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  1. The first measurements of proton emission accompanied by neutron emission in the electromagnetic dissociation (EMD) of Pb 208 nuclei in the ALICE experiment at the Large Hadron Collider are presented. The EMD protons and neutrons emitted at very forward rapidities are detected by the proton and neutron zero degree calorimeters of the ALICE experiment. The emission cross sections of zero, one, two, and three protons accompanied by at least one neutron were measured in ultraperipheral Pb 208 Pb 208 collisions at a center-of-mass energy per nucleon pair s N N = 5.02 TeV . The 0p and 3p cross sections are described by the RELDIS model within their measurement uncertainties, while the 1p and 2p cross sections are underestimated by the model by 17–25%. According to this model, these 0p, 1p, 2p, and 3p cross sections are associated, respectively, with the production of various isotopes of Pb, Tl, Hg, and Au in the EMD of Pb 208 . The cross sections of the emission of a single proton accompanied by the emission of one, two, or three neutrons in EMD were also measured. The data are significantly overestimated by the RELDIS model, which predicts that the (1p,1n), (1p,2n), and (1p,3n) cross sections are very similar to the cross sections for the production of the thallium isotopes Tl 206 , 205 , 204 . ©2025 CERN, for the ALICE Collaboration2025CERN 
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    Free, publicly-accessible full text available May 1, 2026
  2. Abstract The ALICE Collaboration at the CERN LHC has measured the inclusive production cross section of isolated photons at midrapidity as a function of the photon transverse momentum ($$p_{\textrm{T}}^{\gamma }$$ p T γ ), in Pb–Pb collisions in different centrality intervals, and in pp collisions, at centre-of-momentum energy per nucleon pair of$$\sqrt{s_{\textrm{NN}}}~=~5.02$$ s NN = 5.02  TeV. The photon transverse momentum range is between 10–14 and 40–140 GeV/$$c$$ c , depending on the collision system and on the Pb–Pb centrality class. The result extends to lower$$p_{\textrm{T}}^{\gamma }$$ p T γ than previously published results by the ATLAS and CMS experiments at the same collision energy. The covered pseudorapidity range is$$|\eta ^{\gamma } | <0.67$$ | η γ | < 0.67 . The isolation selection is based on a charged particle isolation momentum threshold$$p_{\textrm{T}}^\mathrm{iso,~ch} = 1.5$$ p T iso , ch = 1.5  GeV/$$c$$ c within a cone of radii$$R=0.2$$ R = 0.2 and 0.4. The nuclear modification factor is calculated and found to be consistent with unity in all centrality classes, and also consistent with the HG-PYTHIA model, which describes the event selection and geometry biases that affect the centrality determination in peripheral Pb–Pb collisions. The measurement is compared to next-to-leading order perturbative QCD calculations and to the measurements of isolated photons and Z$$^{0}$$ 0 bosons from the CMS experiment, which are all found to be in agreement. 
