Opacity estimation of OO collision from CoMBolt-ITA hybrid

Fuente: arXiv
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Main Authors: Taghavi, Seyed Farid, Mehr, Seyed Mohammad Ali Tabatabaee
Format: Preprint
Published: 2025
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author Taghavi, Seyed Farid
Mehr, Seyed Mohammad Ali Tabatabaee
author_facet Taghavi, Seyed Farid
Mehr, Seyed Mohammad Ali Tabatabaee
contents Understanding the effect of system size on the applicability of the hydrodynamic description in heavy-ion physics remains unclear. Recent measurements of OO collisions at the LHC offer a new opportunity to refine our understanding of collectivity because of their intermediate size relative to heavy-ion and small-system collisions, as well as the relatively good control over their initial state. We use the CoMBolt-ITA hybrid model to describe recent OO measurements at the LHC. The model employs TrENTo for the initial state. A combination of the pre-equilibration and hydrodynamized medium stages is modeled consistently by CoMBolt-ITA, which evolves the Boltzmann distribution of massless collective excitations. The afterburner stage is included by employing UrQMD. Using this approach, we test whether the system lies in the regime where its spatial size approaches the mean free path, corresponding to low opacity, or in the opposite limit, where its size exceeds the mean free path sufficiently to enter the fluid-like evolution regime with high opacity. We find that, in light of the data-model comparison and considering the current status of the model, OO collisions with centralities larger than $60\%$ gradually leave the domain of fluid-like evolution.
format Preprint
id arxiv_https___arxiv_org_abs_2512_05009
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Opacity estimation of OO collision from CoMBolt-ITA hybrid
Taghavi, Seyed Farid
Mehr, Seyed Mohammad Ali Tabatabaee
Nuclear Theory
Understanding the effect of system size on the applicability of the hydrodynamic description in heavy-ion physics remains unclear. Recent measurements of OO collisions at the LHC offer a new opportunity to refine our understanding of collectivity because of their intermediate size relative to heavy-ion and small-system collisions, as well as the relatively good control over their initial state. We use the CoMBolt-ITA hybrid model to describe recent OO measurements at the LHC. The model employs TrENTo for the initial state. A combination of the pre-equilibration and hydrodynamized medium stages is modeled consistently by CoMBolt-ITA, which evolves the Boltzmann distribution of massless collective excitations. The afterburner stage is included by employing UrQMD. Using this approach, we test whether the system lies in the regime where its spatial size approaches the mean free path, corresponding to low opacity, or in the opposite limit, where its size exceeds the mean free path sufficiently to enter the fluid-like evolution regime with high opacity. We find that, in light of the data-model comparison and considering the current status of the model, OO collisions with centralities larger than $60\%$ gradually leave the domain of fluid-like evolution.
title Opacity estimation of OO collision from CoMBolt-ITA hybrid
topic Nuclear Theory
url https://arxiv.org/abs/2512.05009