Speaker
Dr
Brijesh Kumar Srivastava
(Department of Physics-Purdue University-Unknown)
Description
The high-energy heavy ion collisions at RHIC energies have shown evidence of a new state of matter with very low viscosity to entropy density ratio $\eta/s$ similar to that of a nearly ideal fluid. The $\eta/s$ is obtained for the QGP with in the context of the Color String Percolation Model (CSPM) using data produced in Au-Au collisions at $\sqrt{s_{NN}}$ = 200 A GeV at RHIC and Pb-Pb at $\sqrt{s_{NN}}$ = 2.76 TeV at LHC [1]. The relativistic kinetic theory relation for $\eta/s$ is evaluated using CSPM values for the temperature and the mean free path of the QGP constituents [2].
The experimental transverse momentum spectrum is used to measure the percolation density parameter $\xi$ in Au-Au collisions (STAR)[3]. For Pb-Pb at $\sqrt{s_{NN}}$ = 2.76 TeV, $\xi$ values are obtained from the extrapolation at RHIC energy. The value of $\eta/s$ is 0.184 and 0.278 at the CSPM initial temperature of 193.6 MeV (RHIC) and 262.2 MeV (LHC), respectively. These values are 2.3 and 3.5 times the AdS/CFT conjectured lower bound $1/4\pi$. We compare the CSPM $\eta/s(T/T_{c})$ analytic expression with weak coupling (wQGP) and strong coupling (sQGP) calculations. This indicates that the QGP is a strongly coupled fluid in the phase transition region.
[1] M. A. Braun, C. Pajares, Eu. Phys. J. C16, 349 (2000).
[2] T. Hirano, M. Gyulassy, Nucl. Phys. A769, 71 (2006).
[3] R. P. Scharenberg, B. K. Srivastava and A. S. Hirsch, Eur. Phys. J. C71, 1510 (2011).
Primary author
Dr
Brijesh Kumar Srivastava
(Department of Physics-Purdue University-Unknown)
