Multiplicity dependence of $Ξ_c^+$ and $Ξ_c^0$ production in pp collisions at $\sqrt{s} = 13$ TeV

The ALICE collaboration Abualrob, Ibrahim Jaser ; Acharya, Shreyasi ; Aglieri Rinella, Gianluca ; et al.
CERN-EP-2025-175, 2025.
Inspire Record 2960135 DOI 10.17182/hepdata.166317

The first measurement at midrapidity ($|y| < 0.5$) of the production yield of the strange-charm baryons $Ξ_c^+$ and $Ξ_c^0$ as a function of charged-particle multiplicity in proton-proton collisions at $\sqrt{s} = 13$ TeV with the ALICE experiment at the LHC is reported. The $Ξ_c^+$ baryon is reconstructed via the $Ξ_c^+ \rightarrow Ξ^-π^+π^+$ decay channel in the range $4 < p_{\rm T} < 12$ GeV/$c$, while the $Ξ_c^0$ baryon is reconstructed via both the $Ξ_c^0 \rightarrow Ξ^-π^+$ and $Ξ_c^0 \rightarrow Ξ^-e^+ν_e$ decay channels in the range $2 < p_{\rm T} < 12$ GeV/$c$. The baryon-to-meson ($Ξ_c^{0,+}/D^0$) and the baryon-to-baryon ($Ξ_c^{0,+}/Λ_c^+$) production yield ratios show no significant dependence on multiplicity. In addition, the observed yield ratios are not described by theoretical predictions that model charm-quark fragmentation based on measurements at $e^+e^-$ and $e^-$p colliders, indicating differences in the charm-baryon production mechanism in pp collisions. A comparison with different event generators and tunings, including different modelling of the hadronisation process, is also discussed. Moreover, the branching-fraction ratio of BR($Ξ_c^0 \rightarrow Ξ^-e^+ν_e$)/BR($Ξ_c^0 \rightarrow Ξ^-π^+$) is measured as 0.825 $\pm$ 0.094 (stat.) $\pm$ 0.081 (syst.). This value supersedes the previous ALICE measurement, improving the statistical precision by a factor of 1.6.

9 data tables

$p_{\rm T}$-differential per-event yield of prompt $\Xi_c^0$ baryons measured in the different multiplicity classes.

$p_{\rm T}$-differential per-event yield of prompt $\Xi_c^+$ baryons measured in the different multiplicity classes.

Ratio between the prompt $\Xi_c^0$ baryons in a multiplicity class to the multiplicity-integrated (INEL $>$ 0) class.

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Study of $\langle p_{\rm T} \rangle$ and its higher moments, and extraction of the speed of sound in Pb-Pb collisions with ALICE

The ALICE collaboration Abualrob, Ibrahim Jaser ; Acharya, Shreyasi ; Aglieri Rinella, Gianluca ; et al.
CERN-EP-2025-126, 2025.
Inspire Record 2933773 DOI 10.17182/hepdata.165515

Ultrarelativistic heavy-ion collisions create a quark-gluon plasma (QGP), a hot and dense state of strongly interacting QCD matter. In ultracentral collisions, the QGP volume remains nearly constant event-by-event, while its total entropy can fluctuate due to quantum effects, leading to temperature variations. These features allow the correlation between the mean transverse momentum $(\langle p_{\mathrm{T}} \rangle)$ of charged hadrons and their multiplicity to serve as a probe of the QGP's speed of sound, $c_{s}$. This study extracts $c_{s}$ by analyzing the relative increase in $\langle p_{\mathrm{T}} \rangle$ with respect to the charged-particle density $(\langle \mathrm{d}N_\mathrm{ch}/\mathrm{d}\eta \rangle)$ at midrapidity in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02~\mathrm{TeV}$, using data from the ALICE detector. Centrality is determined with estimators based on multiplicity and transverse energy, applying a pseudorapidity gap to reduce selection biases. The extracted value of $c_{s}^{2}$ is found to strongly depend on the employed centrality estimator and ranges between $0.1146 \pm 0.0028 \,\mathrm{(stat.)} \pm 0.0065 \,\mathrm{(syst.)}$ and $0.4374 \pm 0.0006 \mathrm{(stat.)} \pm 0.0184 \mathrm{(syst.)}$ in natural units. Additionally, the event-by-event $[p_{\mathrm{T}}]$ distribution is studied through its variance, skewness, and kurtosis. A pronounced decrease in the self-normalized variance and a peak followed by a drop in skewness suggest the suppression of impact-parameter fluctuations in ultracentral collisions. These observations provide new insights into the thermodynamic properties and initial-state fluctuations of the QGP.

