Measurements of identified particle anisotropic flow in Cu+Au and U+U collisions by PHENIX experiment

TL;DR

This paper reports new measurements of anisotropic flow ($v_{1}$, $v_{2}$) for identified particles in Cu+Au and U+U collisions, revealing particle flow patterns and scaling behaviors across different centralities and energies.

Contribution

It provides the first detailed measurements of identified particle anisotropic flow in Cu+Au and U+U collisions at RHIC energies, including flow scaling with valence quarks.

Findings

Weak $v_2$ dependence for protons in ultra-central U+U collisions.

Positive $v_1$ observed for charged pions at high $p_T$.

Scaling of $v_2$ with valence quarks confirmed across systems.

Abstract

In this paper, new measurements of anisotropic flow ($v_{1}$, $v_{2}$) for identified particles such as pions and proton in Cu+Au collisions at 200 GeV and U+U collisions at 193 GeV are reported. The anisotropic flow is studied as a function of $p_{T}$ and centrality in these two collision systems. In ultra-central U+U collisions (0--2% centrality), $v_2$ of protons shows a weak $p_{T}$ dependence for $p_T<$~1.0 GeV/c. A positive $v_1$ for charged pions is observed for $p_{T} >$ 1 GeV/c with respect to the first-order event plane, the angle of which is determined by the Au-going spectators. The scaling of identified particles $v_2$ with the number of valence quarks ($n_q$) has been observed, in different centrality bins, with the transverse kinetic energy in these two collision systems.