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Λ c + Production and Baryon-to-Meson Ratios in p p and p -Pb Collisions at s NN = 5.02 TeV at the LHC

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The prompt production of the charm baryon Λc+ and the Λc+/D0 production ratios were measured at midrapidity with the ALICE detector in pp and p-Pb collisions at sNN=5.02 TeV. These new measurements show a clear decrease of the Λc+/D0 ratio with increasing transverse momentum (pT) in both collision systems in the range 2<pT<12 GeV/c, exhibiting similarities with the light-flavor baryon-to-meson ratios p/π and Λ/KS0. At low pT, predictions that include additional color-reconnection mechanisms beyond the leading-color approximation, assume the existence of additional higher-mass charm-baryon states, or include hadronization via coalescence can describe the data, while predictions driven by charm-quark fragmentation processes measured in e+e− and e−p collisions significantly underestimate the data. The results presented in this Letter provide significant evidence that the established assumption of universality (colliding-system independence) of parton-to-hadron fragmentation is not sufficient to describe charm-baryon production in hadronic collisions at LHC energies.
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Λ+
cProduction and Baryon-to-Meson Ratios in pp and p-Pb Collisions
at ffiffiffiffiffiffiffi
sNN
p=5.02 TeV at the LHC
S. Acharya et al.*
(ALICE Collaboration)
(Received 22 December 2020; revised 27 May 2021; accepted 10 August 2021; published 9 November 2021)
The prompt production of the charm baryon Λþ
cand the Λþ
c=D0production ratios were measured at
midrapidity with the ALICE detector in pp and p-Pb collisions at ffiffiffiffiffiffiffi
sNN
p¼5.02 TeV. These new
measurements show a clear decrease of the Λþ
c=D0ratio with increasing transverse momentum (pT) in both
collision systems in the range 2<p
T<12 GeV=c, exhibiting similarities with the light-flavor baryon-to-
meson ratios p=πand Λ=K0
S.AtlowpT, predictions that include additional color-reconnection mechanisms
beyond the leading-color approximation, assume the existence of additional higher-mass charm-baryon
states, or include hadronization via coalescence can describe the data, while predictions driven by charm-
quark fragmentation processes measured in eþeand epcollisions significantly underestimate the data.
The results presented in this Letter provide significant evidence that the established assumption of
universality (colliding-system independence) of parton-to-hadron fragmentation is not sufficient to
describe charm-baryon production in hadronic collisions at LHC energies.
DOI: 10.1103/PhysRevLett.127.202301
Heavy-flavor hadron production in hadronic collisions
occurs through the fragmentation of a charm or beauty
quark, created in hard parton-parton scattering processes,
into a given meson or baryon. Theoretical calculations of
heavy-flavor production generally use the QCD factoriza-
tion theorem [1], which describes the hadron cross section
as the convolution of three terms: the parton distribution
functions, the parton hard-scattering cross sections, and the
fragmentation functions. It is generally assumed that the
fragmentation functions are universal between collision
systems and energies, and the measurement of the relative
production of different heavy-flavor hadron species is
sensitive to fragmentation functions used in perturbative
QCD (pQCD)-based calculations. While perturbative cal-
culations at next-to-leading order with next-to-leading-log
resummation [25] generally describe the D- and B-meson
cross-section measurements [610] and the ratios of strange
and nonstrange Dmesons [6,10] within uncertainties,
heavy-flavor baryon production is less well understood.
The Λþ
cproduction cross section in pp collisions at
ffiffi
s
p¼7TeV and p-Pb collisions at ffiffiffiffiffiffiffi
sNN
p¼5.02 TeV was
reported by ALICE [11]. It was shown that in both collision
systems the pT-differential Λþ
cproduction cross section
is higher than predictions from pQCD calculations with
charm fragmentation tuned on previous eþeand ep
measurements [2,3]. The Λþ
c=D0ratio in pp and p-Pb
collisions is consistent in both collision systems and also
significantly underestimated by several Monte Carlo gen-
erators implementing different charm-quark fragmentation
processes [1215], suggesting that the fragmentation frac-
tions of charm quarks into different hadronic states are
nonuniversal with respect to collision system and center-of-
mass energy. The production of charm baryons has recently
been calculated within the kT-factorization approach using
unintegrated gluon distribution functions and the Peterson
fragmentation functions [16], and with the general-mass
variable-flavor-number scheme using updated fragmenta-
tion functions from OPAL and Belle [17]. These
approaches are unable to simultaneously describe
ALICE and LHCb data with the same set of parameters,
suggesting that the independent parton fragmentation
scheme is insufficient to fully describe the results. An
alternative explanation has been offered by a statistical
hadronization model, taking into account an augmented
list of charm-baryon states based on guidance from the
relativistic quark model (RQM) [18] and lattice QCD [19],
which is able to reproduce the Λþ
c=D0ratio measured by
ALICE. The magnitude of the relative yields of Λ0
bbaryons
and beauty mesons in pp collisions measured by LHCb
[2022] and CMS [23] offers further evidence that the
fragmentation fractions in the beauty sector also vary
between collision systems.
The measurement of baryon production has also been
important in heavy-ion collisions, where the high energy
density and temperature create a color-deconfined state of
matter [24]. A measured enhancement of the light-flavor
*Full author list given at the end of the article.
Published by the American Physical Society under the terms of
the Creative Commons Attribution 4.0 International license.
Further distribution of this work must maintain attribution to
the author(s) and the published articles title, journal citation,
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PHYSICAL REVIEW LETTERS 127, 202301 (2021)
0031-9007=21=127(20)=202301(13) 202301-1 © 2021 CERN, for the ALICE Collaboration
[25,26] and charm [2729] baryon-to-meson ratio at the
LHC and RHIC can be explained via an additional
mechanism of hadronization known as coalescence (or
recombination), where soft quarks from the medium
recombine to form a meson or baryon [30], in addition
to hydrodynamical radial flow. Measurements in p-Pb
collisions are crucial to provide an intermediatecollision
system where the generated particle multiplicities and
energy densities are between those generated in pp and
A-Acollisions. ALICE and CMS reported an enhancement
of the baryon-to-meson ratios in the light-flavor sector
(p=πand Λ=K0
S) at intermediate pT(2<p
T<10 GeV=c)
in high-multiplicity pp and p-Pb collisions similar to that
observed in heavy-ion collisions [31,32]. This adds to the
evidence that small systems also exhibit collective behav-
ior, which may have similar physical origins in pp,p-A,
and A-Acollisions [33]. It has been suggested that
hadronization of charm quarks via coalescence may also
occur in pp and p-Pb collisions [3436].
In this Letter, the measurements of the prompt produc-
tion of the charm baryon Λþ
cin pp collisions at ffiffi
s
p¼
5.02 TeV in jyj<0.5and in p-Pb collisions at ffiffiffiffiffiffiffi
sNN
p¼
5.02 TeV in 0.96 <y<0.04 are presented, with a focus
on the Λþ
c=D0production ratios. The measurement is
performed as an average of the Λþ
cand its charge conjugate
¯
Λ
c, collectively referred to as Λþ
cin the following. Two
hadronic decay channels were measured: Λþ
cpK
πþ
(branching ratio BR ¼6.28 0.33%), and Λþ
cpK0
S
(BR ¼1.59 0.08%)[37], which were reconstructed
exploiting the topology of the weakly decaying Λþ
c
(cτ¼60.7μm) [37]. The results from both decay channels
were averaged to obtain more precise production cross
sections. With respect to the results presented in [11], this
work studies a different center-of-mass energy for pp
collisions, and the cross section is measured in finer pT
intervals and over a wider pTrange. The overall precision of
the measurements is significantly improved by a factor of
1.52, depending on pT, for both pp and p-Pb collisions.
For a detailed description of the analysis techniques,
corrections, systematic uncertainty determination, and sup-
plementary measurements, the reader is referred to [38].
A description of the ALICE detector and its performance
are reported in [39,40]. The pp data sample was collected in
2017, and the p-Pb data sample was collected in 2016 during
the LHC Run 2. Both pp and p-Pb collisions were recorded
using a minimum bias (MB) trigger, which required coinci-
dent signals in the two V0 scintillator detectors located on
either side of the interaction vertex. Further offline selection
was applied in order to remove background from beam-gas
collisions and other machine-induced backgrounds. To
reduce superposition of more than one interaction within
the colliding bunches (pileup), events with multiple recon-
structed primary vertices were rejected. Only events with a z
coordinate of the reconstructed vertex position within 10 cm
of the nominal interaction point were used. With these
requirements, approximately 1×109MB-triggered pp
events were selected, corresponding to an integrated lumi-
nosity of Lint ¼19.5nb1(2.1% [41]). Approximately
600 ×106MB-triggered p-Pb events were selected, corre-
sponding to Lint ¼287 μb1(3.7% [42]).
The analysis techniques used for the results presented
here are described in detail in [38]. Charged-particle tracks
and particle decay vertices are reconstructed in the central
barrel using the Inner Tracking System (ITS) and the Time
Projection Chamber (TPC), which are located inside a
solenoid magnet of field strength 0.5 T. In order to reduce
the large combinatorial background, selections on the Λþ
c
candidates were made based on the particle identification
(PID) signals and the displacement of the decay tracks from
the collision point. The PID was performed using infor-
mation on the specific energy loss of charged particles as
they pass through the gas of the TPC and, where available,
with flight-time measurements given by the Time-Of-Flight
detector (TOF).
