Speaker
Vipul Bairathi
(National Institute of Science Education and Research)
Description
Quark Gluon Plasma (QGP) is a phase of nuclear matter at high temperature and high energy density formed in relativistic nucleus-nucleus collisions. Azimuthal anisotropy is an important tool for understanding the basic properties of QGP and to characterize the collision dynamics in high energy heavy-ion collisions [1]. These anisotropies are expected to arise due to initial pressure gradients and subsequent interactions of the constituents [2]. The second order azimuthal anisotropy namely elliptic flow is defined as the 2$^{nd}$ harmonic coefficients of the Fourier decomposition of the azimuthal distribution of produced particles with respect to the reaction plane angle ($\psi_{n}$), and the azimuthal anisotropy can be expressed as $v_{2}$ = $\langle cos(2(\phi - \psi_{n}))\rangle$, where $\phi$ is the azimuthal angle of produced particles. Recently, a Beam Energy Scan (BES) program at RHIC has been completed. Its aim is to study the QCD phase diagram [3] by extending the range of chemical potential. The BES program extends the range of baryonic chemical potential ($\mu_{B}$) from 20 to about 400 MeV at RHIC [4]. The baryon chemical potential increases with the decrease in the beam energy while the chemical freeze-out temperature increases with increase in beam energy [4]. This allows one to study azimuthal anisotropy at midrapidity with varying net-baryon densities. Here we will present a systematic study of the inclusive charged hadron elliptic flow ($v_{2})$ as function of transverse momentum ($p_{T}$ ) at midrapidity ($\eta \leq 1.0$) in Au+Au collisions at s N N = 14.5 GeV. The $v_{2}$ results will be compared to similar measurements at $\sqrt(s_{NN}$ = 7.7, 11.5, 19.6, 27, 39 and 62.4 GeV. We will discuss inclusive charged hadron $v_{2}$ from different methods, including $\eta$-sub event plane method with a $\eta$-gap of 0.15 and 2(4)-particle cumulants method to reduce non-flow correlations. We will also discuss the centrality dependence of $v_{2}$, and comparison to calculations from a transport model (AMPT) [5].
**References**
1. S. A. Voloshin, A. M. Poskanzer and R. Snellings, arXiv:0809.2949 (2008), R. Snellings, New J. Phys. 13, 055008 (2011).
2. J. Y. Ollitrault, Phys. Rev. D 46, 229 (1992).
3. B. Mohanty (STAR Collaboration), J. Phys. G 38, 124023 (2011)
4. J. Cleymans et al., Phys. Rev. C 73, 034905 (2006).
5. Z. Lin et al., Phys. Rev. C 72, 064901 (2005).
Primary authors
Vipul Bairathi
(National Institute of Science Education and Research)
for the STAR Collaboration
