p_{\rm T}$ with respect to the case
without applying the selection, while having an efficiency of about $95\%$ for
the signal.

Figure 1:  (K, $\pi$) (top row) and (K, $\pi$, $\pi$) (central row) invariant-
mass distributions for the centrality class 0–10%. Bottom row: Distribution of
the mass difference $\Delta M=M({\rm K}\pi\pi)-M({\rm K}\pi)$ for the
centrality class 0–10%. The distributions are reported in three $p_{\rm T}$
intervals for each meson (left, middle and right column). The fit functions
used to describe the background (dash), the background without signal
reflections (only for ${\rm D^{0}}$, long-dash) and the total distribution
including the signal (solid) are shown.

The raw D-meson yields were obtained from fits to the candidate invariant-mass
distributions $M({\rm K}\pi)$ for ${\rm D^{0}}$, $M({\rm K}\pi\pi)$ for ${\rm
D^{+}}$, and the mass difference $\Delta M=M({\rm K}\pi\pi)-M({\rm K}\pi)$ for
${\rm D^{*+}}$. The ${\rm D^{0}}$ and ${\rm D^{+}}$ candidate invariant-mass
distributions were fitted with a function composed of a Gaussian for the
signal and an exponential term to describe the background shape. In the 0–10%
centrality class, the background in the $M({\rm K}\pi)$ distribution for the
interval $1<p_{\rm T}<2\leavevmode\nobreak\ \mathrm{GeV}/c$ could not be
accounted for by an exponential shape and was instead modelled with a fourth-
order polynomial function. The $\Delta M$ distribution of ${\rm D^{*+}}$
candidates was fitted with a Gaussian function for the signal and a threshold
function multiplied by an exponential for the background: $a\,\sqrt{\Delta
M-m_{\pi}}\cdot{\rm e}^{b(\Delta M-m_{\pi})}$.

In the case of ${\rm D^{0}}$ mesons, an additional term was included in the
fit function to account for the background from “reflections”, i.e. signal
candidates that remain in the invariant-mass distribution when the
${\rm(K,\pi)}$ mass hypotheses for the two decay tracks are swapped. A study
of simulations showed that about 70$\%$ of these reflections are rejected by
the PID selection, while the residual contribution results in a broad
invariant-mass distribution, which can be described using a sum of two
Gaussians. In order to account for the contribution of reflections in the data
(2–5% at low $p_{\rm T}$, about 10% at high $p_{\rm T}$), a template
consisting of two Gaussians was included in the fit. The centroids and widths,
as well as the ratios of the integrals of these Gaussians to the signal
integral, were fixed to the values obtained in the simulations (see also
[35]).

Figure 2: (K, $\pi$) invariant-mass distribution for the interval $1<p_{\rm
T}<2\leavevmode\nobreak\ \mathrm{GeV}/c$ for the 0–10% (left) and 30–50%
(right) centrality classes, obtained after the subtraction of the background
estimated by a fourth-order polynomial function for the most central
collisions and an exponential for the 30–50% centrality class. The
contribution of reflections is also included in the fit. The fit function used
to describe the signal (solid line) is shown.

In the centrality class 0–10%, the signal extraction was performed in the
interval $1<p_{\rm T}<24\leavevmode\nobreak\ \mathrm{GeV}/c$ for ${\rm D^{0}}$
mesons, divided in 9 $p_{\rm T}$ bins, and in the interval $3<p_{\rm
T}<36\leavevmode\nobreak\ \mathrm{GeV}/c$ for ${\rm D^{+}}$ and ${\rm D^{*+}}$
mesons, divided in 8 $p_{\rm T}$ bins. In the centrality class 30–50%, the
signal extraction was possible in the interval $1<p_{\rm
T}<16\leavevmode\nobreak\ \mathrm{GeV}/c$ for ${\rm D^{0}}$ mesons and in the
interval $2<p_{\rm T}<16\leavevmode\nobreak\ \mathrm{GeV}/c$ for ${\rm D^{+}}$
and ${\rm D^{*+}}$ mesons. Beyond these intervals, the signal extraction was
prevented by the low signal-over-background ratio at low $p_{\rm T}$, and by
the low signal yield at high $p_{\rm T}$. Figure 1 shows the ${\rm D^{0}}$ and
${\rm D^{+}}$ invariant-mass distributions and ${\rm D^{*+}}$ mass difference
distributions in three $p_{\rm T}$ intervals for the centrality class 0–10%.
In the interval $16<p_{\rm T}<24\leavevmode\nobreak\ \mathrm{GeV}/c$ the fit
range for the ${\rm D^{0}}$ case is asymmetric. The range was limited to
values larger than $1.68\leavevmode\nobreak\ \mathrm{GeV}/c^{2}$ because the
invariant-mass distribution of $({\rm K},\pi)$ pairs from D mesons decaying in
three or more prongs produces a wide structure below about
$1.72\leavevmode\nobreak\ \mathrm{GeV}/c^{2}$, which cannot be accounted for
by the background terms of the fit function.

Figure 2 shows the background-subtracted ${\rm D^{0}}$ invariant-mass
distribution for the interval $1<p_{\rm T}<2\leavevmode\nobreak\
\mathrm{GeV}/c$ for the 0–10% (left panel) and 30–50% (right panel) centrality
classes.

For all three D-meson species, the position of the signal peak was found to be
compatible with the world average value and its $p_{\rm T}$-dependent width
with the values observed in the simulation. The statistical significance of
the observed signals $\rm S/\sqrt{S+B}$ varies from 3 to 18, while the signal-
over-background ratio S/B ranges from 0.01 to 1.8, depending on the meson
species, $p_{\rm T}$ interval and centrality class.

###  3.2 ${\rm d}N/{\rm d}p_{\rm T}$ spectra corrections

The D-meson raw yields were corrected in order to obtain the $p_{\rm
T}$-differential yields of prompt D mesons

$\left.\frac{{\rm d}N^{\rm D}}{{\rm d}p_{\rm
T}}\right|_{|y|<0.5}=\frac{\left.f_{\rm prompt}(p_{\rm
T})\cdot\frac{1}{2}N_{\rm raw}^{\rm D+\overline{D}}(p_{\rm
T})\right|_{|y|<y_{\rm fid}}}{\Delta p_{\rm T}\cdot\alpha_{y}\cdot({\rm
Acc}\times\epsilon)_{\rm prompt}(p_{\rm T})\cdot{\rm BR}\cdot N_{\rm
events}}\,,$ (2)

where prompt refers to mesons not coming from weak decays of B hadrons. The
raw yields $N_{\rm raw}^{\rm D+\overline{D}}$ were divided by a factor of two
to obtain the charge-averaged (particle and antiparticle) yields. To correct
for the contribution of B-meson decay feed-down, the raw yields were
multiplied by the fraction of promptly produced D mesons, $f_{\rm prompt}$
(discussed in details later in this section). Furthermore, they were divided
by the product of prompt D-meson acceptance and efficiency $({\rm
Acc}\times\epsilon)_{\rm prompt}$, by the decay channel branching ratio (BR),
by the transverse momentum interval width ($\Delta p_{\rm T}$) and by the
number of events ($N_{\rm events}$). The factor $\alpha_{y}=y_{\rm fid}/0.5$
normalises the corrected yields measured in $|y|<y_{\rm fid}$ to one unit of
rapidity $|y|<0.5$, assuming a uniform rapidity distribution for D mesons in
the measured range. This assumption was validated to the 1% level with
simulations [45, 46].

The correction for acceptance and efficiency $({\rm Acc}\times\epsilon)_{\rm
prompt}$ was determined using Monte Carlo simulations with a detailed
description of the detector and its response, based on the GEANT3 transport
package [47]. The simulation was tuned to reproduce the (time-dependent)
position and width of the interaction vertex distribution, as well as the
number of active read-out channels and the accuracy of the detector
calibration. The underlying Pb–Pb events at $\sqrt{s_{\scriptscriptstyle\rm
NN}}=2.76$ TeV were simulated using the HIJING v1.383 generator [48] and
D-meson signals were added with the PYTHIA v6.421 generator [49] with
Perugia-0 tune [50]. Each simulated PYTHIA pp event contained a $\rm
c\overline{c}$ or $\rm b\overline{b}$ pair, and D mesons were forced to decay
in the hadronic channels of interest for the analysis. Out of all the
particles produced in these PYTHIA pp events, only the heavy-flavour decay
products were kept and transported through the detector simulation together
with the particles produced according to HIJING. In order to minimise the bias
on the detector occupancy, the number of D mesons injected into each HIJING
event was adjusted according to the Pb–Pb collision centrality. In the most
central event class, the $p_{\rm T}$ distribution of D mesons was weighted in
order to match the shape measured for the $\rm D^{0}$ meson. In the semi-
peripheral centrality class, the D-meson $p_{\rm T}$ distribution was weighted
so as to match the shape given by fixed-order-next-to-leading-log perturbative
QCD calculations (FONLL) [51, 52] multiplied by the $R_{\rm AA}(p_{\rm T})$
computed using the BAMPS model [53, 54, 55].

The efficiencies were evaluated from simulated events that have the same
average charged-particle multiplicity, corresponding to the same detector
occupancy, as observed in data in the centrality classes 0–10% and 30–50%.
Figure 3 shows the ${\rm D^{0}}$, ${\rm D^{+}}$ and ${\rm D^{*+}}$ acceptance-
times-efficiency $({\rm Acc}\times\varepsilon)$ for primary and feed-down D
mesons with rapidity $|y|<y_{\rm fid}(p_{\rm T})$ in the centrality class
0–10%. The efficiencies range from about 0.1$\%$ at low $p_{\rm T}$ to
10–30$\%$ at high $p_{\rm T}$, because of the momentum dependence of the
D-meson decay length and of the topological selections applied in the
different momentum intervals. Also shown in the figure are the $({\rm
Acc}\times\varepsilon)$ values for the case where no PID is applied. The
relative difference with respect to the $({\rm Acc}\times\varepsilon)$
obtained using the PID selection is about 5%, illustrating the high efficiency
of the PID criteria. The $({\rm Acc}\times\varepsilon)$ for D mesons from
B-meson decays is larger than for prompt D mesons by a factor of about 1.5,
because the decay vertices of the feed-down D mesons are more separated from
the primary vertex and are, therefore, more efficiently selected by the
analysis cuts.

Figure 3: Product of acceptance and efficiency for D mesons in Pb–Pb
collisions for the 0–10% centrality class. The rapidity interval is
$|y|<y_{\rm fid}$ (see Section 3.1). The values for prompt (solid lines) and
feed-down (dotted lines) D mesons are shown. Also displayed, for comparison,
are the values for prompt D mesons without PID selection (dashed lines).

The $f_{\rm prompt}$ factor was obtained, following the procedure introduced
in [32], as

$\begin{split}f_{\rm prompt}&=1-\frac{N^{\rm D+\overline{D}\,\textnormal{feed-
down}}_{\rm raw}}{N^{\rm D+\overline{D}}_{\rm raw}}\\\ &=1-R_{\rm
AA}^{\textnormal{feed-down}}\cdot\langle T_{\rm
AA}\rangle\cdot\left(\frac{{\rm d}\sigma}{{\rm d}p_{\rm
T}}\right)^{\textnormal{FONLL,\,EvtGen}}_{{\textnormal{ feed-
down},\,|y|<0.5}}\cdot\frac{\Delta p_{\rm T}\cdot\alpha_{y}\cdot({\rm
Acc}\times\epsilon)_{\textnormal{feed-down}}\cdot{\rm BR}\cdot N_{\rm
events}}{\frac{1}{2}N^{\rm D+\overline{D}}_{\rm raw}}\,.\end{split}$ (3)

In this expression, the symbols denoting the $p_{\rm T}$ dependence have been
omitted for brevity, $N^{\rm D+\overline{D}}_{\rm raw}$ is the measured raw
yields and $N^{{\rm D+\overline{D}}\,\textnormal{feed-down}}_{\rm raw}$ is the
estimated raw yields of $\rm D$ mesons from B-meson decays. In detail, the
B-meson production cross section in pp collisions at
$\sqrt{s}=2.76\leavevmode\nobreak\ \mathrm{TeV}$, estimated with FONLL
calculations [56], was folded with the ${\rm B\rightarrow D}+X$ decay
kinematics using the EvtGen package [57] and multiplied by $\langle T_{\rm
AA}\rangle$ in each centrality class, by the $({\rm Acc}\times\varepsilon)$
for feed-down $\rm D$ mesons, and by the other factors introduced in Eq. (2).
In addition, the nuclear modification factor of D mesons from B-meson decays
was accounted for. The comparison of the $R_{\rm AA}$ of prompt D mesons
($R_{\rm AA}^{\rm prompt}$) [58] with that of $\rm J/\psi$ from B-meson decays
[59] measured in the CMS experiment indicates that charmed hadrons are more
suppressed than beauty hadrons. The value $R_{\rm AA}^{\textnormal{feed-
down}}=2\cdot R_{\rm AA}^{\rm prompt}$ was used to compute the correction, and
the variation over the range $1<R_{\rm AA}^{\textnormal{feed-down}}/R_{\rm
AA}^{\rm prompt}<3$ was considered for the evaluation of the systematic
uncertainties, in order to take into account possible centrality and $p_{\rm
T}$ dependences. Assuming $R_{\rm AA}^{\textnormal{feed-down}}=2\cdot R_{\rm
AA}^{\rm prompt}$, the resulting $f_{\rm prompt}$ ranges from about $0.65$ to
0.85, depending on the D-meson species and on the $p_{\rm T}$ interval.

###  3.3 Proton–proton reference for $R_{\rm AA}$

The $p_{\rm T}$-differential cross section of prompt D mesons with $|y|<0.5$
in pp collisions at $\sqrt{s}=2.76\leavevmode\nobreak\ \mathrm{TeV}$, used as
reference for the nuclear modification factor, was obtained as follows:

  * •

in the interval $2<p_{\rm T}<16\,(24)\leavevmode\nobreak\ \mathrm{GeV}/c$ for
${\rm D^{0}}$ (${\rm D^{+}}$ and ${\rm D^{*+}}$), the measurement at
$\sqrt{s}=7\leavevmode\nobreak\ \mathrm{TeV}$ [45] scaled to
$\sqrt{s}=2.76\leavevmode\nobreak\ \mathrm{TeV}$ with FONLL calculations [56]
was used;

  * •

in the interval $1<p_{\rm T}<2\leavevmode\nobreak\ \mathrm{GeV}/c$ for ${\rm
D^{0}}$, an average of the aforementioned $\sqrt{s}=7\leavevmode\nobreak\
\mathrm{TeV}$ scaled measurement and of the measurement at
$\sqrt{s}=2.76\leavevmode\nobreak\ \mathrm{TeV}$ [60] was used;

  * •

in the interval $16\,(24)<p_{\rm T}<24\,(36)\leavevmode\nobreak\
\mathrm{GeV}/c$ for ${\rm D^{0}}$ (${\rm D^{+}}$ and ${\rm D^{*+}}$), where
their cross sections were not measured in pp collisions, the FONLL calculation
at $\sqrt{s}=2.76\leavevmode\nobreak\ \mathrm{TeV}$ [56] was used as a
reference, after scaling it to match the central value of the data at lower
$p_{\rm T}$.

The $p_{\rm T}$-dependent scaling factor from $\sqrt{s}=7\leavevmode\nobreak\
\mathrm{TeV}$ to $\sqrt{s}=2.76\leavevmode\nobreak\ \mathrm{TeV}$ was
determined with FONLL calculations and its uncertainties were determined by
varying the parameters (charm-quark mass, factorisation and renormalisation
scales) as described in [61]. The uncertainties on the scaling factor range
from ${}^{+57}_{-11}\%$ for $1<p_{\rm T}<2\leavevmode\nobreak\ \mathrm{GeV}/c$
to about $\pm 5\%$ for $p_{\rm T}>10\leavevmode\nobreak\ \mathrm{GeV}/c$. The
result of the scaling of the $\sqrt{s}=7\leavevmode\nobreak\ \mathrm{TeV}$
$p_{\rm T}$-differential cross sections to $\sqrt{s}=2.76\leavevmode\nobreak\
\mathrm{TeV}$ was validated with measurements from a smaller data sample in pp
collisions at $\sqrt{s}=2.76\leavevmode\nobreak\ \mathrm{TeV}$ [60]. These
measurements cover a reduced $p_{\rm T}$ interval with a statistical
uncertainty of 20–25% and therefore they were not used as a pp reference for
$p_{\rm T}>2\leavevmode\nobreak\ \mathrm{GeV}/c$.