For the Λþ
cpK
πþanalysis, candidates were built by
reconstructing triplets of tracks with the correct configu-
ration of charges. For this analysis, the high-resolution
tracking provided by the detectors meant that the decay
vertex of the Λþ
ccandidates could be resolved from the
interaction point. To identify each of the p,K, and π
daughter tracks, information from the TPC and TOF was
combined using the maximum-probabilityBayesian
approach described in [43]. Kinematic selections were
made on the pTof the decay products of the Λþ
c, and
geometrical selections were made on topological properties
related to the displaced vertex of the Λþ
cdecay.
The reconstruction of Λþ
cpK0
Scandidates relied on
reconstructing the V-shaped decay of the K0
Smeson into
two pions, which was then combined with a proton track
(bachelor). In pp collisions, candidates were further
selected using criteria related to PID and properties of
the Λþ
cpK0
Sdecay. The Bayesian probability of the
combined TPC and TOF response for the bachelor track to
be a proton was required to be above 80%. The selection
criteria on kinematical and geometrical variables included
the distance of closest approach between the decay daugh-
ters, the invariant mass, and the cosine of the pointing angle
of the neutral decay vertex (K0
S) to the primary vertex.
For the Λþ
cpK0
Sdecay channel in p-Pb collisions, the
analysis was performed using a multivariate technique
based on the boosted decision tree (BDT) algorithm
provided by the Toolkit for Multivariate Data Analysis
[44]. The BDT algorithm was trained using signal and
background Λþ
cpK0
Sdecay candidates simulated using
PYTHIA
6.4.25 [45] with the Perugia 2011 tune [46], and the
underlying p-Pb event simulated with
HIJING
1.36 [47].
Candidates obtained with the same reconstruction strategy
previously described were preselected using loose geomet-
rical selections and PID selection on the bachelor proton
track. The model was trained independently for each pT
PHYSICAL REVIEW LETTERS 127, 202301 (2021)
202301-2
interval analyzed, with input variables comprising the pT
and Bayesian PID probability of the proton track, the cτ
and invariant mass of the K0
S, and the impact parameters of
the Λþ
cdecay tracks to the primary vertex. This model was
then applied on data, and a selection on the output response
was chosen based on the expected maximum significance
determined from simulations.
For both decay channels, the yield of Λþ
cbaryons was
extracted in each pTinterval via fits to the candidate
invariant-mass distributions. The fitting function con-
sisted of a Gaussian to estimate the signal and an
exponential or polynomial function to estimate the back-
ground. The width of the Gaussian was fixed in each pT
interval to values obtained from Monte Carlo simulations,
and the mean was treated as a free parameter. A statistical
significance higher than 4 standard deviations was
achievedinallpTintervals.
Several corrections were applied to the measurement of
the Λþ
ccross section. The geometrical acceptance of the
detector as well as the selection and reconstruction effi-
ciencies for prompt Λþ
cwere taken into account. These
correction factors were determined from pp collisions
generated with
PYTHIA
6and
PYTHIA
8.243 [48], with each
event including either a c¯
cor a b¯
bpair. For p-Pb collisions,
this was supplemented with an underlying event from the
HIJING
event generator. In p-Pb collisions, the efficiency
was calculated after reweighting the events based on their
charged particle multiplicity. This accounts for the fact that
the event multiplicity in simulation does not reproduce the
one in data, and the efficiency depends on the multiplicity
of the event as a consequence of the improvement of the
resolution of the primary vertex and thus of the perfor-
mance of the topological selections at higher multiplicities.
The fraction of the Λþ
cyield originating from beauty decays
(feed-down) was obtained using the beauty-quark produc-
tion cross section from
FONLL
[4,5], the fraction of beauty
quarks that fragment into beauty hadrons Hbfrom LHCb
measurements [22], and HbΛþ
cþX decay kinematics
from
PYTHIA
8, as well as the selection and reconstruction
efficiency of Λþ
cfrom beauty-hadron decays. The fraction
of the Λþ
cyield from beauty decays was found to be 2% at
low pTand up to 16% at high pT, and was subtracted from
the measured yield. As done in the D-meson analysis [49],
the possible modification of beauty-hadron production
in p-Pb collisions was included in the feed-down calcu-
lation by scaling the beauty-quark production by a nuclear
modification factor Rfeed-down
pPb , where it was assumed that
Rfeed-down
pPb ¼Rprompt
pPb with their ratio varied in the range
0.9<R
feed-down
pPb =Rprompt
pPb <1.3to evaluate the systematic
uncertainties.
Systematic uncertainties on the Λþ
ccross sections were
estimated considering the same sources as described in
[11]. The contributions from the raw-yield extraction were
evaluated by repeating the fits varying the fit interval and
the functional form of the background fit function. For each
of these variations the four combinations of free and fixed
Gaussian mean and width parameters of the fit were
considered. Overall, the relative uncertainty ranged from
4% to 11% depending on the pTand analysis. The
uncertainties on the track reconstruction efficiency were
estimated by adding in quadrature the uncertainty due to
track quality selection and the uncertainty due to the TPC-
ITS matching efficiency (from 3% to 7%). The former is
estimated by varying the track-quality selection criteria,
and the latter is estimated by comparing the probability to
match the tracks from the TPC to the ITS hits in data and
simulation. The uncertainty on the Λþ
cselection efficiency
was estimated by varying the selection on the kinematical
and topological properties of the Λþ
cdecays or the selection
on the BDT response (from 3% to 15%). The uncertainty on
the PID efficiency was estimated by varying the selection
on the Bayesian probability variables (from 2% to 5%). The
systematic effect on the efficiencies due to the shape of the
simulated Λþ
cpTdistribution was evaluated by reweighting
the generated Λþ
cfrom
PYTHIA
6to match the pTdistri-
bution obtained from
FONLL
calculations for Dmesons
(maximum 1% uncertainty). The relative statistical uncer-
tainty on the acceptance and efficiency correction was
considered as an additional systematic uncertainty source
(from 1%2% at low pTto 3%5% at high pT). The
uncertainties on fprompt were estimated by varying the
hypothesis on the production of Λþ
cfrom B-hadron decays
to account for the theoretical uncertainties of b-quark
production within
FONLL
and experimental uncertainties
on B-hadron fragmentation (around 2% at low pTand from
4% to 7% at high pT, depending on the analysis). Global
uncertainties of the measurement include those from the
luminosity and Λþ
cbranching ratios. The raw-yield extrac-
tion uncertainty source are considered to be uncorrelated
across pTbins, while all other sources are considered
to be correlated.
The results in each collision system from the two Λþ
c
decay channels were averaged to obtain the final results.
A weighted average of the results was calculated, with
weights defined as the inverse of the quadratic sum of the
relative statistical and uncorrelated systematic uncertain-
ties. The sources of systematic uncertainty assumed to be
uncorrelated between different decay channels were those
due to the raw-yield extraction, the statistical uncertainties
on the efficiency and acceptance, and those related to the
Λþ
cselection. The remaining uncertainties were assumed to
be correlated, except the branching ratio uncertainties,
which were treated as partially correlated among the
hadronic-decay modes as defined in [37].
Figure 1(left) shows a comparison of the Λþ
cpT-
differential cross sections in pp and in p-Pb collisions
at ffiffiffiffiffiffiffi
sNN
p¼5.02 TeV. The D0pT-differential cross sections
measured in the same collision systems and at the same
center-of-mass energy during the same data taking periods
PHYSICAL REVIEW LETTERS 127, 202301 (2021)
202301-3
[10,50] are also shown. In order to compare the spectral
shapes in the two different collision systems at the same
energy, the results in p-Pb collisions are scaled by the
atomic mass number of the lead nucleus. For Λþ
cbaryons
the spectral shape in p-Pb collisions is slightly harder than
in pp collisions, while for D0mesons the spectral shapes
are fully consistent within uncertainties.
Figure 1(right) shows the baryon-to-meson ratio Λþ
c=D0
measured in pp collisions at ffiffi
s
p¼5.02 TeV as a function
of pTcompared to theoretical predictions. The uncertainty
on the luminosity cancels in the ratio. The Λþ
c=D0ratio is
measured to be 0.40.5 at low pTand decreases to around
0.2 at high pT. The previous results at ffiffi
s
p¼7TeV hinted
at a decrease of the Λþ
c=D0ratio with pT, although the
precision was not enough to confirm this [11]. The results
in pp collisions at ffiffi
s
p¼5.02 TeV, with much higher
precision than ffiffi
s
p¼7TeV results, show a clear decrease
with increasing pT. The strong pTdependence of the
Λþ
c=D0ratio is in contrast to the ratios of strange and
nonstrange Dmesons in pp collisions at ffiffi
s
p¼5.02 TeV
and ffiffi
s
p¼7TeV [10,51] and in p-Pb collisions at ffiffiffiffiffiffiffi
sNN
p¼
5.02 TeV [50], which do not show a significant pT
dependence within uncertainties and thus indicate that
there are no large differences between fragmentation
functions of charm quarks to charm mesons. The result
presented here instead provides strong indications that the
fragmentation functions of baryons and mesons differ
significantly.
The measured Λþ
c=D0ratios in pp collisions are
compared to predictions from several Monte Carlo gen-
erators and models in which different hadronization proc-
esses are implemented. The
PYTHIA
8predictions include
the Monash tune [12] and a tune that implements color
reconnection beyond the leading-color approximation,
corresponding to CR Mode 2 as defined in [13].