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    Free, publicly-accessible full text available May 1, 2026
  3. In this Letter, the first evidence of the He ¯ Λ ¯ 4 antihypernucleus is presented, along with the first measurement at the LHC of the production of (anti)hypernuclei with mass number A = 4 , specifically ( anti ) H Λ 4 and ( anti ) He Λ 4 . In addition, the antiparticle-to-particle ratios for both hypernuclei ( H ¯ Λ ¯ 4 / H Λ 4 and He ¯ Λ ¯ 4 / He Λ 4 ) are shown, which are sensitive to the baryochemical potential of the strongly interacting matter created in heavy-ion collisions. The results are obtained from a data sample of central Pb-Pb collisions, collected during the 2018 LHC data taking at a center-of-mass energy per nucleon pair of s NN = 5.02 TeV . The yields measured for the average of the charge-conjugated states are found to be [ 0.78 ± 0.19 ( stat ) ± 0.17 ( syst ) ] × 10 6 for the ( anti ) H Λ 4 and [ 1.08 ± 0.34 ( stat ) ± 0.20 ( syst ) ] × 10 6 for the ( anti ) He Λ 4 , and the measured antiparticle-to-particle ratios are in agreement with unity. The presence of ( anti ) H Λ 4 and ( anti ) He Λ 4 excited states is expected to strongly enhance the production yield of these hypernuclei. The yield values exhibit a combined deviation of 3.3 σ from the theoretical ground-state-only expectation, while the inclusion of the excited states in the calculations leads to an agreement within 0.6 σ with the present measurements. Additionally, the measured ( anti ) H Λ 4 and ( anti ) He Λ 4 masses are compatible with the world-average values within the uncertainties. © 2025 CERN, for the ALICE Collaboration2025CERN 
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    Free, publicly-accessible full text available April 1, 2026
  4. A<sc>bstract</sc> Short-range correlations between charged particles are studied via two-particle angular correlations in pp collisions at$$ \sqrt{s} $$ s = 13 TeV. The correlation functions are measured as a function of the relative azimuthal angle ∆φand the pseudorapidity separation ∆ηfor pairs of primary charged particles within the pseudorapidity interval |η|<0.9 and the transverse-momentum range 1< pT<8 GeV/c. Near-side (|∆φ|<1.3) peak widths are extracted from a generalised Gaussian fitted over the correlations in full pseudorapidity separation (|∆η|<1.8), while the per-trigger associated near-side yields are extracted for the short-range correlations (|∆η|<1.3). Both are evaluated as a function of charged-particle multiplicity obtained by two different event activity estimators. The width of the near-side peak decreases with increasing multiplicity, and this trend is reproduced qualitatively by the Monte Carlo event generators PYTHIA 8, AMPT, and EPOS. However, the models overestimate the width in the low transverse-momentum region (pT<3 GeV/c). The per-trigger associated near-side yield increases with increasing multiplicity. Although this trend is also captured qualitatively by the considered event generators, the yield is mostly overestimated by the models in the considered kinematic range. The measurement of the shape and yield of the short-range correlation peak can help us understand the interplay between jet fragmentation and event activity, quantify the narrowing trend of the near-side peak as a function of transverse momentum and multiplicity selections in pp collisions, and search for final-state jet modification in small collision systems. 
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    Free, publicly-accessible full text available March 1, 2026
  5. A<sc>bstract</sc> The production of (multi-)strange hadrons is measured at midrapidity in proton-proton collisions at$$ \sqrt{s} $$ s = 13 TeV as a function of the local charged-particle multiplicity in the pseudorapidity interval |η|<0.5 and of the very-forward energy measured by the ALICE Zero-Degree Calorimeters. The latter provides information on the effective energy, i.e. the energy available for particle production in the collision once subtracted from the centre-of-mass energy. The yields of$$ {\textrm{K}}_{\textrm{S}}^0 $$ K S 0 ,$$ \Lambda +\overline{\Lambda} $$ Λ + Λ ¯ , and$$ {\Xi}^{-}+{\overline{\Xi}}^{+} $$ Ξ + Ξ ¯ + per charged-particle increase with the effective energy. In addition, this work exploits a multi-differential approach to decouple the roles of local multiplicity and effective energy in such an enhancement. The results presented in this article provide new insights into the interplay between global properties of the collision, such as the initial available energy in the event, and the locally produced final hadronic state, connected to the charged-particle multiplicity at midrapidity. Notably, a strong increase of strange baryon production with effective energy is observed for fixed charged-particle multiplicity at midrapidity. These results are discussed within the context of existing phenomenological models of hadronisation implemented in different tunes of the PYTHIA 8 event generator. 
