Two-particle correlations on transverse momentum: an untapped resource for studying relativistic heavy-ion collision dynamics

Two-particle correlation projections onto two-dimensional transverse momentum coordinates (pt1, pt2) allow access to properties of the relativistic heavy-ion collision system which are complementary to that studied using angular correlations. Examples include the degree of thermal equilibration and the variance of dynamical fluctuations in hard-scattering processes. Results for minimum-bias Au + Au collisions at √sNN = 200 are presented, with the structures described by two phenomenological models. The correlations structures and extracted physical quantities are then compared to theoretical predictions. Conclusions from these comparisons regarding global equilibration, fluctuations in soft and semi-hard QCD processes, and the effects of the hot, dense collision medium are presented.

Evidence of forward–backward multiplicity correlation at SPS energy

In this paper, a detailed study of two-particle rapidity correlation has been presented by measuring the dynamical fluctuation variable [Formula: see text] in forward and backward pseudo-rapidity window of shower particles produced in the relativistic heavy ion collision, [Formula: see text]O–AgBr interactions at 60[Formula: see text]AGeV and [Formula: see text]S–AgBr interactions at 200[Formula: see text]AGeV. Variations of [Formula: see text] with rapidity gap between forward and backward zones and with the width of each zone have been studied. For both cases, [Formula: see text] increase with increasing either width of the zone or gap between the zones. Our findings show the presence of strong long-range correlation. Comparison of experimental results with MC-RAND events confirms the present correlation to be dynamical in nature. We have also compared our results with FRITIOF and UrQMD events. Such events also show the presence of correlation, but found to fail to reproduce the experimental results both quantitatively and qualitatively. Strength of correlation is dependent on the centrality of collision for experimental events, it decreases with centrality.

Lattice Study of QCD Phase Structure by Canonical Approach

The canonical approach is a powerful tool to circumvent sign problem in LQCD. Although it has its own difficulties it provides opportunity to determine QCD phase transition line. Using improved Wilson fermions we calculated number density at nonzero imaginary chemical potential for confinement and deconfinement phases, restored canonical partition functions Zn and did extrapolation into the real chemical potential region. We computed the higher moments of the baryon number including the kurtosis, and compared our results with information from relativistic heavy ion collision experiments.

Quark–gluon plasma and topological quantum field theory

Based on an analogy with topologically ordered new state of matter in condensed matter systems, we propose a low energy effective field theory for a parity conserving liquid-like quark–gluon plasma (QGP) around critical temperature in quantum chromodynamics (QCD) system. It shows that below a QCD gap which is expected several times of the critical temperature, the QGP behaves like topological fluid. Many exotic phenomena of QGP near the critical temperature discovered at Relativistic Heavy Ion Collision (RHIC) are more readily understood by the suggestion that QGP is a topologically ordered state.

Viscosity to entropy ratio of QGP in relativistic heavy ion collision: Hard thermal loop corrections

In this work, we report on our computation results for the best value of the shear viscosity to entropy ratio of quark–gluon plasma produced in the relativistic Au–Au collisions at [Formula: see text][Formula: see text]GeV. Time evolution of heavy quarks distribution functions is calculated by solving the Fokker–Planck evolution equation using the new technique: Iterative Laplace transform method. We compute the drag and diffusion coefficients by considering the hard thermal loop corrections and also temperature dependence running strong coupling, up to complete interactions of leading order.

Complex potential and bottomonium suppression at LHC energy

We have studied the thermal suppression of the bottomonium states in relativistic heavy-ion collision at LHC energies as function of centrality, rapidity, transverse momentum. First, we address the effects of the nonperturbative confining force and the momentum anisotropy together on heavy quark potential at finite temperature, which are resolved by correcting both the perturbative and nonperturbative terms of the potential at T = 0 in a weakly-anisotropic medium, not its perturbative term alone as usually done in the literature. Second, we model the expansion of medium by the Bjorken hydrodynamics in the presence of both shear and bulk viscosity, followed by an additional pre-equilibrium anisotropic evolution. Finally, we couple them together to quantify the yields of bottomonium production in nucleus–nucleus collisions at LHC energies and found a better agreement with the CMS data. Our estimate of the inclusive ϒ(1S) production indirectly constrains both the uncertainties in isotropization time and the shear-to-entropy density ratio and favors the values as 0.3 fm/c and 0.3 (perturbative result), respectively.