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https://doi.org/10.1140/epja/s10050-024-01419-y

Regular Article - Theoretical Physics

## Dynamics of identified particles production in oxygen–oxygen collisions at $\sqrt{{s}_{\text{NN}}}=7$ TeV using EPOS4

^{1}
University of Science and Technology of China, 230026, Hefei, People’s Republic of China

^{2}
Department of Physics and Astronomy, Wayne State University, 666 W. Hancock, 48201, Detroit, Michigan, USA

^{3}
Key Laboratory of Quark and Lepton Physics (MOE) and Institute of Particle Physics, Central China Normal University, 430079, Wuhan, China

^{4}
Pakistan Institute of Nuclear Science and Technology, 44000, Islamabad, Pakistan

^{b} muashraf@wayne.edu, mashraf@bnl.gov

Received:
5
April
2024

Accepted:
11
September
2024

Published online:
15
October
2024

The Large Hadron Collider (LHC) aims to inject oxygen (^{16}*O*) ions in the next run into its experiments. This include the anticipated one-day physics run focusing on $O+O\phantom{\rule{0.166667em}{0ex}}$collisions at center-of-mass energy $\sqrt{{s}_{\text{NN}}}=7$ TeV . In this study, we have used recently developed version of the EPOS (EPOS4) to study the production of identified particles (${\pi}^{\pm}$, ${K}^{\pm}$ and $p(\overline{p})$) in $O+O\phantom{\rule{0.166667em}{0ex}}$collisions at $\sqrt{{s}_{\text{NN}}}=7$ TeV . Predictions of transverse momentum (${p}_{\text{T}}\phantom{\rule{0.166667em}{0ex}}$) spectra, $\u27e8{p}_{\text{T}}\u27e9\phantom{\rule{0.166667em}{0ex}}$, integrated yield ($\mathrm{d}N/\mathrm{d}\mathit{y}\phantom{\rule{0.166667em}{0ex}}$) for different centrality classes are studied. To provide insight into the collective nature of the produced particles, we look into the ${p}_{\text{T}}\phantom{\rule{0.166667em}{0ex}}$-differential particle ratios ($K/\pi $ and $p/\pi $) and ${p}_{\text{T}}\phantom{\rule{0.166667em}{0ex}}$-integrated particle ratios to (${\pi}^{+}+{\pi}^{-}$) as a function of charge particle multiplicity. The shape of the charge particle multiplicity ($\text{d}{N}_{\text{ch}}/\text{d}\eta \phantom{\rule{0.166667em}{0ex}}$) and mean transverse momentum ($\u27e8{p}_{\text{T}}\u27e9\phantom{\rule{0.166667em}{0ex}}$) is well described by EPOS4. The predictions for the ratios of $K/\pi $ and $p/\pi $ from EPOS4 exhibit a systematic overestimation compared to the trends observed in $p+p\phantom{\rule{0.166667em}{0ex}}$, $p+Pb\phantom{\rule{0.166667em}{0ex}}$and $Pb+Pb\phantom{\rule{0.166667em}{0ex}}$systems as a function of charged-particle multiplicity. Interestingly, the $O+O\phantom{\rule{0.166667em}{0ex}}$results of ${p}_{\text{T}}\phantom{\rule{0.166667em}{0ex}}$-integrated particle ratios shows a clear final state multiplicity overlap with $p+p\phantom{\rule{0.166667em}{0ex}}$, $p+Pb\phantom{\rule{0.166667em}{0ex}}$and $Pb+Pb\phantom{\rule{0.166667em}{0ex}}$collisions. EPOS4 does not only mimics signs of collectivity, but embeds collective expansion by construction, since it relies on relativistic hydrodynamics to model the evolution of the so-called core and is one of the suitable candidates to study ultra-relativistic heavy-ion collisions. Furthermore, the foreseen data from $O+O\phantom{\rule{0.166667em}{0ex}}$collisions at the LHC, when available, will help to better understand the heavy-ion-like behavior in small systems as well as help to put possible constraints on the model parameters.

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*© The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2024. Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.*