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Abstract Two-particle angular correlations probe particle production mechanisms and the underlying event-wide phenomena present in hadronic collisions. The correlations are examined as a function of rapidity and azimuthal-angle differences ($$\Delta y, \Delta \varphi $$ $\Delta y,\Delta \phi$) for pairs of like- and unlike-sign pions, kaons, and (anti-)protons produced in pp collisions at$$\sqrt{s}$$ $\sqrt{s}$= 13 TeV, measured by the ALICE experiment. Two-particle correlation functions are provided together with$$\Delta y$$ $\Delta y$and$$\Delta \varphi $$ $\Delta \phi$projections and compared to Monte Carlo (MC) model predictions. For the first time, the measurement is performed as a function of the event’s charged-particle density. Previous studies conducted for pp collisions at$$\sqrt{s}$$ $\sqrt{s}$= 7 TeV at ALICE revealed a near-side anticorrelation for baryon–baryon and antibaryon–antibaryon pairs, whose origin remains unresolved. Here, an additional approach is introduced to study the multiplicity dependence and the expected inverse multiplicity scaling of the correlation function. This method highlights qualitative differences in the underlying sources of correlations, such as quantum-statistics effects, final-state interactions, and resonance decays. The puzzling near-side anticorrelation in baryon baryon measurements is observed across all multiplicity classes and continues to challenge current particle-production models. Furthermore, the multiplicity dependence of the correlations between mesons provides an independent probe of the sensitivity of current MC models to soft-QCD effects and hadronization dynamics. The presented measurements, together with the baryon results, enrich the experimental picture of two-particle correlations in pp collisions and serve as valuable input for ongoing theoretical developments. 

A<sc>bstract</sc> The probability to observe a specific number of strange and multi-strange hadrons (n_S), denoted as P(n_S), is measured by ALICE at midrapidity (|y|<0.5) in$$\sqrt{s}=5.02$$TeV proton-proton (pp) collisions, dividing events into several multiplicity-density classes. Exploiting, for the first time, a technique based on counting the number of strange-particle candidates event-by-event, this measurement allows one to extend the study of strangeness production beyond the mean of the distribution. This constitutes a new test bench for production mechanisms, probing events with a large imbalance between strange and non-strange content. The analysis of a large-statistics data sample makes it possible to extract P(n_S) up to a maximumn_Sof 7 for$${\text{K}}_{\text{S}}^{0}$$, 5 for Λ and$$\overline{\Lambda }$$, 4 for Ξ⁻and$${\overline{\Xi } }^{+}$$, and 2 for Ω⁻and$${\overline{\Omega } }^{+}$$. From this, the probability of producing strange hadron multiplets per event is calculated, thereby enabling the extension of the study of strangeness enhancement to extreme situations where several strange quarks hadronize in a single event at midrapidity. Moreover, comparing hadron combinations with differentuanddquark compositions and equal overallsquark content, the contribution to the enhancement pattern coming from non-strangeness related mechanisms is isolated. The results are compared with state-of-the-art phenomenological models implemented in commonly used Monte Carlo event generators, including PYTHIA 8 Monash 2013, PYTHIA 8 with QCD-based Color Reconnection and Rope Hadronization (QCD-CR + Ropes), and EPOS LHC, which incorporates both partonic interactions and hydrodynamic evolution. These comparisons show that the new approach dramatically enhances the sensitivity to the different underlying physics mechanisms modeled by each generator. 

