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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$$ {\textrm{K}}_{\textrm{S}}^0 $$ and the double-strange baryon Ξ±is measured, in each event, in the azimuthal direction of the highest-pTparticle (“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$$ \sqrt{s} $$ = 5.02 TeV and$$ \sqrt{s} $$ = 13 TeV using the ALICE detector at the LHC. The per-trigger yields of$$ {\textrm{K}}_{\textrm{S}}^0 $$ 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±/$$ {\textrm{K}}_{\textrm{S}}^0 $$ 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$$ {\textrm{K}}_{\textrm{S}}^0 $$ is higher in transverse-to-leading processes over the whole multiplicity interval covered by the measurement. The$$ {\textrm{K}}_{\textrm{S}}^0 $$ 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$$ {\textrm{K}}_{\textrm{S}}^0 $$ and Ξ±.
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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
A<sc>bstract</sc> The production of strange hadrons ($$ {\textrm{K}}_{\textrm{S}}^0 $$ , Λ, Ξ±, and Ω±), baryon-to-meson ratios (Λ/$$ {\textrm{K}}_{\textrm{S}}^0 $$ , Ξ/$$ {\textrm{K}}_{\textrm{S}}^0 $$ , and Ω/$$ {\textrm{K}}_{\textrm{S}}^0 $$ ), 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 (pT) in pp collisions at$$ \sqrt{s} $$ = 13 TeV and p Pb collisions at$$ \sqrt{s_{\textrm{NN}}} $$ = 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 hadronpT(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 hadronpTregion. 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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- PAR ID:
- 10474230
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Publisher / Repository:
- Springer
- Date Published:
- Journal Name:
- Journal of High Energy Physics
- Volume:
- 2023
- Issue:
- 7
- ISSN:
- 1029-8479
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1007/JHEP07(2023)136