For the lowest $p_{\rm T}$ interval for the ${\rm D^{0}}$ meson, the two
references (obtained from the measurement in pp collisions at
$\sqrt{s}=2.76\leavevmode\nobreak\ \mathrm{TeV}$ and from the
$\sqrt{s}=7\leavevmode\nobreak\ \mathrm{TeV}$ scaled measurement) have
comparable uncertainties. Therefore, in this interval, the two values were
averaged using the inverse of the squared relative uncertainties as weights.
In particular, the statistical uncertainties and the uncorrelated part of the
systematic uncertainties, i.e. the systematic uncertainty from data analysis
(yield extraction, efficiency corrections) and the scaling uncertainty, were
used in the weight. The uncertainties on the feed-down subtraction were
considered as fully correlated among the two measurements, and were propagated
linearly.

The cross section measurements for D mesons in pp collisions at
$\sqrt{s}=7\leavevmode\nobreak\ \mathrm{TeV}$ are limited to $p_{\rm T}\leq
16\leavevmode\nobreak\ \mathrm{GeV}/c$ for ${\rm D^{0}}$ and to $p_{\rm T}\leq
24\leavevmode\nobreak\ \mathrm{GeV}/c$ for ${\rm D^{+}}$ and ${\rm D^{*+}}$.
Beyond these limits the pp reference was obtained using the cross section from
the FONLL calculation at $\sqrt{s}=2.76\leavevmode\nobreak\ \mathrm{TeV}$
[56]. Since the central value of the FONLL calculation underestimates the
measurement for $p_{\rm T}>5\leavevmode\nobreak\ \mathrm{GeV}/c$ at both
$\sqrt{s}=2.76\leavevmode\nobreak\ \mathrm{TeV}$ and
$\sqrt{s}=7\leavevmode\nobreak\ \mathrm{TeV}$ [60, 45], the FONLL cross
section was multiplied by a scaling factor ($\kappa$)

$\frac{{\rm d}\sigma}{{\rm d}p_{\rm T}}=\kappa\cdot\Bigg{(}\frac{{\rm
d}\sigma}{{\rm d}p_{\rm T}}\Bigg{)}^{\textnormal{FONLL}}_{\sqrt{s}=2.76\,{\rm
TeV},\,|y|<0.5}\,.$ (4)

The factor $\kappa$ was determined by fitting with a constant the data-to-
theory ratio at $\sqrt{s}=7\leavevmode\nobreak\ \mathrm{TeV}$ in the interval
$5<p_{\rm T}<16\leavevmode\nobreak\ \mathrm{GeV}/c$. Since the measurements at
$\sqrt{s}=2.76\leavevmode\nobreak\ \mathrm{TeV}$ are less precise, they do not
constrain further the scaling factor. Depending on the D-meson species, the
factor $\kappa$ ranges from 1.4 to 1.5, for the central values of the FONLL
calculation parameters [56]. The statistical uncertainty of the extrapolated
cross section was determined by propagating the statistical uncertainties of
the measurement in the determination of $\kappa$ and it amounts to about
$5\%$. The systematic uncertainties were evaluated under the conservative
assumption that the systematic uncertainties of the measurement are fully
correlated over $p_{\rm T}$, i.e. by repeating the calculation of $\kappa$
after shifting all data points consistently within their systematic
uncertainties. In addition, the calculation in Eq. (4) was performed
considering the FONLL cross sections obtained from combinations of the
renormalisation and factorisation scales with values
$(0.5,1,2)\cdot\sqrt{m_{\rm c}^{2}+p_{\rm T,c}^{2}}$ [56], as well as the
upper and lower limits of their envelope111Where $m_{\rm c}$ and $p_{\rm T,c}$
are respectively the mass and the transverse momentum of the charm quark
considered in the calculations.. This resulted in a total systematic
uncertainty on the $p_{\rm T}$-extrapolated cross section of about
${}^{+50}_{-35}\%$.

##  4 Systematic uncertainties

###  4.1 Systematic uncertainties on the D-meson $p_{\rm T}$ spectra

Particle | ${\rm D^{0}}$ | ${\rm D^{+}}$ | ${\rm D^{*+}}$
---|---|---|---
0–10% centrality class
$p_{\rm T}$ interval ($\mathrm{GeV}/c$) | 1–2 | 6–8 | 16–24 | 3–4 | 6–8 | 24–36 | 3–4 | 6–8 | 24–36
Yield extraction | 15% | 5% | 15% | 10% | 8% | 8% | 12% | 5% | 10%
Tracking efficiency | 10% | 10% | 10% | 15% | 15% | 15% | 15% | 15% | 15%
Selection cuts | 15% | 5% | 5% | 10% | 10% | 10% | 10% | 10% | 10%
PID efficiency |  05% |  05% |  05% |  05% |  05% |  05% |  05% |  05% |  05%
MC $p_{\rm T}$ shape | 15% |  01% |  01% |  06% |  01% |  01% |  04% |  01% |  01%
FONLL feed-down corr. | ${}_{-45}^{+\phantom{0}5}\%$ | ${}_{-13}^{+\phantom{0}8}\%$ | ${}_{-16}^{+10}\%$ | ${}_{-12}^{+\phantom{0}4}\%$ | ${}_{-11}^{+\phantom{0}6}\%$ | ${}_{-14}^{+\phantom{0}8}\%$ | ${}_{-12}^{+\phantom{0}3}\%$ | ${}_{-\phantom{0}7}^{+\phantom{0}4}\%$ | ${}_{-\phantom{0}8}^{+\phantom{0}3}\%$
$R_{{\rm AA}}^{\rm feed-down}/R_{{\rm AA}}^{\rm prompt}$ (Eq. (3)) | ${}^{+\phantom{0}5}_{-\phantom{0}5}\%$ | ${}^{+11}_{-10}\%$ | ${}^{+16}_{-13}\%$ | ${}^{+\phantom{0}6}_{-\phantom{0}5}\%$ | ${}^{+\phantom{0}9}_{-\phantom{0}7}\%$ | ${}^{+14}_{-11}\%$ | ${}^{+\phantom{0}4}_{-\phantom{0}4}\%$ | ${}^{+\phantom{0}6}_{-\phantom{0}6}\%$ | ${}^{+\phantom{0}6}_{-\phantom{0}6}\%$
BR | 1.3% | 2.1% | 1.5%
Centrality class definition | $<1\%$ | $<1\%$ | $<1\%$
30–50% centrality class
$p_{\rm T}$ interval ($\mathrm{GeV}/c$) | 1–2 | 6–8 | 12–16 | 2–3 | 6–8 | 12–16 | 2–3 | 6–8 | 12–16
Yield extraction | 10% |  08% |  08% | 10% | 10% | 12% | 12% |  08% |  05%
Tracking efficiency | 10% | 10% | 10% | 15% | 15% | 15% | 15% | 15% | 15%
Selection cuts | 10% | 10% | 15% | 10% | 10% | 15% | 15% | 10% | 5%
PID efficiency |  05% |  05% |  05% |  05% |  05% |  05% |  05% |  05% |  05%
MC $p_{\rm T}$ shape |  05% |  01% |  03% | 10% |  02% |  02% | 10% |  01% |  01%
FONLL feed-down corr. | ${}_{-45}^{+\phantom{0}5}\%$ | ${}_{-12}^{+\phantom{0}7}\%$ | ${}_{-11}^{+\phantom{0}8}\%$ | ${}_{-21}^{+\phantom{0}6}\%$ | ${}_{-12}^{+\phantom{0}6}\%$ | ${}_{-13}^{+11}\%$ | ${}_{-19}^{+\phantom{0}3}\%$ | ${}_{-\phantom{0}8}^{+\phantom{0}5}\%$ | ${}_{-\phantom{0}8}^{+\phantom{0}4}\%$
$R_{{\rm AA}}^{\rm feed-down}/R_{{\rm AA}}^{\rm prompt}$ (Eq. (3)) | ${}^{+\phantom{0}6}_{-\phantom{0}5}\%$ | ${}^{+11}_{-\phantom{0}9}\%$ | ${}^{+14}_{-11}\%$ | ${}^{+\phantom{0}7}_{-\phantom{0}6}\%$ | ${}^{+\phantom{0}9}_{-\phantom{0}8}\%$ | ${}^{+16}_{-12}\%$ | ${}^{+\phantom{0}4}_{-\phantom{0}4}\%$ | ${}^{+\phantom{0}7}_{-\phantom{0}6}\%$ | ${}^{+\phantom{0}6}_{-\phantom{0}6}\%$
BR | 1.3% | 2.1% | 1.5%
Centrality class definition | $2\%$ | 2% | 2%
Table 2: Relative systematic uncertainties on the prompt D-meson production
yields in Pb–Pb collisions for three selected $p_{\rm T}$ intervals, in the
two centrality classes.

The systematic uncertainties were estimated as a function of transverse
momentum for the two centrality classes. Table 2 lists the uncertainties for
three $p_{\rm T}$ intervals for each meson species.

The systematic uncertainty on the raw yield extraction was evaluated by
repeating the fit of the invariant-mass distributions while varying the fit
range; by fixing the mean and sigma of the Gaussian term to the world-average
value and the expectations from Monte Carlo simulations, respectively; and by
using different fit functions for the background. Specifically, first- and
second-order polynomials were used for ${\rm D^{0}}$ and ${\rm D^{+}}$, and a
power law multiplied by an exponential or a threshold function for ${\rm
D^{*+}}$. A method based on bin counting of the signal after background
subtraction was also used. This method does not assume any particular shape
for the invariant-mass distribution of the signal. The estimated uncertainties
depend on the centrality class and on the $p_{\rm T}$ interval, ranging from
5% to 15% for ${\rm D^{0}}$, 8% to 10% for ${\rm D^{+}}$ and 5% to 10% for
${\rm D^{*+}}$, typically with larger values in the lowest and highest $p_{\rm
T}$ intervals.

For ${\rm D^{0}}$ mesons, the systematic uncertainty due to signal reflections
in the invariant-mass distribution was estimated by changing by $\pm 50\%$ the
ratio of the integral of the reflections over the integral of the signal
(obtained from the simulation) used in the invariant-mass fit with the
reflections template. In addition, the shape of the template was varied using
a polynomial parameterisation (of third or sixth order) of the simulated
distribution, instead of a double-Gaussian parameterisation. A test was
carried out using, in the fit, a template histogram of the reflections
obtained directly from the simulation, rather than a functional form. The
variation observed in the raw yields, ranging from 3% to 7% from low to high
$p_{\rm T}$, was added in quadrature as an independent contribution to the
yield extraction systematic uncertainty.

The systematic uncertainty on the tracking efficiency was estimated by
comparing the probability to match the TPC tracks to the ITS hits in data and
simulation, and by varying the track quality selection criteria (for example,
the minimum number of associated hits in the TPC and in the ITS, and the
maximum $\chi^{2}$/ndf of the momentum fit). The efficiency of the track
matching and the association of hits in the silicon pixel layers was found to
be well reproduced by the simulation with maximal deviations on the level of
5% in the $p_{\rm T}$ range relevant for this analysis (0.5–25
$\mathrm{GeV}/c$) [37]. The effect of mis-associating ITS hits to tracks was
studied using simulations. The mis-association probability is about 5%, for
central collisions, in the transverse momentum interval $1<p_{\rm
T}<3\leavevmode\nobreak\ \mathrm{GeV}/c$ and drops rapidly to zero at larger
$p_{\rm T}$. It was verified that the signal selection efficiencies are the
same for D mesons with and without wrong hit associations. The total
systematic uncertainty on the track reconstruction procedure amounts to 5% for
single tracks, which results in a 10% uncertainty for ${\rm D^{0}}$ mesons
(two-tracks decay) and 15% for ${\rm D^{+}}$ and ${\rm D^{*+}}$ mesons (three-
tracks decay).

The uncertainty on the D-meson selection efficiency reflects a possible non-
exact description of the D-meson kinematic properties and of the detector
resolutions and alignments in the simulation. This effect was estimated by
repeating the analysis with different values of the selection cuts,
significantly modifying the efficiencies, raw yield and background values. As
expected, larger deviations in the corrected yields were observed at low
$p_{\rm T}$, where the efficiencies are low and vary steeply with $p_{\rm T}$,
because of the tighter selections. Due to this, the systematic uncertainties
are slightly larger in these $p_{\rm T}$ intervals. The assigned systematic
uncertainty varies from 5% to 15% for ${\rm D^{0}}$, equals 10% for ${\rm
D^{+}}$, and varies from 10% to 15% for ${\rm D^{*+}}$.

A 5% systematic uncertainty related to the PID selection was evaluated by
comparing the ratio of the corrected yields extracted with and without
particle identification.

The uncertainty on the efficiencies arising from the difference between the
real and simulated D-meson transverse momentum distributions depends on the
width of the $p_{\rm T}$ intervals and on the variation of the efficiencies
within them. This uncertainty also includes the effect of the $p_{\rm T}$
dependence of the nuclear modification factor. As explained in Section 3.2,
for the centrality class 0–10%, the D-meson transverse momentum distribution
from the PYTHIA simulation was re-weighted in order to reproduce the ${\rm
D^{0}}$ spectrum shape observed in data, while for the 30–50% centrality
class, the weights were defined in order to match the $p_{\rm T}$
distributions from FONLL calculations multiplied by the $R_{\rm AA}$ from the
BAMPS model. A systematic uncertainty was estimated by using two alternative
D-meson $p_{\rm T}$ distributions in both centrality classes: i) FONLL $p_{\rm
T}$ distributions, ii) FONLL $p_{\rm T}$ distributions multiplied by $R_{\rm
AA}$ from the BAMPS model. In addition, for the most central events, a
different parameterisation of the measured $p_{\rm T}$ spectrum was used. The
resulting uncertainties decrease with increasing $p_{\rm T}$, varying from
5–6% to 1% in the interval $2<p_{\rm T}<36\leavevmode\nobreak\
\mathrm{GeV}/c$. For ${\rm D^{0}}$ mesons, efficiencies increase by more than
a factor five within the interval $1<p_{\rm T}<2\leavevmode\nobreak\
\mathrm{GeV}/c$ in the most central collisions. As a consequence, a larger
uncertainty of 15% resulted from a detailed study of the stability of the
corrected yields when changing the $p_{\rm T}$ spectrum in the simulation.

The systematic uncertainty on the subtraction of feed-down from B decays (i.e.
the calculation of the $f_{\rm prompt}$ fraction) was estimated i) by varying
the $p_{\rm T}$-differential feed-down D-meson cross section from the FONLL
calculation within the theoretical uncertainties, ii) by varying the
hypothesis on the ratio of the prompt and feed-down D-meson $R_{\rm AA}$ in
the range $1<R_{\rm AA}^{\rm feed-down}/R_{\rm AA}^{\rm prompt}<3$, and iii)
by applying an alternative method to compute $f_{\rm prompt}$. This second
method is based on the ratio of charm and beauty FONLL cross sections, instead
of the absolute beauty cross section. The procedure is the same used for
previous measurements of D-meson production with ALICE [45, 32, 35]. The
resulting uncertainty ranges between ${}_{-45}^{+\phantom{0}5}$% at low
$p_{\rm T}$ and ${}_{-8}^{+3}$% at high $p_{\rm T}$ for the 0–10% centrality
class, and between ${}_{-45}^{+\phantom{0}5}$% at low $p_{\rm T}$ and
${}_{-8}^{+4}$% at high $p_{\rm T}$ for the 30–50% centrality class. The
uncertainty from the variation of the feed-down D-meson $R_{\rm AA}$
hypothesis ranges from 6 to 16%, as shown in Fig. 4, where the relative
variation of the prompt ${\rm D^{0}}$ yield is shown as a function of the
hypothesis on $R_{\rm AA}^{\rm feed-down}/R_{\rm AA}^{\rm prompt}$ for four
$p_{\rm T}$ intervals.

Figure 4: Relative variation of the prompt ${\rm D^{0}}$ yields as a function
of the hypothesis on $R_{\rm AA}^{\rm feed-down}/R_{\rm AA}^{\rm prompt}$ for
the B-meson feed-down subtraction.

