Charge asymmetry dependency of $\pi^{+}/\pi^{-}$ elliptic flow in Au + Au collisions at $\sqrt{s_{NN}}$ = 200 GeV

TL;DR

This study measures the charge-dependent elliptic flow of pions in gold-gold collisions at 200 GeV, finding a linear relationship with charge asymmetry consistent with the Chiral Magnetic Wave, but with unexpected centrality dependence.

Contribution

It provides the first detailed measurement of charge asymmetry dependence of pion elliptic flow at RHIC energies, testing predictions of the Chiral Magnetic Wave model.

Findings

$v_2$ difference is proportional to charge asymmetry $A_{ ext{±}}$

Slope parameters are around 0.01

Centrality dependence differs from predictions

Abstract

In this proceedings, we present STAR's measurement of $v_{2}$ difference between positively charged pions and negatively charged pions at low transverse momentum for Au + Au collisions at $\sqrt{s_{NN}}$ = 200 GeV. The integrated $v_2$ of $\pi^+$ ($\pi^-$), $0.15 < p_T < 0.5 GeV/c$, decreases (increases) linearly with the increasing charge asymmetry $A_{\pm}$. The $v_2$ difference between $\pi^+$ and $\pi^-$ is proportional to $A_{\pm}$ and the slope parameters have their order of magnitude of about 0.01. All of these observed features are consistent with the predication based on Chiral Magnetic Wave. The centrality dependence of the $v_2$ difference is different than that was predicted.