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arXiv · 2610.31611

Nonconformal kinetic theory with transverse dynamics and event-by-event simulations using CoMBolt-RTA

Seyed Farid Taghavi
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Abstract

A new version of CoMBolt, called CoMBolt-RTA, is introduced to solve the Boltzmann equation for massive quasiparticles in the relaxation time approximation (RTA). The inclusion of a constant quasiparticle mass allows one to obtain an equation of state (EOS) closer to that of lattice QCD. The nonequilibrium dynamics of a boost-invariant, nonconformal system with transverse spatial extension are studied, with particular emphasis on the effects of quasiparticle mass on the evolution toward equilibrium. Using the hybrid version, which includes TrENTo for the initial state and UrQMD as an afterburner, the model parameters are manually tuned to describe recent anisotropic-flow and charged-multiplicity measurements in OO collisions by the ALICE Collaboration. The resulting predictions for the $p_T$-spectrum and $\langle p_T\rangle$ are also compared with ATLAS measurements. Based on the preferred parameter tuning, the collective response as a function of opacity is investigated. The results suggest that central OO collisions remain in the fluid-like regime, while smaller systems, namely ${}^3$He-${}^3$He and ${}^4$He-${}^4$He collisions, could provide a better opportunity to investigate the transition from fluid-like to particle-like collective dynamics.

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Seyed Farid Taghavi. 2026-10-22. Nonconformal kinetic theory with transverse dynamics and event-by-event simulations using CoMBolt-RTA. https://arxiv.org/abs/2610.31611

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