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Measurement of the production cross section of prompt Ξc0 baryons at midrapidity in pp collisions at s = 5.02 TeV

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A bstract The transverse momentum ( p T ) differential cross section of the charm-strange baryon $$ {\Xi}_{\mathrm{c}}^0 $$ Ξ c 0 is measured at midrapidity (| y | < 0.5) via its semileptonic decay into e ⁺ Ξ − ν e in pp collisions at $$ \sqrt{s} $$ s = 5 . 02 TeV with the ALICE detector at the LHC. The ratio of the p T -differential $$ {\Xi}_{\mathrm{c}}^0 $$ Ξ c 0 -baryon and D ⁰ -meson production cross sections is also reported. The measurements are compared with simulations with different tunes of the PYTHIA 8 event generator, with predictions from a statistical hadronisation model (SHM) with a largely augmented set of charm-baryon states beyond the current lists of the Particle Data Group, and with models including hadronisation via quark coalescence. The p T -integrated cross section of prompt $$ {\Xi}_{\mathrm{c}}^0 $$ Ξ c 0 -baryon production at midrapidity is also reported, which is used to calculate the baryon-to-meson ratio $$ {\Xi}_{\mathrm{c}}^0 $$ Ξ c 0 / D ⁰ = 0 . 20 ± 0 . 04 $$ {\left(\mathrm{stat}.\right)}_{-0.07}^{+0.08} $$ stat . − 0.07 + 0.08 (syst . ). These results provide an additional indication of a modification of the charm fragmentation from e ⁺ e − and e − p collisions to pp collisions.
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JHEP10(2021)159
Published for SISSA by Springer
Received:July 29, 2021
Accepted:October 4, 2021
Published:October 19, 2021
Measurement of the production cross section of
prompt Ξ0
cbaryons at midrapidity in pp collisions at
s= 5.02 TeV
The ALICE collaboration
E-mail: ALICE-publications@cern.ch
Abstract: The transverse momentum (pT) differential cross section of the charm-strange
baryon Ξ0
cis measured at midrapidity (|y|<0.5) via its semileptonic decay into e+Ξνe
in pp collisions at s= 5.02 TeV with the ALICE detector at the LHC. The ratio of the
pT-differential Ξ0
c-baryon and D0-meson production cross sections is also reported. The
measurements are compared with simulations with different tunes of the PYTHIA 8 event
generator, with predictions from a statistical hadronisation model (SHM) with a largely
augmented set of charm-baryon states beyond the current lists of the Particle Data Group,
and with models including hadronisation via quark coalescence. The pT-integrated cross
section of prompt Ξ0
c-baryon production at midrapidity is also reported, which is used to
calculate the baryon-to-meson ratio Ξ0
c/D0= 0.20 ±0.04 (stat.)+0.08
0.07 (syst.). These results
provide an additional indication of a modification of the charm fragmentation from e+e
and epcollisions to pp collisions.
Keywords: Heavy Ion Experiments
ArXiv ePrint: 2105.05616
Open Access, Copyright CERN,
for the benefit of the ALICE Collaboration.
Article funded by SCOAP3.
https://doi.org/10.1007/JHEP10(2021)159
JHEP10(2021)159
Contents
1 Introduction 1
2 Experimental apparatus and data sample 3
3 Data analysis 4
3.1 Reconstruction of e±and Ξ±candidates 4
3.2 Analysis of e±Ξinvariant mass distribution 5
3.3 Corrections and unfolding 6
3.4 Reconstruction efficiency and feed-down subtraction 8
3.5 Systematic uncertainties 10
4 Results 12
4.1 Comparison with model calculations 14
4.2 Extrapolation down to pT= 0 of the Ξ0
ccross section and the Ξ0
c/D0ratio 16
5 Summary and conclusions 16
The ALICE collaboration 23
1 Introduction
Measurements of the production of heavy-flavour hadrons (i.e. containing charm or beauty
quarks) in high-energy hadronic collisions provide important tests of quantum chromo-
dynamics (QCD) because perturbative techniques are applicable down to low transverse
momentum (pT) thanks to the large masses of charm and beauty quarks compared to
the QCD scale parameter (ΛQCD 200 MeV). The production cross sections of heavy-
flavour hadrons can be calculated using the factorisation approach [1] as a convolution of
three factors: the parton distribution functions (PDFs) of the incoming protons, the hard-
scattering cross section at partonic level, which can be calculated perturbatively in powers
of the strong coupling constant αs, and the fragmentation function, which parametrises
the non-perturbative transition of a heavy quark into a given species of heavy-flavour
hadron. The measurements of D- and B-meson production cross sections at midrapidity
in proton-proton (pp) collisions at several centre-of-mass energies at the LHC [29] are
described within uncertainties by perturbative calculations at next-to-leading order with
next-to-leading-log resummation, such as the general-mass variable-flavour-number scheme
(GM-VFNS [1012]) and the fixed-order next-to-leading-log (FONLL [13,14]) frameworks,
over a wide range of pT. Both calculations use fragmentation functions based on measure-
ments in positron-electron (e+e) collisions.
– 1 –
JHEP10(2021)159
Measurements of the production cross sections of different charm-hadron species, com-
paring in particular baryon and meson production in various collision systems and centre-
of-mass energies, provide insight into the properties of the fragmentation process. Mea-
surements of Λ+
c-baryon production at midrapidity in pp collisions at s= 5.02, 7, and
13 TeV were reported by the ALICE and CMS collaborations in refs. [1519]. A clear de-
creasing trend of the Λ+
c/D0ratio with increasing pTis seen. The Λ+
c/D0ratio is measured
to be substantially larger than previous measurements at lower centre-of-mass energies
in e+e[2022] and electron-proton (ep) collisions [23,24], suggesting that the charm
fragmentation is not universal among different collision systems. Similar indications were
obtained from the measurements of Ξ0,+
c-baryon and Σ0,++
c-baryon production at midra-
pidity in pp collisions at s= 7 and 13 TeV [19,25,26].
The charm-baryon production cross sections measured at the LHC are substantially
larger than the predictions of GM-VFNS calculations and of the POWHEG next-to-leading-
order (NLO) generator matched to PYTHIA 6 for the parton shower and the hadronisation
stages [12,17,27]. Predictions from QCD-inspired event generators like PYTHIA 8 with
Monash tune [28], DIPSY [29], and HERWIG 7 [30] also underestimate the baryon-to-meson
ratios measured at midrapidity. On the other hand, PYTHIA 8 simulations with tunes
including string formation beyond the leading-colour approximation [31] qualitatively de-
scribe the measured Λ+
c/D0and Σ0,+,++
c/D0ratios [17,19], but underestimate the Ξ0,+
c/D0
ratio [25,26]. Calculations with a statistical hadronisation model (SHM) [32] based on
charm-hadron states listed by the Particle Data Group (PDG) [33] underestimate the
measured baryon-to-meson ratios. The Λ+
c/D0and Σ0,+,++
c/D0ratios are qualitatively de-
scribed by the SHM calculations if a larger set of yet-unobserved higher-mass charm-baryon
states is considered under the guidance of the relativistic quark model (RQM) [34] and of
lattice QCD [35]. However, the Ξ0,+
c/D0ratios are still underestimated with the inclusion of
the additional baryonic states [26]. An enhancement of the charmed baryon-to-meson ratio
is expected also by models employing hadronisation of charm quarks via recombination in
pp collisions [36,37]. In the quark (re-)combination mechanism (QCM) model [36], the
charm quark is combined with a co-moving light antiquark or with two co-moving quarks to
form a charmed meson or baryon. The Catania model [37] implements charm-quark hadro-
nisation via both coalescence, implemented via Wigner formalism [38], and fragmentation.
Finally, it should be noted that an increased yield of charmed baryons (Λc,Ξc,c)
has significant consequences on the determination of the total charm cross section in pp
collisions at the LHC [3,4]. In the context of the heavy-ion programme at the LHC, the cc
production cross section per nucleon-nucleon collision is a fundamental ingredient for the
determination of the amount of charmonium production by (re)generation in a quark-gluon
plasma (QGP), a mechanism that is supported by J/ψmeasurements in nucleus-nucleus
collisions at the LHC [39,40]. A precise determination of the cc production cross section
in pp collisions at midrapidity will offer a stronger constraint to models implementing
J/ψregeneration in the QGP [4143]. In addition, measurements of open heavy-flavour
baryon production in heavy-ion collisions provide a unique information on hadronisation
mechanisms in the QGP. Models implementing charm-quark hadronisation via coalescence
in addition to fragmentation [4446] predict an enhanced baryon-to-meson ratio in heavy-
ion collisions with respect to pp collisions.
– 2 –
JHEP10(2021)159
In this article, we report the measurement of the pT-differential production cross section
of prompt Ξ0
cbaryons in pp collisions at s= 5.02 TeV and its ratio to the measured
production cross section of prompt D0mesons (i.e. produced directly in the hadronisation
of charm quarks and in the decays of directly produced excited charm states) [2,9]. The
Ξ0
cbaryons and their antiparticles are reconstructed at midrapidity (|y|<0.5) in the
transverse momentum interval 2 < pT<8 GeV/cvia the semileptonic decay mode Ξ0
c
e+Ξνeand its charge conjugate. We have recently constrained the absolute branching
ratio (BR) of this Ξ0
cdecay in pp collision at s= 13 TeV by measuring the Ξ0
cproduction
via two different decay channels, Ξ0
ce+Ξνeand Ξ0
cπ+Ξ[26]. This BR value is
used in this analysis and it is also used to update the previously published measurement
of inclusive Ξ0
cpT-differential cross section in pp collisions at s= 7 TeV [25].
The article is organised as follows. Section 2describes the experimental setup, focusing
on the detectors employed in the analysis and the data-taking conditions. The analysis
details and the estimation of the systematic uncertainties are discussed in section 3. Sec-
tion 4presents the results, namely the pT-differential production cross section of prompt
Ξ0
cbaryons and the Ξ0
c/D0cross-section ratio, which are compared with different model
calculations. The pT-integrated production cross section of prompt Ξ0
cbaryons, and the
corresponding Ξ0
c/D0ratio, extrapolated down to pT= 0, are also reported and compared
with model calculations. Finally, conclusions are drawn in section 5.
