Search for the Chiral Magnetic Wave with Anisotropic Flow of Identified Particles at RHIC-STAR

Abstract

The chiral magnetic wave (CMW) has been theorized to propagate in the Quark-Gluon Plasma formed in high-energy heavy-ion collisions. It could cause a finite electric quadrupole moment of the collision system, and may be observed as a dependence of elliptic flow, $v_2$, on the asymmetry between positively and negatively charged hadrons, $A_{\mathrm{ch}}$. However, non-CMW mechanisms, such as local charge conservation (LCC) and hydrodynamics with isospin effect, could also contribute to the experimental observations. Here we present the STAR measurements of elliptic flow $v_2$ and triangular flow $v_3$ of charged pions, along with $v_2$ of charged kaons and protons, as functions of $A_{\mathrm{ch}}$ in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV. The slope parameters of $\Delta v_2$($A_{\mathrm{ch}}$) and $\Delta v_3$($A_{\mathrm{ch}}$) are reported and compared to investigate the LCC background. The similarity between pion and kaon slopes suggests that the hydrodynamics is not the dominant mechanism. The difference between the normalized $\Delta v_2$ and $\Delta v_3$ slopes, together with the small slopes in p+Au and d+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV, suggest that the CMW picture remains a viable interpretation at RHIC.

4 pages, 2 figures. Proceedings of Quark Matter 2018, Venice, Italy