Hadronization in
PYTHIA
is built on the Lund string
fragmentation model [52,53], where quarks and gluons
connected by color strings fragment into hadrons, and color
reconnection allows for partons created in the collision to
interact via color strings. The latter tune introduces new
color reconnection topologies beyond the leading-color
approximation, including junctionsthat fragment into
baryons, leading to increased baryon production. As a
technical point, the
PYTHIA
8simulations are generated with
all soft QCD processes switched on [48]. The
PYTHIA
8
Monash tune and
HERWIG
7.2 [15] predictions are driven by
the fragmentation fraction fðcΛþ
cÞimplemented in
these generators, which all suggest a relatively constant
Λþ
c=D0ratio versus pTof about 0.1, significantly under-
estimating the data at low pT. At high pT, the data approach
the predictions from these generators, although the meas-
urement in 8<p
T<12 GeV=c is still underestimated
by about a factor of 2. A significant enhancement of the
Λþ
c=D0ratio is seen with color reconnection beyond the
leading-color approximation (
PYTHIA
8CR Mode 2). This
prediction is consistent with the measured Λþ
c=D0ratio in
pp collisions, also reproducing the downward pTtrend.
The statistical hadronization model (SH modelin the
legend) [19] uses either an underlying charm-baryon
spectrum taken from the Particle Data Group, or includes
additional excited charm baryons that have not yet been
observed but are predicted by the RQM. These additional
states decay strongly to Λþ
cbaryons, which contribute to
the prompt Λþ
cspectrum. The RQM predictions include a
510
)c (GeV/
T
p
0
0.5
1
0
/ D
+
c
= 5.02 TeVspp,
PYTHIA 8 (Monash)
PYTHIA 8 (CR Mode 2)
HERWIG 7
Catania, fragm.+coal.
M. He and R. Rapp:
SH model + PDG
SH model + RQM
ALICE
01020
)c (GeV/
T
p
2
10
1
10
1
10
2
10
)cb/GeV/μ (
T
pdy/dσ
2
d
| < 0.5y|
= 5.02 TeVs
pp,
< 0.04y 0.96 <
= 5.02 TeV
NN
sp-Pb / A,
| < 0.5y|
= 5.02 TeVs
pp,
< 0.04y 0.96 <
= 5.02 TeV
NN
sp-Pb / A,
+
c
ΛPrompt
0
Prompt D
ALICE
2.1%(3.7%) lumi. uncertainty not shown for pp(p-Pb) results±: , DΛ
: 0.8% BR uncertainty not shown
D
FIG. 1. Left: Prompt Λþ
cand D0pT-differential cross section in pp collisions and in p-Pb collisions at ffiffiffiffiffiffiffi
sNN
p¼5.02 TeV. The results
in p-Pb collisions are scaled with the atomic mass number Aof the Pb nucleus. Right: The Λþ
c=D0ratio as a function of pTmeasured in
pp collisions at ffiffi
s
p¼5.02 TeV compared with theoretical predictions (see text for details). Statistical uncertainties are shown as
vertical bars, while systematic uncertainties are shown as boxes, and the bin widths are shown as horizontal bars.
PHYSICAL REVIEW LETTERS 127, 202301 (2021)
202301-4
source of uncertainty related to the branching ratios of the
excited baryon states into Λþ
cfinal states, which is
estimated by varying the branching ratios between 50%
and 100%. With the Particle Data Group charm-baryon
spectrum, the model underpredicts the data. With the
additional baryon states, the model instead gives a good
description of the pp data, both in the magnitude of the
ratio and the decreasing trend with pT. The Catania model
[36] assumes that a color-deconfined state of matter is
formed and hadronization can occur via coalescence in
addition to fragmentation. Coalescence is implemented
through the Wigner formalism, where a blast wave model
is used to determine the pTspectrum of light quarks and
FONLL
pQCD calculations are used for heavy quarks.
Hadronization via coalescence is predicted to dominate
at low pT, while fragmentation dominates at high pT. This
model provides a good description of both the magnitude
and shape of the data over the full pTrange.
Figure 2shows the Λþ
c=D0baryon-to-meson ratio
measured in pp collisions at ffiffi
s
p¼5.02 TeV (left) and
in p-Pb collisions at ffiffiffiffiffiffiffi
sNN
p¼5.02 TeV (right) as a
function of pTcompared to baryon-to-meson ratios in
the light-flavor sector, Λ=K0
S[25,54] and p=π[31,55]
[calculated as the sum of both charged particles and
antiparticles, ðpþ¯
pÞ=ðπþþπ
Þ]. The p=πratio in pp
collisions is shown at both ffiffi
s
p¼5.02 TeV and
ffiffi
s
p¼7TeV, displaying consistent results at both
center-of-mass energies, while the Λ=K0
Sratio in pp
collisions is shown only at ffiffi
s
p¼7TeV. Unlike heavy-
flavor hadron production, which occurs primarily through
the fragmentation of a charm quark produced in the initial
hard scattering, light-flavor hadrons have a significant
contribution from gluon fragmentation. Low-pTlight-
flavor hadrons also primarily originate from soft scattering
processes involving small momentum transfers. All particle
yields in these ratios were corrected for feed-down from
weak decays, although the pion spectrum is expected to
have significant feed-down contributions also from the
strong decays of other particle species, primarily ρand ω
mesons. Despite these differences, the three ratios
Λþ
c=D0,Λ=K0
S, and p=πdemonstrate some remarkably
similar characteristics in both collision systems. All ratios
exhibit a decreasing trend after pT23GeV=c. The
Λþ
c=D0and Λ=K0
Sratios are consistent, in terms of both
shape and magnitude, within uncertainties. The light-flavor
ratios both peak at 23GeV=c in both pp and p-Pb
collisions, and there is an indication of a peak at 2<p
T<
4GeV=c in the Λþ
c=D0ratio in p-Pb collisions. These
similarities between heavy-flavor and light-flavor measure-
ments hint at a potential common mechanism for light- and
charm-baryon formation in pp and p-Pb collisions at LHC
energies. It is interesting to note that all baryon-to-meson
ratios also indicate a shift toward higher momenta in p-Pb
collisions, which for light-flavor particle production is
often attributed to radial flow [54]. However, while flow
effects in the charm sector (D0and heavy-flavor decay
leptons) have been observed in high-multiplicity p-Pb
collisions [56,57], these effects are expected to be smaller
at lower multiplicities as well as smaller for charm than for
light-flavor hadrons.
In summary, Λþ
c-baryon production was measured in pp
collisions at midrapidity (jyj<0.5) and in p-Pb collisions
in the rapidity interval 0.96 <y<0.04 at ffiffiffiffiffiffiffi
sNN
p¼
5.02 TeV. A clear pTdependence of the Λþ
c=D0ratio is
reported, with the ratio decreasing as the pTincreases. This
trend is similar to that of baryon-to-meson ratios measured
in the light-flavor sector in pp and p-Pb collisions,
suggesting common mechanisms for light- and
1 10
)c (GeV/
T
p
0
0.5
1
Baryon-to-meson ratio
= 5.02 TeVspp,
| < 0.5y
|
0
/D
+
c
PRC 101, 044907 (2020)
p/
= 7 TeVspp,
| < 0.5y
|
PRL 111 (2013) 222301
S
0
/K
PLB 760 (2016) 720
p/
ALICE
110
)c (GeV/
T
p
= 5.02 TeV
NN
sPb, p
< 0.04
cms
y0.96 <
0
/D
+
c
, PLB 728 (2014) 25-38
S
0
/K
, PLB 760 (2016) 720p/
FIG. 2. The charm baryon-to-meson ratio Λþ
c=D0in pp collisions (left) and p-Pb collisions (right) at ffiffiffiffiffiffiffi
sNN
p¼5.02 TeV compared to
the light-flavor baryon-to-meson ratios Λ=K0
Sand p=π. Statistical uncertainties are shown as vertical bars, while systematic uncertainties
are shown as boxes, and the bin widths are shown as horizontal bars.
PHYSICAL REVIEW LETTERS 127, 202301 (2021)
202301-5
charm-baryon formation. While models incorporating frag-
mentation parameters from eþeand epcollisions
significantly underestimate the Λþ
c=D0ratio, three models
can reproduce the measurements. The first is a tune of
PYTHIA
8that considers that, in pp collisions at high
energy, multiparton interactions produce a rich hadronic
environment that requires an extension of color reconnec-
tion in hadronization processes beyond the leading-color
approximation. The second method is the statistical
hadronization þRQM model, which relies on the presence
of a large set of yet-unobserved higher-mass charm-baryon
states with relative yields following the statistical hadro-
nization model. The third relies on hadronization via
coalescence and fragmentation after the formation of a
color-deconfined state of matter. All three models imply a
substantially different description of the charm-baryon
production in pp collisions with respect to eþeand
epcollisions, indicating that the assumption of universal
parton-to-hadron fragmentation between collision systems
is not sufficient to describe charm-baryon production.
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 centers and the Worldwide LHC Computing Grid
(WLCG) collaboration. The ALICE Collaboration
acknowledges the following funding agencies for their
support in building and running the ALICE detector: A. I.