The uncertainties on the branching ratios were also considered [44] as well as
the contribution due to the 1.1% uncertainty on the fraction of the hadronic
cross section used in the Glauber fit to determine the centrality classes
[39]. The latter was estimated from the variation of the D-meson ${\rm
d}N/{\rm d}p_{\rm T}$ when the limits of the centrality classes are shifted by
$\pm 1.1\%$ (e.g. shifted from 30–50% to 30.3–50.6% and 29.7–49.5%) [32]. The
resulting uncertainty, common to all $p_{\rm T}$ intervals, is smaller than 1%
for the 0–10% centrality class and about 2% for the 30–50% centrality class.

###  4.2 Systematic uncertainties on $R_{\rm AA}$

Particle | ${\rm D^{0}}$ | ${\rm D^{+}}$ | ${\rm D^{*+}}$
---|---|---|---
0–10% centrality class
$p_{\rm T}$ interval ($\mathrm{GeV}/c$) | 1–2 | 6–8 | 16–24 | 3–4 | 6–8 | 24–36 | 3–4 | 6–8 | 24–36
d$N_{\rm Pb-Pb}/$d$p_{\rm T}$ (excl. feed-down) | 28% | 14% | 22% | 22% | 20% | 22% | 24% | 20% | 21%
d$N_{\rm pp}/$d$p_{\rm T}$ (excl. feed-down) | 21%* | 16% | 17% | 20% | 19% | 20% | 17% | 17% | 18%
$\sqrt{s}-\rm{scaling}$ of the pp ref. |  ${}_{-30}^{+\phantom{0}6}\%$* | ${}_{-10}^{+\phantom{0}6}\%$ | – | ${}_{-19}^{+\phantom{0}8}\%$ | ${}_{-10}^{+\phantom{0}6}\%$ | – | ${}_{-20}^{+\phantom{0}9}\%$ | ${}_{-10}^{+\phantom{0}6}\%$ | –
High-$p_{\rm T}$ extrapolation | – | – | ${}^{+34}_{-51}\%$ | – | – | ${}^{+37}_{-56}\%$ | – | – | ${}^{+34}_{-53}\%$
FONLL feed-down corr. | ${}_{-\phantom{0}4}^{+\phantom{0}1}\%$ | ${}_{-\phantom{0}4}^{+\phantom{0}2}\%$ | ${}_{-16}^{+10}\%$ | ${}_{-\phantom{0}1}^{+\phantom{0}2}\%$ | ${}_{-\phantom{0}2}^{+\phantom{0}1}\%$ | ${}_{-14}^{+\phantom{0}8}\%$ | ${}_{-\phantom{0}4}^{+\phantom{0}1}\%$ | ${}_{-\phantom{0}4}^{+\phantom{0}2}\%$ | ${}_{-\phantom{0}8}^{+\phantom{0}3}\%$
$R_{{\rm AA}}^{\rm feed-down}/R_{{\rm AA}}^{\rm prompt}$ (Eq. (3)) | ${}^{+12}_{-\phantom{0}9}\%$ | ${}^{+14}_{-11}\%$ | ${}^{+19}_{-13}\%$ | ${}^{+\phantom{0}8}_{-\phantom{0}7}\%$ | ${}^{+12}_{-\phantom{0}9}\%$ | ${}^{+16}_{-12}\%$ | ${}^{+\phantom{0}6}_{-\phantom{0}6}\%$ | ${}^{+\phantom{0}8}_{-\phantom{0}7}\%$ | ${}^{+\phantom{0}8}_{-\phantom{0}7}\%$
Normalisation | 4.8% | 4.8% | 4.8%
30–50% centrality class
$p_{\rm T}$ interval ($\mathrm{GeV}/c$) | 1–2 | 6–8 | 12–16 | 2–3 | 6–8 | 12–16 | 2–3 | 6–8 | 12–16
d$N_{\rm Pb-Pb}/$d$p_{\rm T}$ (excl. feed-down) | 20% | 20% | 22% | 25% | 21% | 22% | 29% | 19% | 18%
d$N_{\rm pp}/$d$p_{\rm T}$ (excl. feed-down) | 21%* | 16% | 17% | 20% | 19% | 20% | 17% | 17% | 18%
$\sqrt{s}-\rm{scaling}$ of the pp ref. |  ${}_{-30}^{+\phantom{0}6}\%$* | ${}_{-10}^{+\phantom{0}6}\%$ | ${}_{-6}^{+5}\%$ | ${}_{-19}^{+\phantom{0}8}\%$ | ${}_{-10}^{+\phantom{0}6}\%$ | ${}_{-6}^{+5}\%$ | ${}_{-20}^{+\phantom{0}9}\%$ | ${}_{-10}^{+\phantom{0}6}\%$ | ${}_{-6}^{+5}\%$
FONLL feed-down corr. | ${}_{-\phantom{0}5}^{+\phantom{0}1}\%$ | ${}_{-\phantom{0}3}^{+\phantom{0}2}\%$ | ${}_{-\phantom{0}4}^{+\phantom{0}3}\%$ | ${}_{-\phantom{0}2}^{+\phantom{0}1}\%$ | ${}_{-\phantom{0}3}^{+\phantom{0}1}\%$ | ${}_{-\phantom{0}4}^{+\phantom{0}3}\%$ | ${}_{-\phantom{0}2}^{+\phantom{0}1}\%$ | ${}_{-\phantom{0}5}^{+\phantom{0}3}\%$ | ${}_{-\phantom{0}3}^{+\phantom{0}2}\%$
$R_{{\rm AA}}^{\rm feed-down}/R_{{\rm AA}}^{\rm prompt}$ (Eq. (3)) | ${}^{+12}_{-\phantom{0}9}\%$ | ${}^{+14}_{-11}\%$ | ${}^{+15}_{-11}\%$ | ${}^{+\phantom{0}9}_{-\phantom{0}7}\%$ | ${}^{+13}_{-10}\%$ | ${}^{+17}_{-13}\%$ | ${}^{+\phantom{0}7}_{-\phantom{0}6}\%$ | ${}^{+10}_{-\phantom{0}8}\%$ | ${}^{+\phantom{0}9}_{-\phantom{0}8}\%$
Normalisation | 6.2% | 6.2% | 6.2%
Table 3: Relative systematic uncertainties on the prompt D-meson $R_{\rm AA}$
for three $p_{\rm T}$ intervals, in the two centrality classes. Uncertainties
marked with a * were obtained as the average of the measurement at
$\sqrt{s}=2.76\leavevmode\nobreak\ \mathrm{TeV}$ and the measurement at
$\sqrt{s}=7\leavevmode\nobreak\ \mathrm{TeV}$, scaled using FONLL [56], as
described in Section 3.3.

The systematic uncertainties on the $R_{\rm AA}$ measurement include those on
the D-meson corrected yields, those on the proton–proton cross section
reference, and the uncertainties on the average nuclear overlap function.

The systematic uncertainties on the D-meson corrected yields are obtained
considering as uncorrelated the different contributions described in the
previous section.

The uncertainty on the pp reference used for the calculation of $R_{\rm AA}$
has two contributions. The first is the systematic uncertainty on the measured
$p_{\rm T}$-differential D-meson cross section at $\sqrt{s}=7$ TeV. This
uncertainty is about 25% at the lowest $p_{\rm T}$ and 17% at the highest
$p_{\rm T}$ for ${\rm D^{0}}$ mesons, excluding the uncertainty for feed-down
corrections, and few percent larger for ${\rm D^{+}}$ and ${\rm D^{*+}}$
mesons [45]. The systematic uncertainty on the feed-down subtraction deriving
from the variation of the parameters of the FONLL calculation and from the use
of the alternative method to compute $f_{\rm prompt}$ was considered to be
correlated in the Pb–Pb and pp measurements. These variations were carried out
simultaneously for the numerator and denominator of $R_{\rm AA}$, so only the
residual effect was attributed as a systematic uncertainty. Therefore, the
variation of the value of $R_{\rm AA}^{\rm feed-down}/R_{\rm AA}^{\rm prompt}$
between 1 and 3 is the main contribution to the feed-down uncertainty on
$R_{\rm AA}$.

The second contribution to the pp reference uncertainty is the scaling to
$\sqrt{s}=2.76$ TeV. It ranges from ${}^{+27}_{-10}$% in the interval
$2<p_{\rm T}<3\leavevmode\nobreak\ \mathrm{GeV}/c$ to about 5% for $p_{\rm
T}>10\leavevmode\nobreak\ \mathrm{GeV}/c$ [61]. Note that the upper/lower
uncertainties are reversed when considering $R_{\rm AA}$, where the pp
reference is in the denominator. In the interval 1–2 GeV/$c$, this scaling
uncertainty is much larger (${}^{+57}_{-11}$%), but its impact on the pp
reference was reduced by about a factor of two by using a weighted average of
the cross section scaled from 7 TeV and the measured cross section at 2.76 TeV
(see Section 3.2).

The extrapolation of the pp reference to the intervals $16<p_{\rm
T}<24\leavevmode\nobreak\ \mathrm{GeV}/c$ for ${\rm D^{0}}$ mesons and
$24<p_{\rm T}<36\leavevmode\nobreak\ \mathrm{GeV}/c$ for ${\rm D^{+}}$ and
${\rm D^{*+}}$ mesons resulted in a total systematic uncertainty of about
${}_{-50}^{+35}\%$, as described in Section 3.2.

The uncertainties on $R_{\rm AA}$ are listed in Tab. 3. The uncertainties on
the normalisation are the quadratic sum of the pp normalisation uncertainty
(3.5%) and the uncertainty on $\langle T_{\rm AA}\rangle$, which is 3.2% and
4.7% in the 0–10% and 30–50% centrality classes, respectively.

All the uncertainties described in this Section that result from detector
effects are considered to be largely correlated over transverse momentum, with
the exception of the yield extraction uncertainty that depends on the S/B in
each $p_{\rm T}$ interval. The uncertainties related to the feed-down
assumptions and to the $\sqrt{s}$-scaled pp reference are fully correlated
over $p_{\rm T}$, with the exception of that for the hypothesis on the ratio
of the prompt and feed-down D-meson $R_{\rm AA}$ that might not be constant as
a function of $p_{\rm T}$.

##  5 Results and discussion

###  5.1 D-meson $p_{\rm T}$ spectra and $R_{\rm AA}$

The transverse momentum distributions $\mathrm{d}N/\mathrm{d}p_{\rm T}$ of
prompt ${\rm D^{0}}$, ${\rm D^{+}}$ and ${\rm D^{*+}}$ mesons are shown in
Figs. 5, 5 and 5 for the 10% most central Pb–Pb collisions. The results are
presented in the interval $1<p_{\rm T}<24\leavevmode\nobreak\ \mathrm{GeV}/c$
for the ${\rm D^{0}}$ mesons and $3<p_{\rm T}<36\leavevmode\nobreak\
\mathrm{GeV}/c$ for ${\rm D^{+}}$ and ${\rm D^{*+}}$ mesons. They are compared
to the corresponding pp cross section reference multiplied by $\langle T_{\rm
AA}\rangle$. The vertical bars represent the statistical uncertainties, the
empty boxes the systematic uncertainties from the data analysis, and the
shaded boxes the systematic uncertainty due to the subtraction of the feed-
down from B-hadron decays. Uncertainties on the pp cross section normalisation
and on the branching ratios are quoted separately. A clear suppression of the
D-meson yields is observed at intermediate ($3<p_{\rm T}<8\leavevmode\nobreak\
\mathrm{GeV}/c$) and high transverse momenta ($p_{\rm T}>8\leavevmode\nobreak\
\mathrm{GeV}/c$) in central Pb–Pb collisions as compared to the binary-scaled
pp reference. In Fig. 5 the transverse momentum distributions of prompt ${\rm
D^{0}}$, ${\rm D^{+}}$ and ${\rm D^{*+}}$ mesons in the 10% most central
collisions are compared to each other. The $\mathrm{d}N/\mathrm{d}p_{\rm T}$
values of ${\rm D^{*+}}$ mesons are scaled by a factor of five for visibility.

Figure 5: Transverse momentum distributions $\mathrm{d}N/\mathrm{d}p_{\rm T}$
of prompt ${\rm D^{0}}$ (a), ${\rm D^{+}}$ (b) and ${\rm D^{*+}}$ (c) mesons
in the 0–10% centrality class in Pb–Pb collisions at
$\sqrt{s_{\scriptscriptstyle\rm NN}}=2.76\leavevmode\nobreak\ \mathrm{TeV}$.
The pp reference distributions $\left\langle T_{\rm
AA}\right\rangle\,\mathrm{d}\sigma/\mathrm{d}p_{\rm T}$ are shown as well.
Statistical uncertainties (bars) and systematic uncertainties from data
analysis (empty boxes) and from feed-down subtraction (shaded boxes) are
shown. Horizontal bars represent bin widths, symbols are placed at the centre
of the bin. The $\mathrm{d}N/\mathrm{d}p_{\rm T}$ distributions of the three
D-meson species in the 10% most central Pb–Pb collisions are compared to each
other in panel (d), where the ${\rm D^{*+}}$ production yields are scaled by a
factor of five for visibility.

Figure 6: Transverse momentum distributions $\mathrm{d}N/\mathrm{d}p_{\rm T}$
of prompt ${\rm D^{0}}$ (a), ${\rm D^{+}}$ (b) and ${\rm D^{*+}}$ (c) mesons
in the 30–50% centrality class in Pb–Pb collisions at
$\sqrt{s_{\scriptscriptstyle\rm NN}}=2.76\leavevmode\nobreak\ \mathrm{TeV}$.
The pp reference distributions $\left\langle T_{\rm
AA}\right\rangle\,\mathrm{d}\sigma/\mathrm{d}p_{\rm T}$ are shown as well.
Statistical uncertainties (bars) and systematic uncertainties from data
analysis (empty boxes) and from feed-down subtraction (shaded boxes) are
shown. Horizontal bars represent bin widths, symbols are placed at the centre
of the bin. The $\mathrm{d}N/\mathrm{d}p_{\rm T}$ distributions of the three
D-meson species in Pb–Pb collisions in the 30–50% centrality class are
compared to each other in panel (d), where the ${\rm D^{*+}}$ production
yields are scaled by a factor of five for visibility.

The D-meson $\mathrm{d}N/\mathrm{d}p_{\rm T}$ distributions measured in the
30–50% centrality class are shown in Fig. 6. Also for this centrality class, a
clear suppression of the D-meson yields as compared to the expectation based
on binary scaling of the pp yields is observed for $p_{\rm
T}>3\leavevmode\nobreak\ \mathrm{GeV}/c$. In Fig. 6, the
$\mathrm{d}N/\mathrm{d}p_{\rm T}$ of prompt ${\rm D^{0}}$, ${\rm D^{+}}$ and
${\rm D^{*+}}$ (the latter scaled by a factor of five) are compared to each
other.

Figure 7 shows the $p_{\rm T}$-dependent ratios of ${\rm D^{+}}$/${\rm D^{0}}$
and ${\rm D^{*+}}$/${\rm D^{0}}$ for central Pb–Pb collisions. They are found
to be compatible within uncertainties with those measured in pp collisions at
$\sqrt{s}=7\leavevmode\nobreak\ \mathrm{TeV}$ [62]. Similar results were also
found for the 30–50% centrality class. Therefore, no modification of the
relative abundances of these three D-meson species is observed within the
current uncertainties in central and semi-central Pb–Pb collisions relative to
the pp ones at LHC energies.

Figure 7: Ratio of prompt D-meson yields (${\rm D^{+}}$/${\rm D^{0}}$ and
${\rm D^{*+}}$/${\rm D^{0}}$) as a function of $p_{\rm T}$ in the 10% most
central Pb–Pb collisions at $\sqrt{s_{\scriptscriptstyle\rm
NN}}=2.76\leavevmode\nobreak\ \mathrm{TeV}$ compared to the results in pp
collisions at $\sqrt{s}=7\leavevmode\nobreak\ \mathrm{TeV}$. Statistical
(bars) and systematic (boxes) uncertainties are shown.

Figure 8: $R_{\rm AA}$ of prompt ${\rm D^{0}}$, ${\rm D^{+}}$, and ${\rm
D^{*+}}$ mesons for the 0–10% (left) and 30–50% (right) centrality classes.
Statistical (bars), systematic (empty boxes), and normalisation (shaded box)
uncertainties are shown. Horizontal bars represent bin widths. ${\rm D^{0}}$
symbols are placed at the centre of the bin. ${\rm D^{+}}$, and ${\rm D^{*+}}$
are shifted for visibility.