Abstract The azimuthal-correlation distributions between electrons from the decays of heavy-flavor hadrons and associated charged particles in Pb–Pb collisions at$$\sqrt{s_{\textrm{NN}}} = 5.02$$ $\sqrt{s_{\text{NN}}}=5.02$TeV are reported for the 0–10% and 30–50% centrality classes. This measurement provides access to the jet-like correlation observables in the heavy-flavor sector in Pb–Pb collisions. The analysis is performed for trigger electrons from heavy-flavor hadron decays with transverse momentum$$4< p_\textrm{T}^\textrm{e} < 16~\textrm{GeV}/c$$ $4<p_{\text{T}}^{\text{e}}<16\text{GeV}/c$, considering associated particles within the transverse-momentum range$$1< p_\textrm{T}^\textrm{assoc} < 7$$ $1<p_{\text{T}}^{\text{assoc}}<7$$$\textrm{GeV}/c$$ $\text{GeV}/c$, and a pseudorapidity difference of$$|\Delta \eta |<1$$ $\left|\Delta \eta \right|<1$between the trigger electron and associated particles. The per-trigger nuclear modification factor ($$I_\textrm{AA}$$ $I_{\text{AA}}$) is calculated to compare the near- and away-side peak yields to those in pp collisions at$$\sqrt{s} = 5.02$$ $\sqrt{s}=5.02$TeV. In 0–10% central collisions, the$$I_\textrm{AA}$$ $I_{\text{AA}}$indicates a hint of enhancement of associated-particle yields with$$p_\textrm{T}<3$$ $p_{\text{T}}<3$GeV/con the near side, and a suppression of yields with$$p_\textrm{T}>4$$ $p_{\text{T}}>4$GeV/con the away side. The$$I_\textrm{AA}$$ $I_{\text{AA}}$for electron triggers from heavy-flavor hadron decays is compared with that for light-flavor and strange-particle triggers to investigate the dependence on different fragmentation processes and parton-medium dynamics, and is found to be the same within uncertainties. 

Abstract The transverse momentum spectra and integrated yields of anti-$$\Sigma $$ $\Sigma$hyperons ($$\overline{\Sigma }^{\pm } $$ ${\overline{\Sigma }}^{\pm }$) have been measured in$$\text {pp}$$ $\text{pp}$and$$\text {p}{-}\text {Pb}$$ $\text{p}-\text{Pb}$collisions at$$\sqrt{s_{\textrm{NN}}}=5.02$$ $\sqrt{s_{\text{NN}}}=5.02$TeV with the ALICE experiment. Measurements are performed via the newly accessed decay channel$$\overline{\Sigma }^{\pm } \!\!\rightarrow \mathrm{\overline{n}} \pi ^{\pm }$$ ${\overline{\Sigma }}^{\pm }\to \overline{n}{\pi }^{\pm }$. A new method of antineutron reconstruction with the PHOS electromagnetic spectrometer is developed and applied to this analysis. The$$p_{\textrm{T}}$$ $p_{\text{T}}$spectra of$$\overline{\Sigma }^{\pm } $$ ${\overline{\Sigma }}^{\pm }$are measured in the range$$0.5<3$$ $0.5<p_{\text{T}}<3$GeV/$$c$$ $c$and compared to predictions of the PYTHIA 8, DPMJET, PHOJET, EPOS LHC and EPOS4 models. The EPOS LHC and EPOS4 models provide the best descriptions of the measured spectra both in$$\text {pp}$$ $\text{pp}$and$$\text {p}{-}\text {Pb}$$ $\text{p}-\text{Pb}$collisions, while models which do not account for multiparton interactions provide a considerably worse description at high$$p_{\textrm{T}}$$ $p_{\text{T}}$. The total yields of$$\overline{\Sigma }^{\pm } $$ ${\overline{\Sigma }}^{\pm }$in both$$\text {pp}$$ $\text{pp}$and$$\text {p}{-}\text {Pb}$$ $\text{p}-\text{Pb}$collisions are compared to predictions of the Thermal-FIST model and dynamical models PYTHIA 8, DPMJET, PHOJET, EPOS LHC and EPOS4. All models reproduce the total yields in both colliding systems within uncertainties. The nuclear modification factors$$R_\textrm{pPb}$$ $R_{\text{pPb}}$for both$$\overline{\Sigma }^{+} $$ ${\overline{\Sigma }}^{+}$and$$\overline{\Sigma }^{-} $$ ${\overline{\Sigma }}^{-}$are evaluated and compared to those of protons,$$\Lambda $$ $\Lambda$and$$\Xi $$ $\Xi$hyperons, and predictions of EPOS LHC and EPOS4 models. No deviations of$$R_\textrm{pPb}$$ $R_{\text{pPb}}$for$$\overline{\Sigma }^{\pm } $$ ${\overline{\Sigma }}^{\pm }$from the model predictions or measurements for other hadrons are found within uncertainties. 

