Speaker
AMAL SARKAR
(iit-bombay)
Description
The main goal of the Beam Energy Scan (BES) program at RHIC is to map the
phase diagram of QCD. A critical point (CP) is expected at large baryonic
chemical potential ($\mu_{B}$) in the $T$ vs. $\mu_{B}$ phase diagram. Its
location experimentally will provide one of the most stringent tests of
QCD calculations. In the BES program $T$ and $\mu_{B}$ are varied by
changing the center of mass energy ($\sqrt{s_{NN}}$) from 200 to 7.7 GeV.
The observables chosen for CP search are the product of moments of
conserved(like net-charge) multiplicity distributions or their proxies
(such as net-kaon for net-strangeness and net-proton for net-baryons)
measured in the experiments. The various moments (mean ($M$), standard
deviation ($\sigma$), skewness ($S$) and kurtosis ($\kappa$)) are related
to correlation length ($\xi$) of the system (variance: $\sigma^{2}$ $\sim$
$\xi^{2}$; skewness: $S$ $\sim$ $\xi^{4.5}$ and kurtosis: $\kappa$ $\sim$
$\xi^{7}$) [1] and are expected to show a non-monotonic variation with
beam energy in the presence of CP.
We report new measurements of product of moments: $\sigma^{2}/M$,
$S\sigma$ and $\kappa\sigma^{2}$ of net-kaon distributions ($\Delta N_{K}$
= $N_K^+$ - $N_K^-$) obtained by the STAR detector at midrapidity
for various centrality in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 11.5,
19.6, 27, 39, 62.4 and 200 GeV. These results will be presented along with
the corresponding results from net-charge [2] and net-proton
distributions[3]. All the results are corrected for particle
reconstruction efficiency and will be compared to baseline distributions
constructed following Poisson and Negative Binomial/Binomial statistics.
They will also be compared to calculations from HIJING, AMPT and UrQMD
models, which do not include a CP. Deviations from some of the baseline
measures and model calculations are observed for net-kaon and net-proton
distributions. The implications of the observation to CP physics will be
presented.
References
1. M. A. Stephanov, Phys. Rev. Lett. 102, 032301 (2009); Phys. Rev. Lett.
107, 052301 (2011); C. Athanasiou, et al., Phys. Rev. D 82, 074008 (2010).
2. L. Adamczyk, et al., (STAR Collaboration), arXiv:1402.1558.
3. L. Adamczyk, et al., (STAR Collaboration), Phys. Rev. Lett. 112,
| On behalf of collaboration: | STAR |
|---|
Primary author
AMAL SARKAR
(iit-bombay)
