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The production of the $\psi \left(2S\right)$charmonium state was measured with ALICE in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{TeV}$, in the dimuon decay channel. A significant signal was observed for the first time at LHC energies down to zero transverse momentum, at forward rapidity ( $2.5<y<4$). The measurement of the ratio of the inclusive production cross sections of the $\psi \left(2S\right)$and $\mathrm{J}/\psi$resonances is reported as a function of the centrality of the collisions and of transverse momentum, in the region $p_T<12\mathrm{GeV}/c$. The results are compared with the corresponding measurements in $pp$collisions, by forming the double ratio $[{\sigma }^{\psi \left(2S\right)}/{\sigma }^{J/\psi }{]}_{\mathrm{Pb}\text{−}\mathrm{Pb}}/[{\sigma }^{\psi \left(2S\right)}/{\sigma }^{J/\psi }{]}_{pp}$. It is found that in Pb-Pb collisions the $\psi \left(2S\right)$is suppressed by a factor of $\sim 2$with respect to the $J/\psi$. The $\psi \left(2S\right)$nuclear modification factor $R_{\mathrm{AA}}$was also obtained as a function of both centrality and $p_T$. The results show that the $\psi \left(2S\right)$resonance yield is strongly suppressed in Pb-Pb collisions, by a factor of up to $\sim 3$with respect to $pp$. Comparisons of cross section ratios with previous Super Proton Synchrotron findings by the NA50 experiment and of $R_{\mathrm{AA}}$with higher- $p_T$results at LHC energy are also reported. These results and the corresponding comparisons with calculations of transport and statistical models address questions on the presence and properties of charmonium states in the quark-gluon plasma formed in nuclear collisions at the LHC. © 2024 CERN, for the ALICE Collaboration2024CERN 

A<sc>bstract</sc> Measurements of the production cross sections of prompt D⁰, D⁺, D^*+,$$ {\textrm{D}}_{\textrm{s}}^{+} $$ $D_s^{+}$,$$ {\Lambda}_{\textrm{c}}^{+} $$ ${\Lambda }_c^{+}$, and$$ {\Xi}_{\textrm{c}}^{+} $$ ${\Xi }_c^{+}$charm hadrons at midrapidity in proton-proton collisions at$$ \sqrt{s} $$ $\sqrt{s}$= 13 TeV with the ALICE detector are presented. The D-meson cross sections as a function of transverse momentum (p_T) are provided with improved precision and granularity. The ratios ofp_T-differential meson production cross sections based on this publication and on measurements at different rapidity and collision energy provide a constraint on gluon parton distribution functions at low values of Bjorken-x(10⁻⁵–10⁻⁴). The measurements of$$ {\Lambda}_{\textrm{c}}^{+} $$ ${\Lambda }_c^{+}$($$ {\Xi}_{\textrm{c}}^{+} $$ ${\Xi }_c^{+}$) baryon production extend the measuredp_Tintervals down top_T= 0(3) GeV/c. These measurements are used to determine the charm-quark fragmentation fractions and the$$ \textrm{c}\overline{\textrm{c}} $$ $c\overline{c}$production cross section at midrapidity (|y|<0.5) based on the sum of the cross sections of the weakly-decaying ground-state charm hadrons D⁰, D⁺,$$ {\textrm{D}}_{\textrm{s}}^{+} $$ $D_s^{+}$,$$ {\Lambda}_{\textrm{c}}^{+} $$ ${\Lambda }_c^{+}$,$$ {\Xi}_{\textrm{c}}^0 $$ ${\Xi }_c^0$and, for the first time,$$ {\Xi}_{\textrm{c}}^{+} $$ ${\Xi }_c^{+}$, and of the strongly-decaying J/ψmesons. The first measurements of$$ {\Xi}_{\textrm{c}}^{+} $$ ${\Xi }_c^{+}$and$$ {\Sigma}_{\textrm{c}}^{0,++} $$ ${\Sigma }_c^{0,++}$fragmentation fractions at midrapidity are also reported. A significantly larger fraction of charm quarks hadronising to baryons is found compared to e⁺e⁻and ep collisions. The$$ \textrm{c}\overline{\textrm{c}} $$ $c\overline{c}$production cross section at midrapidity is found to be at the upper bound of state-of-the-art perturbative QCD calculations. 

