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

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 ${\pi }^{+}$ (${\pi }^{-}$), $0.15<p_T<0.5GeV\mathrm{/}c$, 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.