# Quark Matter 2012

12-18 August 2012
US/Eastern timezone

## Charge Asymmetry Dependency of $\pi^+/\pi^-$ Azimuthal Anisotropy in Au + Au Collisions at STAR

16 Aug 2012, 16:00
2h

Poster Global and collective dynamics

### Speaker

Hongwei Ke (Central China Normal University)

### Description

A recent theoretical study indicates that a chiral magnetic wave at finite baryon density could induce an electric quadrupole moment in the quark-gluon plasma produced in heavy ion collisions. The quadrupole deformation will lead to a difference in azimuthal anisotropy $v_2$, between positive and negative pions, and the magnitude of this difference is predicted to be proportional to net charge asymmetry. The net charge asymmetry is defined as $(N_+ - N_-)/(N_+ + N_-)$, while $N_+ (N_-)$ is the number of positive (negative) particles. STAR experiment has observed the different $v_2$ of particles and anti-particles at $\sqrt{s_{NN}}$ = 7.7, 11.5, 19.6, 27, 39 and 62.4 GeV. Study on the charge asymmetry dependency of $\pi^+/\pi^-$ azimuthal anisotropy will shed light on the possible sources of the $v_2$ difference of particles and anti-particles. We present STAR's measurement of azimuthal anisotropy difference between positive and negative pions at low transverse momentum for Au + Au collisions at $\sqrt{s_{NN}}$ = 7.7, 11.5, 19.6, 27, 39, 62.4 and 200 GeV. The azimuthal anisotropy difference between $\pi^+$ and $\pi^-$ will be shown as a function of net charge asymmetry and centrality. In addition, these results will be compared with model calculations.

### Primary author

Hongwei Ke (Central China Normal University)

 Poster