2 Experimental apparatus and data sample
The ALICE apparatus, described in detail in refs. [47,48], consists of a central barrel cov-
ering the pseudorapidity region |η|<0.9placed inside a solenoidal magnet that provides a
B= 0.5 T field parallel to the beam direction, a muon spectrometer at forward pseudora-
pidity (4< η < 2.5), and a set of detectors at forward/backward rapidity for triggering
and event selection. The detectors used for reconstruction and identification of the Ξ0
c
decay products are the Inner Tracking System (ITS) [49], the Time Projection Chamber
(TPC) [50], and the Time-Of-Flight detector (TOF) [51]. The ITS consists of six cylindrical
layers of silicon detectors. The two innermost layers, equipped with Silicon Pixel Detectors
(SPD), provide a space-point position resolution of 12 µm and 100 µm in the and the
beam direction, respectively. The third and fourth layers consist of Silicon Drift Detectors
(SDD), while the two outermost layers are equipped with Silicon Strip Detectors (SSD).
The TPC is the main tracking detector in the central barrel. With up to 159 space
points to reconstruct the charged-particle trajectory, it provides charged-particle momen-
tum measurement together with excellent two-track separation and particle identification
via dE/dxdetermination with a resolution better than 5% [50].
The TOF detector provides the measurement of the flight time of charged particles
from the interaction point to the detector radius of 3.8 m, with an overall resolution of
about 80 ps. The collision time is obtained using either the information from the T0
detector [52], or the TOF detector, or a combination of the two. The T0 detector consists
of two arrays of Čerenkov counters, located on both sides of the interaction point, covering
the pseudorapidity intervals 3.28 < η < 2.97 and 4.61 < η < 4.92.
– 3 –
JHEP10(2021)159
The V0 detector [53], composed of two arrays of 32 scintillators each, covering the
pseudorapidity intervals 3.7< η < 1.7and 2.8< η < 5.1, provides the minimum bias
(MB) trigger used to collect the data sample. In addition, the timing information of the two
V0 arrays and the correlation between the number of hits and track segments in the SPD
were used for an offline event selection, in order to remove background due to interactions
between one of the beams and the residual gas present in the beam vacuum tube.
In order to maintain a uniform acceptance in pseudorapidity, collision vertices were
required to be within ±10 cm from the centre of the detector along the beam line direction.
The pile-up events (less than 1%) were rejected by detecting multiple primary vertices using
track segments defined with the SPD layers. After the aforementioned selections, the data
sample used for the analysis consists of about 990 million MB events, corresponding to an
integrated luminosity of Lint = (19.3 ±0.4) nb1[54], collected during the 2017 pp run at
s= 5.02 TeV.
3 Data analysis
The analysis is performed using similar techniques to those reported in ref. [25]. The Ξ0
c
baryons are reconstructed via the semileptonic decay mode Ξ0
ce+Ξνe, and its charge
conjugate. The Ξ0
ccandidates are defined from e+Ξpairs formed by combining positrons
and Ξbaryons. The Ξ0
craw yield is obtained by counting the e+Ξpairs in p
Tintervals,
where p
Tis the transverse momentum of the e+Ξpair, after subtracting the combinatorial
background, as described in section 3.2. The p
Tdistribution of e+Ξpairs is corrected for
the missing momentum of the neutrino using unfolding techniques, in order to obtain the Ξ0
c
raw yield in intervals of Ξ0
cpT, as described in section 3.3. The contribution of Ξ0
cbaryons
originating from beauty-hadron decays is subtracted from the measured yield by using
perturbative quantum chromodynamics (pQCD) calculations of the beauty-quark cross
section together with the fragmentation fractions of beauty quarks into hadrons measured
by LHCb [55], and the acceptance and efficiency values estimated from simulations as
described in section 3.4. Charge conjugate modes are implied everywhere, unless otherwise
stated. The final results are obtained as the average of particles and antiparticles.
3.1 Reconstruction of e±and Ξ±candidates
Candidate electron and positron tracks satisfying |η|<0.8 and pT>0.5GeV/care re-
quired to have a number of crossed TPC pad rows larger than 80, a χ2normalised to
the number of associated TPC clusters smaller than 4, and at least 3 hits in the ITS.
These selection criteria suppress the contribution from short tracks, which are unlikely to
originate from the primary vertex. In order to reject electrons from photon conversions
occurring in the detector material outside the innermost SPD layer, the electron candidate
tracks are required to have associated hits in the two SPD layers of the ITS [56,57]. In
addition, at least 50 TPC clusters are required for the calculation of the dE/dxsignal.
Electrons are identified using the dE/dxand the time-of-flight measurements in the TPC
and TOF detectors. The selection is applied on the nTPC
σ,e and nTOF
σ,e variables defined as
the difference between the measured dE/dxor time-of-flight values and the ones expected
– 4 –
JHEP10(2021)159
for electrons, divided by the corresponding detector resolution. In the left panel of figure 1,
the nTPC
σ,e distribution as a function of the candidate electron pTis shown for tracks with
a time-of-flight compatible with the value expected for an electron within |nTOF
σ,e |<3.
The following criterion is applied on the TPC dE/dxsignal to select electron candidates:
3.9 + 1.2pT0.094p2
T<|nTPC
σ,e (pT)|<3 (with pTin units of GeV/c), which is
represented by the red lines in the left panel of figure 1. The pT-dependent lower limit on
|nTPC
σ,e |is optimised to reject hadrons. An electron purity of 98% is achieved over the whole
pTrange.
Further rejection of background electrons originating from Dalitz decays of neutral
mesons and photon conversions in the detector material (“photonic” electrons) is obtained
using a technique based on the invariant mass of e+epairs [40,58]. The electron (positron)
candidates are paired with opposite-sign tracks from the same event passing loose identi-
fication criteria (|nTPC
σ,e |<5 without any TOF requirement) and are rejected if they form
at least one e+epair with an invariant mass smaller than 50 MeV/c2. Loose electron
identification criteria are used in order to have a high efficiency of finding the partners [59].
With this selection the fraction of signal lost due to mistagging is less than 2%, as discussed
in section 3.3.
The Ξbaryons are reconstructed from the decay chain ΞΛπ(BR = 99.887 ±
0.035%), followed by Λpπ(BR = 63.9±0.5%) [33]. Tracks used to define Ξcandi-
dates are required to have a number of crossed TPC pad rows larger than 70 and a dE/dx
signal in the TPC consistent with the expected value for protons (pions) within 4σ. The
Ξand Λbaryons have long lifetimes (of about 4.91 cm and 7.89 cm, respectively [33]),
and thus they can be selected exploiting their characteristic decay topologies [60]. Pions
originating directly from Ξdecays are selected by requiring a minimum distance of closest
approach (d0) of their tracks to the primary vertex, d0>0.05 cm, while protons and pions
originating from Λdecays are required to have d0>0.07 cm. The d0of the Λtrajectory
to the primary vertex is required to be larger than 0.05 cm, while the cosine of the Λ
pointing angle, which is the angle between the reconstructed Λmomentum and the line
connecting the Λand Ξdecay vertices, is required to be larger than 0.98. The cosine of
the pointing angle of the reconstructed Ξmomentum to the primary vertex is required to
be larger than 0.983. The radial distances of the Ξand Λdecay vertices from the beam
line are required to be larger than 0.4 and 2.7 cm, respectively. These selection criteria are
tuned to reduce the background and enhance the purity of the signal. In the right panel
of figure 1the Ξpeak in the πΛinvariant mass distribution integrated for pΞ
T>0is
shown. Only Ξcandidates with invariant masses within 8 MeV/c2from the world average
Ξmass (1321.71 ±0.07 MeV/c2[33]), indicated by an arrow in the right panel of figure 1,
are kept for further analysis.
3.2 Analysis of e±Ξinvariant mass distribution
The Ξ0
ccandidates are defined from e+Ξpairs. Only pairs with an opening angle smaller
than 90 degrees are used for the analysis. Due to the undetected neutrino, the invariant
mass distribution of e+Ξpairs does not show a peak at the Ξ0
cmass. Following the same
approach adopted and described in ref. [25], the background contributions are estimated
– 5 –
JHEP10(2021)159
0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
)c (GeV/
T
p
8
6
4
2
0
2
4
6
8
10
TPC
,eσ
n
1
10
2
10
3
10
4
10
5
10
6
10
ALICE
= 5.02 TeVs
pp,
| < 0.8y|
| < 3
,eσ
TOF
n|
e
1.3 1.31 1.32 1.33 1.34
)
2
c(GeV/
)Λπ(
M
0
50
100
150
200
3
10×
)
2
c
Entries/(1 MeV/
ALICE
= 5.02 TeVs
pp,
Λ
-
π
-
Ξ
and charge conj.
Figure 1. Left panel: nTPC
σ,e distribution as a function of the electron pTafter applying the
particle identification criteria on the TOF signal (see text for details). Right panel: invariant mass
distribution of ΞπΛ(and charge conjugate) candidates integrated over pΞ
T. The arrow
indicates the world average Ξmass [33] and the dashed lines define the interval in which the Ξ
candidates are selected for the Ξ0
creconstruction (see text for details).
exploiting the fact that Ξ0
cbaryons and their antiparticles decay only into pairs with
opposite charge sign (e+Ξand eΞ+), denoted as right-sign (RS), and not into same-sign
pairs (eΞand e+Ξ+), denoted as wrong-sign (WS), while combinatorial background
candidates contribute equally to both RS and WS pairs. The Ξ0
craw yield is obtained
from the invariant mass distribution of RS pairs after subtracting the WS contribution.
Other contributions to eΞpairs, such as those from Ξ0,
bsemileptonic decays to WS pairs,
which do not give rise to RS pairs, are corrected for after the subtraction, as described
in section 3.3. In the left panel of figure 2the uncorrected invariant mass distributions
of WS and RS pairs in the interval 2 < p
T<8 GeV/care shown for illustration. In
the right panel of figure 2the invariant mass distribution of Ξ0
ccandidates obtained after
subtracting the WS pair yield from the RS yield is shown. Only e+Ξpairs satisfying
m<2.5 GeV/c2are considered.
