Dependence of elliptic flow on number of parton degrees of freedom

TL;DR

This study investigates how the elliptic flow parameter $v_2$ in heavy-ion collisions depends on the number of parton degrees of freedom, revealing sensitivity in $v_2(p_T)$ but not in the $p_T$-averaged $v_2$, and showing that including quarks affects the flow and spectra.

Contribution

It introduces an analysis of elliptic flow dependence on parton degrees of freedom using the BAMPS model with quark interactions approximated, highlighting the impact on $v_2(p_T)$ and spectra.

Findings

$v_2(p_T)$ is sensitive to the number of parton degrees of freedom.

Including quarks shifts $v_2(p_T)$ to lower $p_T$ values.

Parton spectra become softer with quark inclusion.

Abstract

We calculate the elliptic flow parameter $v_2$ for Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV employing the parton cascade BAMPS (Boltzmann Approach of Multiparton Scatterings). Besides gluon interactions including the bremsstrahlung process, interactions with quarks are considered in an effective, but approximate way to investigate the dependence of the collective flow on the number of parton degrees of freedom. We find that $v_2$ as a function of the transverse momentum $p_T$ is sensitive to the number of parton degrees of freedom, whereas the $p_T$ averaged $v_2$ does not. When including quarks, $v_2(p_T)$ shifts to lower $p_T$, the parton transverse momentum spectra become softer and the mean parton transverse momenta decrease.