The $R_{\rm AA}$ of prompt ${\rm D^{0}}$, ${\rm D^{+}}$ and ${\rm D^{*+}}$
mesons is shown in Fig. 8 for the 0–10% (left panel) and 30–50% (right panel)
centrality classes. The statistical uncertainties, represented by the vertical
error bars, range from 10% in the intermediate $p_{\rm T}$ range up to about
25–30% in the lowest and highest $p_{\rm T}$ intervals, for the 10% most
central collisions. The statistical uncertainty on the reference measurement
at $\sqrt{s}=7\leavevmode\nobreak\ \mathrm{TeV}$ dominates this uncertainty in
the interval $2<p_{\rm T}<16\leavevmode\nobreak\ \mathrm{GeV}/c$. For the
30–50% centrality class, the statistical uncertainties at low and intermediate
$p_{\rm T}$ are similar in magnitude to those of central collisions and are
about 20% in the interval $12<p_{\rm T}<16\leavevmode\nobreak\
\mathrm{GeV}/c$. The total $p_{\rm T}$-dependent systematic uncertainties,
described in the previous Section, are shown as empty boxes. The normalisation
uncertainty is represented by a filled box at $R_{\rm AA}=1$. The nuclear
modification factors of the three D-meson species are compatible within
statistical uncertainties for both centrality classes. For the 10% most
central collisions, the measured $R_{\rm AA}$ shows a suppression that is
maximal at around $p_{\rm T}=10\leavevmode\nobreak\ \mathrm{GeV}/c$, where a
reduction of the yields by a factor of 5–6 with respect to the binary-scaled
pp reference is observed. The suppression decreases with decreasing $p_{\rm
T}$ for $p_{\rm T}<10\leavevmode\nobreak\ \mathrm{GeV}/c$, and it is of the
order of a factor of 3 in the interval $3<p_{\rm T}<4\leavevmode\nobreak\
\mathrm{GeV}/c$, while the $R_{\rm AA}$ ranges from about 0.35 to 1 in the
first two $p_{\rm T}$ intervals. For $p_{\rm T}>10\leavevmode\nobreak\
\mathrm{GeV}/c$, the suppression appears to decrease with increasing $p_{\rm
T}$, but the large statistical uncertainties do not allow us to determine the
trend of the $R_{\rm AA}$. A suppression ($R_{\rm AA}<0.5$) is still observed
for D mesons with $p_{\rm T}>25\leavevmode\nobreak\ \mathrm{GeV}/c$. For the
30–50% centrality class, the suppression amounts to about a factor of 3 at
$p_{\rm T}=10\leavevmode\nobreak\ \mathrm{GeV}/c$, which indicates that the
suppression of the high-$p_{\rm T}$ D-meson yields is smaller than in the
0–10% centrality class. As for the central collisions, the suppression reduces
at lower momenta, with $R_{\rm AA}$ increasing with decreasing $p_{\rm T}$ up
to a value of about 0.6 in the interval $3<p_{\rm T}<4\leavevmode\nobreak\
\mathrm{GeV}/c$. For lower $p_{\rm T}$ the suppression is further reduced and
$R_{\rm AA}$ is compatible with unity.

The average nuclear modification factor of ${\rm D^{0}}$, ${\rm D^{+}}$ and
${\rm D^{*+}}$ mesons was computed using the inverse of the squared relative
statistical uncertainties as weights. The systematic uncertainties were
propagated through the averaging procedure, considering the contributions from
the tracking efficiency, the B-meson feed-down subtraction and the FONLL-based
$\sqrt{s}$-scaling of the pp cross section from
$\sqrt{s}=7\leavevmode\nobreak\ \mathrm{TeV}$ to
$\sqrt{s}=2.76\leavevmode\nobreak\ \mathrm{TeV}$ as fully correlated
uncertainties among the three D-meson species. The average D-meson $R_{\rm
AA}$ for the two centrality classes is shown in the left panel of Fig. 9. A
larger suppression, by about a factor of two, is observed in the 10% most
central collisions compared to the 30–50% centrality class for $p_{\rm
T}>5\leavevmode\nobreak\ \mathrm{GeV}/c$. The stronger suppression observed in
central collisions can be understood as resulting from to the increasing
medium density, size and lifetime from peripheral to central collisions. The
$R_{\rm AA}$ values measured for the 0–10% centrality class are slightly
lower, although compatible within uncertainties, than those reported in Ref.
[32] for the 20% most central collisions, measured with the 2010 data sample.
As a consistency check, the analysis on the 2011 data sample was also
performed in the 0-20% centrality class and the resulting $R_{\rm AA}$ value
was found to be compatible with the one measured with the 2010 sample within
statistical and systematic uncertainties, considering that the pp reference
uncertainties are the same in the two measurements. In addition, the larger
sample of central Pb–Pb collisions used in this analysis, compared to that
used in the previous publication, enables the measurement of the D-meson
$R_{\rm AA}$ in a wider $p_{\rm T}$ range (the intervals $1<p_{\rm
T}<2\leavevmode\nobreak\ \mathrm{GeV}/c$ and $p_{\rm T}>16\leavevmode\nobreak\
\mathrm{GeV}/c$ were not accessible with the previous sample), with a
substantial reduction (by a factor of about 2–3) of the statistical
uncertainties.

Figure 9 (left) also shows the average D-meson nuclear modification factor
measured in minimum-bias p–Pb collisions at $\sqrt{s_{\scriptscriptstyle\rm
NN}}=5.02\leavevmode\nobreak\ \mathrm{TeV}$ [33]. Since no significant
modification of the D-meson production is observed in p–Pb collisions for
$p_{\rm T}>2\leavevmode\nobreak\ \mathrm{GeV}/c$, the strong suppression of
the D-meson yields for $p_{\rm T}>3\leavevmode\nobreak\ \mathrm{GeV}/c$
observed in central and semi-central Pb–Pb collisions cannot be explained in
terms of cold nuclear matter effects and is predominantly due to final-state
effects induced by the hot and dense medium created in the collisions.

###  5.2 Comparison with results at lower collision energy

In the right panel of Fig. 9, the average D-meson $R_{\rm AA}$ for the 10%
most central Pb–Pb collisions is compared to the ${\rm D^{0}}$ nuclear
modification factor measured by the STAR Collaboration for the 10% most
central Au–Au collisions at $\sqrt{s_{\scriptscriptstyle\rm
NN}}=200\leavevmode\nobreak\ \mathrm{GeV}$ [31]. The D-meson $R_{\rm AA}$
measured at the two energies are compatible within uncertainties for $p_{\rm
T}>2\leavevmode\nobreak\ \mathrm{GeV}/c$. It should be noted that the similar
$R_{\rm AA}$ of D mesons with high momentum, $p_{\rm T}>5\leavevmode\nobreak\
\mathrm{GeV}/c$, i.e. in the range where the nuclear modification factor is
expected to be dominated by the effect of in-medium parton energy loss, does
not necessarily imply a similar charm-quark energy loss at the two collision
energies. Since the nuclear modification factor is also sensitive to the slope
of the $p_{\rm T}$ spectra in pp collisions, the combined effect of a denser
medium and of the harder $p_{\rm T}$ spectra at the LHC could result in
similar values of $R_{\rm AA}$ as at lower collision energies (see e.g. Ref.
[63]).

At low momentum ($1<p_{\rm T}<2\leavevmode\nobreak\ \mathrm{GeV}/c$), the
$R_{\rm AA}$ measured by STAR shows a maximum. This effect can be described by
models including parton energy loss, collective radial flow and the
contribution of the recombination mechanism to charm-quark hadronisation [30].
The ALICE results at higher $\sqrt{s_{\scriptscriptstyle\rm NN}}$ do not show
a maximum. However, the large uncertainties and the coarser binning at low
$p_{\rm T}$ prevent a firm conclusion from being drawn. A different pattern
could be explained by the different role of initial-state effects or of radial
flow at the two collision energies. In the initial state, the modification of
the parton distribution functions in a nuclear environment is predicted to
lead to a stronger suppression of the heavy-quark production yields at low
$p_{\rm T}$ with increasing $\sqrt{s_{\scriptscriptstyle\rm NN}}$ [64],
because of the smaller values of Bjorken-$x$ probed. In addition, the momentum
($k_{\rm T}$) broadening effect, which gives rise to an enhancement of the
$R_{\rm AA}$ at intermediate $p_{\rm T}$ (Cronin peak), is known to be more
pronounced at lower collision energies [65, 66]. In the final state, in
addition to energy loss, the collective expansion of the medium is also
predicted to affect the momentum distribution of charmed hadrons in heavy-ion
collisions. Indeed, the interactions with the medium constituents are expected
to transfer momentum to low-$p_{\rm T}$ charm quarks, which could take part in
the collective radial flow of the medium. This effect could be enhanced by
hadronisation via recombination, which is predicted in some models to
contribute significantly to hadron formation at low and intermediate $p_{\rm
T}$ [15]. The momentum distributions of identified light-flavour hadrons at
the LHC [67, 68] indicate that the radial flow of the medium at LHC energies
is about 10% higher than at RHIC [69]. However, this stronger radial flow does
not necessarily give rise to a more pronounced bump-like structure in the
$R_{\rm AA}$ at low $p_{\rm T}$ with increasing collision energy, because its
effect can be counterbalanced by the different shape of the momentum spectra
in pp collisions at different $\sqrt{s}$ [70, 71].

Figure 9: Left: prompt D-meson $R_{\rm AA}$ (average of ${\rm D^{0}}$, ${\rm
D^{+}}$ and ${\rm D^{*+}}$) as a function of $p_{\rm T}$ in Pb–Pb collisions
at $\sqrt{s_{\scriptscriptstyle\rm NN}}=2.76\leavevmode\nobreak\ \mathrm{TeV}$
in the 0–10% and 30–50% centrality classes. Prompt D-meson nuclear
modification factor (average of ${\rm D^{0}}$, ${\rm D^{+}}$ and ${\rm
D^{*+}}$) as a function of $p_{\rm T}$ in p–Pb collisions at
$\sqrt{s_{\scriptscriptstyle\rm NN}}=5.02\leavevmode\nobreak\ \mathrm{TeV}$
[33]. Right: prompt D-meson $R_{\rm AA}$ (average of ${\rm D^{0}}$, ${\rm
D^{+}}$ and ${\rm D^{*+}}$) as a function of $p_{\rm T}$ in the 10% most
central Pb–Pb collisions at $\sqrt{s_{\scriptscriptstyle\rm
NN}}=2.76\leavevmode\nobreak\ \mathrm{TeV}$ compared to ${\rm D^{0}}$ $R_{\rm
AA}$ measured by the STAR Collaboration in Au–Au collisions at RHIC at
$\sqrt{s_{\scriptscriptstyle\rm NN}}=200\leavevmode\nobreak\ \mathrm{GeV}$
[31]. A zoomed-in plot of the interval $0<p_{\rm T}<8\leavevmode\nobreak\
\mathrm{GeV}/c$ is shown in the inset. Statistical (bars), systematic (empty
boxes), and normalisation (shaded boxes at $R_{\rm AA}=1$) uncertainties are
shown. Horizontal bars represent bin widths. Symbols are placed at the centre
of the bin.

Figure 10: Prompt D-meson $R_{\rm AA}$ (average of ${\rm D^{0}}$, ${\rm
D^{+}}$ and ${\rm D^{*+}}$) as a function of $p_{\rm T}$ compared to the
nuclear modification factors of pions [72] and charged particles [73] in the
0–10% (left) and 30–50% (right) centrality classes. Statistical (bars),
systematic (empty boxes), and normalisation (shaded box at $R_{\rm AA}=1$)
uncertainties are shown. Horizontal bars represent bin widths. Symbols are
placed at the centre of the bin.

###  5.3 Comparison with pion and charged-hadron $R_{\rm AA}$

As described in Section 1, the colour-charge and quark-mass dependence of the
energy loss can be tested with the comparison of D-meson and pion nuclear
modification factors. In the left panel of Fig. 10, the D-meson $R_{\rm AA}$
(average of ${\rm D^{0}}$, ${\rm D^{+}}$ and ${\rm D^{*+}}$) measured for the
10% most central Pb–Pb collisions is compared with the pion $R_{\rm AA}$ in
the interval $1<p_{\rm T}<20\leavevmode\nobreak\ \mathrm{GeV}/c$ and with the
$R_{\rm AA}$ of charged particles in $16<p_{\rm T}<40\leavevmode\nobreak\
\mathrm{GeV}/c$. The charged-particle $R_{\rm AA}$ is shown in order to extend
the comparison up to the higher $p_{\rm T}$ interval in which the D-meson
yield was measured. The comparison of D mesons with charged hadrons at
high-$p_{\rm T}$ is relevant because the $R_{\rm AA}$ of different light-
flavour hadron species are consistent with one another for $p_{\rm
T}>8\leavevmode\nobreak\ \mathrm{GeV}/c$ [72]. Moreover the contribution of
pions dominates the charged-hadron yields at $p_{\rm T}$ of about
$20\leavevmode\nobreak\ \mathrm{GeV}/c$ with respect to other hadron species
(about 65%) [74]. A similar comparison is performed in the right panel of Fig.
10 for the 30–50% centrality class.

The $R_{\rm AA}$ of D mesons and light-flavour hadrons are consistent for
$p_{\rm T}>6\leavevmode\nobreak\ \mathrm{GeV}/c$ for both centrality classes.
For $p_{\rm T}<6\leavevmode\nobreak\ \mathrm{GeV}/c$, the $R_{\rm AA}$ of D
mesons tends to be slightly higher than that of pions. This can be also
observed from the ratio of nuclear modification factors, presented in Fig. 13.
Considering that the systematic uncertainties of D-meson yields are mainly
correlated with $p_{\rm T}$, we observe $R_{\rm AA}^{\rm D}>R_{\rm AA}^{\pi}$
at low $p_{\rm T}$ with a significance of about 1 $\sigma$ in four $p_{\rm T}$
intervals, in the most central events. In the 30–50% centrality class, the
significance of the effect is smaller than in central collisions.

A direct interpretation of a possible difference between the D-meson and pion
$R_{\rm AA}$ at low $p_{\rm T}$ is not straightforward. In the presence of a
colour-charge and quark-mass dependent energy loss, the harder $p_{\rm T}$
distribution and the harder fragmentation function of charm quarks compared to
those of light quarks and gluons could lead to similar values of D-meson and
pion $R_{\rm AA}$, as discussed in Ref. [13]. In addition, it should be
considered that the pion yield could have a substantial contribution from soft
production processes up to transverse momenta of about 2–3 $\mathrm{GeV}/c$
due to the strong radial flow at LHC energies. This soft contribution, which
is not present in the D-meson yield, does not scale with the number of binary
nucleon–nucleon collisions. Finally, the effects of radial flow and
hadronisation via recombination, as well as initial-state effects, could
affect D-meson and pion (light-flavour particle) yields differently at a given
$p_{\rm T}$, thus introducing an additional complication in interpreting the
magnitude of the $R_{\rm AA}$ in terms of different in-medium parton energy
loss of charm quarks, light quarks and gluons.

###  5.4 Comparison with models

Figure 11 shows the comparison of the average D-meson $R_{\rm AA}$ for the two
centrality classes 0–10% (a and b) and 30–50% (c and d) with most of the
available model calculations. The model calculations are described and
compared in a recent review [15]. A concise summary is given in the following
paragraphs.

Figure 11: Average of prompt $\rm D^{0}$, $\rm D^{+}$ and $\rm D^{*+}$ $R_{\rm
AA}$ in the centrality classes 0–10% (a and b) and 30–50% (c and d) compared
with model calculations: Djordjevic [75], CUJET3.0 [76, 77], WHDG [20, 21,
22], Vitev [78] (a and c), TAMU elastic [70], Cao, Qin and Bass [79],
MC@sHQ+EPOS, Coll+Rad(LPM) [80], POWLANG [81, 82], BAMPS [53, 54, 55], PHSD
[83] (b and d). Some of the model calculations are shown by two lines to
represent their uncertainties.

The interaction of heavy quarks with the medium constituents is computed
considering radiative and collisional processes in the calculations indicated
as Djordjevic [75], WHDG [20, 21, 22], CUJET3.0 [76, 77], MC@sHQ+EPOS [80],
BAMPS [53, 54, 55], and Cao, Qin , Bass [79]. Only collisional interactions
are considered in the model calculations POWLANG [81, 82], TAMU elastic [70]
and PHSD [83]. In BAMPS, two different options are considered: including only
collisional energy loss but introducing a scaling factor to match RHIC
high-$p_{\rm T}$ data (where radiative energy loss is expected to be dominant)
or including both collisional and radiative energy loss. Also for the Vitev
model [78] two different options are considered: including only radiative
energy loss (Vitev rad) or also considering the in-medium dissociation of
heavy-flavour hadrons (Vitev rad+dissoc).