3.3 Corrections and unfolding
The raw yield obtained by counting the e+Ξcandidates in bins of p
Tafter the subtraction
of the WS pairs needs to be corrected for the signal loss due to mistagging of photonic
electrons, and for the Ξ0,
bcontribution in the WS pairs. Finally, the p
T-differential
spectrum is corrected for the missing neutrino momentum to obtain the Ξ0
craw yield in
intervals of Ξ0
cpT.
The probability of wrongly tagging an electron as photonic is estimated by applying
the tagging algorithm, described in section 3.1, to e+e+and eepairs. The resulting
correction is smaller than 2%, with a mild dependence on the pTof the e+Ξpair, as it
was also observed in refs. [25,26].
– 6 –
JHEP10(2021)159
1.5 2 2.5 3 3.5
)
2
c) (GeV/Ξ(eM
0
500
1000
)
2
cEntries/(0.2 GeV/
Right sign
Wrong sign
ALICE
= 5.02 TeVs
pp,
e
ν
+
e
-
Ξ
0
c
Ξ
c < 8 GeV/
T
Ξe
p2 <
1.5 2 2.5 3 3.5
)
2
c) (GeV/Ξ(eM
0
200
400
)
2
c
Entries/(0.2 GeV/
ALICE
= 5.02 TeVs
pp,
e
ν
+
e
-
Ξ
0
c
Ξ
c < 8 GeV/
T
Ξe
p2 <
WS subtracted
Figure 2. Left panel: invariant mass distributions of right-sign and wrong-sign pairs with 2
< pT<8 GeV/c. Right panel: invariant mass distribution of Ξ0
ccandidates obtained by subtracting
the wrong-sign pair yield from the right-sign pair yield.
Decays of Ξ0,
bto electrons, Ξ0,
bHceX(where Hcis any charmed baryon), followed
by Hcdecays to Ξ,HcΞX, contribute to the WS invariant mass distribution and
not to the RS one, giving rise to a background over-subtraction. In order to estimate this
contribution, assumptions must be made for the branching ratio of Ξ0,
binto eΞ¯νeX
and for the Ξ0,
bproduction cross sections, which are not measured. First, the shape
of the transverse momentum distribution of Ξ0,
bbaryons is assumed to be the same as
that of Λ0
bbaryons. The CMS collaboration reported a measurement of the pT-differential
Λ0
bproduction cross section multiplied by the BR(Λ0
bJΛ) in pp collisions at s=
7 TeV [61]. To scale the Λ0
bmeasurement at the centre-of-mass energy of 5.02TeV, the ratio
of the beauty-hadron cross sections at s= 7 TeV and 5.02 TeV obtained with FONLL
pQCD calculations is used [13,14]. The second assumption is that the fraction of beauty
quarks that hadronise into Λ0
band Ξ0,
bare the same as those in e+ecollisions. The yield
of Ξ0,
beΞ¯νeXis therefore computed using i) the s-scaled Λ0
bcross section, ii) the
values of f(b Ξ0,
b)×BR(Ξ0,
beΞ¯νeX) [33] and f(b Λ0
b)×BR(Λ0
bJΛ) [62]
measured in e+ecollisions, and iii) the Ξ0,
beΞ¯νeXacceptance ×efficiency (Acc×ε)
from the simulations described below. The contribution to the WS pair yield from Ξ0,
b
baryon decays is estimated to be about 2%.
The correction for the missing momentum of the neutrino is performed by using an
unfolding technique with a response matrix which represents the correlation between the
pTof the Ξ0
cbaryon and that of the reconstructed e+Ξpair. The response matrix is
determined through a simulation with the PYTHIA 8.243 event generator [63] and the
GEANT 3 transport code [64], including a realistic description of the detector conditions
and alignment during the data taking period. The response matrix needs to be determined
using a realistic Ξ0
c-baryon pTdistribution which is not known a priori. Therefore, a two-
step iterative procedure is adopted. In the first step, the response matrix is obtained with
– 7 –
JHEP10(2021)159
2 4 6 8 10 12
)c (GeV/
c
0
Ξ
T
pGenerated
2
4
6
8
10
12
)c (GeV/
Ξe
T
pReconstructed
1
10
2
10
3
10
4
10
ALICE
= 5.02 TeVs
pp,
e
ν
+
e
-
Ξ
0
c
Ξ
and charge conj.
Figure 3. Correlation matrix between the generated Ξ0
c-baryon pTand the reconstructed e+Ξ
pair pT, obtained from the simulation based on PYTHIA 8 described in the text.
the pTdistribution generated with PYTHIA 8. This matrix is used to calculate a first
estimate of the Ξ0
cpT-differential spectrum from the measured pTdistribution of e+Ξ
pairs. The Ξ0
cpTdistribution from this first iteration is used to reweight the response
matrix, which is then used for the second iteration. The response matrix obtained from
this procedure is shown in figure 3. The Bayesian unfolding technique [65] implemented in
the RooUnfold package [66] is used. In this analysis the Bayesian procedure required three
iterations to converge. The response matrix used in the unfolding procedure is defined in
the transverse momentum interval 1.4<pT<12 GeV/c, which is wider than the pTinterval
used for the cross section measurement, to avoid edge effects at the lowest and highest pT
intervals of the measurement.
3.4 Reconstruction efficiency and feed-down subtraction
The pT-differential cross section of prompt Ξ0
c-baryon production is obtained as
d2σΞ0
c
dpTdy=1
BR ×1
2∆ypT×fprompt ×NΞ0
c0
c
raw
(Acc ×ε)prompt ×1
Lint
,(3.1)
where NΞ0
c0
c
raw is the raw yield after the unfolding correction in a given pTinterval with
width pT,fprompt is the fraction of prompt Ξ0
cin the raw yield of Ξ0
c, BR is the branching
ratio for the considered decay mode, and Lint is the integrated luminosity. The (Acc ×
ε)prompt factor is the product of detector acceptance and efficiency for prompt Ξ0
cbaryons,
where εaccounts for the reconstruction and selection of the Ξ0
cdecay-product tracks and
the Ξ0
c-candidate selection. The factor yrepresents the width of the rapidity interval in
which the generated Ξ0
care considered and it is applied to obtain the cross section in one
unit of rapidity. The factor 1/2 takes into account that NΞ0
c
raw includes both particles and
antiparticles, while the cross section is given for particles only. The BR of the considered
semileptonic decay channel is calculated from the ratio BR(Ξ0
cΞe+νe)/BR(Ξ0
c
– 8 –
JHEP10(2021)159
0 1 2 3 4 5 6 7 8
)c (GeV/
c
0
Ξ
T
p
2
10
1
10
ε
×
Acc
Prompt
Feed-down
ALICE
= 5.02 TeVs
pp,
e
ν
+
e
-
Ξ
0
c
Ξ
and charge conj.
Figure 4. Left panel: product of acceptance and efficiency for prompt and feed-down Ξ0
cbaryons in
pp collisions at s=5.02 TeV as a function of pT. Right panel: fraction of prompt Ξ0
cbaryons in the
raw yield (fprompt) as a function of pT. The systematic uncertainties of fprompt are shown as boxes.
Ξπ+)= 1.36 ±0.14 (stat.) ±0.19 (syst.), measured by ALICE in pp collisions at s=
13 TeV [26], which is multiplied by the hadronic decay branching ratio BR(Ξ0
cΞπ+)
reported in the PDG [33] to get BR(Ξ0
cΞe+νe)= (1.94±0.55)%.
The (Acc ×ε)factor is obtained from the same simulations used to determine the
response matrix in which the detector and data taking conditions are reproduced. The
(Acc ×ε)is computed separately for prompt and feed-down (produced in beauty-hadron
decays) Ξ0
cbaryons and is reported in the left panel of figure 4. The efficiencies of prompt
and feed-down baryons are consistent with each other within uncertainties because the
applied selection criteria are not sensitive to the displacement by a few hundred micrometers
of the prompt and feed-down Ξ0
cdecay vertices from the collision point. In order to compute
the efficiency with a realistic momentum distribution of Ξ0
cbaryons, the pTshape of the
Ξ0
cbaryons from the PYTHIA 8 simulation is reweighted to match the measured one via a
two-step iterative procedure similar to the one used for the response matrix.
The factor fprompt is calculated as
fprompt =1NΞ0
cfeed-down
NΞ0
c0
c
raw /2
=1(Acc×ε)feed-down·y·pT·BR·Lint
NΞ0
c0
c
raw /2× d2σ
dpTdy!Ξ0
cfeed-down
,
(3.2)
where NΞ0
c0
c
raw /2is the raw yield divided by a factor of two to account for particles and
antiparticles, (Acc×ε)feed-down is the product of detector acceptance and efficiency for feed-
down Ξ0
cbaryons and d2σ
dpTdyΞ0
cfeed-down is the pT-differential cross section of feed-down
Ξ0
cbaryon production. The production cross section of Ξ0
cfrom beauty-baryon decays is
not known, hence a strategy based on the estimation made in ref. [17] for the cross section
of feed-down Λ+
cis adopted. The production cross section of Λ+
cfrom Λ0
b-baryon decays is
calculated using the b-quark pT-differential cross section from FONLL calculations, multi-
– 9 –
JHEP10(2021)159
plied by the fraction of beauty quarks that fragment into Λ0
b. The latter is derived from the
LHCb measurement of beauty fragmentation fractions in pp collisions at s= 13TeV [55],
taking into account its pTdependence. The Λ0
bΛ+
c+ X decay kinematics is modeled
using PYTHIA 8.243 simulations [63]. The cross section of Λ+
cfrom Λ0
b-baryon decays is
scaled by the fraction of Ξ
bdecaying in a final state with a Ξ0
cover the fraction of Λ0
b
decaying to Λ+
c, which are taken to be 50% and 82%, respectively, from the PYTHIA 8.243
generator [63]. The cross section of Ξ0
cfrom beauty feed-down is then calculated from the
cross section of Λ+
coriginating from Λ0
bdecays, which is scaled by the ratio of the measured
pT-differential yields of inclusive Ξ0
cand prompt Λ+
cbaryons. This procedure relies on the
assumptions that the pTshape of the cross sections of feed-down Λ+
cand Ξ0
cis the same
and that the ratio Ξ0
c/Λ+
cis the same for inclusive and feed-down baryons, along with the
consideration that the inclusive Λ+
c-baryon yield is dominated by the prompt production,
based on the fprompt values close to unity reported in ref. [18]. The value of fprompt as a
function of pTis shown in the right panel of figure 4.