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    Free, publicly-accessible full text available March 1, 2026
  6. This paper reports the first measurement of the transverse momentum ( p T ) spectra of primary charged pions, kaons, (anti)protons, and unidentified particles as a function of the charged-particle flattenicity in pp collisions at s = 13 TeV . Flattenicity is a novel event shape observable that is measured in the pseudorapidity intervals covered by the V0 detector, 2.8 < η < 5.1 and 3.7 < η < 1.7 . According to QCD-inspired phenomenological models, it shows sensitivity to multiparton interactions and is less affected by biases toward larger p T due to local multiplicity fluctuations in the V0 acceptance than multiplicity. The analysis is performed in minimum-bias (MB) as well as in high-multiplicity events up to p T = 20 GeV / c . The event selection requires at least one charged particle produced in the pseudorapidity interval | η | < 1 . The measured p T distributions, average p T , kaon-to-pion and proton-to-pion particle ratios, presented in this paper, are compared to model calculations using 8 based on color strings and EPOS LHC. The modification of the p T -spectral shapes in low-flattenicity events that have large event activity with respect to those measured in MB events develops a pronounced peak at intermediate p T ( 2 < p T < 8 GeV / c ), and approaches the vicinity of unity at higher p T . The results are qualitatively described by , and they show different behavior than those measured as a function of charged-particle multiplicity based on the V0M estimator. © 2025 CERN, for the ALICE Collaboration2025CERN 
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    Free, publicly-accessible full text available January 1, 2026
  7. This Letter presents the first measurement of event-by-event fluctuations of the net number (difference between the particle and antiparticle multiplicities) of multistrange hadrons Ξ and Ξ ¯ + and its correlation with the net-kaon number using the data collected by the ALICE Collaboration in pp, p-Pb, and Pb-Pb collisions at a center-of-mass energy per nucleon pair s NN = 5.02 TeV . The statistical hadronization model with a correlation over three units of rapidity between hadrons having the same and opposite strangeness content successfully describes the results. On the other hand, string-fragmentation models that mainly correlate strange hadrons with opposite strange quark content over a small rapidity range fail to describe the data. © 2025 CERN, for the ALICE Collaboration2025CERN 
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    Free, publicly-accessible full text available January 1, 2026
  8. Abstract The production cross section of inclusive isolated photons has been measured by the ALICE experiment at the CERN LHC in pp collisions at centre-of-momentum energy of$$\sqrt{s} =13$$ s = 13  TeV collected during the LHC Run 2 data-taking period. The measurement is performed by combining the measurements of the electromagnetic calorimeter EMCal and the central tracking detectors ITS and TPC, covering a pseudorapidity range of$$|\eta ^{\gamma }|<0.67$$ | η γ | < 0.67 and a transverse momentum range of$$7 7 < p T γ < 200 GeV/$$c$$ c . The result extends to lower$$p_\textrm{T}^{\gamma }$$ p T γ and$$x_\textrm{T}^{\gamma } = 2p_\textrm{T}^{\gamma }/\sqrt{s} $$ x T γ = 2 p T γ / s ranges, the lowest$$x_\textrm{T}^{\gamma }$$ x T γ of any isolated photon measurements to date, extending significantly those measured by the ATLAS and CMS experiments towards lower$$p_\textrm{T}^{\gamma }$$ p T γ at the same collision energy with a small overlap between the measurements. The measurement is compared with next-to-leading order perturbative QCD calculations and the results from the ATLAS and CMS experiments as well as with measurements at other collision energies. The measurement and theory prediction are in agreement with each other within the experimental and theoretical uncertainties. 