Alikhanyan National Science Laboratory (Yerevan Physics
Institute) Foundation (ANSL), State Committee of Science
and World Federation of Scientists (WFS), Armenia;
Austrian Academy of Sciences, Austrian Science Fund
(FWF): [M 2467-N36] and Nationalstiftung für Forschung,
Technologie und Entwicklung, Austria; Ministry of
Communications and High Technologies, National
Nuclear Research Center, Azerbaijan; Conselho Nacional
de Desenvolvimento Científico e Tecnológico (CNPq),
Financiadora de Estudos e Projetos (Finep), Fundação de
Amparo `a Pesquisa do Estado de São Paulo (FAPESP) and
Universidade Federal do Rio Grande do Sul (UFRGS),
Brazil; Ministry of Education of China (MOEC), Ministry
of Science and Technology of China (MSTC) and National
Natural Science Foundation of China (NSFC), China;
Ministry of Science and Education and Croatian Science
Foundation, Croatia; Centro de Aplicaciones Tecnológicas
y Desarrollo Nuclear (CEADEN), Cubaenergía, Cuba;
Ministry of Education, Youth and Sports of the Czech
Republic, Czech Republic; The Danish Council for
Independent ResearchNatural Sciences, the VILLUM
FONDEN and Danish National Research Foundation
(DNRF), Denmark; Helsinki Institute of Physics (HIP),
Finland; Commissariat `alEnergie Atomique (CEA) and
Institut National de Physique Nucl´eaire et de Physique des
Particules (IN2P3) and Centre National de la Recherche
Scientifique (CNRS), France; Bundesministerium für
Bildung und Forschung (BMBF) and GSI
Helmholtzzentrum für Schwerionenforschung GmbH,
Germany; General Secretariat for Research and
Technology, Ministry of Education, Research and
Religions, Greece; National Research, Development and
Innovation Office, Hungary; Department of Atomic Energy
Government of India (DAE), Department of Science and
Technology, Government of India (DST), University
Grants Commission, Government of India (UGC) and
Council of Scientific and Industrial Research (CSIR),
India; Indonesian Institute of Science, Indonesia; Istituto
Nazionale di Fisica Nucleare (INFN), Italy; Institute for
Innovative Science and Technology, Nagasaki Institute of
Applied Science (IIST), Japanese Ministry of Education,
Culture, Sports, Science and Technology (MEXT) and
Japan Society for the Promotion of Science (JSPS)
KAKENHI, Japan; Consejo Nacional de Ciencia
(CONACYT) y Tecnología, through Fondo de
Cooperación Internacional en Ciencia y Tecnología
(FONCICYT) and Dirección General de Asuntos del
Personal Academico (DGAPA), Mexico; Nederlandse
Organisatie voor Wetenschappelijk Onderzoek (NWO),
Netherlands; The Research Council of Norway, Norway;
Commission on Science and Technology for Sustainable
Development in the South (COMSATS), Pakistan;
Pontificia Universidad Católica del Perú, Peru; Ministry
of Science and Higher Education, National Science Centre
and WUT ID-UB, Poland; Korea Institute of Science and
Technology Information and National Research
Foundation of Korea (NRF), Republic of Korea;
Ministry of Education and Scientific Research, Institute
of Atomic Physics and Ministry of Research and
Innovation and Institute of Atomic Physics, Romania;
Joint Institute for Nuclear Research (JINR), Ministry of
Education and Science of the Russian Federation, National
Research Centre Kurchatov Institute, Russian Science
Foundation and Russian Foundation for Basic Research,
Russia; Ministry of Education, Science, Research and Sport
of the Slovak Republic, Slovakia; National Research
Foundation of South Africa, South Africa; Swedish
Research Council (VR) and Knut & Alice Wallenberg
Foundation (KAW), Sweden; European Organization for
Nuclear Research, Switzerland; Suranaree University of
Technology (SUT), National Science and Technology
Development Agency (NSDTA) and Office of the
Higher Education Commission under NRU project of
Thailand, Thailand; Turkish Atomic Energy Agency
(TAEK), Turkey; National Academy of Sciences of
Ukraine, Ukraine; Science and Technology Facilities
Council (STFC), United Kingdom; National Science
Foundation of the United States of America (NSF) and
United States Department of Energy, Office of Nuclear
Physics (DOE NP), United States of America.
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G. Herrera Corral,9F. Herrmann,145 K. F. Hetland,37 H. Hillemanns,35 C. Hills,129 B. Hippolyte,138 B. Hohlweger,107
J. Honermann,145 G. H. Hong,148 D. Horak,38 S. Hornung,109 R. Hosokawa,15 P. Hristov,35 C. Huang,79 C. Hughes,132
P. Huhn,69 T. J. Humanic,99 H. Hushnud,112 L. A. Husova,145 N. Hussain,43 D. Hutter,40 J. P. Iddon,35,129 R. Ilkaev,111
H. Ilyas,14 M. Inaba,135 G. M. Innocenti,35 M. Ippolitov,90 A. Isakov,38,97 M. S. Islam,112 M. Ivanov,109 V. Ivanov,100
V. Izucheev,93 B. Jacak,81 N. Jacazio,35,55 P. M. Jacobs,81 S. Jadlovska,119 J. Jadlovsky,119 S. Jaelani,63 C. Jahnke,123
M. J. Jakubowska,143 M. A. Janik,143 T. Janson,75 M. Jercic,101 O. Jevons,113 M. Jin,127 F. Jonas,98,145 P. G. Jones,113
J. Jung,69 M. Jung,69 A. Jusko,113 P. Kalinak,65 A. Kalweit,35 V. Kaplin,95 S. Kar,7A. Karasu Uysal,78 D. Karatovic,101
O. Karavichev,64 T. Karavicheva,64 P. Karczmarczyk,143 E. Karpechev,64 A. Kazantsev,90 U. Kebschull,75 R. Keidel,48
M. Keil,35 B. Ketzer,44 Z. Khabanova,92 A. M. Khan,7S. Khan,16 A. Khanzadeev,100 Y. Kharlov,93 A. Khatun,16
A. Khuntia,120 B. Kileng,37 B. Kim,62 D. Kim,148 D. J. Kim,128 E. J. Kim,74 H. Kim,17 J. Kim,148 J. S. Kim,42 J. Kim,106
J. Kim,148 J. Kim,74 M. Kim,106 S. Kim,18 T. Kim,148 T. Kim,148 S. Kirsch,69 I. Kisel,40 S. Kiselev,94 A. Kisiel,143 J. L. Klay,6
J. Klein,35,60 S. Klein,81 C. Klein-Bösing,145 M. Kleiner,69 T. Klemenz,107 A. Kluge,35 A. G. Knospe,127 C. Kobdaj,118
M. K. Köhler,106 T. Kollegger,109 A. Kondratyev,76 N. Kondratyeva,95 E. Kondratyuk,93 J. Konig,69 S. A. Konigstorfer,107
P. J. Konopka,2,35 G. Kornakov,143 S. D. Koryciak,2L. Koska,119 O. Kovalenko,87 V. Kovalenko,115 M. Kowalski,120
I. Králik,65 A. Kravčáková,39 L. Kreis,109 M. Krivda,113,65 F. Krizek,97 K. Krizkova Gajdosova,38 M. Kroesen,106
M. Krüger,69 E. Kryshen,100 M. Krzewicki,40 V. K u čera,35 C. Kuhn,138 P. G. Kuijer,92 T. Kumaoka,135 L. Kumar,102
S. Kundu,88 P. Kurashvili,87 A. Kurepin,64 A. B. Kurepin,64 A. Kuryakin,111 S. Kushpil,97 J. Kvapil,113 M. J. Kweon,62
J. Y. Kwon,62 Y. Kwon,148 S. L. La Pointe,40 P. La Rocca,27 Y. S. Lai,81 A. Lakrathok,118 M. Lamanna,35 R. Langoy,131
K. Lapidus,35 P. Larionov,53 E. Laudi,35 L. Lautner,35 R. Lavicka,38 T. Lazareva,115 R. Lea,24 J. Lee,135 S. Lee,148
J. Lehrbach,40 R. C. Lemmon,96 I. León Monzón,122 E. D. Lesser,19 M. Lettrich,35 P. L ´evai,146 X. Li,11 X. L. Li,7J. Lien,131
R. Lietava,113 B. Lim,17 S. H. Lim,17 V. Lindenstruth,40 A. Lindner,49 C. Lippmann,109 A. Liu,19 J. Liu,129 I. M. Lofnes,21
V. Loginov,95 C. Loizides,98 P. Loncar,36 J. A. Lopez,106 X. Lopez,136 E. López Torres,8J. R. Luhder,145 M. Lunardon,28
PHYSICAL REVIEW LETTERS 127, 202301 (2021)
202301-9
G. Luparello,61 Y. G. Ma,41 A. Maevskaya,64 M. Mager,35 S. M. Mahmood,20 T. Mahmoud,44 A. Maire,138 R. D. Majka,147,
M. Malaev,100 Q. W. Malik,20 L. Malinina,76,c D. MalKevich,94 N. Mallick,51 P. Malzacher,109 G. Mandaglio,33,57
V. Manko,90 F. Manso,136 V. Manzari,54 Y. Mao,7M. Marchisone,137 J. Mareš,67 G. V. Margagliotti,24 A. Margotti,55
A. Marín,109 C. Markert,121 M. Marquard,69 N. A. Martin,106 P. Martinengo,35 J. L. Martinez,127 M. I. Martínez,46
G. Martínez García,117 S. Masciocchi,109 M. Masera,25 A. Masoni,56 L. Massacrier,79 A. Mastroserio,140,54 A. M. Mathis,107
O. Matonoha,82 P. F. T. Matuoka,123 A. Matyja,120 C. Mayer,120 F. Mazzaschi,25 M. Mazzilli,54 M. A. Mazzoni,59
A. F. Mechler,69 F. Meddi,22 Y. Melikyan,64 A. Menchaca-Rocha,72 C. Mengke,7E. Meninno,116,30 A. S. Menon,127
M. Meres,13 S. Mhlanga,126 Y. Miake,135 L. Micheletti,25 L. C. Migliorin,137 D. L. Mihaylov,107 K. Mikhaylov,76,94
A. N. Mishra,146,70 D. Miśkowiec,109 A. Modak,4N. Mohammadi,35 A. P. Mohanty,63 B. Mohanty,88 M. Mohisin Khan,16
Z. Moravcova,91 C. Mordasini,107 D. A. Moreira De Godoy,145 L. A. P. Moreno,46 I. Morozov,64 A. Morsch,35 T. Mrnjavac,35
V. Muccifora,53 E. Mudnic,36 D. Mühlheim,145 S. Muhuri,142 J. D. Mulligan,81 A. Mulliri,23,56 M. G. Munhoz,123
R. H. Munzer,69 H. Murakami,134 S. Murray,126 L. Musa,35 J. Musinsky,65 C. J. Myers,127 J. W. Myrcha,143 B. Naik,50