3.5 Systematic uncertainties
The systematic uncertainty on the Ξ0
cproduction cross section has different contribu-
tions, which are summarised in table 1for three representative pTintervals, namely
2< pT<3 GeV/c, 4 < pT<5 GeV/c, and 6 < pT<8 GeV/c, and discussed in the
following. The overall systematic uncertainty is calculated summing in quadrature the
different contributions, which are assumed to be uncorrelated among each other.
The systematic uncertainty on the tracking efficiency is estimated by comparing the
probability of prolonging a track from the TPC to the ITS (“matching efficiency”) in data
and simulation, and by varying the track-selection criteria in the analysis. The uncertainty
on the matching efficiency affects only the electron track, and not the tracks of the Ξ
decay particles, for which the prolongation to ITS is not required. It is defined as the
relative difference in the ITS-TPC matching efficiency between simulation and data. The
uncertainty, which slightly depends on the track pT, is propagated from the electron track
to the Ξ0
ctaking into account the decay kinematics and is 2% independent of Ξ0
cpT. The
second contribution to the track reconstruction uncertainty is estimated by repeating the
analysis varying the TPC track selection criteria separately for the electron track and for
the Ξdaughter tracks. The uncertainty is obtained from the root mean square (RMS)
of the Ξ0
ccross section values obtained with the different track selection criteria and is 2%
for the electron track and 4% for the Ξdaughters independent of Ξ0
cpT.
Systematic uncertainties can arise from discrepancies in the particle-identification ef-
ficiency between simulation and data. The analysis is repeated by varying the selection
criteria applied to identify the electron candidate tracks. The systematic uncertainty ranges
from 4% to 7% depending on the Ξ0
cpT.
The systematic uncertainty of the efficiency correction for the Ξtopological selection
is 6% and it is estimated from the RMS of the distribution of the Ξ0
ccorrected yields, when
the Ξtopological selection criteria are varied relative to the default measurement.
The uncertainty of the e+Ξ-pair selection efficiency is estimated by varying the se-
lection criteria of the opening angle and the invariant mass of the pair. A 3% uncertainty
is assigned, independent of Ξ0
cpT.
– 10 –
JHEP10(2021)159
pT(GeV/c) 2–3 4–5 6–8
ITS-TPC matching 2% 2% 2%
Electron track selection 2% 2% 2%
Ξ±-daughter track selection 4% 4% 4%
Electron identification 4% 7% 5%
Ξ±topological selection 6% 6% 6%
eΞ-pair selection 3% 3% 3%
Bayesian-unfolding iterations 5% 9% 2%
Unfolding method 5% 6% 4%
Response-matrix pTrange and binning 6%
Ξboversubtraction 1% 1% 1%
Generated pTshape 2% 2% 2%
Sensitivity to rapidity interval 4% 4% 4%
Feed-down subtraction +2
2%+3
3%+5
5%
Total systematic uncertainty +14
14%+16
16%+13
13%
Branching ratio 28.4%
Luminosity 2.1%
Table 1. Contributions to the systematic uncertainty of the Ξ0
ccross section for the pTintervals
2< pT<3 GeV/c, 4 < pT<5 GeV/c, and 6 < pT<8 GeV/c.
The systematic uncertainty of the correction for the missing neutrino momentum is
studied testing the stability of the results when varying the unfolding procedure. As a
first test, the number of iterations in the Bayesian unfolding procedure is varied. The
contribution ranges from 5% (9%) at low (intermediate) pTto 2% in the highest pTinterval
of the measurement. The second contribution arises from the variation of the unfolding
method. The Singular Value Decomposition (SVD) method [67] is used and a pT-dependent
systematic uncertainty between 4% and 7% is assigned based on the difference with respect
to the Bayesian method. The last contribution is related to the pTrange and the binning
of the response matrix used in the unfolding. Systematic uncertainties of 6% and 4% are
assigned in the intervals 2< pT<3GeV/cand 3< pT<4GeV/c, respectively. At higher
pT, this contribution is negligible. For these three contributions, the systematic uncertainty
is defined as the RMS of the yield values obtained after the unfolding.
The systematic uncertainty due to the subtraction of the Ξ0,
bcontribution to the
WS pairs is estimated by varying the Ξ0,
byield and momentum distribution based on
the uncertainties of the Λ0
bpT-differential cross section in pp collisions [61]. The assigned
systematic uncertainty is 1%, independent of Ξ0
cpT.
The systematic uncertainty due to the uncertainty of the generated Ξ0
cpTshape used
in the determination of the efficiency is estimated by using the shape from the PYTHIA 8
– 11 –
JHEP10(2021)159
generator instead of the one from the iterative procedure and is found to be 2%, independent
of pT. An additional source of uncertainty originates from possible differences between the
Ξ0
c-rapidity distributions in data and in the simulation, which affect the measured cross
section because the (Acc ×ε) depends on the Ξ0
crapidity. The systematic uncertainty
is estimated to be 4% by comparing the cross section values obtained using the values
of (Acc ×ε) and yobtained considering the generated Ξ0
cbaryons in different rapidity
intervals (from |y|<0.5 to |y|<0.8).
The systematic uncertainty due to the subtraction of the feed-down from beauty-
hadron decays is estimated by considering the uncertainty on the FONLL predictions and
by varying the assumption on the ratio Ξ0
c/Λ+
cin the fprompt calculation. The FONLL
uncertainty is calculated by varying the b-quark mass and the factorisation and renormal-
isation scales as prescribed in ref. [14]. The ratio of inclusive Ξ0
cover prompt Λ+
cyield,
used to multiply the feed-down Ξ0
ccross section, is scaled up by a factor of 2 to account for
possible differences between the Ξ0
c/Λ+
cand Ξ0,
b/Λ0
bratios, and scaled down in order to
cover the Ξ0,
b/Λ0
bvalue of about 0.12 measured at forward rapidity by the LHCb collabo-
ration [68]. The uncertainty ranges between 2% and 5% depending on the pTinterval. An
alternative method for the estimation of the fprompt factor, which consists in the usage of
the prompt and feed-down Ξ0
cyields generated with PYTHIA 8 colour reconnection (CR)
Mode 2 [31], was tested and the obtained results are compatible with the method described
above and therefore no systematic uncertainty from this additional method is considered.
All the different sources of systematic uncertainty are considered correlated among the
different pTintervals except the systematic uncertainties due to the unfolding and the pair
selection. The pT-differential cross section has an additional global normalisation uncer-
tainty due to the uncertainties of the integrated luminosity [54] and the branching ratio.
These contributions are not summed in quadrature with the other sources of uncertainty
in figure 5and 6.
4 Results
The pT-differential cross section of prompt Ξ0
c-baryon production in pp collisions at s=
5.02 TeV, measured in the rapidity interval |y|<0.5 and pTrange 2 < pT<8 GeV/c, is
shown in the left panel of figure 5. It is compared with the previously published measure-
ments of inclusive Ξ0
c-baryon production in pp collisions at s= 7 TeV [25], updated with
the BR value from ref. [26], and of prompt Ξ0
c-baryon production at s= 13 TeV [26],
which is measured as the average of two decay channels (Ξ0
cΞe+νeand Ξ0
cΞπ+).
The prompt fraction in the Ξ0
c-baryon yield is close to unity (see right panel of figure 4),
hence the comparison of the inclusive Ξ0
ccross section measured at s= 7 TeV with the
prompt ones at s= 5 and 13 TeV provides a meaningful insight into the sdependence
of the production cross section. The vertical bars and empty boxes represent the statis-
tical and systematic uncertainties. The systematic uncertainties of the BR are shown as
shaded boxes. The uncertainty of the integrated luminosity is not included in the boxes.
The data points are positioned at the centre of the pTintervals. As expected, a smaller Ξ0
c
production cross section is measured at lower collision energies. The difference between the
– 12 –
JHEP10(2021)159
0 2 4 6 8 10 12 14
)c (GeV/
T
p
1
10
1
10
2
10
)c
-1
b GeVµ) (yd
T
p/(d
σ
2
d
ALICE
baryon
0
c
Ξ
| < 0.5ypp, |
3.5% (7 TeV) lumi. unc. not shown± 2.1% (5.02 TeV), ±
1.6% (13 TeV) lumi. unc. not shown±
= 5.02 TeV (Prompt)s
= 7 TeV (Inclusive)s
BR unc.
= 13 TeV (Prompt)s
0 2 4 6 8 10 12 14
)c (GeV/
T
p
0.2
0.4
0.6
0.8
0
/ D
0
c
Ξ
= 5.02 TeVs
= 7 TeVs
= 13 TeVs
BR unc.
ALICE
| < 0.5ypp, |
Figure 5. Left panel: pT-differential production cross sections of prompt Ξ0
cbaryons in pp collisions
at s= 5.02 TeV and 13 TeV [26] and of inclusive Ξ0
cbaryons in pp collisions at s= 7 TeV [25]
with updated decay BR as discussed in the text. The uncertainty of the BR of the cross sections of
prompt Ξ0
cbaryons in pp collisions at s= 13 TeV is lower because it consists in the combination
of two different decay channels (Ξ0
ce+Ξνeand Ξ0
cπ+Ξ) [26]. Right panel: Ξ0
c/D0ratio
measured in pp collisions at s= 5.02 TeV, compared with the measurements at s= 7 TeV [25]
and s= 13 TeV [26]. The uncertainty of the BR of D0and Ξ0
care shown as shaded boxes.
cross sections at different svalues increases with increasing pT, indicating a hardening of
the pT-differential spectrum with increasing collision energy. This behaviour is consistent
with that observed for the D-meson and Λ+
c-baryon cross sections at s= 5.02, 7 and
13 TeV [2,3,16,18,19], and with the expectations from pQCD calculations [13,14]. The
visible cross section is computed by integrating the pT-differential cross section in the pT
interval of the measurement.
dσΞ0
c
pp, 5.02 TeV
dy
(2<pT<8GeV/c)
|y|<0.5
= 33.9±6.0(stat.) ±10.6(syst.) ±0.7(lumi.) µb.(4.1)
The BR uncertainty is included in the systematic uncertainty.