35 data tables

Average number of participating nucleons ($\langle N_{\mathrm{part}} \rangle$) as a function of centrality percentile in $\mathrm{Pb}-\mathrm{Pb}$ collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02~\mathrm{TeV}$. Data points are shown for centrality estimators based on $N_{\mathrm{ch}}$, ${N_{\mathrm{tracklets}}}$, and $E_{\mathrm{T}}$ within $|\eta|\leq 0.8$.

Average number of participating nucleons ($\langle N_{\mathrm{part}} \rangle$) as a function of centrality percentile in $\mathrm{Pb}-\mathrm{Pb}$ collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02~\mathrm{TeV}$. Data points are shown for centrality estimator based on $N_{\mathrm{ch}} \in$ $-3.7<\eta<-1.7$ and $2.8 < \eta <5.1$.

Normalized $p_{\mathrm{T}}$-spectrum ratio as a function as a function of centrality in $\mathrm{Pb}-\mathrm{Pb}$ collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02~\mathrm{TeV}$. Data points are shown for centrality estimator based on $N_{\mathrm{ch}} \in$ $0.5 \leq |\eta|\leq 0.8$.

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Femtoscopic study of the proton-proton and proton-deuteron systems in heavy-ion collisions at the LHC

The ALICE collaboration Acharya, Shreyasi ; Aglieri Rinella, Gianluca ; Aglietta, Luca ; et al.
CERN-EP-2025-096, 2025.
Inspire Record 2917986 DOI 10.17182/hepdata.165812

This work reports femtoscopic correlations of p$-$p ($\bar{\rm p}-\bar{\rm p}$) and p$-$d ($\bar{\rm p}-\bar{\rm d}$) pairs measured in Pb$-$Pb collisions at center-of-mass energy $\sqrt{s_{\rm NN}}$ = 5.02 TeV by the ALICE Collaboration. A fit to the measured proton-proton correlation functions allows one to extract the dependence of the nucleon femtoscopic radius of the particle-emitting source on the pair transverse mass ($m_\text{T}$) and on the average charge particle multiplicity $\langle\text{dN}_\text{ch}/\text{d}\eta\rangle^{1/3}$ for three centrality intervals (0$-$10$\%$, 10$-$30$\%$, 30$-$50$\%$). In both cases, the expected power-law and linear scalings are observed, respectively. The measured p$-$d correlations can be described by both two- and three-body calculations, indicating that the femtoscopy observable is not sensitive to the short-distance features of the dynamics of the p$-$(p$-$n) system, due to the large inter-particle distances in Pb$-$Pb collisions at the LHC. Indeed, in this study, the minimum measured femtoscopic source sizes for protons and deuterons have a minimum value at $2.73^{+0.05}_{-0.05}$ and $3.10^{+1.04}_{-0.86}$ fm, respectively, for the 30$-$50$\%$ centrality collisions. Moreover, the $m_{\rm{T}}$-scaling obtained for the p$-$p and p$-$d systems is compatible within 1$\sigma$ of the uncertainties. These findings provide new input for fundamental studies on the production of light (anti)nuclei under extreme conditions.

23 data tables

proton-proton (same charge) correlation function for centrality 0-10% from Pb-Pb collisions at 5020 GeV

proton-proton (same charge) correlation function for centrality 10-30% from Pb-Pb collisions at 5020 GeV

proton-proton (same charge) correlation function for centrality 30-50% from Pb-Pb collisions at 5020 GeV

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First measurement of D$^{*+}$ vector spin alignment in Pb-Pb collisions at $\mathbf{\sqrt{s_{\rm NN}} = 5.02}$ TeV

The ALICE collaboration Acharya, Shreyasi ; Agarwal, Apar ; Aglieri Rinella, Gianluca ; et al.
JHEP 10 (2025) 094, 2025.
Inspire Record 2906994 DOI 10.17182/hepdata.165763

The first measurement of prompt D$^{*+}$-meson spin alignment in ultrarelativistic heavy-ion collisions with respect to the direction orthogonal to the reaction plane is presented. The spin alignment is quantified by measuring the element $\rho_{00}$ of the diagonal spin-density matrix for prompt D$^{*+}$ mesons with $4<p_{\rm T}<30$ GeV/$c$ in two rapidity intervals, $|y|<0.3$ and $0.3<|y|<0.8$, in central (0-10%) and midcentral (30-50%) Pb-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV. Evidence of spin alignment $\rho_{00}>1/3$ has been found for $p_{\rm T}>15$ GeV/$c$ and $0.3<|y|<0.8$ with a significance of $3.1\sigma$. The measured spin alignment of prompt D$^{*+}$ mesons is compared with the one of inclusive J/$\psi$ mesons measured at forward rapidity ($2.5 < y < 4$).