The medium is described using an underlying hydrodynamical model in CUJET3.0,
Cao, Qin, Bass, MC@sHQ+EPOS, BAMPS, POWLANG, TAMU elastic and PHSD, while
Djordjevic, WHDG and Vitev use a Glauber model nuclear overlap without radial
expansion.

The initial heavy-quark $p_{\rm T}$ distributions are based on next-to-leading
order (NLO) or FONLL perturbative QCD calculations in all model calculations,
except for Cao, Qin, Bass, which uses the PYTHIA event generator [49]. The
EPS09 NLO parameterisation [64] of the nuclear parton distribution functions
is included by POWLANG, MC@sHQ+EPOS, TAMU elastic, PHSD and Cao, Qin, Bass.

All model calculations use in-vacuum fragmentation of heavy quarks for the
high-momentum region. At low momentum this is supplemented by hadronisation
via recombination in the MC@sHQ+EPOS, POWLANG 222Note that recombination was
not included in the version of the POWLANG model used for the comparison with
the D-meson $v_{2}$ measurement in [35]., Cao, Qin, Bass, TAMU elastic and
PHSD models. The two last models also include scattering of D mesons in the
hadronic phase of the medium. Also for the Cao, Qin, Bass model, the hadronic-
rescattering effects have been studied in a recent publication [84] and no
large differences in the $R_{\rm AA}$ are observed, when these processes are
considered.

Several model calculations provide a good description of the measured $R_{\rm
AA}$ for both centrality classes. The MC@sHQ+EPOS model has recently improved
the description of the $R_{\rm AA}$ in the $p_{\rm T}$ interval 2–8
$\mathrm{GeV}/c$ including the EPS09 shadowing parameterisation in addition to
in-medium energy loss, the TAMU elastic model overestimates the $R_{\rm AA}$
in central collisions in the $p_{\rm T}$ interval 6–30 $\mathrm{GeV}/c$ and
the POWLANG model underestimates it in the interval 5–36 (8–16)
$\mathrm{GeV}/c$ in the 0–10% (30–50%) centrality class. Interestingly, these
model calculations provide a fair description of the D-meson $v_{2}$ measured
at LHC [35] and of the D-meson $R_{\rm AA}$ measured at RHIC [31]. On the
other hand, the model calculations that do not include a hydrodynamical medium
expansion and hadronisation via recombination, namely Djordjevic, Vitev, WHDG
—and as a consequence do not describe the features observed for the $v_{2}$ at
the LHC and the $R_{\rm AA}$ at RHIC in the momentum region up to about 3–5
$\mathrm{GeV}/c$— provide a good description of the $R_{\rm AA}$ in the full
“high $p_{\rm T}$ interval”, above $5\leavevmode\nobreak\ \mathrm{GeV}/c$. The
Vitev model shows a better agreement when including the D-meson in-medium
dissociation mechanism. The BAMPS model with collisional energy loss describes
the data better for the low-$p_{\rm T}$ interval, as is the case for the
D-meson $v_{2}$ [35]. The inclusion of radiative energy loss improves the
agreement at high $p_{\rm T}$. The Cao, Qin, Bass model describes the $R_{\rm
AA}$ in both centrality classes, but underestimates the D-meson $v_{2}$ [35].
The PHSD model describes the $R_{\rm AA}$ in both centrality classes.

Figure 12: Average of prompt $\rm D^{0}$, $\rm D^{+}$ and $\rm D^{*+}$ $R_{\rm
AA}$ in the centrality classes 0–10% compared with TAMU elastic and
MC@sHQ+EPOS models calculations with and without including EPS09 shadowing
parameterisations [64].

Figure 12 shows the TAMU elastic and MC@sHQ+EPOS calculations of the nuclear
modification factor, for the 10% most central events, with and without
including the EPS09 shadowing parameterisation. For both models the inclusion
of shadowing reduces the $R_{\rm AA}$ by up to about 30–40% in the interval
$p_{\rm T}<5\leavevmode\nobreak\ \mathrm{GeV}/c$, resulting in a better
description of the data.

Figure 13: Left: $R_{\rm AA}$ of charged pions ($p_{\rm
T}<16\leavevmode\nobreak\ \mathrm{GeV}/c$) [72] and of charged particles
($p_{\rm T}>16\leavevmode\nobreak\ \mathrm{GeV}/c$) [73] compared with model
calculations that compute also the D-meson $R_{\rm AA}$. Right: ratio of the
$R_{\rm AA}$ of prompt D mesons (average of $\rm D^{0}$, $\rm D^{+}$ and $\rm
D^{*+}$ as shown in Fig. 11) and the $R_{\rm AA}$ of charged pions (for
$p_{\rm T}<20\leavevmode\nobreak\ \mathrm{GeV}/c$) or charged particles (for
$p_{\rm T}>20\leavevmode\nobreak\ \mathrm{GeV}/c$), compared with the same
model calculations shown in the left panel.

Four of the model calculations also provide the nuclear modification factor of
pions and charged particles (Djordjevic, CUJET3.0, WHDG and Vitev). All these
calculations include radiative and collisional energy loss333The in-medium
formation and dissociation process, included by Vitev for D mesons, is not
relevant for pions, which have a much larger formation time.. The left panel
of Fig. 13 shows the comparison with the measured charged-pion $R_{\rm
AA}^{\pi}$ ($p_{\rm T}<16\leavevmode\nobreak\ \mathrm{GeV}/c$) [72] and
charged-particle $R_{\rm AA}^{ch}$ ($p_{\rm T}>16\leavevmode\nobreak\
\mathrm{GeV}/c$) [73]. The model calculations provide a reasonable description
of the measurements, with WHDG generally showing smaller $R_{\rm AA}$ values
than seen in data, although consistent within experimental and theoretical
uncertainties.

The right panel of Fig. 13 shows the $R_{\rm AA}^{\rm D}/R_{\rm AA}^{\pi}$
($p_{\rm T}<16\leavevmode\nobreak\ \mathrm{GeV}/c$) and $R_{\rm AA}^{\rm
D}/R_{\rm AA}^{ch}$ ($p_{\rm T}>16\leavevmode\nobreak\ \mathrm{GeV}/c$) ratios
for data and for these four model calculations. In the case of data, the
uncertainties of D-meson and charged-pion (or charged-particle) measurements
were propagated as uncorrelated uncertainties, except for the uncertainty on
$\left\langle T_{\rm AA}\right\rangle$, which cancels in the ratio444The
uncertainty on the normalisation (integrated luminosity) of the pp reference
cross sections for D mesons and pions (charged particles) does not cancel in
the ratio, because the two cross sections were measured in two data samples at
different centre-of-mass energies.. In the case of model calculations, the
theoretical uncertainty, when provided, was propagated assuming full
correlation between D mesons and pions (charged particles), since it accounts
for a variation of the medium density (or temperature). Only the Djordjevic
and CUJET3.0 models, which use radiative and collisional energy loss, can
describe the two $R_{\rm AA}$ results and their ratio over the full $p_{\rm
T}$ interval in which they provide the calculations ($p_{\rm T}>5$ and 8
GeV/$c$, respectively). The Vitev model can describe the data at the lowest
$p_{\rm T}$ (2–6 GeV/$c$) only if the dissociation mechanism is included,
suggesting that the effect is relevant in this model. However, the model
overestimates the data in the interval 6–12 GeV/$c$.

##  6 Conclusions

We have presented the measurements of the production of prompt ${\rm D^{0}}$,
${\rm D^{+}}$ and ${\rm D^{*+}}$ mesons at central rapidity in Pb–Pb
collisions at a centre-of-mass energy per nucleon pair
$\sqrt{s_{\scriptscriptstyle\rm NN}}=2.76\leavevmode\nobreak\ \mathrm{TeV}$,
as well as their nuclear modification factor $R_{\rm AA}$. The measurements
cover the interval $1<p_{\rm T}<36\leavevmode\nobreak\ \mathrm{GeV}/c$ for the
0–10% centrality class and $1<p_{\rm T}<16\leavevmode\nobreak\ \mathrm{GeV}/c$
for the 30–50% centrality class.

The nuclear modification factor shows a maximum reduction of the yields with
respect to binary scaling by a factor 5–6, for transverse momenta of about
$10\leavevmode\nobreak\ \mathrm{GeV}/c$ for the 10% most central Pb–Pb
collisions. A suppression of a factor about 2–3 persists in the highest
$p_{\rm T}$ interval covered by the measurements (24–36 GeV/$c$). At low
$p_{\rm T}$ (1–3 GeV/$c$), the $R_{\rm AA}$ has large uncertainties, that span
the range from 0.35 (factor of three suppression) to 1 (no suppression). In
all $p_{\rm T}$ intervals above $5\leavevmode\nobreak\ \mathrm{GeV}/c$, the
$R_{\rm AA}$ for the 30–50% centrality class is about twice that for the 0–10%
centrality class. The suppression observed for $p_{\rm
T}>3\leavevmode\nobreak\ \mathrm{GeV}/c$ is interpreted to be due to
interactions of the charm quarks within the high-energy density medium formed
in the final-state of Pb–Pb collisions. This is demonstrated by the nuclear
modification factor measurements in p–Pb collisions at
$\sqrt{s_{\scriptscriptstyle\rm NN}}=5.02\leavevmode\nobreak\ \mathrm{TeV}$,
which indicate that D-meson production is consistent with binary collision
scaling [33].

The D-meson $R_{\rm AA}$ was compared with that of charged pions in the
interval $1<p_{\rm T}<16\leavevmode\nobreak\ \mathrm{GeV}/c$, also in terms of
the ratio $R_{\rm AA}^{\rm D}/R_{\rm AA}^{\pi}$, and with that of charged
particles up to $p_{\rm T}=36\leavevmode\nobreak\ \mathrm{GeV}/c$ ($R_{\rm
AA}^{\rm D}/R_{\rm AA}^{ch}$). In the interval $1<p_{\rm
T}<6\leavevmode\nobreak\ \mathrm{GeV}/c$, the $R_{\rm AA}$ values of D mesons
are higher than those of pions, although consistent within uncertainties. For
the 10% most central collisions, the ratio $R_{\rm AA}^{\rm D}/R_{\rm
AA}^{\pi,\,ch}$ is larger than unity by about $1\,\sigma$ of the total
uncertainties, which are to some extent correlated among $p_{\rm T}$
intervals. For $p_{\rm T}>8\leavevmode\nobreak\ \mathrm{GeV}/c$, the $R_{\rm
AA}$ values are compatible with those of pions and charged particles up to
$p_{\rm T}=36\leavevmode\nobreak\ \mathrm{GeV}/c$.

Several models provide a good description of the $R_{\rm AA}$ for both
centrality classes. Interestingly, the models that show larger deviation from
the data, especially in the high-$p_{\rm T}$ region, are among those that
provide a good description of the D-meson $v_{2}$ measured at the LHC and of
the D-meson $R_{\rm AA}$ measured at RHIC, in the low-$p_{\rm T}$ region. On
the other hand, the models that do not include a hydrodynamical medium
expansion and recombination, and as a consequence do not describe $v_{2}$ in
the momentum region up to about 3–5 GeV/$c$, provide a good description of the
$R_{\rm AA}$ at the LHC in the full high-$p_{\rm T}$ interval, above 5
GeV/$c$.

Only two out of the four models that compute $R_{\rm AA}^{\rm D}/R_{\rm
AA}^{\pi,\,ch}$ can describe this measurement over the full $p_{\rm T}$
interval for which they provide the calculations. In these models, the nuclear
modification factors of D mesons and pions turn out to be very similar as a
consequence of a compensation among the larger energy loss of gluons with
respect to that of charm quarks (mainly due to the larger colour coupling
factor), the different amount of gluon and light quark yields on the pion
$R_{\rm AA}$ and the harder $p_{\rm T}$ distribution and fragmentation of
charm quarks with respect to those of gluons and of light quarks.

## 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: State
Committee of Science, World Federation of Scientists (WFS) and Swiss Fonds
Kidagan, Armenia; Conselho Nacional de Desenvolvimento Científico e
Tecnológico (CNPq), Financiadora de Estudos e Projetos (FINEP), Fundação de
Amparo à Pesquisa do Estado de São Paulo (FAPESP); National Natural Science
Foundation of China (NSFC), the Chinese Ministry of Education (CMOE) and the
Ministry of Science and Technology of China (MSTC); Ministry of Education and
Youth of the Czech Republic; Danish Natural Science Research Council, the
Carlsberg Foundation and the Danish National Research Foundation; The European
Research Council under the European Community’s Seventh Framework Programme;
Helsinki Institute of Physics and the Academy of Finland; French CNRS-IN2P3,
the ‘Region Pays de Loire’, ‘Region Alsace’, ‘Region Auvergne’ and CEA,
France; German Bundesministerium fur Bildung, Wissenschaft, Forschung und
Technologie (BMBF) and the Helmholtz Association; General Secretariat for
Research and Technology, Ministry of Development, Greece; Hungarian Orszagos
Tudomanyos Kutatasi Alappgrammok (OTKA) and National Office for Research and
Technology (NKTH); Department of Atomic Energy and Department of Science and
Technology of the Government of India; Istituto Nazionale di Fisica Nucleare
(INFN) and Centro Fermi - Museo Storico della Fisica e Centro Studi e Ricerche
“Enrico Fermi”, Italy; MEXT Grant-in-Aid for Specially Promoted Research,
Japan; Joint Institute for Nuclear Research, Dubna; National Research
Foundation of Korea (NRF); Consejo Nacional de Cienca y Tecnologia (CONACYT),
Direccion General de Asuntos del Personal Academico(DGAPA), México, Amerique
Latine Formation academique - European Commission (ALFA-EC) and the EPLANET
Program (European Particle Physics Latin American Network); Stichting voor
Fundamenteel Onderzoek der Materie (FOM) and the Nederlandse Organisatie voor
Wetenschappelijk Onderzoek (NWO), Netherlands; Research Council of Norway
(NFR); National Science Centre, Poland; Ministry of National
Education/Institute for Atomic Physics and National Council of Scientific
Research in Higher Education (CNCSI-UEFISCDI), Romania; Ministry of Education
and Science of Russian Federation, Russian Academy of Sciences, Russian
Federal Agency of Atomic Energy, Russian Federal Agency for Science and
Innovations and The Russian Foundation for Basic Research; Ministry of
Education of Slovakia; Department of Science and Technology, South Africa;
Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas
(CIEMAT), E-Infrastructure shared between Europe and Latin America (EELA),
Ministerio de Economía y Competitividad (MINECO) of Spain, Xunta de Galicia
(Consellería de Educación), Centro de Aplicaciones Tecnológicas y Desarrollo
Nuclear (CEADEN), Cubaenergía, Cuba, and IAEA (International Atomic Energy
Agency); Swedish Research Council (VR) and Knut $\&$ Alice Wallenberg
Foundation (KAW); Ukraine Ministry of Education and Science; United Kingdom
Science and Technology Facilities Council (STFC); The United States Department
of Energy, the United States National Science Foundation, the State of Texas,
and the State of Ohio; Ministry of Science, Education and Sports of Croatia
and Unity through Knowledge Fund, Croatia; Council of Scientific and
Industrial Research (CSIR), New Delhi, India; Pontificia Universidad Católica
del Perú.