In the right panel of figure 5the Ξ0
c/D0cross section ratio measured in pp collisions at
s= 5.02 TeV as a function of pTis shown and compared with the same baryon-to-meson
ratio measured at s= 7 [25] and 13 TeV [26]. The prompt D0cross section is reported
in ref. [9] in finer pTintervals than those used in the prompt Ξ0
canalysis and is thus
rebinned to match the pTintervals of the Ξ0
cmeasurement. When merging the D0cross
section in different pTintervals, the systematic uncertainties are propagated considering
the yield extraction uncertainty as fully uncorrelated and all the other sources as fully
correlated among the pTintervals. The systematic uncertainty on the Ξ0
c/D0ratio is
calculated assuming all the uncertainties of the Ξ0
cand D0cross sections as uncorrelated,
except for the tracking and feed-down systematic uncertainties, which partially cancel in
the ratio. The uncertainty of the luminosity fully cancels in the baryon-to-meson ratio.
The Ξ0
c/D0ratios at the three centre-of-mass energies are consistent with each other within
– 13 –
JHEP10(2021)159
uncertainties. At low pT, the ratio is about 0.2 and it decreases with increasing pT, reaching
a value of about 0.1 for pT>6GeV/c. The Ξ0
c/D0ratio in pp collisions at s= 5.02 TeV
integrated in 2 < pT<8 GeV/cis 0.21 ±0.04 (stat.)±0.07 (syst.), which is calculated as
the ratio of the integrated cross sections of Ξ0
cand D0in the considered pTinterval.
4.1 Comparison with model calculations
The left panel of figure 6shows the comparison of the pT-differential production cross sec-
tion of Ξ0
cbaryons with predictions from different tunes of the PYTHIA 8.243 generator,
including the Monash tune [28], and tunes that implement CR beyond the leading-colour
approximation [31]. In the PYTHIA 8 simulations, all soft QCD processes are enabled.
In the Monash tune, the parameters governing the heavy-quark fragmentation are tuned
on measurements in e+ecollisions. The Monash tune significantly underestimates the
Ξ0
c-baryon production cross section by a factor of about 23 in the lowest pTinterval of
the measurement and around a factor 5 in the highest pTinterval. This prodives an ad-
ditional information on the non-universality of charm fragmentation that was reported in
refs. [17,19,26] based on the different baryon-to-meson ratios in e+eand pp collisions
and on the consideration that event generators tuned on e+edata do not describe the
baryon cross sections measured in pp collisions at LHC energies. The CR tunes introduce
new colour reconnection topologies, including “junctions”, which favour baryon formation.
The three considered tunes (Mode 0, 2, and 3) apply different constraints on the allowed
reconnection, taking into account causal connection of dipoles involved in a reconnection
and time dilation effects caused by relative boosts between string pieces. It is noted that
Mode 2 is recommended in ref. [31] as the standard tune, and contains the strictest con-
straints on the allowed reconnection. The three CR modes yield similar Ξ0
cpT-differential
cross sections, and predict a significantly larger Ξ0
cproduction cross section with respect
to the Monash tune. However, for all three CR modes, the measured Ξ0
cproduction cross
section is underestimated by a factor of about 5–6 for 2< pT<3GeV/c, and by a fac-
tor of about 3–4 for pT>6GeV/c, depending on the CR mode. The production cross
section of the Ξ0
cbaryon is also compared with a model using a coalescence approach in
hadronic collisions in the framework of QCM [36,69], in which quarks with equal velocity
are combined into hadrons. A free parameter, R(c)
B/M, characterises the relative produc-
tion of single-charm baryons to single-charm mesons and it is set to 0.425, which is tuned
to reproduce the Λ+
c/D0ratio measured by ALICE in pp collisions at s= 7 TeV [70].
The relative abundances of the different charm-baryon species are determined by thermal
weights. The QCM model is closer to the data as compared to PYTHIA 8 with CR tunes,
however it underpredicts the measured cross section by a factor 2–3 for pT<4GeV/c.
The measured Ξ0
c/D0ratio is compared in the right panel of figure 6with the differ-
ent tunes of the PYTHIA 8 event generator previously described. All PYTHIA 8 tunes
underestimate the measured pT-differential Ξ0
c/D0ratio. The Monash tune significantly
underestimates the data by a factor of about 21–24 in the low pTregion and by a factor
of about 7 in the highest pTinterval, as also observed for the Λ+
c/D0ratio [17]. All three
CR modes yield a similar magnitude and shape of the Ξ0
c/D0ratio, and despite predicting
a larger baryon-to-meson ratio with respect to the Monash tune, they still underestimate
– 14 –
JHEP10(2021)159
0 2 4 6 8 10
)c (GeV/
T
p
2
10
1
10
1
10
2
10
3
10
)c
-1
b GeVµ) (yd
T
p/(d
σ
2
d
2.1% lumi. unc. not shown±
ALICE
baryon
0
c
Ξ
= 5.02 TeVs
pp,
| < 0.5y|
Data
BR unc.
PYTHIA 8 Monash2013
PYTHIA 8 Mode 2
PYTHIA 8 Mode 0
PYTHIA 8 Mode 3
QCM
0 2 4 6 8 10
)c (GeV/
T
p
0.1
0.2
0.3
0.4
0
/ D
0
c
Ξ
Data
BR unc.
PYTHIA 8 Monash2013
PYTHIA 8 Mode 2
PYTHIA 8 Mode 0
PYTHIA 8 Mode 3
QCM
Catania (coal.+fragm.)
SHM+RQM
ALICE
= 5.02 TeVs
pp,
| < 0.5y|
Figure 6. Left panel: pT-differential production cross section of prompt Ξ0
cbaryons in pp collisions
at s= 5.02 TeV compared with model calculations [28,31,36]. Right panel: Ξ0
c/D0ratio as a
function of pTmeasured in pp collisions at s= 5.02 TeV compared with model calculations [28,
31,32,36,37] (see text for details).
the measured Ξ0
c/D0ratio by a factor of about 4–5 at low pT. The models with CR tunes
describe better the Λ+
c/D0and the Σ0,+,++
c/D0ratios than the Ξ0
c/D0one [9,17,19,26],
which involves a charm-strange baryon.
The measured Ξ0
c/D0ratio is also compared with a SHM calculation [32] in which ad-
ditional excited charm-baryon states not yet observed are included. The additional states
are added based on the relativistic quark model (RQM) [34] and lattice QCD calcula-
tions [35]. Charm- and strange-quark fugacity factors are used in the model to account for
the suppression of quarks heavier than u and d in elementary collisions. The uncertainty
band in the model is obtained by varying the assumption of the branching ratios of excited
charm-baryon states decaying to the ground state Ξ0,+
c, where an exact isospin symmetry
between Ξ+
cand Ξ0
cis assumed. This model, which was observed to describe the Λ+
c/D0
ratio [17], underestimates the measured Ξ0
c/D0ratio by the same amount as PYTHIA 8
with CR tunes.
The QCM model [36] underpredicts the Ξ0
c/D0ratio by the same amount as it does for
the Ξ0
c-baryon production cross section. The Catania model [37,46] implements charm-
quark hadronisation via both coalescence and fragmentation. In the model a blast wave
parametrisation [71] for light quarks at the hadronisation time with the inclusion of a con-
tribution from mini-jets is considered, while for charm quarks the spectra from FONLL
calculations are used. The coalescence process of heavy quarks with light quarks, which is
modelled using the Wigner function formalism, is tuned to have all charm quarks hadro-
nising via coalescence at pT'0. At finite pT, charm quarks not undergoing coalescence
are hadronised via an independent fragmentation. The Catania model describes the Ξ0
c/D0
ratio in the full pTinterval of the measurement.
– 15 –
JHEP10(2021)159
This new Ξ0
cmeasurement therefore provides important constraints to models of charm
quark hadronisation in pp collisions, being in particular sensitive to the description of
charm-strange baryon production in the colour reconnection approach, and to the possible
contribution of coalescence to charm quark hadronisation in pp collisions.
4.2 Extrapolation down to pT= 0 of the Ξ0
ccross section and the Ξ0
c/D0ratio
The pT-integrated production cross section of prompt Ξ0
cbaryons at midrapidity is ob-
tained by extrapolating the visible cross section, reported in eq. (4.1), to the full pTrange.
The PYTHIA 8 generator with CR Mode 2 is used to calculate the central value of the
extrapolation factor following what was done for the Λ+
cbaryon [17]. This prediction was
chosen because the PYTHIA 8 generator with CR Mode 2 describes the pTshape of the
measured cross section of Ξ0
cbetter than the other models that provide predictions of Ξ0
c
production in the full pTrange. The pT-differential Ξ0
ccross section values for 0 < pT<
2 GeV/cand for pT>8GeV/care obtained by multiplying the measured Ξ0
ccross section in
2< pT<8 GeV/cby the ratio of the cross sections obtained with PYTHIA 8 in the full and
in the measured pTrange. The systematic uncertainty is estimated from the difference with
respect to the extrapolation factors obtained using all the other available model calcula-
tions [31,32,36,37] except for the Monash tune [28], which fails to reproduce the pTshape
of the Ξ0
c-baryon cross section. The extrapolation factor is 2.65+0.54
0.44. The resulting pT-
integrated cross section of prompt Ξ0
c-baryon production in pp collisions at s= 5.02 TeV is
dσΞ0
c
pp, 5.02 TeV
dy|y|<0.5
= 89.8±16.0(stat.) ±28.1(syst.) ±1.9(lumi.) +18.2
15.0(extrap.) µb.
(4.2)
The pT-integrated cross section is used to calculate the ratio to the one of the D0meson
which is measured at the same collision energy [9]. The pT-integrated Ξ0
c/D0ratio is 0.20±
0.04 (stat.)+0.08
0.07 (syst.). In the baryon-to-meson ratio the tracking, the FONLL contribution
to the feed-down, and the luminosity components of the systematic uncertainty are con-
sidered as correlated between the Ξ0
cand the D0cross sections, while the other sources are
treated as uncorrelated. The extrapolation uncertainty is included in the total systematic
uncertainty. For an accurate measurement of the cc production cross section at midrapidity
in pp collisions at the LHC, it is therefore necessary to include the large yield of Ξ0
cbaryons.
