ComBolt-ITA: a (2+1)-dimensional framework to study flow observables across systems ranging from small to large

• Seyed Mohammad Ali Tabatabaee Mehr (School of Particles and Accelerators - IPM)

Collisions of various systems, from high-multiplicity pp to p/d/He+Au, exhibit clear signatures of collectivity. Overall, the hydrodynamic description provides the most comprehensive and quantitative account of the experimental data, successfully capturing many of these collective features across system sizes. However, the observation of such ubiquitous collective phenomena, even in small systems, and the attempts to describe them through hydrodynamic evolution have raised important questions about the applicability and limits of hydrodynamics itself. To address these questions, as well as the issues of hydrodynamization and thermalization in the quark–gluon plasma (QGP), I will introduce ComBolt-ITA. This framework offers a unified approach to describing collectivity in the QGP by coupling the pre-equilibrium dynamics with the hydrodynamic evolution through the solution of a (2+1)-dimensional relativistic Boltzmann equation. By implementing the freeze-out process together with a hadronic afterburner, ComBolt-ITA enables the calculation of flow observables across a wide range of systems — from small (pp) to mesoscopic (O+O) and large (Pb+Pb) collisions.