3 data tables

$\rho_{00}$ of prompt D$^{*\pm}$ mesons as a function of transverse momentum ($p_{\rm T}$) in the rapidity interval $0.0 < |y| < 0.3$ for mid-central (30--50\%) Pb--Pb collisions at $\sqrt{s_{\rm NN}}=5.02~TeV$.

$\rho_{00}$ of prompt D$^{*\pm}$ mesons as a function of transverse momentum ($p_{\rm T}$) in the rapidity interval $0.3 < |y| < 0.8$ for mid-central (30--50\%) Pb--Pb collisions at $\sqrt{s_{\rm NN}}=5.02~TeV$.

$\rho_{00}$ of prompt D$^{*\pm}$ mesons as a function of transverse momentum ($p_{\rm T}$) in the rapidity interval $0.0 < |y| < 0.3$ for central (0--10\%) Pb--Pb collisions at $\sqrt{s_{\rm NN}}=5.02~TeV$.


Multiplicity-dependent inclusive J/$\psi$ production at forward rapidity in pp collisions at $\mathbf{\sqrt{s} = 13}$ TeV

The ALICE collaboration Acharya, Shreyasi ; Agarwal, Apar ; Aglieri Rinella, Gianluca ; et al.
JHEP 07 (2025) 238, 2025.
Inspire Record 2906995 DOI 10.17182/hepdata.159409

This paper presents a study of the inclusive forward J/$\psi$ yield as a function of forward charged-particle multiplicity in pp collisions at $\sqrt{s} = 13$ TeV using data collected by the ALICE experiment at the CERN LHC. The results are presented in terms of relative J/$\psi$ yields and relative charged-particle multiplicities with respect to these quantities obtained in inelastic collisions having at least one charged particle in the pseudorapidity range $|\eta| < 1$. The J/$\psi$ mesons are reconstructed via their decay into $\mu^+ \mu^-$ pairs in the forward rapidity region ($2.5 < y < 4$). The relative multiplicity is estimated in the forward pseudorapidity range $-3.7 < \eta < -1.7$, which overlaps with the J/$\psi$ rapidity region. The results show a steeper-than-linear increase of the J/$\psi$ yields versus the multiplicity. They are compared with previous measurements and theoretical model calculations.

1 data table

Forward inclusive J/$\psi$ relative yield as a function of the relative multiplicity in −3.7 < $\eta$ < −1.7 in INEL > 0 pp collisions at $\sqrt{s}$ = 13 TeV.


Measurement of correlations among net-charge, net-proton, and net-kaon multiplicity distributions in Pb-Pb collisions at $\sqrt{s_\text{NN}}=5.02$ TeV

The ALICE collaboration Acharya, Shreyasi ; Agarwal, Apar ; Aglieri Rinella, Gianluca ; et al.
JHEP 08 (2025) 210, 2025.
Inspire Record 2903549 DOI 10.17182/hepdata.160697

Correlations among conserved quantum numbers, such as the net-electric charge, the net-baryon, and the net-strangeness in heavy-ion collisions, are crucial for exploring the QCD phase diagram. In this letter, these correlations are investigated using net-proton number (as a proxy for the net-baryon), net-kaon number (for the net-strangeness), and net-charged particle number in Pb-Pb collisions at $\sqrt{s_\text{NN}}=5.02$ TeV with the ALICE detector. The observed correlations deviate from the Poissonian baseline, with a more pronounced deviation at LHC energies than at RHIC. Theoretical calculations of the Thermal-FIST hadron resonance gas model, HIJING, and EPOS LHC event generators are compared with experimental results, where a significant impact of resonance decays is observed. Thermal-FIST calculations under the grand canonical and canonical ensembles highlight significant differences, underscoring the role of local charge conservation in explaining the data. Recent lattice QCD studies have demonstrated that the magnetic field generated by spectator protons in heavy-ion collisions affects susceptibility ratios, in particular those related to the net-electric charge and the net-baryon numbers. The experimental findings are in qualitative agreement with the expectations of lattice QCD.