5 Summary and conclusions
The measurement of the production of prompt Ξ0
cbaryons in pp collisions at s= 5.02 TeV
at midrapidity (|y|<0.5) with the ALICE detector at the LHC is reported. The analysis
was performed via the semileptonic decay channel Ξ0
ce+Ξνeand its charge conjugate.
The pT-differential cross section was measured in the transverse-momentum interval 2
< pT<8 GeV/c.
The measured pT-differential cross section and Ξ0
c/D0ratio were compared with differ-
ent tunes of the PYTHIA 8 event generator that implement different particle production
and hadronisation mechanisms. The predictions from the default PYTHIA 8 tune (Monash
– 16 –
JHEP10(2021)159
2013) and from CR tunes utilising string formation beyond the leading-colour approxima-
tion are systematically lower than the experimental measurement. The PYTHIA 8 simula-
tions with the colour-reconnection mechanism predict an enhanced production of baryons
and are closer to the data, as compared to the simulation with the Monash tune. The
pT-differential Ξ0
c/D0ratio was also compared with the statistical hadronisation model,
which underestimates the measured ratio also in the case in which the calculations are per-
formed assuming the existence of a large set of yet-unobserved charm-baryon states. Note
that PYTHIA 8 with CR and the statistical hadronisation model with additional baryons
describe reasonably well the Λ+
c/D0ratio. The measured Ξ0
c/D0ratio is better described
by the Catania model, which implements a possible new scenario for pp collisions at LHC
energies allowing low-pTcharm quarks to hadronise also via coalescence in addition to the
fragmentation mechanism.
The measurements reported in this article provide an additional information of non-
universality of charm fragmentation and set important and stringent constraints on models
of charm-quark hadronisation in pp collisions.
Acknowledgments
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 ac-
knowledges the following funding agencies for their support in building and running the
ALICE detector: A. I. Alikhanyan National Science Laboratory (Yerevan Physics Insti-
tute) Foundation (ANSL), State Committee of Science and World Federation of Scientists
(WFS), Armenia; Austrian Academy of Sciences, Austrian Science Fund (FWF): [M 2467-
N36] and Nationalstiftung für Forschung, Technologie und Entwicklung, Austria; Ministry
of Communications and High Technologies, National Nuclear Research Center, Azerbaijan;
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Financiadora de
Estudos e Projetos (Finep), Fundação de Amparo à Pesquisa do Estado de São Paulo
(FAPESP) and Universidade Federal do Rio Grande do Sul (UFRGS), Brazil; Ministry of
Education of China (MOEC), Ministry of Science & Technology of China (MSTC) and
National Natural Science Foundation of China (NSFC), China; Ministry of Science and
Education and Croatian Science Foundation, Croatia; Centro de Aplicaciones Tecnológi-
cas y Desarrollo Nuclear (CEADEN), Cubaenergía, Cuba; Ministry of Education, Youth
and Sports of the Czech Republic, Czech Republic; The Danish Council for Independent
Research | Natural Sciences, the VILLUM FONDEN and Danish National Research Foun-
dation (DNRF), Denmark; Helsinki Institute of Physics (HIP), Finland; Commissariat à
l’Energie Atomique (CEA) and Institut National de Physique Nucléaire et de Physique
des Particules (IN2P3) and Centre National de la Recherche Scientifique (CNRS), France;
Bundesministerium für Bildung und Forschung (BMBF) and GSI Helmholtzzentrum für
Schwerionenforschung GmbH, Germany; General Secretariat for Research and Technol-
– 17 –
JHEP10(2021)159
ogy, Ministry of Education, Research and Religions, Greece; National Research, Develop-
ment 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, Sci-
ence 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 Gen-
eral de Asuntos del Personal Academico (DGAPA), Mexico; Nederlandse Organisatie voor
Wetenschappelijk Onderzoek (NWO), Netherlands; The Research Council of Norway, Nor-
way; Commission on Science and Technology for Sustainable Development in the South
(COMSATS), Pakistan; Pontificia Universidad Católica del Perú, Peru; Ministry of Edu-
cation and Science, National Science Centre and WUT ID-UB, Poland; Korea Institute of
Science and Technology Information and National Research Foundation of Korea (NRF),
Republic of Korea; Ministry of Education and Scientific Research, Institute of Atomic
Physics and Ministry of Research and Innovation and Institute of Atomic Physics, Roma-
nia; Joint Institute for Nuclear Research (JINR), Ministry of Education and Science of the
Russian Federation, National Research Centre Kurchatov Institute, Russian Science Foun-
dation 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 Energy, Nuclear and Mineral Research Agency (TENMAK),
Turkey; National Academy of Sciences of Ukraine, Ukraine; Science and Technology Facil-
ities 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.
Open Access. This article is distributed under the terms of the Creative Commons
Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in
any medium, provided the original author(s) and source are credited.
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S. Acharya143, D. Adamová98, A. Adler76, J. Adolfsson83, G. Aglieri Rinella35 , M. Agnello31,
N. Agrawal55, Z. Ahammed143, S. Ahmad16 , S.U. Ahn78 , I. Ahuja39, Z. Akbar52 , A. Akindinov95,
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L. Altenkamper21 , I. Altsybeev115 , M.N. Anaam7, C. Andrei49 , D. Andreou93, A. Andronic146 ,
M. Angeletti35, V. Anguelov107 , F. Antinori58, P. Antonioli55, C. Anuj16, N. Apadula82,
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Y.W. Baek42, X. Bai131,110 , R. Bailhache70, Y. Bailung51 , R. Bala104 , A. Balbino31,
A. Baldisseri140, B. Balis2, M. Ball44 , D. Banerjee4, R. Barbera27, L. Barioglio108,25 , M. Barlou87 ,
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JHEP10(2021)159
G. Fiorenza35,109, F. Flor127 , A.N. Flores121 , S. Foertsch74, P. Foka110, S. Fokin91,
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J. Honermann146, G.H. Hong149 , D. Horak38 , S. Hornung110, A. Horzyk2, R. Hosokawa15,
P. Hristov35, C. Huang80 , C. Hughes133 , P. Huhn70, T.J. Humanic100, H. Hushnud112,
L.A. Husova146, A. Hutson127, D. Hutter40 , J.P. Iddon35,130, R. Ilkaev111, H. Ilyas14 , M. Inaba136,
G.M. Innocenti35, M. Ippolitov91, A. Isakov38,98, M.S. Islam112 , M. Ivanov110, V. Ivanov101,
V. Izucheev94, M. Jablonski2, B. Jacak82 , N. Jacazio35, P.M. Jacobs82, S. Jadlovska119,
J. Jadlovsky119, S. Jaelani64 , C. Jahnke124,123, M.J. Jakubowska144 , M.A. Janik144 , T. Janson76,
M. Jercic102, O. Jevons113 , F. Jonas99,146, P.G. Jones113, J.M. Jowett 35,110, J. Jung70 , M. Jung70 ,
A. Junique35, A. Jusko113 , J. Kaewjai118, P. Kalinak66, A. Kalweit35, V. Kaplin96 , S. Kar7,
A. Karasu Uysal79, D. Karatovic102 , O. Karavichev65, T. Karavicheva65, P. Karczmarczyk144,
E. Karpechev65, A. Kazantsev91 , U. Kebschull76, R. Keidel48, D.L.D. Keijdener64, M. Keil35 ,
B. Ketzer44, Z. Khabanova93, A.M. Khan7, S. Khan16 , A. Khanzadeev101, Y. Kharlov94 ,
A. Khatun16, A. Khuntia120, B. Kileng37 , B. Kim17,63 , D. Kim149, D.J. Kim128, E.J. Kim75 ,
J. Kim149, J.S. Kim42 , J. Kim107 , J. Kim149, J. Kim75, M. Kim107 , S. Kim18 , T. Kim149,
S. Kirsch70, I. Kisel40 , S. Kiselev95, A. Kisiel144 , J.P. Kitowski2, J.L. Klay6, J. Klein35 , S. Klein82,
C. Klein-Bösing146, M. Kleiner70 , T. Klemenz108 , A. Kluge35, A.G. Knospe127 , C. Kobdaj118 ,
M.K. Köhler107, T. Kollegger110, A. Kondratyev77, N. Kondratyeva96, E. Kondratyuk94,
J. Konig70, S.A. Konigstorfer108, P.J. Konopka35,2, G. Kornakov144, S.D. Koryciak2, L. Koska119,
A. Kotliarov98, O. Kovalenko88, V. Kovalenko115, M. Kowalski120, I. Králik66 , A. Kravčáková39,
L. Kreis110, M. Krivda113,66 , F. Krizek98 , K. Krizkova Gajdosova38, M. Kroesen107 , M. Krüger70 ,
E. Kryshen101, M. Krzewicki40 , V. Kučera35, C. Kuhn139 , P.G. Kuijer93, T. Kumaoka136 ,
D. Kumar143, L. Kumar103 , N. Kumar103 , S. Kundu35,89, P. Kurashvili88, A. Kurepin65,
A.B. Kurepin65, A. Kuryakin111 , S. Kushpil98, J. Kvapil113, M.J. Kweon63, J.Y. Kwon63,
Y. Kwon149, S.L. La Pointe40, P. La Rocca27 , Y.S. Lai82 , A. Lakrathok118, M. Lamanna35 ,