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    Free, publicly-accessible full text available January 1, 2026
  9. Abstract The total charm-quark production cross section per unit of rapidity$$\textrm{d}\sigma ({{\textrm{c}}\overline{\textrm{c}}})/\textrm{d}y$$ d σ ( c c ¯ ) / d y , and the fragmentation fractions of charm quarks to different charm-hadron species$$f(\textrm{c}\rightarrow {\textrm{h}}_{\textrm{c}})$$ f ( c h c ) , are measured for the first time in p–Pb collisions at$$\sqrt{s_\textrm{NN}} = 5.02~\text {Te}\hspace{-1.00006pt}\textrm{V} $$ s NN = 5.02 Te V at midrapidity ($$-0.96<0.04$$ - 0.96 < y < 0.04 in the centre-of-mass frame) using data collected by ALICE at the CERN LHC. The results are obtained based on all the available measurements of prompt production of ground-state charm-hadron species:$$\textrm{D}^{0}$$ D 0 ,$$\textrm{D}^{+}$$ D + ,$$\textrm{D}_\textrm{s}^{+}$$ D s + , and$$\mathrm {J/\psi }$$ J / ψ mesons, and$$\Lambda _\textrm{c}^{+}$$ Λ c + and$$\Xi _\textrm{c}^{0}$$ Ξ c 0 baryons. The resulting cross section is$$ \textrm{d}\sigma ({{\textrm{c}}\overline{\textrm{c}}})/\textrm{d}y =219.6 \pm 6.3\;(\mathrm {stat.}) {\;}_{-11.8}^{+10.5}\;(\mathrm {syst.}) {\;}_{-2.9}^{+8.3}\;(\mathrm {extr.})\pm 5.4\;(\textrm{BR})\pm 4.6\;(\mathrm {lumi.}) \pm 19.5\;(\text {rapidity shape})+15.0\;(\Omega _\textrm{c}^{0})\;\textrm{mb} $$ d σ ( c c ¯ ) / d y = 219.6 ± 6.3 ( stat . ) - 11.8 + 10.5 ( syst . ) - 2.9 + 8.3 ( extr . ) ± 5.4 ( BR ) ± 4.6 ( lumi . ) ± 19.5 ( rapidity shape ) + 15.0 ( Ω c 0 ) mb , which is consistent with a binary scaling of pQCD calculations from pp collisions. The measured fragmentation fractions are compatible with those measured in pp collisions at$$\sqrt{s} = 5.02$$ s = 5.02 and 13 TeV, showing an increase in the relative production rates of charm baryons with respect to charm mesons in pp and p–Pb collisions compared with$$\mathrm {e^{+}e^{-}}$$ e + e - and$$\mathrm {e^{-}p}$$ e - p collisions. The$$p_\textrm{T}$$ p T -integrated nuclear modification factor of charm quarks,$$R_\textrm{pPb}({\textrm{c}}\overline{\textrm{c}})= 0.91 \pm 0.04\;\mathrm{(stat.)} ^{+0.08}_{-0.09}\;\mathrm{(syst.)} ^{+0.05}_{-0.03}\;\mathrm{(extr.)} \pm 0.03\;\mathrm{(lumi.)}$$ R pPb ( c c ¯ ) = 0.91 ± 0.04 ( stat . ) - 0.09 + 0.08 ( syst . ) - 0.03 + 0.05 ( extr . ) ± 0.03 ( lumi . ) , is found to be consistent with unity and with theoretical predictions including nuclear modifications of the parton distribution functions. 
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    Free, publicly-accessible full text available December 1, 2025
  10. A<sc>bstract</sc> The production cross sections of D0, D+, and$$ {\Lambda}_{\textrm{c}}^{+} $$ Λ c + hadrons originating from beauty-hadron decays (i.e. non-prompt) were measured for the first time at midrapidity in proton–lead (p–Pb) collisions at the center-of-mass energy per nucleon pair of$$ \sqrt{s_{\textrm{NN}}} $$ s NN = 5.02 TeV. Nuclear modification factors (RpPb) of non-prompt D0, D+, and$$ {\Lambda}_{\textrm{c}}^{+} $$ Λ c + are calculated as a function of the transverse momentum (pT) to investigate the modification of the momentum spectra measured in p–Pb collisions with respect to those measured in proton–proton (pp) collisions at the same energy. TheRpPbmeasurements are compatible with unity and with the measurements in the prompt charm sector, and do not show a significantpTdependence. ThepT-integrated cross sections andpT-integratedRpPbof non-prompt D0and D+mesons are also computed by extrapolating the visible cross sections down topT= 0. The non-prompt D-mesonRpPbintegrated overpTis compatible with unity and with model calculations implementing modification of the parton distribution functions of nucleons bound in nuclei with respect to free nucleons. The non-prompt$$ {\Lambda}_{\textrm{c}}^{+} $$ Λ c + /D0and D+/D0production ratios are computed to investigate hadronisation mechanisms of beauty quarks into mesons and baryons. The measured ratios as a function ofpTdisplay a similar trend to that measured for charm hadrons in the same collision system. 
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    Free, publicly-accessible full text available November 1, 2025