R. Nair,87 B. K. Nandi,50 R. Nania,55 E. Nappi,54 M. U. Naru,14 A. F. Nassirpour,82 C. Nattrass,132 R. Nayak,50
S. Nazarenko,111 A. Neagu,20 L. Nellen,70 S. V. Nesbo,37 G. Neskovic,40 D. Nesterov,115 B. S. Nielsen,91 S. Nikolaev,90
S. Nikulin,90 V. Nikulin,100 F. Noferini,55 S. Noh,12 P. Nomokonov,76 J. Norman,129 N. Novitzky,135 P. Nowakowski,143
A. Nyanin,90 J. Nystrand,21 M. Ogino,84 A. Ohlson,82 J. Oleniacz,143 A. C. Oliveira Da Silva,132 M. H. Oliver,147
B. S. Onnerstad,128 C. Oppedisano,60 A. Ortiz Velasquez,70 T. Osako,47 A. Oskarsson,82 J. Otwinowski,120 K. Oyama,84
Y. Pachmayer,106 S. Padhan,50 D. Pagano,141 G. Paić,70 J. Pan,144 S. Panebianco,139 P. Pareek,142 J. Park,62 J. E. Parkkila,128
S. Parmar,102 S. P. Pathak,127 B. Paul,23 J. Pazzini,141 H. Pei,7T. Peitzmann,63 X. Peng,7L. G. Pereira,71
H. Pereira Da Costa,139 D. Peresunko,90 G. M. Perez,8S. Perrin,139 Y. Pestov,5V. Petráček,38 M. Petrovici,49 R. P. Pezzi,71
S. Piano,61 M. Pikna,13 P. Pillot,117 O. Pinazza,55,35 L. Pinsky,127 C. Pinto,27 S. Pisano,53 M. Płoskoń,81 M. Planinic,101
F. Pliquett,69 M. G. Poghosyan,98 B. Polichtchouk,93 N. Poljak,101 A. Pop,49 S. Porteboeuf-Houssais,136 J. Porter,81
V. Pozdniakov,76 S. K. Prasad,4R. Preghenella,55 F. Prino,60 C. A. Pruneau,144 I. Pshenichnov,64 M. Puccio,35 S. Qiu,92
L. Quaglia,25 R. E. Quishpe,127 S. Ragoni,113 J. Rak,128 A. Rakotozafindrabe,139 L. Ramello,32 F. Rami,138
S. A. R. Ramirez,46 A. G. T. Ramos,34 R. Raniwala,104 S. Raniwala,104 S. S. Räsänen,45 R. Rath,51 I. Ravasenga,92
K. F. Read,98,132 A. R. Redelbach,40 K. Redlich,87,d A. Rehman,21 P. Reichelt,69 F. Reidt,35 R. Renfordt,69 Z. Rescakova,39
K. Reygers,106 A. Riabov,100 V. Riabov,100 T. Richert,82,91 M. Richter,20 P. Riedler,35 W. Riegler,35 F. Riggi,27 C. Ristea,68
S. P. Rode,51 M. Rodríguez Cahuantzi,46 K. Røed,20 R. Rogalev,93 E. Rogochaya,76 T. S. Rogoschinski,69 D. Rohr,35
D. Röhrich,21 P. F. Rojas,46 P. S. Rokita,143 F. Ronchetti,53 A. Rosano,33,57 E. D. Rosas,70 A. Rossi,58 A. Rotondi,29 A. Roy,51
P. Ro y, 112 O. V. Rueda,82 R. Rui,24 B. Rumyantsev,76 A. Rustamov,89 E. Ryabinkin,90 Y. Ryabov,100 A. Rybicki,120
H. Rytkonen,128 O. A. M. Saarimaki,45 R. Sadek,117 S. Sadovsky,93 J. Saetre,21 K. Šafaˇ
rík,38 S. K. Saha,142 S. Saha,88
B. Sahoo,50 P. Sahoo,50 R. Sahoo,51 S. Sahoo,66 D. Sahu,51 P. K. Sahu,66 J. Saini,142 S. Sakai,135 S. Sambyal,103
V. Samsonov,100,95 D. Sarkar,144 N. Sarkar,142 P. Sarma,43 V. M. Sarti,107 M. H. P. Sas,147,63 J. Schambach,98,121
H. S. Scheid,69 C. Schiaua,49 R. Schicker,106 A. Schmah,106 C. Schmidt,109 H. R. Schmidt,105 M. O. Schmidt,106
M. Schmidt,105 N. V. Schmidt,98,69 A. R. Schmier,132 R. Schotter,138 J. Schukraft,35 Y. Schutz,138 K. Schwarz,109
K. Schweda,109 G. Scioli,26 E. Scomparin,60 J. E. Seger,15 Y. Sekiguchi,134 D. Sekihata,134 I. Selyuzhenkov,109,95
S. Senyukov,138 J. J. Seo,62 D. Serebryakov,64 L. Šerkšnytė,107 A. Sevcenco,68 A. Shabanov,64 A. Shabetai,117
R. Shahoyan,35 W. Shaikh,112 A. Shangaraev,93 A. Sharma,102 H. Sharma,120 M. Sharma,103 N. Sharma,102 S. Sharma,103
O. Sheibani,127 A. I. Sheikh,142 K. Shigaki,47 M. Shimomura,85 S. Shirinkin,94 Q. Shou,41 Y. Sibiriak,90 S. Siddhanta,56
T. Siemiarczuk,87 D. Silvermyr,82 G. Simatovic,92 G. Simonetti,35 B. Singh,107 R. Singh,88 R. Singh,103 R. Singh,51
V. K. Singh,142 V. Singhal,142 T. Sinha,112 B. Sitar,13 M. Sitta,32 T. B. Skaali,20 M. Slupecki,45 N. Smirnov,147
R. J. M. Snellings,63 C. Soncco,114 J. Song,127 A. Songmoolnak,118 F. Soramel,28 S. Sorensen,132 I. Sputowska,120
J. Stachel,106 I. Stan,68 P. J. Steffanic,132 S. F. Stiefelmaier,106 D. Stocco,117 M. M. Storetvedt,37 L. D. Stritto,30
C. P. Stylianidis,92 A. A. P. Suaide,123 T. Sugitate,47 C. Suire,79 M. Suljic,35 R. Sultanov,94 M. Šumbera,97 V. Sumberia,103
S. Sumowidagdo,52 S. Swain,66 A. Szabo,13 I. Szarka,13 U. Tabassam,14 S. F. Taghavi,107 G. Taillepied,136 J. Takahashi,124
G. J. Tambave,21 S. Tang,136,7 Z. Tang,130 M. Tarhini,117 M. G. Tarzila,49 A. Tauro,35 G. Tejeda Muñoz,46 A. Telesca,35
L. Terlizzi,25 C. Terrevoli,127 G. Tersimonov,3S. Thakur,142 D. Thomas,121 F. Thoresen,91 R. Tieulent,137 A. Tikhonov,64
A. R. Timmins,127 M. Tkacik,119 A. Toia,69 N. Topilskaya,64 M. Toppi,53 F. Torales-Acosta,19 S. R. Torres,38,9 A. Trifiró,33,57
S. Tripathy,70 T. Tripathy,50 S. Trogolo,28 G. Trombetta,34 L. Tropp,39 V. Trubnikov,3W. H. Trzaska,128 T. P. Trzcinski,143
PHYSICAL REVIEW LETTERS 127, 202301 (2021)
202301-10
B. A. Trzeciak,38 A. Tumkin,111 R. Turrisi,58 T. S. Tveter,20 K. Ullaland,21 E. N. Umaka,127 A. Uras,137 G. L. Usai,23
M. Vala,39 N. Valle,29 S. Vallero,60 N. van der Kolk,63 L. V. R. van Doremalen,63 M. van Leeuwen,92 P. Vande Vyvre,35
D. Varga,146 Z. Varga,146 M. Varga-Kofarago,146 A. Vargas,46 M. Vasileiou,86 A. Vasiliev,90 O. Vázquez Doce,107
V. Vechernin,115 E. Vercellin,25 S. Vergara Limón,46 L. Vermunt,63 R. V´ertesi,146 M. Verweij,63 L. Vickovic,36 Z. Vilakazi,133
O. Villalobos Baillie,113 G. Vino,54 A. Vinogradov,90 T. Virgili,30 V. Vislavicius,91 A. Vodopyanov,76 B. Volkel,35
M. A. Völkl,105 K. Voloshin,94 S. A. Voloshin,144 G. Volpe,34 B. von Haller,35 I. Vorobyev,107 D. Voscek,119 J. Vrláková,39
B. Wagner,21 M. Weber,116 A. Wegrzynek,35 S. C. Wenzel,35 J. P. Wessels,145 J. Wiechula,69 J. Wikne,20 G. Wilk,87
J. Wilkinson,109 G. A. Willems,145 E. Willsher,113 B. Windelband,106 M. Winn,139 W. E. Witt,132 J. R. Wright,121 Y. W u , 130
R. Xu,7S. Yalcin,78 Y. Yamaguchi,47 K. Yamakawa,47 S. Yang,21 S. Yano,47,139 Z. Yin,7H. Yokoyama,63 I.-K. Yoo,17
J. H. Yoon,62 S. Yuan,21 A. Yuncu,106 V. Yurchenko,3V. Zaccolo,24 A. Zaman,14 C. Zampolli,35 H. J. C. Zanoli,63
N. Zardoshti,35 A. Zarochentsev,115 P. Závada,67 N. Zaviyalov,111 H. Zbroszczyk,143 M. Zhalov,100 S. Zhang,41 X. Zhang,7
Y. Zhang,130 V. Zherebchevskii,115 Y. Zhi,11 D. Zhou,7Y. Zhou,91 J. Zhu,7,109 Y. Zhu,7A. Zichichi,26
G. Zinovjev,3and N. Zurlo141
(ALICE Collaboration)
1A.I. Alikhanyan National Science Laboratory (Yerevan Physics Institute) Foundation, Yerevan, Armenia
2AGH University of Science and Technology, Cracow, Poland
3Bogolyubov Institute for Theoretical Physics, National Academy of Sciences of Ukraine, Kiev, Ukraine
4Bose Institute, Department of Physics and Centre for Astroparticle Physics and Space Science (CAPSS), Kolkata, India
5Budker Institute for Nuclear Physics, Novosibirsk, Russia
6California Polytechnic State University, San Luis Obispo, California, USA
7Central China Normal University, Wuhan, China
8Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear (CEADEN), Havana, Cuba
9Centro de Investigación y de Estudios Avanzados (CINVESTAV), Mexico City and M´erida, Mexico
10Chicago State University, Chicago, Illinois, USA
11China Institute of Atomic Energy, Beijing, China
12Chungbuk National University, Cheongju, Republic of Korea
13Comenius University Bratislava, Faculty of Mathematics, Physics and Informatics, Bratislava, Slovakia
14COMSATS University Islamabad, Islamabad, Pakistan
15Creighton University, Omaha, Nebraska, USA
16Department of Physics, Aligarh Muslim University, Aligarh, India
17Department of Physics, Pusan National University, Pusan, Republic of Korea
18Department of Physics, Sejong University, Seoul, Republic of Korea
19Department of Physics, University of California, Berkeley, California, USA
20Department of Physics, University of Oslo, Oslo, Norway
21Department of Physics and Technology, University of Bergen, Bergen, Norway
22Dipartimento di Fisica dellUniversit `a La Sapienzaand Sezione INFN, Rome, Italy
23Dipartimento di Fisica dellUniversit `a and Sezione INFN, Cagliari, Italy
24Dipartimento di Fisica dellUniversit `a and Sezione INFN, Trieste, Italy
25Dipartimento di Fisica dellUniversit `a and Sezione INFN, Turin, Italy
26Dipartimento di Fisica e Astronomia dellUniversit `a and Sezione INFN, Bologna, Italy
27Dipartimento di Fisica e Astronomia dellUniversit `a and Sezione INFN, Catania, Italy
28Dipartimento di Fisica e Astronomia dellUniversit `a and Sezione INFN, Padova, Italy
29Dipartimento di Fisica e Nucleare e Teorica, Universit `a di Pavia and Sezione INFN, Pavia, Italy
30Dipartimento di Fisica E.R. CaianiellodellUniversit `a and Gruppo Collegato INFN, Salerno, Italy