R. Langoy132, K. Lapidus35 , P. Larionov53, E. Laudi35 , L. Lautner35,108 , R. Lavicka38,
T. Lazareva115, R. Lea142,24,59, J. Lee136 , J. Lehrbach40, R.C. Lemmon97 , I. León Monzón122 ,
E.D. Lesser19, M. Lettrich35,108 , P. Lévai147, X. Li11 , X.L. Li7, J. Lien132, R. Lietava113 , B. Lim17,
S.H. Lim17, V. Lindenstruth40 , A. Lindner49 , C. Lippmann110, A. Liu19, J. Liu130 , I.M. Lofnes21 ,
V. Loginov96, C. Loizides99 , P. Loncar36 , J.A. Lopez107 , X. Lopez137 , E. López Torres8,
J.R. Luhder146, M. Lunardon28 , G. Luparello62 , Y.G. Ma41, A. Maevskaya65, M. Mager35,
T. Mahmoud44, A. Maire139 , M. Malaev101 , Q.W. Malik20, L. MalininaIV,77, D. Mal’Kevich95 ,
N. Mallick51, P. Malzacher110 , G. Mandaglio33,57, V. Manko91 , F. Manso137, V. Manzari54 ,
– 24 –
JHEP10(2021)159
Y. Mao7, J. Mareš68, G.V. Margagliotti24 , A. Margotti55 , A. Marín110, C. Markert121,
M. Marquard70, N.A. Martin107 , P. Martinengo35, J.L. Martinez127, M.I. Martínez46, G. Martínez
García117, S. Masciocchi110, M. Masera25 , A. Masoni56, L. Massacrier80, A. Mastroserio141,54 ,
A.M. Mathis108, O. Matonoha83 , P.F.T. Matuoka123, A. Matyja120, C. Mayer120,
A.L. Mazuecos35, F. Mazzaschi25 , M. Mazzilli35, M.A. Mazzoni60 , J.E. Mdhluli134 ,
A.F. Mechler70, F. Meddi22 , Y. Melikyan65, A. Menchaca-Rocha73, E. Meninno116,30,
A.S. Menon127, M. Meres13 , S. Mhlanga126,74 , Y. Miake136, L. Micheletti61,25, L.C. Migliorin138,
D.L. Mihaylov108, K. Mikhaylov77,95, A.N. Mishra147, D. Miśkowiec110, A. Modak4,
A.P. Mohanty64, B. Mohanty89, M. Mohisin Khan16 , Z. Moravcova92, C. Mordasini108 ,
D.A. Moreira De Godoy146, L.A.P. Moreno46, I. Morozov65, A. Morsch35 , T. Mrnjavac35,
V. Muccifora53, E. Mudnic36 , D. Mühlheim146 , S. Muhuri143, J.D. Mulligan82 , A. Mulliri23 ,
M.G. Munhoz123, R.H. Munzer70 , H. Murakami135 , S. Murray126, L. Musa35 , J. Musinsky66 ,
C.J. Myers127, J.W. Myrcha144, B. Naik134,50 , R. Nair88 , B.K. Nandi50, R. Nania55, E. Nappi54 ,
M.U. Naru14, A.F. Nassirpour83, A. Nath107 , C. Nattrass133 , A. Neagu20, L. Nellen71,
S.V. Nesbo37 , G. Neskovic40, D. Nesterov115, B.S. Nielsen92 , S. Nikolaev91, S. Nikulin91 ,
V. Nikulin101, F. Noferini55 , S. Noh12 , P. Nomokonov77, J. Norman130 , N. Novitzky136,
P. Nowakowski144, A. Nyanin91 , J. Nystrand21 , M. Ogino85, A. Ohlson83 , V.A. Okorokov96,
J. Oleniacz144, A.C. Oliveira Da Silva133, M.H. Oliver148, A. Onnerstad128, C. Oppedisano61,
A. Ortiz Velasquez71 , T. Osako47, A. Oskarsson83 , J. Otwinowski120, K. Oyama85,
Y. Pachmayer107, S. Padhan50, D. Pagano142,59, G. Paić71, A. Palasciano54 , J. Pan145,
S. Panebianco140, P. Pareek143 , J. Park63, J.E. Parkkila128, S.P. Pathak127, R.N. Patra104,35,
B. Paul23, J. Pazzini142,59, H. Pei7, T. Peitzmann64, X. Peng7, L.G. Pereira72, H. Pereira Da
Costa140, D. Peresunko91, G.M. Perez8, S. Perrin140, Y. Pestov5, V. Petráček38, M. Petrovici49,
R.P. Pezzi117,72, S. Piano62 , M. Pikna13 , P. Pillot117, O. Pinazza55,35, L. Pinsky127 , C. Pinto27,
S. Pisano53, M. Płoskoń82 , M. Planinic102, F. Pliquett70 , M.G. Poghosyan99, B. Polichtchouk94,
S. Politano31, N. Poljak102, A. Pop49 , S. Porteboeuf-Houssais137 , J. Porter82, V. Pozdniakov77,
S.K. Prasad4, R. Preghenella55, F. Prino61 , C.A. Pruneau145 , I. Pshenichnov65, M. Puccio35 ,
S. Qiu93, L. Quaglia25 , R.E. Quishpe127 , S. Ragoni113 , A. Rakotozafindrabe140 , L. Ramello32,
F. Rami139, S.A.R. Ramirez46 , A.G.T. Ramos34 , T.A. Rancien81, R. Raniwala105 , S. Raniwala105,
S.S. Räsänen45, R. Rath51 , I. Ravasenga93, K.F. Read99,133, A.R. Redelbach40 , K. RedlichV,88,
A. Rehman21, P. Reichelt70, F. Reidt35, H.A. Reme-ness37 , R. Renfordt70 , Z. Rescakova39,
K. Reygers107, A. Riabov101, V. Riabov101 , T. Richert83,92, M. Richter20, W. Riegler35 ,
F. Riggi27, C. Ristea69 , S.P. Rode51, M. Rodríguez Cahuantzi46, K. Røed20 , R. Rogalev94 ,
E. Rogochaya77, T.S. Rogoschinski70, D. Rohr35 , D. Röhrich21, P.F. Rojas46, P.S. Rokita144,
F. Ronchetti53, A. Rosano33,57 , E.D. Rosas71, A. Rossi58 , A. Rotondi29,59 , A. Roy51, P. Roy112,
S. Roy50, N. Rubini26, O.V. Rueda83 , R. Rui24, B. Rumyantsev77 , P.G. Russek2, A. Rustamov90,
E. Ryabinkin91, Y. Ryabov101, A. Rybicki120, H. Rytkonen128, W. Rzesa144, O.A.M. Saarimaki45 ,
R. Sadek117, S. Sadovsky94 , J. Saetre21, K. Šafařík38 , S.K. Saha143 , S. Saha89 , B. Sahoo50 ,
P. Sahoo50 , R. Sahoo51 , S. Sahoo67 , D. Sahu51, P.K. Sahu67, J. Saini143, S. Sakai136 ,
S. Sambyal104, V. SamsonovI,101,96, D. Sarkar145 , N. Sarkar143, P. Sarma43, V.M. Sarti108 ,
M.H.P. Sas148, J. Schambach99,121 , H.S. Scheid70, C. Schiaua49, R. Schicker107, A. Schmah107,
C. Schmidt110, H.R. Schmidt106, M.O. Schmidt107 , M. Schmidt106, N.V. Schmidt99,70,
A.R. Schmier133, R. Schotter139, J. Schukraft35, Y. Schutz139, K. Schwarz110, K. Schweda110,
G. Scioli26, E. Scomparin61 , J.E. Seger15 , Y. Sekiguchi135, D. Sekihata135 , I. Selyuzhenkov110,96,
S. Senyukov139, J.J. Seo63, D. Serebryakov65, L. Šerkšnyt˙e108, A. Sevcenco69, T.J. Shaba74,
A. Shabanov65, A. Shabetai117 , R. Shahoyan35, W. Shaikh112 , A. Shangaraev94, A. Sharma103,
H. Sharma120, M. Sharma104 , N. Sharma103 , S. Sharma104, O. Sheibani127, K. Shigaki47 ,
M. Shimomura86, S. Shirinkin95 , Q. Shou41, Y. Sibiriak91 , S. Siddhanta56 , T. Siemiarczuk88,
– 25 –
JHEP10(2021)159
T.F. Silva123, D. Silvermyr83, G. Simonetti35, B. Singh108 , R. Singh89 , R. Singh104 , R. Singh51,
V.K. Singh143, V. Singhal143 , T. Sinha112 , B. Sitar13, M. Sitta32, T.B. Skaali20 ,
G. Skorodumovs107, M. Slupecki45 , N. Smirnov148, R.J.M. Snellings64 , C. Soncco114 , J. Song127,
A. Songmoolnak118 , F. Soramel28, S. Sorensen133 , I. Sputowska120, J. Stachel107, I. Stan69 ,
P.J. Steffanic133 , S.F. Stiefelmaier107, D. Stocco117, I. Storehaug20, M.M. Storetvedt37 ,
C.P. Stylianidis93, A.A.P. Suaide123, T. Sugitate47 , C. Suire80, M. Suljic35 , R. Sultanov95,
M. Šumbera98, V. Sumberia104 , S. Sumowidagdo52, S. Swain67 , A. Szabo13 , I. Szarka13 ,
U. Tabassam14, S.F. Taghavi108, G. Taillepied137, J. Takahashi124, G.J. Tambave21, S. Tang137,7,
Z. Tang131, M. Tarhini117 , M.G. Tarzila49 , A. Tauro35, G. Tejeda Muñoz46, A. Telesca35,
L. Terlizzi25, C. Terrevoli127, G. Tersimonov3, S. Thakur143, D. Thomas121, R. Tieulent138 ,
A. Tikhonov65, A.R. Timmins127 , M. Tkacik119, A. Toia70, N. Topilskaya65, M. Toppi53,
F. Torales-Acosta19, T. Tork80, S.R. Torres38, A. Trifiró33,57, S. Tripathy55,71, T. Tripathy50,
S. Trogolo35,28, G. Trombetta34 , V. Trubnikov3, W.H. Trzaska128, T.P. Trzcinski144,
B.A. Trzeciak38, A. Tumkin111 , R. Turrisi58 , T.S. Tveter20, K. Ullaland21 , A. Uras138 ,
M. Urioni59,142, G.L. Usai23 , M. Vala39, N. Valle59,29 , S. Vallero61, N. van der Kolk64, L.V.R. van
Doremalen64, M. van Leeuwen93, P. Vande Vyvre35 , D. Varga147, Z. Varga147,
M. Varga-Kofarago147, A. Vargas46, M. Vasileiou87, A. Vasiliev91, O. Vázquez Doce108 ,
V. Vechernin115, E. Vercellin25, S. Vergara Limón46, L. Vermunt64, R. Vértesi147, M. Verweij64,
L. Vickovic36, Z. Vilakazi134, O. Villalobos Baillie113, G. Vino54 , A. Vinogradov91, T. Virgili30,
V. Vislavicius92, A. Vodopyanov77, B. Volkel35, M.A. Völkl107, K. Voloshin95, S.A. Voloshin145 ,
G. Volpe34 , B. von Haller35, I. Vorobyev108 , D. Voscek119, J. Vrláková39, B. Wagner21, C. Wang41,
D. Wang41, M. Weber116 , R.J.G.V. Weelden93, A. Wegrzynek35, S.C. Wenzel35, J.P. Wessels146,
J. Wiechula70, J. Wikne20, G. Wilk88 , J. Wilkinson110 , G.A. Willems146 , E. Willsher113,
B. Windelband107, M. Winn140 , W.E. Witt133 , J.R. Wright121, W. Wu41, Y. Wu131 , R. Xu7,
S. Yalcin79, Y. Yamaguchi47, K. Yamakawa47, S. Yang21, S. Yano47,140, Z. Yin7, H. Yokoyama64,
I.-K. Yoo17 , J.H. Yoon63, S. Yuan21, A. Yuncu107, V. Zaccolo24, A. Zaman14 , C. Zampolli35 ,
H.J.C. Zanoli64, N. Zardoshti35 , A. Zarochentsev115, P. Závada68, N. Zaviyalov111,
H. Zbroszczyk144, M. Zhalov101 , S. Zhang41, X. Zhang7, Y. Zhang131 , V. Zherebchevskii115 ,
Y. Zhi11, D. Zhou7, Y. Zhou92 , J. Zhu7,110 , Y. Zhu7, A. Zichichi26, G. Zinovjev3and N. Zurlo142,59
IDeceased
II Also at: Italian National Agency for New Technologies, Energy and Sustainable Economic
Development (ENEA), Bologna, Italy
III Also at: Dipartimento DET del Politecnico di Torino, Turin, Italy
IV Also at: M.V. Lomonosov Moscow State University, D.V. Skobeltsyn Institute of Nuclear, Physics,