Abstract The interactions of kaons (K) and antikaons ($$\mathrm {\overline{K}}$$ $\overline{K}$) with few nucleons (N) were studied so far using kaonic atom data and measurements of kaon production and interaction yields in nuclei. Some details of the three-body KNN and$$\mathrm {\overline{K}}$$ $\overline{K}$NN dynamics are still not well understood, mainly due to the overlap with multi-nucleon interactions in nuclei. An alternative method to probe the dynamics of three-body systems with kaons is to study the final state interaction within triplet of particles emitted in pp collisions at the Large Hadron Collider, which are free from effects due to the presence of bound nucleons. This Letter reports the first femtoscopic study of p–p–K$$^+$$ ${}^{+}$and p–p–K$$^-$$ ${}^{-}$correlations measured in high-multiplicity pp collisions at$$\sqrt{s}$$ $\sqrt{s}$= 13 TeV by the ALICE Collaboration. The analysis shows that the measured p–p–K$$^+$$ ${}^{+}$and p–p–K$$^-$$ ${}^{-}$correlation functions can be interpreted in terms of pairwise interactions in the triplets, indicating that the dynamics of such systems is dominated by the two-body interactions without significant contributions from three-body effects or bound states. 

Abstract The elliptic flow$$(v_2)$$ $\left(v_2\right)$of$${\textrm{D}}^{0}$$ ${\text{D}}^0$mesons from beauty-hadron decays (non-prompt$${\textrm{D}}^{0})$$ ${\text{D}}^0)$was measured in midcentral (30–50%) Pb–Pb collisions at a centre-of-mass energy per nucleon pair$$\sqrt{s_{\textrm{NN}}} = 5.02$$ $\sqrt{s_{\text{NN}}}=5.02$ TeV with the ALICE detector at the LHC. The$${\textrm{D}}^{0}$$ ${\text{D}}^0$mesons were reconstructed at midrapidity$$(|y|<0.8)$$ $\left(\right|y|<0.8)$from their hadronic decay$$\mathrm {D^0 \rightarrow K^-\uppi ^+}$$ $D^0\to K^{-}{\pi }^{+}$, in the transverse momentum interval$$2< p_{\textrm{T}} < 12$$ $2<p_{\text{T}}<12$ GeV/c. The result indicates a positive$$v_2$$ $v_2$for non-prompt$${{\textrm{D}}^{0}}$$ ${\text{D}}^0$mesons with a significance of 2.7$$\sigma $$ $\sigma$. The non-prompt$${{\textrm{D}}^{0}}$$ ${\text{D}}^0$-meson$$v_2$$ $v_2$is lower than that of prompt non-strange D mesons with 3.2$$\sigma $$ $\sigma$significance in$$2< p_\textrm{T} < 8~\textrm{GeV}/c$$ $2<p_{\text{T}}<8\text{GeV}/c$, and compatible with the$$v_2$$ $v_2$of beauty-decay electrons. Theoretical calculations of beauty-quark transport in a hydrodynamically expanding medium describe the measurement within uncertainties. 

A<sc>bstract</sc> Correlations in azimuthal angle extending over a long range in pseudorapidity between particles, usually called the “ridge” phenomenon, were discovered in heavy-ion collisions, and later found in pp and p–Pb collisions. In large systems, they are thought to arise from the expansion (collective flow) of the produced particles. Extending these measurements over a wider range in pseudorapidity and final-state particle multiplicity is important to understand better the origin of these long-range correlations in small collision systems. In this Letter, measurements of the long-range correlations in p–Pb collisions at$$ \sqrt{s_{\textrm{NN}}} $$ $\sqrt{s_{\mathrm{NN}}}$= 5.02 TeV are extended to a pseudorapidity gap of ∆η~ 8 between particles using the ALICE forward multiplicity detectors. After suppressing non-flow correlations, e.g., from jet and resonance decays, the ridge structure is observed to persist up to a very large gap of ∆η~ 8 for the first time in p–Pb collisions. This shows that the collective flow-like correlations extend over an extensive pseudorapidity range also in small collision systems such as p–Pb collisions. The pseudorapidity dependence of the second-order anisotropic flow coefficient,v₂(η), is extracted from the long-range correlations. Thev₂(η) results are presented for a wide pseudorapidity range of –3.1< η <4.8 in various centrality classes in p–Pb collisions. To gain a comprehensive understanding of the source of anisotropic flow in small collision systems, thev₂(η) measurements are compared with hydrodynamic and transport model calculations. The comparison suggests that the final-state interactions play a dominant role in developing the anisotropic flow in small collision systems.