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1. Strange hadron collectivity in pPb and PbPb collisions

   https://doi.org/10.1007/JHEP05(2023)007  

   Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Dragicevic, M.; Escalante Del Valle, A.; Frühwirth, R.; Jeitler, M.; Krammer, N.; et al (May 2023, Journal of High Energy Physics)

   A<sc>bstract</sc> The collective behavior of$$ {\textrm{K}}_{\textrm{S}}^0 $$ $K_S^0$and$$ \Lambda /\overline{\Lambda} $$ $\Lambda /\overline{\Lambda }$strange hadrons is studied by measuring the elliptic azimuthal anisotropy (v₂) using the scalar-product and multiparticle correlation methods. Proton-lead (pPb) collisions at a nucleon-nucleon center-of-mass energy$$ \sqrt{s_{\textrm{NN}}} $$ $\sqrt{s_{\mathrm{NN}}}$= 8.16 TeV and lead-lead (PbPb) collisions at$$ \sqrt{s_{\textrm{NN}}} $$ $\sqrt{s_{\mathrm{NN}}}$= 5.02 TeV collected by the CMS experiment at the LHC are investigated. Nonflow effects in the pPb collisions are studied by using a subevent cumulant analysis and by excluding events where a jet with transverse momentum greater than 20 GeV is present. The strange hadronv₂values extracted in pPb collisions via the four- and six-particle correlation method are found to be nearly identical, suggesting the collective behavior. Comparisons of the pPb and PbPb results for both strange hadrons and charged particles illustrate how event-by-event flow fluctuations depend on the system size. 

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2. Production of $$ {\textrm{K}}_{\textrm{S}}^0 $$ , Λ ($$ \overline{\Lambda} $$), Ξ±, and Ω± in jets and in the underlying event in pp and p–Pb collisions

   https://doi.org/10.1007/JHEP07(2023)136  

   Acharya, S.; Adamová, D.; Adler, A.; Aglieri Rinella, G.; Agnello, M.; Agrawal, N.; Ahammed, Z.; Ahmad, S.; Ahn, S. U.; Ahuja, I.; et al (July 2023, Journal of High Energy Physics)

   A<sc>bstract</sc> The production of strange hadrons ($$ {\textrm{K}}_{\textrm{S}}^0 $$ $K_S^0$, Λ, Ξ^±, and Ω^±), baryon-to-meson ratios (Λ/$$ {\textrm{K}}_{\textrm{S}}^0 $$ $K_S^0$, Ξ/$$ {\textrm{K}}_{\textrm{S}}^0 $$ $K_S^0$, and Ω/$$ {\textrm{K}}_{\textrm{S}}^0 $$ $K_S^0$), and baryon-to-baryon ratios (Ξ/Λ, Ω/Λ, and Ω/Ξ) associated with jets and the underlying event were measured as a function of transverse momentum (p_T) in pp collisions at$$ \sqrt{s} $$ $\sqrt{s}$= 13 TeV and p Pb collisions at$$ \sqrt{s_{\textrm{NN}}} $$ $\sqrt{s_{\mathrm{NN}}}$= 5.02 TeV with the ALICE detector at the LHC. The inclusive production of the same particle species and the corresponding ratios are also reported. The production of multi-strange hadrons, Ξ^±and Ω^±, and their associated particle ratios in jets and in the underlying event are measured for the first time. In both pp and p–Pb collisions, the baryon-to-meson and baryon-to-baryon yield ratios measured in jets differ from the inclusive particle production for low and intermediate hadronp_T(0.6–6 GeV/c). Ratios measured in the underlying event are in turn similar to those measured for inclusive particle production. In pp collisions, the particle production in jets is compared with Pythia8 predictions with three colour-reconnection implementation modes. None of them fully reproduces the data in the measured hadronp_Tregion. The maximum deviation is observed for Ξ^±and Ω^±which reaches a factor of about six. The event multiplicity dependence is further investigated in p−Pb collisions. In contrast to what is observed in the underlying event, there is no significant event-multiplicity dependence for particle production in jets. The presented measurements provide novel constraints on hadronisation and its Monte Carlo description. In particular, they demonstrate that the fragmentation of jets alone is insufficient to describe the strange and multi-strange particle production in hadronic collisions at LHC energies. 

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3. Measurement of the production cross section of prompt $$\Xi ^0_{\textrm{c}}$$ baryons in p–Pb collisions at $$\sqrt{s_{{\textrm{NN}}}}=5.02$$ TeV

   https://doi.org/10.1140/epjc/s10052-024-13531-w  

   Acharya, S; Adamová, D; Agarwal, A; Aglieri_Rinella, G; Aglietta, L; Agnello, M; Agrawal, N; Ahammed, Z; Ahmad, S; Ahn, S U; et al (January 2025, The European Physical Journal C)