## References

  * [1] F. Karsch, “Lattice simulations of the thermodynamics of strongly interacting elementary particles and the exploration of new phases of matter in relativistic heavy ion collisions,” J.Phys.Conf.Ser. 46 (2006) 122–131, arXiv:hep-lat/0608003 [hep-lat].
  * [2] Wuppertal-Budapest Collaboration, S. Borsanyi et al., “Is there still any $T_{c}$ mystery in lattice QCD? Results with physical masses in the continuum limit III,” JHEP 1009 (2010) 073, arXiv:1005.3508 [hep-lat].
  * [3] S. Borsanyi, Z. Fodor, C. Hoelbling, S. D. Katz, S. Krieg, et al., “Full result for the QCD equation of state with 2+1 flavors,” Phys.Lett. B730 (2014) 99–104, arXiv:1309.5258 [hep-lat].
  * [4] A. Bazavov, T. Bhattacharya, M. Cheng, C. DeTar, H. Ding, et al., “The chiral and deconfinement aspects of the QCD transition,” Phys.Rev. D85 (2012) 054503, arXiv:1111.1710 [hep-lat].
  * [5] F.-M. Liu and S.-X. Liu, “Quark-gluon plasma formation time and direct photons from heavy ion collisions,” Phys. Rev. C89 no. 3, (2014) 034906, arXiv:1212.6587 [nucl-th].
  * [6] M. Gyulassy and M. Plumer, “Jet Quenching in Dense Matter,” Phys.Lett. B243 (1990) 432–438.
  * [7] R. Baier, Y. L. Dokshitzer, A. H. Mueller, S. Peigne, and D. Schiff, “Radiative energy loss and p(T) broadening of high-energy partons in nuclei,” Nucl.Phys. B484 (1997) 265–282, arXiv:hep-ph/9608322 [hep-ph].
  * [8] M. H. Thoma and M. Gyulassy, “Quark Damping and Energy Loss in the High Temperature QCD,” Nucl.Phys. B351 (1991) 491–506.
  * [9] E. Braaten and M. H. Thoma, “Energy loss of a heavy fermion in a hot plasma,” Phys.Rev. D44 (1991) 1298–1310.
  * [10] E. Braaten and M. H. Thoma, “Energy loss of a heavy quark in the quark - gluon plasma,” Phys.Rev. D44 (1991) 2625–2630.
  * [11] R. Glauber and G. Matthiae, “High-energy scattering of protons by nuclei,” Nucl.Phys. B21 (1970) 135–157.
  * [12] M. L. Miller, K. Reygers, S. J. Sanders, and P. Steinberg, “Glauber modeling in high energy nuclear collisions,” Ann.Rev.Nucl.Part.Sci. 57 (2007) 205–243, arXiv:nucl-ex/0701025 [nucl-ex].
  * [13] M. Djordjevic, “Heavy flavor puzzle at LHC: a serendipitous interplay of jet suppression and fragmentation,” Phys.Rev.Lett. 112 no. 4, (2014) 042302, arXiv:1307.4702 [nucl-th].
  * [14] N. Armesto, A. Dainese, C. A. Salgado, and U. A. Wiedemann, “Testing the color charge and mass dependence of parton energy loss with heavy-to-light ratios at RHIC and CERN LHC,” Phys.Rev. D71 (2005) 054027, arXiv:hep-ph/0501225 [hep-ph].
  * [15] A. Andronic, F. Arleo, R. Arnaldi, A. Beraudo, E. Bruna, et al., “Heavy-flavour and quarkonium production in the LHC era: from proton-proton to heavy-ion collisions,” arXiv:1506.03981 [nucl-ex].
  * [16] Y. L. Dokshitzer and D. Kharzeev, “Heavy quark colorimetry of QCD matter,” Phys.Lett. B519 (2001) 199–206, arXiv:hep-ph/0106202 [hep-ph].
  * [17] N. Armesto, C. A. Salgado, and U. A. Wiedemann, “Medium induced gluon radiation off massive quarks fills the dead cone,” Phys.Rev. D69 (2004) 114003, arXiv:hep-ph/0312106 [hep-ph].
  * [18] M. Djordjevic and M. Gyulassy, “Heavy quark radiative energy loss in QCD matter,” Nucl.Phys. A733 (2004) 265–298, arXiv:nucl-th/0310076 [nucl-th].
  * [19] B.-W. Zhang, E. Wang, and X.-N. Wang, “Heavy quark energy loss in nuclear medium,” Phys.Rev.Lett. 93 (2004) 072301, arXiv:nucl-th/0309040 [nucl-th].
  * [20] S. Wicks, W. Horowitz, M. Djordjevic, and M. Gyulassy, “Elastic, inelastic, and path length fluctuations in jet tomography,” Nucl.Phys. A784 (2007) 426–442, arXiv:nucl-th/0512076 [nucl-th].
  * [21] W. Horowitz and M. Gyulassy, “The Surprising Transparency of the sQGP at LHC,” Nucl.Phys. A872 (2011) 265–285, arXiv:1104.4958 [hep-ph].
  * [22] W. Horowitz, “Testing pQCD and AdS/CFT Energy Loss at RHIC and LHC,” AIP Conf.Proc. 1441 (2012) 889–891, arXiv:1108.5876 [hep-ph].
  * [23] H. van Hees, V. Greco, and R. Rapp, “Heavy-quark probes of the quark-gluon plasma at RHIC,” Phys.Rev. C73 (2006) 034913, arXiv:nucl-th/0508055 [nucl-th].
  * [24] S. Batsouli, S. Kelly, M. Gyulassy, and J. L. Nagle, “Does the charm flow at RHIC?,” Phys. Lett. B557 (2003) 26–32, arXiv:nucl-th/0212068 [nucl-th].
  * [25] V. Greco, C. M. Ko, and R. Rapp, “Quark coalescence for charmed mesons in ultrarelativistic heavy ion collisions,” Phys. Lett. B595 (2004) 202–208, arXiv:nucl-th/0312100 [nucl-th].
  * [26] A. Andronic, P. Braun-Munzinger, K. Redlich, and J. Stachel, “Statistical hadronization of charm in heavy ion collisions at SPS, RHIC and LHC,” Phys. Lett. B571 (2003) 36–44, arXiv:nucl-th/0303036 [nucl-th].
  * [27] PHENIX Collaboration, S. Adler et al., “Nuclear modification of electron spectra and implications for heavy quark energy loss in Au+Au collisions at $\sqrt{s_{{}_{\text{NN}}}}$ = 200 GeV,” Phys.Rev.Lett. 96 (2006) 032301, arXiv:nucl-ex/0510047 [nucl-ex].
  * [28] PHENIX Collaboration, A. Adare et al., “Heavy Quark Production in $p+p$ and Energy Loss and Flow of Heavy Quarks in Au+Au Collisions at $\sqrt{s_{NN}}=200$ GeV,” Phys.Rev. C84 (2011) 044905, arXiv:1005.1627 [nucl-ex].
  * [29] PHENIX Collaboration, A. Adare et al., “Nuclear-Modification Factor for Open-Heavy-Flavor Production at Forward Rapidity in Cu+Cu Collisions at $\sqrt{s_{NN}}=200$ GeV,” Phys.Rev. C86 (2012) 024909, arXiv:1204.0754 [nucl-ex].
  * [30] STAR Collaboration, B. Abelev et al., “Transverse momentum and centrality dependence of high-$p_{T}$ non-photonic electron suppression in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV,” Phys.Rev.Lett. 98 (2007) 192301, arXiv:nucl-ex/0607012 [nucl-ex].
  * [31] STAR Collaboration, L. Adamczyk et al., “Observation of $D^{0}$ Meson Nuclear Modifications in Au+Au Collisions at $\sqrt{s_{NN}}=200$ GeV,” Phys.Rev.Lett. 113 no. 14, (2014) 142301, arXiv:1404.6185 [nucl-ex].
  * [32] ALICE Collaboration, B. Abelev et al., “Suppression of high transverse momentum D mesons in central Pb-Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV,” JHEP 1209 (2012) 112, arXiv:1203.2160 [nucl-ex].
  * [33] ALICE Collaboration, B. Abelev et al., “Measurement of prompt $D$-meson production in $p-Pb$ collisions at $\sqrt{s_{NN}}$ = 5.02 TeV,” Phys.Rev.Lett. 113 no. 23, (2014) 232301, arXiv:1405.3452 [nucl-ex].
  * [34] ALICE Collaboration, B. Abelev et al., “D meson elliptic flow in non-central Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76TeV,” Phys.Rev.Lett. 111 (2013) 102301, arXiv:1305.2707 [nucl-ex].
  * [35] ALICE Collaboration, B. Abelev et al., “Azimuthal anisotropy of D meson production in Pb-Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV,” Phys.Rev. C90 no. 3, (2014) 034904, arXiv:1405.2001 [nucl-ex].
  * [36] ALICE Collaboration, K. Aamodt et al., “The ALICE experiment at the CERN LHC,” JINST 3 (2008) S08002.
  * [37] ALICE Collaboration, 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].
  * [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, B. Abelev et al., “Centrality determination of Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV with ALICE,” Phys.Rev. C88 no. 4, (2013) 044909, arXiv:1301.4361 [nucl-ex].
  * [40] R. Fruhwirth, “Application of Kalman filtering to track and vertex fitting,” Nucl.Instrum.Meth. A262 (1987) 444–450.
  * [41] ALICE Collaboration, J. Alme et al., “The ALICE TPC, a large 3-dimensional tracking device with fast readout for ultra-high multiplicity events,” Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 622 no. 1, (2010) 316 – 367.
  * [42] ALICE Collaboration, K. Aamodt et al., “Alignment of the ALICE Inner Tracking System with cosmic-ray tracks,” JINST 5 (2010) P03003, arXiv:1001.0502 [physics.ins-det].
  * [43] A. Akindinov et al., “Performance of the ALICE Time-Of-Flight detector at the LHC,” Eur. Phys. J. Plus 128 (2013) 44.
  * [44] Particle Data Group Collaboration, K. Olive et al., “Review of Particle Physics,” Chin.Phys. C38 (2014) 090001.
  * [45] ALICE Collaboration, B. Abelev et al., “Measurement of charm production at central rapidity in proton-proton collisions at $\sqrt{s}=7$ TeV,” JHEP 1201 (2012) 128, arXiv:1111.1553 [hep-ex].
  * [46] P. Z. Skands, “The Perugia Tunes,” FERMILAB-CONF-09-113-T, arXiv:0905.3418 [hep-ph] (2009) 284–297, arXiv:0905.3418 [hep-ph].
  * [47] R. Brun, F. Carminati, and S. Giani, “CERN Program Library Long Write-up, W5013 GEANT Detector Description and Simulation Tool,”.
  * [48] X.-N. Wang and M. Gyulassy, “HIJING: A Monte Carlo model for multiple jet production in p p, p A and A A collisions,” Phys.Rev. D44 (1991) 3501–3516.
  * [49] T. Sjostrand, S. Mrenna, and P. Z. Skands, “PYTHIA 6.4 Physics and Manual,” JHEP 0605 (2006) 026, arXiv:hep-ph/0603175 [hep-ph].
  * [50] P. Z. Skands, “Tuning Monte Carlo Generators: The Perugia Tunes,” Phys.Rev. D82 (2010) 074018, arXiv:1005.3457 [hep-ph].
  * [51] M. Cacciari, M. Greco, and P. Nason, “The P(T) spectrum in heavy flavor hadroproduction,” JHEP 9805 (1998) 007, arXiv:hep-ph/9803400 [hep-ph].
  * [52] M. Cacciari, S. Frixione, and P. Nason, “The p(T) spectrum in heavy flavor photoproduction,” JHEP 0103 (2001) 006, arXiv:hep-ph/0102134 [hep-ph].
  * [53] J. Uphoff, O. Fochler, Z. Xu, and C. Greiner, “Elliptic Flow and Energy Loss of Heavy Quarks in Ultra-Relativistic heavy Ion Collisions,” Phys.Rev. C84 (2011) 024908, arXiv:1104.2295 [hep-ph].
  * [54] O. Fochler, J. Uphoff, Z. Xu, and C. Greiner, “Jet quenching and elliptic flow at RHIC and LHC within a pQCD-based partonic transport model,” J.Phys. G38 (2011) 124152, arXiv:1107.0130 [hep-ph].
  * [55] J. Uphoff, O. Fochler, Z. Xu, and C. Greiner, “Open Heavy Flavor in Pb+Pb Collisions at $\sqrt{s}=2.76$ TeV within a Transport Model,” Phys.Lett. B717 (2012) 430–435, arXiv:1205.4945 [hep-ph].
  * [56] M. Cacciari, S. Frixione, N. Houdeau, M. L. Mangano, P. Nason, et al., “Theoretical predictions for charm and bottom production at the LHC,” JHEP 1210 (2012) 137, arXiv:1205.6344 [hep-ph].
  * [57] D. J. Lange, “The evtgen particle decay simulation package,” Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 462 no. 1 - 2, (2001) 152 – 155. BEAUTY2000, Proceedings of the 7th Int. Conf. on B-Physics at Hadron Machines.
  * [58] ALICE Collaboration, J. Adam et al., “Centrality dependence of high-$p_{\rm T}$ D meson suppression in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV,” arXiv:1506.06604 [nucl-ex].
  * [59] CMS Collaboration, CMS, “J/psi results from CMS in PbPb collisions, with 150mub-1 data,” CMS-PAS-HIN-12-014.
  * [60] ALICE Collaboration, B. Abelev et al., “Measurement of charm production at central rapidity in proton-proton collisions at $\sqrt{s}=2.76$ TeV,” JHEP 1207 (2012) 191, arXiv:1205.4007 [hep-ex].
  * [61] Z. Conesa del Valle, G. Corcella, F. Fleuret, E. G. Ferreiro, V. Kartvelishvili, et al., “Quarkonium production in high energy proton-proton and proton-nucleus collisions,” Nucl.Phys.Proc.Suppl. 214 (2011) 3–36, arXiv:1105.4545 [hep-ph].
  * [62] ALICE Collaboration, B. Abelev et al., “$D_{s}^{+}$ meson production at central rapidity in proton–proton collisions at $\sqrt{s}=7$ TeV,” Phys.Lett. B718 (2012) 279–294, arXiv:1208.1948 [hep-ex].
  * [63] R. Baier, “Jet quenching,” Nucl. Phys. A715 (2003) 209–218, arXiv:hep-ph/0209038 [hep-ph].
  * [64] K. Eskola, H. Paukkunen, and C. Salgado, “EPS09: A New Generation of NLO and LO Nuclear Parton Distribution Functions,” JHEP 0904 (2009) 065, arXiv:0902.4154 [hep-ph].
  * [65] X.-N. Wang, “Systematic study of high $p_{T}$ hadron spectra in $pp$, $p$ A and A A collisions from SPS to RHIC energies,” Phys.Rev. C61 (2000) 064910, arXiv:nucl-th/9812021 [nucl-th].
  * [66] Hard Probe Collaboration, R. Vogt, “The A dependence of open charm and bottom production,” Int.J.Mod.Phys. E12 (2003) 211–270, arXiv:hep-ph/0111271 [hep-ph].
  * [67] ALICE Collaboration, B. Abelev et al., “Pion, Kaon, and Proton Production in Central Pb–Pb Collisions at $\sqrt{s_{NN}}=2.76$ TeV,” Phys.Rev.Lett. 109 (2012) 252301, arXiv:1208.1974 [hep-ex].
  * [68] ALICE Collaboration, B. Abelev et al., “Centrality dependence of $\pi$, K, p production in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV,” Phys.Rev. C88 (2013) 044910, arXiv:1303.0737 [hep-ex].
  * [69] STAR Collaboration, B. Abelev et al., “Systematic Measurements of Identified Particle Spectra in $pp\leavevmode\nobreak\ $, d+Au and Au+Au Collisions from STAR,” Phys.Rev. C79 (2009) 034909, arXiv:0808.2041 [nucl-ex].
  * [70] M. He, R. J. Fries, and R. Rapp, “Heavy Flavor at the Large Hadron Collider in a Strong Coupling Approach,” Phys.Lett. B735 (2014) 445–450, arXiv:1401.3817 [nucl-th].
  * [71] M. He, R. J. Fries, and R. Rapp, “Heavy-Quark Diffusion and Hadronization in Quark-Gluon Plasma,” Phys. Rev. C86 (2012) 014903, arXiv:1106.6006 [nucl-th].
  * [72] ALICE Collaboration, B. Abelev et al., “Production of charged pions, kaons and protons at large transverse momenta in pp and PbÐPb collisions at $\sqrt{s_{\rm NN}}$ =2.76 TeV,” Phys.Lett. B736 (2014) 196–207, arXiv:1401.1250 [nucl-ex].
  * [73] ALICE Collaboration, B. Abelev et al., “Centrality Dependence of Charged Particle Production at Large Transverse Momentum in Pb–Pb Collisions at $\sqrt{s_{\rm{NN}}}=2.76$ TeV,” Phys.Lett. B720 (2013) 52–62, arXiv:1208.2711 [hep-ex].
  * [74] 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,” arXiv:1506.07287 [nucl-ex].
  * [75] M. Djordjevic, M. Djordjevic, and B. Blagojevic, “RHIC and LHC jet suppression in non-central collisions,” Phys.Lett. B737 (2014) 298–302, arXiv:1405.4250 [nucl-th].
  * [76] J. Xu, J. Liao, and M. Gyulassy, “Consistency of Perfect Fluidity and Jet Quenching in semi-Quark-Gluon Monopole Plasmas,” Chin. Phys. Lett. 32 no. 9, (2015) 092501, arXiv:1411.3673 [hep-ph].
  * [77] J. Xu, J. Liao, and M. Gyulassy, “Robustness and Consistency of Jet Quenching and Perfect Fluidity in semi Quark Gluon Monopole Plasmas (sQGMP) Produced at RHIC and LHC,” arXiv:1508.00552 [hep-ph].
  * [78] R. Sharma, I. Vitev, and B.-W. Zhang, “Light-cone wave function approach to open heavy flavor dynamics in QCD matter,” Phys.Rev. C80 (2009) 054902, arXiv:0904.0032 [hep-ph].
  * [79] S. Cao, G.-Y. Qin, and S. A. Bass, “Heavy-quark dynamics and hadronization in ultrarelativistic heavy-ion collisions: Collisional versus radiative energy loss,” Phys.Rev. C88 no. 4, (2013) 044907, arXiv:1308.0617 [nucl-th].
  * [80] M. Nahrgang, J. Aichelin, P. B. Gossiaux, and K. Werner, “Influence of hadronic bound states above $T_{c}$ on heavy-quark observables in Pb + Pb collisions at at the CERN Large Hadron Collider,” Phys.Rev. C89 no. 1, (2014) 014905, arXiv:1305.6544 [hep-ph].
  * [81] W. Alberico, A. Beraudo, A. De Pace, A. Molinari, M. Monteno, et al., “Heavy-flavour spectra in high energy nucleus-nucleus collisions,” Eur.Phys.J. C71 (2011) 1666, arXiv:1101.6008 [hep-ph].
  * [82] A. Beraudo, A. De Pace, M. Monteno, M. Nardi, and F. Prino, “Heavy flavors in heavy-ion collisions: quenching, flow and correlations,” Eur. Phys. J. C75 no. 3, (2015) 121, arXiv:1410.6082 [hep-ph].
  * [83] T. Song, H. Berrehrah, D. Cabrera, W. Cassing, and E. Bratkovskaya, “Charm production in Pb+Pb collisions at the Large Hadron Collider energy,” arXiv:1512.00891 [nucl-th].
  * [84] S. Cao, G.-Y. Qin, and S. A. Bass, “Energy loss, hadronization and hadronic interactions of heavy flavors in relativistic heavy-ion collisions,” Phys. Rev. C92 no. 2, (2015) 024907, arXiv:1505.01413 [nucl-th].