Moscow, Russia
VAlso at: Institute of Theoretical Physics, University of Wroclaw, Poland
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
– 26 –
JHEP10(2021)159
6California Polytechnic State University, San Luis Obispo, California, United States
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 Mérida, Mexico
10 Chicago State University, Chicago, Illinois, United States
11 China Institute of Atomic Energy, Beijing, China
12 Chungbuk National University, Cheongju, Republic of Korea
13 Comenius University Bratislava, Faculty of Mathematics, Physics and Informatics, Bratislava,
Slovakia
14 COMSATS University Islamabad, Islamabad, Pakistan
15 Creighton University, Omaha, Nebraska, United States
16 Department of Physics, Aligarh Muslim University, Aligarh, India
17 Department of Physics, Pusan National University, Pusan, Republic of Korea
18 Department of Physics, Sejong University, Seoul, Republic of Korea
19 Department of Physics, University of California, Berkeley, California, United States
20 Department of Physics, University of Oslo, Oslo, Norway
21 Department of Physics and Technology, University of Bergen, Bergen, Norway
22 Dipartimento di Fisica dell’Università ‘La Sapienza’ and Sezione INFN, Rome, Italy
23 Dipartimento di Fisica dell’Università and Sezione INFN, Cagliari, Italy
24 Dipartimento di Fisica dell’Università and Sezione INFN, Trieste, Italy
25 Dipartimento di Fisica dell’Università and Sezione INFN, Turin, Italy
26 Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN, Bologna, Italy
27 Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN, Catania, Italy
28 Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN, Padova, Italy
29 Dipartimento di Fisica e Nucleare e Teorica, Università di Pavia, Pavia, Italy
30 Dipartimento di Fisica ‘E.R. Caianiello’ dell’Università and Gruppo Collegato INFN, Salerno, Italy
31 Dipartimento DISAT del Politecnico and Sezione INFN, Turin, Italy
32 Dipartimento di Scienze e Innovazione Tecnologica dell’Università del Piemonte Orientale and
INFN Sezione di Torino, Alessandria, Italy
33 Dipartimento di Scienze MIFT, Università di Messina, Messina, Italy
34 Dipartimento Interateneo di Fisica ‘M. Merlin’ and Sezione INFN, Bari, Italy
35 European Organization for Nuclear Research (CERN), Geneva, Switzerland
36 Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture, University of
Split, Split, Croatia
37 Faculty of Engineering and Science, Western Norway University of Applied Sciences, Bergen,
Norway
38 Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague,
Prague, Czech Republic
39 Faculty of Science, P.J. Šafárik University, Košice, Slovakia
40 Frankfurt Institute for Advanced Studies, Johann Wolfgang Goethe-Universität Frankfurt,
Frankfurt, Germany
41 Fudan University, Shanghai, China
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JHEP10(2021)159
42 Gangneung-Wonju National University, Gangneung, Republic of Korea
43 Gauhati University, Department of Physics, Guwahati, India
44 Helmholtz-Institut für Strahlen- und Kernphysik, Rheinische Friedrich-Wilhelms-Universität Bonn,
Bonn, Germany
45 Helsinki Institute of Physics (HIP), Helsinki, Finland
46 High Energy Physics Group, Universidad Autónoma de Puebla, Puebla, Mexico
47 Hiroshima University, Hiroshima, Japan
48 Hochschule Worms, Zentrum für Technologietransfer und Telekommunikation (ZTT), Worms,
Germany
49 Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest, Romania
50 Indian Institute of Technology Bombay (IIT), Mumbai, India
51 Indian Institute of Technology Indore, Indore, India
52 Indonesian Institute of Sciences, Jakarta, Indonesia
53 INFN, Laboratori Nazionali di Frascati, Frascati, Italy
54 INFN, Sezione di Bari, Bari, Italy
55 INFN, Sezione di Bologna, Bologna, Italy
56 INFN, Sezione di Cagliari, Cagliari, Italy
57 INFN, Sezione di Catania, Catania, Italy
58 INFN, Sezione di Padova, Padova, Italy
59 INFN, Sezione di Pavia, Pavia, Italy
60 INFN, Sezione di Roma, Rome, Italy
61 INFN, Sezione di Torino, Turin, Italy
62 INFN, Sezione di Trieste, Trieste, Italy
63 Inha University, Incheon, Republic of Korea
64 Institute for Gravitational and Subatomic Physics (GRASP), Utrecht University/Nikhef, Utrecht,
Netherlands
65 Institute for Nuclear Research, Academy of Sciences, Moscow, Russia
66 Institute of Experimental Physics, Slovak Academy of Sciences, Košice, Slovakia
67 Institute of Physics, Homi Bhabha National Institute, Bhubaneswar, India
68 Institute of Physics of the Czech Academy of Sciences, Prague, Czech Republic
69 Institute of Space Science (ISS), Bucharest, Romania
70 Institut für Kernphysik, Johann Wolfgang Goethe-Universität Frankfurt, Frankfurt, Germany
71 Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Mexico City, Mexico
72 Instituto de Física, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, Brazil
73 Instituto de Física, Universidad Nacional Autónoma de México, Mexico City, Mexico
74 iThemba LABS, National Research Foundation, Somerset West, South Africa
75 Jeonbuk National University, Jeonju, Republic of Korea
76 Johann-Wolfgang-Goethe Universität Frankfurt Institut für Informatik, Fachbereich Informatik und
Mathematik, Frankfurt, Germany
77 Joint Institute for Nuclear Research (JINR), Dubna, Russia
78 Korea Institute of Science and Technology Information, Daejeon, Republic of Korea
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JHEP10(2021)159
79 KTO Karatay University, Konya, Turkey
80 Laboratoire de Physique des 2 Infinis, Irène Joliot-Curie, Orsay, France
81 Laboratoire de Physique Subatomique et de Cosmologie, Université Grenoble-Alpes, CNRS-IN2P3,
Grenoble, France
82 Lawrence Berkeley National Laboratory, Berkeley, California, United States
83 Lund University Department of Physics, Division of Particle Physics, Lund, Sweden
84 Moscow Institute for Physics and Technology, Moscow, Russia
85 Nagasaki Institute of Applied Science, Nagasaki, Japan
86 Nara Women’s University (NWU), Nara, Japan
87 National and Kapodistrian University of Athens, School of Science, Department of Physics ,
Athens, Greece
88 National Centre for Nuclear Research, Warsaw, Poland
89 National Institute of Science Education and Research, Homi Bhabha National Institute, Jatni, India
90 National Nuclear Research Center, Baku, Azerbaijan
91 National Research Centre Kurchatov Institute, Moscow, Russia
92 Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
93 Nikhef, National institute for subatomic physics, Amsterdam, Netherlands
94 NRC Kurchatov Institute IHEP, Protvino, Russia
95 NRC «Kurchatov»Institute - ITEP, Moscow, Russia
96 NRNU Moscow Engineering Physics Institute, Moscow, Russia
97 Nuclear Physics Group, STFC Daresbury Laboratory, Daresbury, United Kingdom
98 Nuclear Physics Institute of the Czech Academy of Sciences, Řež u Prahy, Czech Republic
99 Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
100 Ohio State University, Columbus, Ohio, United States
101 Petersburg Nuclear Physics Institute, Gatchina, Russia
102 Physics department, Faculty of science, University of Zagreb, Zagreb, Croatia
103 Physics Department, Panjab University, Chandigarh, India
104 Physics Department, University of Jammu, Jammu, India
105 Physics Department, University of Rajasthan, Jaipur, India
106 Physikalisches Institut, Eberhard-Karls-Universität Tübingen, Tübingen, Germany
107 Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany
108 Physik Department, Technische Universität München, Munich, Germany
109 Politecnico di Bari and Sezione INFN, Bari, Italy
110 Research Division and ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum für
Schwerionenforschung GmbH, Darmstadt, Germany
111 Russian Federal Nuclear Center (VNIIEF), Sarov, Russia
112 Saha Institute of Nuclear Physics, Homi Bhabha National Institute, Kolkata, India
113 School of Physics and Astronomy, University of Birmingham, Birmingham, United Kingdom
114 Sección Física, Departamento de Ciencias, Pontificia Universidad Católica del Perú, Lima, Peru
115 St. Petersburg State University, St. Petersburg, Russia
116 Stefan Meyer Institut für Subatomare Physik (SMI), Vienna, Austria
– 29 –
JHEP10(2021)159
117 SUBATECH, IMT Atlantique, Université de Nantes, CNRS-IN2P3, Nantes, France