31Dipartimento DISAT del Politecnico and Sezione INFN, Turin, Italy
32Dipartimento di Scienze e Innovazione Tecnologica dellUniversit `a del Piemonte Orientale and INFN Sezione di Torino,
Alessandria, Italy
33Dipartimento di Scienze MIFT, Universit `a di Messina, Messina, Italy
34Dipartimento Interateneo di Fisica M. Merlinand Sezione INFN, Bari, Italy
35European Organization for Nuclear Research (CERN), Geneva, Switzerland
36Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture, University of Split, Split, Croatia
37Faculty of Engineering and Science, Western Norway University of Applied Sciences, Bergen, Norway
38Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, Prague, Czech Republic
39Faculty of Science, P.J. Šafárik University, Košice, Slovakia
PHYSICAL REVIEW LETTERS 127, 202301 (2021)
202301-11
40Frankfurt Institute for Advanced Studies, Johann Wolfgang Goethe-Universität Frankfurt, Frankfurt, Germany
41Fudan University, Shanghai, China
42Gangneung-Wonju National University, Gangneung, Republic of Korea
43Gauhati University, Department of Physics, Guwahati, India
44Helmholtz-Institut für Strahlen- und Kernphysik, Rheinische Friedrich-Wilhelms-Universität Bonn, Bonn, Germany
45Helsinki Institute of Physics (HIP), Helsinki, Finland
46High Energy Physics Group, Universidad Autónoma de Puebla, Puebla, Mexico
47Hiroshima University, Hiroshima, Japan
48Hochschule Worms, Zentrum für Technologietransfer und Telekommunikation (ZTT), Worms, Germany
49Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest, Romania
50Indian Institute of Technology Bombay (IIT), Mumbai, India
51Indian Institute of Technology Indore, Indore, India
52Indonesian Institute of Sciences, Jakarta, Indonesia
53INFN, Laboratori Nazionali di Frascati, Frascati, Italy
54INFN, Sezione di Bari, Bari, Italy
55INFN, Sezione di Bologna, Bologna, Italy
56INFN, Sezione di Cagliari, Cagliari, Italy
57INFN, Sezione di Catania, Catania, Italy
58INFN, Sezione di Padova, Padova, Italy
59INFN, Sezione di Roma, Rome, Italy
60INFN, Sezione di Torino, Turin, Italy
61INFN, Sezione di Trieste, Trieste, Italy
62Inha University, Incheon, Republic of Korea
63Institute for Gravitational and Subatomic Physics (GRASP), Utrecht University/Nikhef, Utrecht, Netherlands
64Institute for Nuclear Research, Academy of Sciences, Moscow, Russia
65Institute of Experimental Physics, Slovak Academy of Sciences, Košice, Slovakia
66Institute of Physics, Homi Bhabha National Institute, Bhubaneswar, India
67Institute of Physics of the Czech Academy of Sciences, Prague, Czech Republic
68Institute of Space Science (ISS), Bucharest, Romania
69Institut für Kernphysik, Johann Wolfgang Goethe-Universität Frankfurt, Frankfurt, Germany
70Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de M´exico, Mexico City, Mexico
71Instituto de Física, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, Brazil
72Instituto de Física, Universidad Nacional Autónoma de M´exico, Mexico City, Mexico
73iThemba LABS, National Research Foundation, Somerset West, South Africa
74Jeonbuk National University, Jeonju, Republic of Korea
75Johann-Wolfgang-Goethe Universität Frankfurt Institut für Informatik, Fachbereich Informatik und Mathematik, Frankfurt, Germany
76Joint Institute for Nuclear Research (JINR), Dubna, Russia
77Korea Institute of Science and Technology Information, Daejeon, Republic of Korea
78KTO Karatay University, Konya, Turkey
79Laboratoire de Physique des 2 Infinis, Ir `ene Joliot-Curie, Orsay, France
80Laboratoire de Physique Subatomique et de Cosmologie, Universit´e Grenoble-Alpes, CNRS-IN2P3, Grenoble, France
81Lawrence Berkeley National Laboratory, Berkeley, California, USA
82Lund University Department of Physics, Division of Particle Physics, Lund, Sweden
83Moscow Institute for Physics and Technology, Moscow, Russia
84Nagasaki Institute of Applied Science, Nagasaki, Japan
85Nara Womens University (NWU), Nara, Japan
86National and Kapodistrian University of Athens, School of Science, Department of Physics, Athens, Greece
87National Centre for Nuclear Research, Warsaw, Poland
88National Institute of Science Education and Research, Homi Bhabha National Institute, Jatni, India
89National Nuclear Research Center, Baku, Azerbaijan
90National Research Centre Kurchatov Institute, Moscow, Russia
91Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
92Nikhef, National institute for subatomic physics, Amsterdam, Netherlands
93NRC Kurchatov Institute IHEP, Protvino, Russia
94NRC «Kurchatov» Institute - ITEP, Moscow, Russia
95NRNU Moscow Engineering Physics Institute, Moscow, Russia
96Nuclear Physics Group, STFC Daresbury Laboratory, Daresbury, United Kingdom
97Nuclear Physics Institute of the Czech Academy of Sciences, Řežu Prahy, Czech Republic
98Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
99Ohio State University, Columbus, Ohio, USA
PHYSICAL REVIEW LETTERS 127, 202301 (2021)
202301-12
100Petersburg Nuclear Physics Institute, Gatchina, Russia
101Physics department, Faculty of science, University of Zagreb, Zagreb, Croatia
102Physics Department, Panjab University, Chandigarh, India
103Physics Department, University of Jammu, Jammu, India
104Physics Department, University of Rajasthan, Jaipur, India
105Physikalisches Institut, Eberhard-Karls-Universität Tübingen, Tübingen, Germany
106Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany
107Physik Department, Technische Universität München, Munich, Germany
108Politecnico di Bari and Sezione INFN, Bari, Italy
109Research Division and ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum für Schwerionenforschung GmbH,
Darmstadt, Germany
110Rudjer BoškovićInstitute, Zagreb, Croatia
111Russian Federal Nuclear Center (VNIIEF), Sarov, Russia
112Saha Institute of Nuclear Physics, Homi Bhabha National Institute, Kolkata, India
113School of Physics and Astronomy, University of Birmingham, Birmingham, United Kingdom
114Sección Física, Departamento de Ciencias, Pontificia Universidad Católica del Perú, Lima, Peru
115St. Petersburg State University, St. Petersburg, Russia
116Stefan Meyer Institut für Subatomare Physik (SMI), Vienna, Austria
117SUBATECH, IMT Atlantique, Universit´e de Nantes, CNRS-IN2P3, Nantes, France
118Suranaree University of Technology, Nakhon Ratchasima, Thailand
119Technical University of Košice, Košice, Slovakia
120The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Cracow, Poland
121The University of Texas at Austin, Austin, Texas, USA
122Universidad Autónoma de Sinaloa, Culiacán, Mexico
123Universidade de S ao Paulo (USP), São Paulo, Brazil
124Universidade Estadual de Campinas (UNICAMP), Campinas, Brazil
125Universidade Federal do ABC, Santo Andre, Brazil
126University of Cape Town, Cape Town, South Africa
127University of Houston, Houston, Texas, USA
128University of Jyväskylä, Jyväskylä, Finland
129University of Liverpool, Liverpool, United Kingdom
130University of Science and Technology of China, Hefei, China
131University of South-Eastern Norway, Tonsberg, Norway
132University of Tennessee, Knoxville, Tennessee, USA
133University of the Witwatersrand, Johannesburg, South Africa
134University of Tokyo, Tokyo, Japan
135University of Tsukuba, Tsukuba, Japan
136Universit´e Clermont Auvergne, CNRS/IN2P3, LPC, Clermont-Ferrand, France
137Universit´e de Lyon, CNRS/IN2P3, Institut de Physique des 2 Infinis de Lyon, Lyon, France
138Universit´e de Strasbourg, CNRS, IPHC UMR 7178, F-67000 Strasbourg, France, Strasbourg, France
139Universit´e Paris-Saclay Centre dEtudes de Saclay (CEA), IRFU, D´epartment de Physique Nucl´eaire (DPhN), Saclay, France
140Universit`a degli Studi di Foggia, Foggia, Italy
141Universit`a di Brescia and Sezione INFN, Brescia, Italy
142Variable Energy Cyclotron Centre, Homi Bhabha National Institute, Kolkata, India
143Warsaw University of Technology, Warsaw, Poland
144Wayne State University, Detroit, Michigan, USA
145Westfälische Wilhelms-Universität Münster, Institut für Kernphysik, Münster, Germany
146Wigner Research Centre for Physics, Budapest, Hungary
147Yale University, New Haven, Connecticut, USA
148Yonsei University, Seoul, Republic of Korea
Deceased.