30 data tables

$\kappa^{2}_{\pi}$ as a function of centrality (%) in Pb$-$Pb collisions at $\sqrt{s_\mathrm{NN}}$ = 5.02 TeV for Set 1 $p_\mathrm{T}$ acceptance.

$\kappa^{2}_{\pi}$ as a function of centrality (%) in Pb$-$Pb collisions at $\sqrt{s_\mathrm{NN}}$ = 5.02 TeV for Set 2 $p_\mathrm{T}$ acceptance.

$\kappa^{2}_\mathrm{K}$ as a function of centrality (%) in Pb$-$Pb collisions at $\sqrt{s_\mathrm{NN}}$ = 5.02 TeV for Set 1 $p_\mathrm{T}$ acceptance.

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Measurement of $\omega$ meson production in pp and p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV

The ALICE collaboration Acharya, Shreyasi ; Agarwal, Apar ; Aglieri Rinella, Gianluca ; et al.
Phys.Rev.C 112 (2025) 044904, 2025.
Inspire Record 2895572 DOI 10.17182/hepdata.165463

We present the measurement of the $p_{\rm T}$-differential production cross section of $\omega$ mesons in pp and p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV at midrapidity by ALICE. In addition, the first measurement of the nuclear modification factor $R_{\rm{pPb}}$ for $\omega$ mesons at LHC energies is presented, complementing the existing measurements of lighter neutral mesons such as the $\pi^0$ and $\eta$. Within the measured $p_{\rm T}$-range, the $R_{\rm{pPb}}$ of $\omega$ mesons shows no cold nuclear matter effects within the uncertainties, consistent with previous measurements at lower energies. The $\omega/\pi^0$ ratio is presented for both collision systems, showing no collision system dependence within the uncertainties. The comparison to previously published $\omega/\pi^0$ ratios at lower and higher collision energies in pp collisions suggests a decreasing trend of the ratio above $p_{\rm T} = 4$ GeV/$c$ with increasing collision energy. The data in both collision systems are compared to predictions from PYTHIA 8, EPOS LHC and DPMJET event generators, revealing significant shortcomings in these models' ability to describe the production of $\omega$ mesons.

5 data tables

Differential production cross section of $\omega$ mesons in pp collisions at 5.02 TeV. In addition to the edges of the $p_{\rm T}$ intervals, the table shows the corresponding $p_{\rm T}$ position as described in the publication.

Differential production cross section of $\omega$ mesons in p--Pb collisions at 5.02 TeV. In addition to the edges of the $p_{\rm T}$ intervals, the table shows the corresponding $p_{\rm T}$ position as described in the publication.

Production ratio of $\omega$ to $\pi^{0}$ mesons in pp collisions at 5.02 TeV.

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Investigating the p-$\pi^{\pm}$ and p-p-$\pi^{\pm}$ dynamics with femtoscopy in pp collisions at $\sqrt{s} = 13$ TeV

The ALICE collaboration Acharya, Shreyasi ; Agarwal, Apar ; Aglieri Rinella, Gianluca ; et al.
Eur.Phys.J.A 61 (2025) 194, 2025.
Inspire Record 2895576 DOI 10.17182/hepdata.159769

The interaction between pions and nucleons plays a crucial role in hadron physics. It represents a fundamental building block of the low-energy QCD dynamics and is subject to several resonance excitations. This work studies the p-$\pi^{\pm}$ dynamics using femtoscopic correlations in high-multiplicity pp collisions at $\sqrt{s} = 13$ TeV measured by ALICE at the LHC. As the final-state interaction between protons and pions is well constrained by scattering experiments and the study of pionic hydrogen, the results give access to information on the particle-emitting source in pp collisions using the femtoscopy methods. The scaling of the source size of primordial protons and pions against their pair transverse mass is extracted. The results are compared with the source sizes studied with p-p, p-K$^+$, and $\pi^{\pm}$-$\pi^{\pm}$ pairs by ALICE in the same collision system and are found to be in agreement for the different particle pairs. This reinforces recent findings by ALICE of a common emission source for all hadron-pairs in pp collisions at LHC energies. Furthermore, the p-p-$\pi^{\pm}$ systems are studied using three-particle femtoscopy in pp collisions at $\sqrt{s} = 13$ TeV. The presence of three-body effects is analyzed utilizing the cumulant expansion method. In this formalism, the known two-body interactions are subtracted in order to isolate the three-body effects. For both, p-p-$\pi^{+}$ and p-p-$\pi^{-}$, a non-zero cumulant is found, indicating effects beyond pairwise interactions. These results give information on the coupling of the pion to multiple nucleons.