##  Appendix A The ALICE Collaboration

J. Adamorg40&D. Adamováorg83&M.M. Aggarwalorg87&G. Aglieri Rinellaorg36&M.
Agnelloorg110&N. Agrawalorg48&Z. Ahammedorg132&S.U. Ahnorg68&S. Aiolaorg136&A.
Akindinovorg58&S.N. Alamorg132&D. Aleksandrovorg99&B. Alessandroorg110&D.
Alexandreorg101&R. Alfaro Molinaorg64&A. Aliciorg12,org104&A. Alkinorg3&J.R.M.
Almarazorg119&J. Almeorg38&T. Altorg43&S. Altinpinarorg18&I.
Altsybeevorg131&C. Alves Garcia Pradoorg120&C. Andreiorg78&A. Andronicorg96&V.
Anguelovorg93&J. Anielskiorg54&T. Antičićorg97&F. Antinoriorg107&P.
Antonioliorg104&L. Aphecetcheorg113&H. Appelshäuserorg53&S. Arcelliorg28&R.
Arnaldiorg110&O.W. Arnoldorg37,org92&I.C. Arseneorg22&M. Arslandokorg53&B.
Audurierorg113&A. Augustinusorg36&R. Averbeckorg96&M.D. Azmiorg19&A.
Badalàorg106&Y.W. Baekorg67,org44&S. Bagnascoorg110&R. Bailhacheorg53&R.
Balaorg90&A. Baldisseriorg15&R.C. Baralorg61&A.M. Barbanoorg27&R.
Barberaorg29&F. Barileorg33&G.G. Barnaföldiorg135&L.S. Barnbyorg101&V.
Barretorg70&P. Bartaliniorg7&K. Barthorg36&J. Bartkeorg117&E. Bartschorg53&M.
Basileorg28&N. Bastidorg70&S. Basuorg132&B. Bathenorg54&G. Batigneorg113&A.
Batista Camejoorg70&B. Batyunyaorg66&P.C. Batzingorg22&I.G. Beardenorg80&H.
Beckorg53&C. Beddaorg110&N.K. Beheraorg50&I. Belikovorg55&F. Belliniorg28&H.
Bello Martinezorg2&R. Bellwiedorg122&R. Belmontorg134&E. Belmont-
Morenoorg64&V. Belyaevorg75&G. Bencediorg135&S. Beoleorg27&I. Berceanuorg78&A.
Bercuciorg78&Y. Berdnikovorg85&D. Berenyiorg135&R.A. Bertensorg57&D.
Berzanoorg36&L. Betevorg36&A. Bhasinorg90&I.R. Bhatorg90&A.K. Bhatiorg87&B.
Bhattacharjeeorg45&J. Bhomorg128&L. Bianchiorg122&N. Bianchiorg72&C.
Bianchinorg57,org134&J. Bielčíkorg40&J. Bielčíkováorg83&A. Bilandzicorg80&R.
Biswasorg4&S. Biswasorg79&S. Bjelogrlicorg57&J.T. Blairorg118&D. Blauorg99&C.
Blumeorg53&F. Bockorg93,org74&A. Bogdanovorg75&H. Bøggildorg80&L.
Boldizsárorg135&M. Bombaraorg41&J. Bookorg53&H. Borelorg15&A. Borissovorg95&M.
Borriorg82,org124&F. Bossúorg65&E. Bottaorg27&S. Böttgerorg52&C.
Bourjauorg80&P. Braun-Munzingerorg96&M. Bregantorg120&T. Breitnerorg52&T.A.
Brokerorg53&T.A. Browningorg94&M. Brozorg40&E.J. Bruckenorg46&E.
Brunaorg110&G.E. Brunoorg33&D. Budnikovorg98&H. Bueschingorg53&S.
Bufalinoorg27,org36&P. Buncicorg36&O. Buschorg93,org128&Z. Butheleziorg65&J.B.
Buttorg16&J.T. Buxtonorg20&D. Caffarriorg36&X. Caiorg7&H. Cainesorg136&L.
Calero Diazorg72&A. Calivaorg57&E. Calvo Villarorg102&P. Cameriniorg26&F.
Carenaorg36&W. Carenaorg36&F. Carnesecchiorg28&J. Castillo
Castellanosorg15&A.J. Castroorg125&E.A.R. Casulaorg25&C. Ceballos
Sanchezorg9&J. Cepilaorg40&P. Cerelloorg110&J. Cerkalaorg115&B. Changorg123&S.
Chapelandorg36&M. Chartierorg124&J.L. Charvetorg15&S. Chattopadhyayorg132&S.
Chattopadhyayorg100&V. Chelnokovorg3&M. Cherneyorg86&C. Cheshkovorg130&B.
Cheynisorg130&V. Chibante Barrosoorg36&D.D. Chinellatoorg121&S. Choorg50&P.
Chochulaorg36&K. Choiorg95&M. Chojnackiorg80&S. Choudhuryorg132&P.
Christakoglouorg81&C.H. Christensenorg80&P. Christiansenorg34&T.
Chujoorg128&S.U. Chungorg95&C. Cicaloorg105&L. Cifarelliorg12,org28&F.
Cindoloorg104&J. Cleymansorg89&F. Colamariaorg33&D. Colellaorg33,org36&A.
Colluorg74,org25&M. Colocciorg28&G. Conesa Balbastreorg71&Z. Conesa del
Valleorg51&M.E. Connorsidp1745888,org136&J.G. Contrerasorg40&T.M.
Cormierorg84&Y. Corrales Moralesorg110&I. Cortés Maldonadoorg2&P.
Corteseorg32&M.R. Cosentinoorg120&F. Costaorg36&P. Crochetorg70&R. Cruz
Albinoorg11&E. Cuautleorg63&L. Cunqueiroorg36&T. Dahmsorg92,org37&A.
Daineseorg107&A. Danuorg62&D. Dasorg100&I. Dasorg51,org100&S. Dasorg4&A.
Dashorg121,org79&S. Dashorg48&S. Deorg120&A. De Caroorg31,org12&G. de
Cataldoorg103&C. de Contiorg120&J. de Cuvelandorg43&A. De Falcoorg25&D. De
Gruttolaorg12,org31&N. De Marcoorg110&S. De Pasqualeorg31&A.
Deistingorg96,org93&A. Delofforg77&E. Dénesorg1350&C. Deplanoorg81&P.
Dhankherorg48&D. Di Bariorg33&A. Di Mauroorg36&P. Di Nezzaorg72&M.A. Diaz
Corcheroorg10&T. Dietelorg89&P. Dillensegerorg53&R. Diviàorg36&Ø.
Djuvslandorg18&A. Dobrinorg57,org81&D. Domenicis Gimenezorg120&B.
Dönigusorg53&O. Dordicorg22&T. Drozhzhovaorg53&A.K. Dubeyorg132&A.
Dublaorg57&L. Ducrouxorg130&P. Dupieuxorg70&R.J. Ehlersorg136&D. Eliaorg103&H.
Engelorg52&E. Eppleorg136&B. Erazmusorg113&I. Erdemirorg53&F. Erhardtorg129&B.
Espagnonorg51&M. Estienneorg113&S. Esumiorg128&J. Eumorg95&D. Evansorg101&S.
Evdokimovorg111&G. Eyyubovaorg40&L. Fabbiettiorg92,org37&D. Fabrisorg107&J.
Faivreorg71&A. Fantoniorg72&M. Faselorg74&L. Feldkamporg54&A.
Felicielloorg110&G. Feofilovorg131&J. Ferenceiorg83&A. Fernández
Téllezorg2&E.G. Ferreiroorg17&A. Ferrettiorg27&A. Festantiorg30&V.J.G.
Feuillardorg15,org70&J. Figielorg117&M.A.S. Figueredoorg124,org120&S.
Filchaginorg98&D. Finogeevorg56&F.M. Fiondaorg25&E.M. Fioreorg33&M.G.
Fleckorg93&M. Florisorg36&S. Foertschorg65&P. Fokaorg96&S. Fokinorg99&E.
Fragiacomoorg109&A. Francesconorg30,org36&U. Frankenfeldorg96&U. Fuchsorg36&C.
Furgetorg71&A. Fursorg56&M. Fusco Girardorg31&J.J. Gaardhøjeorg80&M.
Gagliardiorg27&A.M. Gagoorg102&M. Gallioorg27&D.R. Gangadharanorg74&P.
Ganotiorg36,org88&C. Gaoorg7&C. Garabatosorg96&E. Garcia-Solisorg13&C.
Gargiuloorg36&P. Gasikorg37,org92&E.F. Gaugerorg118&M. Germainorg113&A.
Gheataorg36&M. Gheataorg62,org36&P. Ghoshorg132&S.K. Ghoshorg4&P.
Gianottiorg72&P. Giubellinoorg36,org110&P. Giubilatoorg30&E. Gladysz-
Dziadusorg117&P. Glässelorg93&D.M. Goméz Coralorg64&A. Gomez Ramirezorg52&V.
Gonzalezorg10&P. González-Zamoraorg10&S. Gorbunovorg43&L. Görlichorg117&S.
Gotovacorg116&V. Grabskiorg64&O.A. Grachovorg136&L.K. Graczykowskiorg133&K.L.
Grahamorg101&A. Grelliorg57&A. Grigorasorg36&C. Grigorasorg36&V.
Grigorievorg75&A. Grigoryanorg1&S. Grigoryanorg66&B. Grinyovorg3&N.
Grionorg109&J.M. Gronefeldorg96&J.F. Grosse-Oetringhausorg36&J.-Y.
Grossiordorg130&R. Grossoorg96&F. Guberorg56&R. Guernaneorg71&B.
Guerzoniorg28&K. Gulbrandsenorg80&T. Gunjiorg127&A. Guptaorg90&R.
Guptaorg90&R. Haakeorg54&Ø. Haalandorg18&C. Hadjidakisorg51&M. Haiducorg62&H.
Hamagakiorg127&G. Hamarorg135&J.W. Harrisorg136&A. Hartonorg13&D.
Hatzifotiadouorg104&S. Hayashiorg127&S.T. Heckelorg53&M. Heideorg54&H.
Helstruporg38&A. Herghelegiuorg78&G. Herrera Corralorg11&B.A. Hessorg35&K.F.
Hetlandorg38&H. Hillemannsorg36&B. Hippolyteorg55&R. Hosokawaorg128&P.
Hristovorg36&M. Huangorg18&T.J. Humanicorg20&N. Hussainorg45&T.
Hussainorg19&D. Hutterorg43&D.S. Hwangorg21&R. Ilkaevorg98&M. Inabaorg128&M.
Ippolitovorg75,org99&M. Irfanorg19&M. Ivanovorg96&V. Ivanovorg85&V.
Izucheevorg111&P.M. Jacobsorg74&M.B. Jadhavorg48&S. Jadlovskaorg115&J.
Jadlovskyorg115,org59&C. Jahnkeorg120&M.J. Jakubowskaorg133&H.J.
Jangorg68&M.A. Janikorg133&P.H.S.Y. Jayarathnaorg122&C. Jenaorg30&S.
Jenaorg122&R.T. Jimenez Bustamanteorg96&P.G. Jonesorg101&H. Jungorg44&A.
Juskoorg101&P. Kalinakorg59&A. Kalweitorg36&J. Kaminorg53&J.H. Kangorg137&V.
Kaplinorg75&S. Karorg132&A. Karasu Uysalorg69&O. Karavichevorg56&T.
Karavichevaorg56&L. Karayanorg96,org93&E. Karpechevorg56&U. Kebschullorg52&R.
Keidelorg138&D.L.D. Keijdenerorg57&M. Keilorg36&M. Mohisin Khanorg19&P.
Khanorg100&S.A. Khanorg132&A. Khanzadeevorg85&Y. Kharlovorg111&B.
Kilengorg38&D.W. Kimorg44&D.J. Kimorg123&D. Kimorg137&H. Kimorg137&J.S.
Kimorg44&M. Kimorg44&M. Kimorg137&S. Kimorg21&T. Kimorg137&S. Kirschorg43&I.
Kiselorg43&S. Kiselevorg58&A. Kisielorg133&G. Kissorg135&J.L. Klayorg6&C.
Kleinorg53&J. Kleinorg36,org93&C. Klein-Bösingorg54&S. Klewinorg93&A.
Klugeorg36&M.L. Knichelorg93&A.G. Knospeorg118&T. Kobayashiorg128&C.
Kobdajorg114&M. Kofaragoorg36&T. Kolleggerorg96,org43&A. Kolojvariorg131&V.
Kondratievorg131&N. Kondratyevaorg75&E. Kondratyukorg111&A. Konevskikhorg56&M.
Kopcikorg115&M. Kourorg90&C. Kouzinopoulosorg36&O. Kovalenkoorg77&V.
Kovalenkoorg131&M. Kowalskiorg117&G. Koyithatta Meethaleveeduorg48&I.
Králikorg59&A. Kravčákováorg41&M. Kretzorg43&M. Krivdaorg59,org101&F.
Krizekorg83&E. Kryshenorg36&M. Krzewickiorg43&A.M. Kuberaorg20&V.
Kučeraorg83&C. Kuhnorg55&P.G. Kuijerorg81&A. Kumarorg90&J. Kumarorg48&L.
Kumarorg87&S. Kumarorg48&P. Kurashviliorg77&A. Kurepinorg56&A.B.
Kurepinorg56&A. Kuryakinorg98&M.J. Kweonorg50&Y. Kwonorg137&S.L. La
Pointeorg110&P. La Roccaorg29&P. Ladron de Guevaraorg11&C. Lagana
Fernandesorg120&I. Lakomovorg36&R. Langoyorg42&C. Laraorg52&A. Lardeuxorg15&A.
Lattucaorg27&E. Laudiorg36&R. Leaorg26&L. Leardiniorg93&G.R. Leeorg101&S.
Leeorg137&F. Lehasorg81&R.C. Lemmonorg82&V. Lentiorg103&E. Leograndeorg57&I.
León Monzónorg119&H. León Vargasorg64&M. Leoncinoorg27&P. Lévaiorg135&S.
Liorg70,org7&X. Liorg14&J. Lienorg42&R. Lietavaorg101&S. Lindalorg22&V.
Lindenstruthorg43&C. Lippmannorg96&M.A. Lisaorg20&H.M. Ljunggrenorg34&D.F.
Lodatoorg57&P.I. Loenneorg18&V. Loginovorg75&C. Loizidesorg74&X. Lopezorg70&E.
López Torresorg9&A. Loweorg135&P. Luettigorg53&M. Lunardonorg30&G.
Luparelloorg26&A. Maevskayaorg56&M. Magerorg36&S. Mahajanorg90&S.M.
Mahmoodorg22&A. Maireorg55&R.D. Majkaorg136&M. Malaevorg85&I. Maldonado
Cervantesorg63&L. Malininaidp3782096,org66&D. Mal’Kevichorg58&P.
Malzacherorg96&A. Mamonovorg98&V. Mankoorg99&F. Mansoorg70&V.
Manzariorg36,org103&M. Marchisoneorg27,org65,org126&J. Marešorg60&G.V.
Margagliottiorg26&A. Margottiorg104&J. Marguttiorg57&A. Marínorg96&C.
Markertorg118&M. Marquardorg53&N.A. Martinorg96&J. Martin Blancoorg113&P.
Martinengoorg36&M.I. Martínezorg2&G. Martínez Garcíaorg113&M. Martinez
Pedreiraorg36&A. Masorg120&S. Masciocchiorg96&M. Maseraorg27&A.
Masoniorg105&L. Massacrierorg113&A. Mastroserioorg33&A. Matyjaorg117&C.
Mayerorg117&J. Mazerorg125&M.A. Mazzoniorg108&D. Mcdonaldorg122&F.
Meddiorg24&Y. Melikyanorg75&A. Menchaca-Rochaorg64&E. Meninnoorg31&J. Mercado
Pérezorg93&M. Meresorg39&Y. Miakeorg128&M.M. Mieskolainenorg46&K.
