SMuK 2021 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 17: Heavy-Ion Collisions and QCD Phases III

HK 17.6: Talk

Wednesday, September 1, 2021, 18:00–18:15, H1

Linear and Nonlinear Kinetic Description of Momentum Anisotropies in pp and pA Collisions in RTA — •Clemens Werthmann and Sören Schlichting — Universität Bielefeld, Bielefeld, Germany

Momentum anisotropies caused by collective flow phenomena in HICs have been known to convey a rich amount of information on the collision geometry. In pp and pA collisions the system size is too small for the hydrodynamic description of these anisotropies to be applicable. Instead, a microscopic description of the non-equilibrium dynamics has to be employed. Indeed, kinetic theory simulations have reproduced the anisotropies, but detailed insight into the mechanisms of their emergence is obscured by the algorithmical implementation. This prompts attempts to complement them with analytical treatments, which is highly nontrivial. We present an in-depth study of analyitcal and numerical descriptions of the problem formulated in relaxation time approximation. The analytical description employs an opacity expansion scheme of the Boltzmann equation and a linearization in small anisotropic perturbations on top of an isotropic Gaussian background. The nonlinear numerical description allows to estimate the range of validity of these appoximations via comparison and to study how the flow behaviour evolves from the free-streaming to the hydrodynamic regime.