aAlso at Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA), Bologna, Italy.
bAlso at Dipartimento DET del Politecnico di Torino, Turin, Italy.
cAlso at M.V. Lomonosov Moscow State University, D.V. Skobeltsyn Institute of Nuclear, Physics, Moscow, Russia.
dAlso at Institute of Theoretical Physics, University of Wroclaw, Poland.
PHYSICAL REVIEW LETTERS 127, 202301 (2021)
202301-13
... This introduces a source of systematic uncertainty in the extraction of transport coefficients; on the other hand it can be considered an issue of interest in itself, in particular to study how hadronization changes in the presence of a medium acting as a color reservoir. This, in the case of charm quarks, will be the subject of our study, carried out to provide an interpretation of non-trivial results concerning heavy-flavor hadrochemistry in heavy-ion collisions, but with the potential to shed light also on analogous puzzling findings obtained in smaller systems [2]. Any hadronization model must start clustering colored partons into color-singlet structures which will give rise to the final hadrons. ...
... Interfacing our new hadronization model to numerical simulations of heavy-quark transport in the deconfined fireball one can obtain a satisfactory description of important and partially unexpected experimental findings, in particular the strong enhancement of charmed-baryon production recently observed in heavy-ion [6] and also in proton-proton collisions [2], which cannot be explained by any hadronization model tuned to reproduce + − data. An example of our results is given in Fig. 2, where we plot as a function of the + / 0 , + / 0 and Λ + / 0 ratios in Pb-Pb collisions at √ NN = 5.02 TeV, comparing our predictions to recent ALICE data [6][7][8]. ...
... The only difference with our model is that charm quarks are recombined with light partons belonging to the beam remnant, while in our case they are taken from the hot medium produced in the nuclear collision. More recently, changes in the heavyflavor hadrochemistry in proton-proton collisions, with for example an enhanced production of charmed baryons [2], were interpreted as due to Color Reconnection [12]. The mechanism of CR is schematically illustrated in Fig. 5, where in the left panel we draw the strings constructed following the color-flow of the event in the large-approximation. ...
... This introduces a source of systematic uncertainty in the extraction of transport coefficients; on the other hand it can be considered an issue of interest in itself, in particular to study how hadronization changes in the presence of a medium acting as a color reservoir. This, in the case of charm quarks, will be the subject of our study, carried out to provide an interpretation of non-trivial results concerning heavy-flavor hadrochemistry in heavy-ion collisions, but with the potential to shed light also on analogous puzzling findings obtained in smaller systems [2]. ...
... Interfacing our new hadronization model to numerical simulations of heavy-quark transport in the deconfined fireball one can obtain a satisfactory description of important and partially unexpected experimental findings, in particular the strong enhancement of charmed-baryon production recently observed in heavy-ion [6] and also in proton-proton collisions [2], which cannot be explained by any hadronization model tuned to reproduce + − data. An example of our results is given in Fig. 2, where we plot as a function of the + / 0 , + / 0 and Λ + / 0 ratios in Pb-Pb collisions at √ NN = 5.02 TeV, comparing our predictions to recent ALICE data [6][7][8]. ...
... The only difference with our model is that charm quarks are recombined with light partons belonging to the beam remnant, while in our case they are taken from the hot medium produced in the nuclear collision. More recently, changes in the heavyflavor hadrochemistry in proton-proton collisions, with for example an enhanced production of charmed baryons [2], were interpreted as due to Color Reconnection [12]. The mechanism of CR is schematically illustrated in Fig. 5, where in the left panel we draw the strings constructed following the color-flow of the event in the large-approximation. ...
Preprint
We present a new model for the description of heavy-flavor hadronization in high-energy nuclear (and possibly hadronic) collisions, where the process takes place not in the vacuum, but in the presence of other color charges. We explore its effect on the charmed hadron yields and kinematic distributions once the latter is applied at the end of transport calculations used to simulate the propagation of heavy quarks in the deconfined fireball produced in nuclear collisions. The model is based on the formation of color-singlet clusters through the recombination of charm quarks with light antiquarks or diquarks from the same fluid cell. This local mechanism of color neutralization leads to a strong space-momentum correlation, which provides a substantial enhancement of charmed baryon production -- with respect to expectations based on $e^+e^-$ collisions -- and of the collective flow of all charmed hadrons. We also discuss the similarities between our model and recently developed mechanisms implemented in QCD event generators to simulate medium corrections to hadronization in the presence of other nearby color charges.
... However, as also confirmed by measurements of e.g. baryon yields in pp collisions at the LHC [7,94], additional hadronization mechanisms may exist, whereby quarks that are close in phase space can combine into colourless hadrons. Dynamic modeling of these processes, in particular in the strange and charm sector, has led to many novel approaches that were implemented in established event generator models, such as PYTHIA. ...
... These led to refinements of the transport codes that were then followed up by more detailed measurements of baryon to meson formation in the strange sector. Such advancements have been studied in the charm sector, as a function of system size [94]. In heavy-ion collisions, where partons may travel freely over distances much larger than the typical hadron sizes, and a dense system of partons close to thermal equilibrium is formed, recombination mechanisms become more dominant. ...
Preprint
Full-text available
The ALICE-USA collaboration presents its plans for the 2023 U.S. Long Range Plan for Nuclear Science.
... It is believed that this anomaly strange baryon enhancement and the shift of the Λ/K 0 S peaks towards higher p T can be described by the introduction of the parton recombination mechanism to the hadronization process and the hydrodynamic parton radial flow induced due to the formation of the QGP phase. However, the enhanced strange baryon to meson ratio at intermediate p T , together with many other QGP like phenomena [2][3][4][5], has also been observed in high multiplicity pp and p-Pb collisions [2,[6][7][8]. ...
... Studying strange hadron correlations with other charged hadrons in different kinematic ranges can be useful to expose the effects of jet fragmentation, parton shower and hydrodynamic evolution [14]. From previous studies, it is known that high-p T,trig particles are more likely to come from hard processes, such as jet fragmentation, while at intermediate p T,trig region the particle yield contains also contributions from soft processes like multiple parton interactions, parton radiation effects which cannot be easily separated in experiments [2,6,7,15,16]. Particles from jet fragmentation are more collimated with the jet axis, resulting in the near-side (∆ϕ = 0) and the back-to-back away-side (∆ϕ = π) peaks, where minijet contributions with the momentum conservation are dominant [17]. ...
Preprint
Full-text available
Strange hadron production in pp collisions at $\sqrt{s}= 7$ TeV is studied with PYTHIA 8 and EPOS event generators via the two-particle correlation method. After pairing charged particles as trigger particles with associated strange hadrons $(\mathrm{K}^{0}_{S}$ and $(\Lambda/\overline{\Lambda})$ , the strange baryon to meson per trigger yield ratios ${Y_{\Delta\varphi}^{\mathrm{h}-(\Lambda+\overline{\Lambda})}}$/$/{2Y_{\Delta\varphi}^{\mathrm{h}-\mathrm{K}^{0}_{S}}}$ dependent on transverse momentum ($p_{T})$ are investigated within the near- and away-side jet region as well as the underlying event (UE) region. The modified string fragmentation effects of color reconnection and string shoving mechanisms implemented in PYTHIA 8 and the final state evolution effects built in EPOS are compared in this study. It is found that $p_{T}$ dependence of the $\Lambda/\mathrm{K}^{0}_{S}$ per trigger yield ratio in UE is similar to that in the inclusive measurements while the in-jet result is smaller. We also show that the $\Lambda/\mathrm{K}^{0}_{S}$ ratio at both near- and away-side jet region in the intermediate $p_{T}$ region decreases significantly with trigger $p_{T}$, which suggests the hard process effects might contribute to the strange baryon to meson enhancement at intermediate $p_{T}$. The much higher $\Lambda/\mathrm{K}^{0}_{S}$ ratio in UE and the striking difference between the near and away side of the in-jet results with low trigger $p_{T}$ predicted by the EPOS model indicate that the soft process effects induced by the final state evolution further increase the strange baryon production and can be still effective in a higher $p_{T}$ region compared to the string fragmentation type models.