Abstract The measurement of$$\Sigma ^{+}$$ ${\Sigma }^{+}$production in pp collisions at$$\sqrt{s}=13$$ $\sqrt{s}=13$ TeV is presented. The measurement is performed at midrapidity in both minimum-bias and high-multiplicity pp collisions at$$\sqrt{s} =13$$ $\sqrt{s}=13$ TeV. The$$\Sigma ^{+}$$ ${\Sigma }^{+}$is reconstructed via its weak-decay topology in the decay channel$$\Sigma ^{+} \rightarrow \mathrm{{p}} + \pi ^{0}$$ ${\Sigma }^{+}\to p+{\pi }^0$with$$\pi ^{0} \rightarrow \gamma + \gamma .$$ ${\pi }^0\to \gamma +\gamma .$In a novel approach, the neutral pion is reconstructed by combining photons that convert in the detector material with photons measured in the calorimeters. The transverse-momentum$$(p_{\textrm{T}})$$ $\left(p_{\text{T}}\right)$distributions of the$$\Sigma ^{+}$$ ${\Sigma }^{+}$and its rapidity densities$${\textrm{d}}N$$ $\text{d}N$/$${\textrm{d}}y$$ $\text{d}y$in both event classes are reported. The$$p_{\textrm{T}}$$ $p_{\text{T}}$spectrum in minimum-bias collisions is compared to QCD-inspired event generators. The ratio of$$\Sigma ^{+}$$ ${\Sigma }^{+}$to previously measured$$\Lambda $$ $\Lambda$baryons is in good agreement with calculations from the Statistical Hadronization Model. The high efficiency and purity of the novel reconstruction method for$$\Sigma ^{+}$$ ${\Sigma }^{+}$presented here will enable future studies of the interaction of$$\Sigma ^{+}$$ ${\Sigma }^{+}$with protons in the context of femtoscopic measurements, which could be crucial for understanding the equation of state of neutron stars. 

Abstract The dependence of$$\textrm{f}_{0}$$ ${\text{f}}_0$(980) production on the final-state charged-particle multiplicity is reported for proton–proton (pp) collisions at the centre-of-mass energy,$$\sqrt{s}=$$ $\sqrt{s}=$ 13 TeV. The production of$$\textrm{f}_{0}$$ ${\text{f}}_0$(980) is measured with the ALICE detector via the$$\textrm{f}_0 (980) \rightarrow \pi ^{+}\pi ^{-}$$ ${\text{f}}_0\left(980\right)\to {\pi }^{+}{\pi }^{-}$decay channel in a midrapidity region of$$|y|<$$ $\left|y\right|<$ 0.5. The evolution of the integrated yields and mean transverse momentum of f$$_{0}$$ $_0^{}$(980) as a function of charged-particle multiplicity measured in pp at$$\sqrt{s}=$$ $\sqrt{s}=$ 13 TeV follows the trends observed in pp at$$\sqrt{s}=$$ $\sqrt{s}=$ 5.02 TeV and in proton–lead (p–Pb) collisions at$$\sqrt{s_{\textrm{NN}}}=$$ $\sqrt{s_{\text{NN}}}=$ 5.02 TeV. Particle yield ratios of$$\textrm{f}_{0}$$ ${\text{f}}_0$(980) to$$\pi ^{\pm }$$ ${\pi }^{\pm }$and$$\textrm{K}^{*}$$ $\text{K}_{}^{\ast }$(892)$$^{0}$$ $_{}^0$are found to decrease with increasing charged-particle multiplicity. These particle ratios are compared with calculations from the canonical statistical thermal model as a function of charged-particle multiplicity. The thermal model calculations provide a better description of the decreasing trend of particle ratios when no strange or antistrange quark composition for f$$_{0}$$ $_0^{}$(980) is assumed, which suggests that the data do not support significant hidden strangeness in the$$\textrm{f}_{0} (980)$$ ${\text{f}}_0\left(980\right)$.