Mikhaylovorg66,org58&L. Milanoorg36&J. Milosevicorg22&L.M.
Minerviniorg103,org23&A. Mischkeorg57&A.N. Mishraorg49&D. Miśkowiecorg96&J.
Mitraorg132&C.M. Mituorg62&N. Mohammadiorg57&B. Mohantyorg79,org132&L.
Molnarorg55,org113&L. Montaño Zetinaorg11&E. Montesorg10&D.A. Moreira De
Godoyorg54,org113&L.A.P. Morenoorg2&S. Morettoorg30&A. Morrealeorg113&A.
Morschorg36&V. Mucciforaorg72&E. Mudnicorg116&D. Mühlheimorg54&S.
Muhuriorg132&M. Mukherjeeorg132&J.D. Mulliganorg136&M.G. Munhozorg120&R.H.
Munzerorg92,org37&S. Murrayorg65&L. Musaorg36&J. Musinskyorg59&B. Naikorg48&R.
Nairorg77&B.K. Nandiorg48&R. Naniaorg104&E. Nappiorg103&M.U. Naruorg16&H.
Natal da Luzorg120&C. Nattrassorg125&K. Nayakorg79&T.K. Nayakorg132&S.
Nazarenkoorg98&A. Nedosekinorg58&L. Nellenorg63&F. Ngorg122&M.
Nicassioorg96&M. Niculescuorg62&J. Niedzielaorg36&B.S. Nielsenorg80&S.
Nikolaevorg99&S. Nikulinorg99&V. Nikulinorg85&F. Noferiniorg12,org104&P.
Nomokonovorg66&G. Noorenorg57&J.C.C. Norisorg2&J. Normanorg124&A.
Nyaninorg99&J. Nystrandorg18&H. Oeschlerorg93&S. Ohorg136&S.K. Ohorg67&A.
Ohlsonorg36&A. Okatanorg69&T. Okuboorg47&L. Olahorg135&J. Oleniaczorg133&A.C.
Oliveira Da Silvaorg120&M.H. Oliverorg136&J. Onderwaaterorg96&C.
Oppedisanoorg110&R. Oravaorg46&A. Ortiz Velasquezorg63&A. Oskarssonorg34&J.
Otwinowskiorg117&K. Oyamaorg93,org76&M. Ozdemirorg53&Y. Pachmayerorg93&P.
Paganoorg31&G. Paićorg63&S.K. Palorg132&J. Panorg134&A.K. Pandeyorg48&P.
Papcunorg115&V. Papikyanorg1&G.S. Pappalardoorg106&P. Pareekorg49&W.J.
Parkorg96&S. Parmarorg87&A. Passfeldorg54&V. Paticchioorg103&R.N.
Patraorg132&B. Paulorg100&T. Peitzmannorg57&H. Pereira Da Costaorg15&E.
Pereira De Oliveira Filhoorg120&D. Peresunkoorg99,org75&C.E. Pérez
Laraorg81&E. Perez Lezamaorg53&V. Peskovorg53&Y. Pestovorg5&V.
Petráčekorg40&V. Petrovorg111&M. Petroviciorg78&C. Pettaorg29&S.
Pianoorg109&M. Piknaorg39&P. Pillotorg113&O. Pinazzaorg104,org36&L.
Pinskyorg122&D.B. Piyarathnaorg122&M. Płoskońorg74&M. Planinicorg129&J.
Plutaorg133&S. Pochybovaorg135&P.L.M. Podesta-Lermaorg119&M.G.
Poghosyanorg84,org86&B. Polichtchoukorg111&N. Poljakorg129&W.
Poonsawatorg114&A. Poporg78&S. Porteboeuf-Houssaisorg70&J. Porterorg74&J.
Pospisilorg83&S.K. Prasadorg4&R. Preghenellaorg36,org104&F. Prinoorg110&C.A.
Pruneauorg134&I. Pshenichnovorg56&M. Puccioorg27&G. Pudduorg25&P.
Pujahariorg134&V. Puninorg98&J. Putschkeorg134&H. Qvigstadorg22&A.
Rachevskiorg109&S. Rahaorg4&S. Rajputorg90&J. Rakorg123&A.
Rakotozafindrabeorg15&L. Ramelloorg32&F. Ramiorg55&R. Raniwalaorg91&S.
Raniwalaorg91&S.S. Räsänenorg46&B.T. Rascanuorg53&D. Ratheeorg87&K.F.
Readorg125,org84&K. Redlichorg77&R.J. Reedorg134&A. Rehmanorg18&P.
Reicheltorg53&F. Reidtorg93,org36&X. Renorg7&R. Renfordtorg53&A.R.
Reolonorg72&A. Reshetinorg56&J.-P. Revolorg12&K. Reygersorg93&V.
Riabovorg85&R.A. Ricciorg73&T. Richertorg34&M. Richterorg22&P. Riedlerorg36&W.
Rieglerorg36&F. Riggiorg29&C. Risteaorg62&E. Roccoorg57&M. Rodríguez
Cahuantziorg2,org11&A. Rodriguez Mansoorg81&K. Røedorg22&E. Rogochayaorg66&D.
Rohrorg43&D. Röhrichorg18&R. Romitaorg124&F. Ronchettiorg72,org36&L.
Ronfletteorg113&P. Rosnetorg70&A. Rossiorg30,org36&F. Roukoutakisorg88&A.
Royorg49&C. Royorg55&P. Royorg100&A.J. Rubio Monteroorg10&R. Ruiorg26&R.
Russoorg27&E. Ryabinkinorg99&Y. Ryabovorg85&A. Rybickiorg117&S.
Sadovskyorg111&K. Šafaříkorg36&B. Sahlmullerorg53&P. Sahooorg49&R.
Sahooorg49&S. Sahooorg61&P.K. Sahuorg61&J. Sainiorg132&S. Sakaiorg72&M.A.
Salehorg134&J. Salzwedelorg20&S. Sambyalorg90&V. Samsonovorg85&L.
Šándororg59&A. Sandovalorg64&M. Sanoorg128&D. Sarkarorg132&E.
Scapparoneorg104&F. Scarlassaraorg30&C. Schiauaorg78&R. Schickerorg93&C.
Schmidtorg96&H.R. Schmidtorg35&S. Schuchmannorg53&J. Schukraftorg36&M.
Schulcorg40&T. Schusterorg136&Y. Schutzorg36,org113&K. Schwarzorg96&K.
Schwedaorg96&G. Scioliorg28&E. Scomparinorg110&R. Scottorg125&M.
Šefčíkorg41&J.E. Segerorg86&Y. Sekiguchiorg127&D. Sekihataorg47&I.
Selyuzhenkovorg96&K. Senosiorg65&S. Senyukovorg3,org36&E.
Serradillaorg10,org64&A. Sevcencoorg62&A. Shabanovorg56&A. Shabetaiorg113&O.
Shaduraorg3&R. Shahoyanorg36&A. Shangaraevorg111&A. Sharmaorg90&M.
Sharmaorg90&M. Sharmaorg90&N. Sharmaorg125&K. Shigakiorg47&K.
Shtejerorg9,org27&Y. Sibiriakorg99&S. Siddhantaorg105&K.M. Sielewiczorg36&T.
Siemiarczukorg77&D. Silvermyrorg84,org34&C. Silvestreorg71&G.
Simatovicorg129&G. Simonettiorg36&R. Singarajuorg132&R. Singhorg79&S.
Singhaorg132,org79&V. Singhalorg132&B.C. Sinhaorg132&T. Sinhaorg100&B.
Sitarorg39&M. Sittaorg32&T.B. Skaaliorg22&M. Slupeckiorg123&N.
Smirnovorg136&R.J.M. Snellingsorg57&T.W. Snellmanorg123&C. Søgaardorg34&J.
Songorg95&M. Songorg137&Z. Songorg7&F. Soramelorg30&S. Sorensenorg125&F.
Sozziorg96&M. Spacekorg40&E. Spiritiorg72&I. Sputowskaorg117&M. Spyropoulou-
Stassinakiorg88&J. Stachelorg93&I. Stanorg62&G. Stefanekorg77&E.
Stenlundorg34&G. Steynorg65&J.H. Stillerorg93&D. Stoccoorg113&P.
Strmenorg39&A.A.P. Suaideorg120&T. Sugitateorg47&C. Suireorg51&M.
Suleymanovorg16&M. Suljicorg260&R. Sultanovorg58&M. Šumberaorg83&A.
Szaboorg39&A. Szanto de Toledoorg1200&I. Szarkaorg39&A.
Szczepankiewiczorg36&M. Szymanskiorg133&U. Tabassamorg16&J.
Takahashiorg121&G.J. Tambaveorg18&N. Tanakaorg128&M.A. Tangaroorg33&M.
Tarhiniorg51&M. Tariqorg19&M.G. Tarzilaorg78&A. Tauroorg36&G. Tejeda
Muñozorg2&A. Telescaorg36&K. Terasakiorg127&C. Terrevoliorg30&B.
Teyssierorg130&J. Thäderorg74&D. Thomasorg118&R. Tieulentorg130&A.R.
Timminsorg122&A. Toiaorg53&S. Trogoloorg27&G. Trombettaorg33&V.
Trubnikovorg3&W.H. Trzaskaorg123&T. Tsujiorg127&A. Tumkinorg98&R.
Turrisiorg107&T.S. Tveterorg22&K. Ullalandorg18&A. Urasorg130&G.L.
Usaiorg25&A. Utrobicicorg129&M. Vajzerorg83&M. Valaorg59&L. Valencia
Palomoorg70&S. Valleroorg27&J. Van Der Maarelorg57&J.W. Van Hoorneorg36&M. van
Leeuwenorg57&T. Vanatorg83&P. Vande Vyvreorg36&D. Vargaorg135&A. Vargasorg2&M.
Vargyasorg123&R. Varmaorg48&M. Vasileiouorg88&A. Vasilievorg99&A.
Vauthierorg71&V. Vecherninorg131&A.M. Veenorg57&M. Veldhoenorg57&A.
Velureorg18&M. Venaruzzoorg73&E. Vercellinorg27&S. Vergara Limónorg2&R.
Vernetorg8&M. Verweijorg134&L. Vickovicorg116&G. Viestiorg300&J.
Viinikainenorg123&Z. Vilakaziorg126&O. Villalobos Baillieorg101&A. Villatoro
Telloorg2&A. Vinogradovorg99&L. Vinogradovorg131&Y. Vinogradovorg980&T.
Virgiliorg31&V. Vislaviciusorg34&Y.P. Viyogiorg132&A. Vodopyanovorg66&M.A.
Völklorg93&K. Voloshinorg58&S.A. Voloshinorg134&G. Volpeorg135&B. von
Hallerorg36&I. Vorobyevorg37,org92&D. Vranicorg96,org36&J. Vrlákováorg41&B.
Vulpescuorg70&A. Vyushinorg98&B. Wagnerorg18&J. Wagnerorg96&H. Wangorg57&M.
Wangorg7,org113&D. Watanabeorg128&Y. Watanabeorg127&M. Weberorg112,org36&S.G.
Weberorg96&D.F. Weiserorg93&J.P. Wesselsorg54&U. Westerhofforg54&A.M.
Whiteheadorg89&J. Wiechulaorg35&J. Wikneorg22&M. Wildeorg54&G. Wilkorg77&J.
Wilkinsonorg93&M.C.S. Williamsorg104&B. Windelbandorg93&M. Winnorg93&C.G.
Yaldoorg134&H. Yangorg57&P. Yangorg7&S. Yanoorg47&C. Yasarorg69&Z. Yinorg7&H.
Yokoyamaorg128&I.-K. Yooorg95&J.H. Yoonorg50&V. Yurchenkoorg3&I.
Yushmanovorg99&A. Zaborowskaorg133&V. Zaccoloorg80&A. Zamanorg16&C.
Zampolliorg104&H.J.C. Zanoliorg120&S. Zaporozhetsorg66&N. Zardoshtiorg101&A.
Zarochentsevorg131&P. Závadaorg60&N. Zaviyalovorg98&H. Zbroszczykorg133&I.S.
Zguraorg62&M. Zhalovorg85&H. Zhangorg18&X. Zhangorg74&Y. Zhangorg7&C.
Zhangorg57&Z. Zhangorg7&C. Zhaoorg22&N. Zhigarevaorg58&D. Zhouorg7&Y.
Zhouorg80&Z. Zhouorg18&H. Zhuorg18&J. Zhuorg113,org7&A. Zichichiorg28,org12&A.
Zimmermannorg93&M.B. Zimmermannorg54,org36&G. Zinovjevorg3&M. Zyzakorg43

## Affiliation notes

0Deceased

idp1745888Also at: Georgia State University, Atlanta, Georgia, United States

idp3782096Also at: M.V. Lomonosov Moscow State University, D.V. Skobeltsyn
Institute of Nuclear, Physics, Moscow, Russia

## 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, 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, France

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

org10Centro de Investigaciones Energéticas Medioambientales y Tecnológicas
(CIEMAT), Madrid, Spain

org11Centro de Investigación y de Estudios Avanzados (CINVESTAV), Mexico City
and Mérida, Mexico

org12Centro Fermi - Museo Storico della Fisica e Centro Studi e Ricerche
“Enrico Fermi”, Rome, Italy

org13Chicago State University, Chicago, Illinois, USA

org14China Institute of Atomic Energy, Beijing, China

org15Commissariat à l’Energie Atomique, IRFU, Saclay, France

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

org17Departamento de Física de Partículas and IGFAE, Universidad de Santiago
de Compostela, Santiago de Compostela, Spain

org18Department of Physics and Technology, University of Bergen, Bergen,
Norway

org19Department of Physics, Aligarh Muslim University, Aligarh, India

org20Department of Physics, Ohio State University, Columbus, Ohio, United
States

org21Department of Physics, Sejong University, Seoul, South Korea

org22Department of Physics, University of Oslo, Oslo, Norway

org23Dipartimento di Elettrotecnica ed Elettronica del Politecnico, Bari,
Italy

org24Dipartimento di Fisica dell’Università ’La Sapienza’ and Sezione INFN
Rome, Italy

org25Dipartimento di Fisica dell’Università and Sezione INFN, Cagliari, Italy

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

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

org28Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN,
Bologna, Italy

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

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

org31Dipartimento di Fisica ‘E.R. Caianiello’ dell’Università and Gruppo
Collegato INFN, Salerno, Italy

org32Dipartimento di Scienze e Innovazione Tecnologica dell’Università del
Piemonte Orientale and Gruppo Collegato INFN, Alessandria, Italy