... The ratios show a clear decrease with increasing p T in both pp and p-Pb collisions in the range 2 < p T < 12 GeV/c. At low p T , predictions that include additional colorreconnection mechanisms beyond the leading-color approximation (CR2) describe rather well the overall features [38]. Figure 9 shows the p/π, Λ/K 0 s and Λ + c /D 0 FIG. ...
... The 0-1% 1-ρ nch class for the highest 0-5% V0M classes allows se-lecting events an isotropic event topology. From Fig. 9, a clear picture is evolved where the baryon to meson ratio is further enhanced and for the first time we observe a clear peak structure for Λ + c /D 0 for pp collisions, which is earlier observed in p-Pb collisions by ALICE collaboration [38]. This enhancement is suppressed for p/π ratio for the 95-100% 1-ρ nch event class that corresponds to jet topologies, whereas for Λ/K 0 s and Λ + c /D 0 the peak structure at intermediate p T is completely absent. ...
Preprint
Full-text available
Event classifiers based either on the charged-particle multiplicity or the event shape have been extensively used in proton-proton (pp) collisions by the ALICE collaboration at the LHC. The use of these tools became very instrumental since the observation of fluid-like behavior in high-multiplicity pp collisions. In particular, the study as a function of the charged-particle multiplicity registered in the forward V0 ALICE detector allowed for the discovery of strangeness enhancement in high-multiplicity pp collisions. However, one drawback of the multiplicity-based event classifiers is that requiring a high charged-particle multiplicity biases the sample towards hard processes like multi-jet final states. These biases make it difficult to perform jet-quenching searches in high-multiplicity pp collisions. In this context, the present paper explores the use of the new event classifier, flattenicity; which uses the multiplicity calculated in the forward pseudorapidity region. To illustrate how this tool works, pp collisions at $\sqrt{s}=13.6$ TeV simulated with PYTHIA~8 are explored. The sensitivity of flattencity to multi-partonic interactions as well as to the ``hardness'' of the collision are discussed. PYTHIA 8 predictions for the transverse momentum spectra of light- and heavy-flavored hadrons as a function of flattenicity are presented.
... However, as also confirmed by measurement of e.g. baryon yields in pp collisions at the LHC [40][41][42][43], additional hadronisation mechanisms may exist, whereby quarks that are close in phase space can combine into colourless hadrons. ...
... In heavy-ion collisions, where partons may travel freely over distances much larger than the typical hadron sizes and a dense system of partons close to thermal equilibrium is formed, such mechanisms become dominant, making the production of baryons and other heavy hadrons more favourable than in pp collisions. Measurements in ultra-relativistic nuclear collisions of light and multi-strange baryon yields normalised to pions indeed show a significant increase with respect to the corresponding ones in pp collisions [40][41][42][43]. Most of the measured yields are well described by the Statistical Hadronisation Model (SHM), in which the abundances of light and strange hadrons follow the equilibrium populations of a hadron-resonance gas at the freeze-out temperature T ch of about 155 MeV [44][45][46][47][48][49]. ...
Preprint
Full-text available
This document describes the plans of the ALICE Collaboration for a major upgrade of its detector, referred to as ALICE 3, which is proposed for physics data-taking in the LHC Run 5 and beyond. ALICE 3 will enable an extensive programme to fully exploit the LHC for the study of the properties of strongly interacting matter with high-energy nuclear collisions. The proposed detector layout, based on advanced silicon sensors, features superb pointing resolution, excellent tracking and particle identification over a large acceptance and high readout-rate capabilities. This document discusses the proposed physics programme, the detector concept, and its physics performance for a suite of benchmark measurements.
... Recent charmed-baryon measurements show a low-momentum enhancement over model predictions which are based on e + e − collisions, which challenges this traditional assumption of universality [1,2]. One of the latest measurements also shows that the charm-baryon enhancement depends on the final-state multiplicity of the collision event [3]. ...
Preprint
Full-text available
We study the enhanced production of $\Lambda_c$ charmed baryons relative to that of charmed $D^0$ mesons in proton-proton collisions at LHC energies. We simulated collision events with the enhanced color-reconnection model in PYTHIA 8 MC generator and propose measurements based on the comparative use of different event-activity classifiers to identify the source of the charmed-baryon enhancement. We demonstrate that in this enhanced color-reconnection scenario the excess production is primarily linked to the underlying event and not to the production of high-momentum jets.
Article
Quark-Gluon Plasma (QGP), a QCD state of matter created in ultra-relativistic heavy-ion collisions, has remarkable properties including, for example, a low shear viscosity over entropy ratio. By detecting the collection of low-momentum particles that arise from the collision, it is possible to gain quantitative insight into the created matter. However, its fast evolution and thermalization properties remain elusive. Only the usage of high momentum objects as probes of QGP can unveil its constituents at different wavelengths. In this review, we attempt to provide a comprehensive picture of what was, so far, possible to infer about QGP given our current theoretical understanding of jets, heavy-flavor, and quarkonia. We will bridge the resulting qualitative picture to the experimental observations done at both the LHC and RHIC. We will focus on the phenomenological description of experimental observations, provide a brief analytical summary of the description of hard probes, and an outlook towards the main difficulties we will need to surpass in the following years. To benchmark QGP-related effects, we will also address nuclear modifications to the initial state and hadronization effects.
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We study $D$-meson collisions during the hadronic break-up phase as a production mechanism for charmonium in relativistic heavy ion collisions at the Large Hadron Collider. Our calculation is based on chemical reaction rates with thermal cross sections for an effective meson interaction among pseudoscalar and vector mesons. We make use of published yields for $D$-mesons in Pb+Pb collisions and a schematic description of the expansion of the hadron gas. We find that the expected $J/\psi$ yield from hadronic regeneration is comparable to that predicted in the thermal equilibrium model. Our result implies that it will be difficult to distinguish regeneration during hadronization from regeneration by final-state hadronic interactions.
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The measurements of the production of prompt \({{\mathrm{D}}^0}\), \({{\mathrm{D}}^+}\), \({{\mathrm{D}}^{*+}}\), and \({{\mathrm{D}}^+_{\mathrm{s}}}\) mesons in proton–proton (pp) collisions at \(\sqrt{s}=5.02~\mathrm {TeV}\) with the ALICE detector at the Large Hadron Collider (LHC) are reported. D mesons were reconstructed at mid-rapidity (\(|y|<0.5\)) via their hadronic decay channels \(\mathrm{D}^0 \rightarrow {\mathrm{K}}^-\pi ^+\), \(\mathrm{D}^+\rightarrow {\mathrm{K}}^-\pi ^+\pi ^+\), \({\mathrm{D}}^{*+} \rightarrow {\mathrm{D}}^0 \pi ^+ \rightarrow {\mathrm{K}}^- \pi ^+ \pi ^+\), \({{\mathrm{D}}^{+}_{\mathrm{s}}\rightarrow \phi \pi ^+\rightarrow {\mathrm{K}}^{+} {\mathrm{K}}^{-} \pi ^{+}}\), and their charge conjugates. The production cross sections were measured in the transverse momentum interval \(0<p_{\mathrm{T}}<36~\mathrm {GeV}/c\) for \({{\mathrm{D}}^0}\), \(1<p_{\mathrm{T}}<36~\mathrm {GeV}/c\) for \({{\mathrm{D}}^+}\) and \({{\mathrm{D}}^{*+}}\), and in \(2<p_{\mathrm{T}}<24~\mathrm {GeV}/c\) for \({{\mathrm{D}}^+_{\mathrm{s}}}\) mesons. Thanks to the higher integrated luminosity, an analysis in finer \(p_{\mathrm{T}}\) bins with respect to the previous measurements at \(\sqrt{s}=7~\mathrm {TeV}\) was performed, allowing for a more detailed description of the cross-section \(p_{\mathrm{T}}\) shape. The measured \(p_{\mathrm{T}}\)-differential production cross sections are compared to the results at \(\sqrt{s}=7\) TeV and to four different perturbative QCD calculations. Its rapidity dependence is also tested combining the ALICE and LHCb measurements in pp collisions at \(\sqrt{s}=5.02~\mathrm {TeV}\). This measurement will allow for a more accurate determination of the nuclear modification factor in p–Pb and Pb–Pb collisions performed at the same nucleon–nucleon centre-of-mass energy.
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We report on the first measurement of the charmed baryon Λc± production at midrapidity (|y|<1) in Au+Au collisions at sNN=200 GeV collected by the STAR experiment at the Relativistic Heavy Ion Collider. The Λc/D0 [denoting (Λc++Λc−)/(D0+D¯0)] yield ratio is measured to be 1.08±0.16 (stat)±0.26 (sys) in the 0%–20% most central Au+Au collisions for the transverse momentum (pT) range 3<pT<6 GeV/c. This is significantly larger than the pythia model calculations for p+p collisions. The measured Λc/D0 ratio, as a function of pT and collision centrality, is comparable to the baryon-to-meson ratios for light and strange hadrons in Au+Au collisions. Model calculations including coalescence hadronization for charmed baryon and meson formation reproduce the features of our measured Λc/D0 ratio.