   Abstract The transverse momentum ($$p_{\textrm{T}}$$ $p_{\text{T}}$) differential production cross section of the promptly produced charm-strange baryon$$\mathrm {\Xi _{c}^{0}}$$ ${\Xi }_c^0$(and its charge conjugate$$\overline{\mathrm {\Xi _{c}^{0}}}$$ $\overline{{\Xi }_c^0}$) is measured at midrapidity via its hadronic decay into$$\mathrm{\pi ^{+}}\Xi ^{-}$$ ${\pi }^{+}{\Xi }^{-}$in p–Pb collisions at a centre-of-mass energy per nucleon–nucleon collision$$\sqrt{s_{\textrm{NN}}}~=~5.02$$ $\sqrt{s_{\text{NN}}}=5.02$ TeV with the ALICE detector at the LHC. The$$\mathrm {\Xi _{c}^{0}}$$ ${\Xi }_c^0$nuclear modification factor ($$R_{\textrm{pPb}}$$ $R_{\text{pPb}}$), calculated from the cross sections in pp and p–Pb collisions, is presented and compared with the$$R_{\textrm{pPb}}$$ $R_{\text{pPb}}$of$$\mathrm {\Lambda _{c}^{+}}$$ ${\Lambda }_c^{+}$baryons. The ratios between the$$p_{\textrm{T}}$$ $p_{\text{T}}$-differential production cross section of$$\mathrm {\Xi _{c}^{0}}$$ ${\Xi }_c^0$baryons and those of$$\mathrm {D^0}$$ $D^0$mesons and$$\mathrm {\Lambda _{c}^{+}}$$ ${\Lambda }_c^{+}$baryons are also reported and compared with results at forward and backward rapidity from the LHCb Collaboration. The measurements of the production cross section of prompt$$\Xi ^0_\textrm{c}$$ ${\Xi }_{\text{c}}^0$baryons are compared with a model based on perturbative QCD calculations of charm-quark production cross sections, which includes only cold nuclear matter effects in p–Pb collisions, and underestimates the measurement by a factor of about 50. This discrepancy is reduced when the data is compared with a model that includes string formation beyond leading-colour approximation or in which hadronisation is implemented via quark coalescence. The$$p_{\textrm{T}}$$ $p_{\text{T}}$-integrated cross section of prompt$$\Xi ^0_\textrm{c}$$ ${\Xi }_{\text{c}}^0$-baryon production at midrapidity extrapolated down to$$p_{\textrm{T}}$$ $p_{\text{T}}$= 0 is also reported. These measurements offer insights and constraints for theoretical calculations of the hadronisation process. Additionally, they provide inputs for the calculation of the charm production cross section in p–Pb collisions at midrapidity. 

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4. Investigating strangeness enhancement with multiplicity in pp collisions using angular correlations

   https://doi.org/10.1007/JHEP09(2024)204  

   Acharya, S; Adamová, D; Agarwal, A; Aglieri_Rinella, G; Aglietta, L; Agnello, M; Agrawal, N; Ahammed, Z; Ahmad, S; Ahn, S U; et al (September 2024, Journal of High Energy Physics)

   A<sc>bstract</sc> A study of strange hadron production associated with hard scattering processes and with the underlying event is conducted to investigate the origin of the enhanced production of strange hadrons in small collision systems characterised by large charged-particle multiplicities. For this purpose, the production of the single-strange meson$$ {\textrm{K}}_{\textrm{S}}^0 $$ $K_S^0$and the double-strange baryon Ξ^±is measured, in each event, in the azimuthal direction of the highest-p_Tparticle (“trigger” particle), related to hard scattering processes, and in the direction transverse to it in azimuth, associated with the underlying event, in pp collisions at$$ \sqrt{s} $$ $\sqrt{s}$= 5.02 TeV and$$ \sqrt{s} $$ $\sqrt{s}$= 13 TeV using the ALICE detector at the LHC. The per-trigger yields of$$ {\textrm{K}}_{\textrm{S}}^0 $$ $K_S^0$and Ξ^±are dominated by the transverse-to-leading production (i.e., in the direction transverse to the trigger particle), whose contribution relative to the toward-leading production is observed to increase with the event charged-particle multiplicity. The transverse-to-leading and the toward-leading Ξ^±/$$ {\textrm{K}}_{\textrm{S}}^0 $$ $K_S^0$yield ratios increase with the multiplicity of charged particles, suggesting that strangeness enhancement with multiplicity is associated with both hard scattering processes and the underlying event. The relative production of Ξ^±with respect to$$ {\textrm{K}}_{\textrm{S}}^0 $$ $K_S^0$is higher in transverse-to-leading processes over the whole multiplicity interval covered by the measurement. The$$ {\textrm{K}}_{\textrm{S}}^0 $$ $K_S^0$and Ξ^±per-trigger yields and yield ratios are compared with predictions of three different phenomenological models, namely Pythia8.2 with the Monash tune, Pythia8.2 with ropes and EPOS LHC. The comparison shows that none of them can quantitatively describe either the transverse-to-leading or the toward-leading yields of$$ {\textrm{K}}_{\textrm{S}}^0 $$ $K_S^0$and Ξ^±. 

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5. Measurement of electrons from open heavy-flavor hadron decays in Au+Au collisions at $$ \sqrt{s_{\textrm{NN}}} $$ = 200 GeV with the STAR detector

   https://doi.org/10.1007/JHEP06(2023)176  

   Abdulhamid, M I; Aboona, B E; Adam, J; Adamczyk, L; Adams, J R; Aggarwal, I; Aggarwal, M M; Ahammed, Z; Anderson, D M; Aschenauer, E C; et al (June 2023, Journal of High Energy Physics)

   A<sc>bstract</sc> We report a new measurement of the production of electrons from open heavy-flavor hadron decays (HFEs) at mid-rapidity (|y|<0.7) in Au+Au collisions at$$ \sqrt{s_{\textrm{NN}}} $$ $\sqrt{s_{\mathrm{NN}}}$= 200 GeV. Invariant yields of HFEs are measured for the transverse momentum range of 3.5< p_T<9 GeV/cin various configurations of the collision geometry. The HFE yields in head-on Au+Au collisions are suppressed by approximately a factor of 2 compared to that inp+pcollisions scaled by the average number of binary collisions, indicating strong interactions between heavy quarks and the hot and dense medium created in heavy-ion collisions. Comparison of these results with models provides additional tests of theoretical calculations of heavy quark energy loss in the quark-gluon plasma. 

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