Speaker
Description
Cumulants of conserved quantities are the powerful tools to study the QCD phase structure. According to the Lattice Gauge Theory calculations, at vanishing baryon chemical potential ($\mu_{B}$) a "smooth crossover" for the transition from quark-gluon plasma to hadronic system occurs in heavy-ion collisions [1]. One of the possible experimental ways to search for the evidence is to analyze the higher-order cumulant ratios of net-baryon distributions from high-energy nuclear collisions. The sixth-order ($C_{6}$) to second-order ($C_{2}$) cumulant ratio of baryon number fluctuations is predicted to be negative at the freeze-out temperature if it is close to the chiral transition temperature [2]. Net-proton multiplicity distributions can be studied as a reasonable proxy for net-baryon distributions [3,4]. In this poster, we present the centrality dependence of net-proton $C_{6}/C_{2}$ at $\sqrt{s_{\rm NN}}=$ 54.4 and 200 GeV from a high statistics Au+Au collisions data set in the STAR experiment. The transverse momentum and rapidity dependence of $C_{6}/C_{2}$ for net-proton distributions will be also discussed.
[1] Y. Aoki et al., Nature, 443 (2006) 675.
[2] B. Friman et al., Eur. Phys. J. C, 71 (2011) 1694.
[3] Y. Hatta, M. A. Stephanov, Phys. Rev. Lett. 91 (2003) 129901.
[4] M. Kitazawa, M. Asakawa, Phys. Rev. C 86 (2012) 024904.