52 data tables

p-$\pi^{+}$ + antip-$\pi^{-}$ correlation function in high-multiplicity (0-0.17%) pp collisions at $\sqrt{s}=13$ TeV for $m_\text{T} \in [0.54, 0.75)$ GeV/$c^2$

p-$\pi^{+}$ + antip-$\pi^{-}$ correlation function in high-multiplicity (0-0.17%) pp collisions at $\sqrt{s}=13$ TeV for $m_\text{T} \in [0.75, 0.95)$ GeV/$c^2$

p-$\pi^{+}$ + antip-$\pi^{-}$ correlation function in high-multiplicity (0-0.17%) pp collisions at $\sqrt{s}=13$ TeV for $m_\text{T} \in [0.95, 1.20)$ GeV/$c^2$

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Charged-particle multiplicity distributions over a wide pseudorapidity range in p-Pb collisions at $\mathbf{\sqrt{s}_{NN} = 5.02}$ TeV

The ALICE collaboration Acharya, Shreyasi ; Agarwal, Apar ; Aglieri Rinella, Gianluca ; et al.
Eur.Phys.J.C 85 (2025) 919, 2025.
Inspire Record 2895567 DOI 10.17182/hepdata.160246

This paper presents the primary charged-particle multiplicity distributions in proton-lead collisions at a centre-of-mass energy per nucleon-nucleon collision of $\sqrt{s_{\rm NN}} = 5.02$ TeV. The distributions are reported for non-single diffractive collisions in different pseudorapidity ranges. The measurements are performed using the combined information from the Silicon Pixel Detector and the Forward Multiplicity Detector of ALICE. The multiplicity distributions are parametrised with a double negative binomial distribution function which provides satisfactory descriptions of the distributions for all the studied pseudorapidity intervals. The data are compared to models and analysed quantitatively, evaluating the first four moments (mean, standard deviation, skewness, and kurtosis). The shape evolution of the measured multiplicity distributions is studied in terms of KNO variables and it is found that none of the considered models reproduces the measurements. This paper also reports on the average charged-particle multiplicity, normalised by the average number of participating nucleon pairs, as a function of the collision energy. The multiplicity results are then compared to measurements made in proton-proton and nucleus-nucleus collisions across a wide range of collision energies.

10 data tables

Charged-particle multiplicity distributions for different pseudorapidity intervals measured in NSD p-Pb collisions at $\sqrt{s_\mathrm{NN}} = 5020~\mathrm{GeV}$.

The pseudorapidity dependence of the double NBD parameters $\langle n \rangle_1$, $\langle n \rangle_2$, $k_1$, and $k_2$ in NSD p-Pb collisions at $\sqrt{s_\mathrm{NN}} = 5020~\mathrm{GeV}$.

First four moments ($\langle N_{\mathrm{ch}}\rangle$, $\sigma$, $S$, and $\kappa$) of charged-particle multiplicity distributions for different pseudorapidity intervals in NSD p-Pb collisions at $\sqrt{s_\mathrm{NN}} = 5020~\mathrm{GeV}$.

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First measurement of symmetric cumulants of hexagonal flow harmonics in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV

The ALICE collaboration Acharya, Shreyasi ; Agarwal, Apar ; Aglieri Rinella, Gianluca ; et al.
Phys.Rev.C 112 (2025) 024905, 2025.
Inspire Record 2865181 DOI 10.17182/hepdata.159493

Correlations between event-by-event fluctuations of anisotropic flow harmonics are measured in Pb-Pb collisions at a center-of-mass energy per nucleon pair of 5.02 TeV, as recorded by the ALICE detector at the LHC. This study presents correlations up to the hexagonal flow harmonic, $v_6$, which was measured for the first time. The magnitudes of these higher-order correlations are found to vary as a function of collision centrality and harmonic order. These measurements are compared to viscous hydrodynamic model calculations with EKRT initial conditions and to the iEBE-VISHNU model with TRENTo initial conditions. The observed discrepancies between the data and the model calculations vary depending on the harmonic combinations. Due to the sensitivity of model parameters estimated with Bayesian analyses to these higher-order observables, the results presented in this work provide new and independent constraints on the initial conditions and transport properties in theoretical models used to describe the system created in heavy-ion collisions.

5 data tables

NSC(5,2) vs centrality in Pb-Pb collisions at 5.02 TeV

NSC(5,3) vs centrality in Pb-Pb collisions at 5.02 TeV

NSC(6,2) vs centrality in Pb-Pb collisions at 5.02 TeV

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