# Quark Matter 2012

12-18 August 2012
US/Eastern timezone

## Observation of a difference in $v_{2}$ between particles and anti-particles in Au+Au collisions at $\sqrt{s_{NN}}=$ 7.7-62.4 GeV with STAR

16 Aug 2012, 16:00
2h

Poster Global and collective dynamics

### Speaker

Alexander Schmah (Lawrence Berkeley National Lab)

### Description

The RHIC Beam Energy Scan covers a wide range in the QCD phase diagram temperature vs. baryon chemical potential. A phase transition between the Quark Gluon Plasma and the hadron gas phase is expected in this region of the QCD phase diagram. The elliptic flow $v_{2}$ is one of the observables which is sensitive to the pressure gradients in the initial stage of heavy-ion collisions. Hence it can provide important information about the properties of the fireball in the early stage of heavy ion collisions. Elliptic flow measurements at midrapidity from Au+Au collisions at \\ $\sqrt{s_{NN}}=$ 7.7, 11.5, 19.6, 27, 39 and 62.4 GeV for identified hadrons ($\pi^{\pm}$,$K^{\pm}$, K$_{s}^{0}$, $p$, $\bar{p}$, $\phi$, $\Lambda$, $\bar{\Lambda}$, $\Xi^{-}$,$\bar{\Xi}^{+}$, $\Omega^{-}$, $\bar{\Omega}^{+}$) are presented. We observe a significant difference in $v_{2}$ between particles and corresponding anti-particles at the lowest energies of the beam energy scan. Baryons show a larger difference compared to mesons. The centrality, particle species and energy dependence of the difference will be presented. Furthermore we compare the data to several models and discuss their implications.

### Primary author

Alexander Schmah (Lawrence Berkeley National Lab)

### Presentation Materials

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