A. K. Chaudhuri

Dissipative hydrodynamics for viscous relativistic fluids

Explicit equations are given for describing the space-time evolution of nonideal (viscous) relativistic fluids undergoing boost-invariant longitudinal and arbitrary transverse expansion. The equations are derived from the second-order Israel-Stewart approach which ensures causal evolution. Both azimuthally symmetric (1+1)dimensional and nonsymmetric (2+1)-dimensional transverse expansion are discussed. The latter provides the formal basis for the hydrodynamic computation of elliptic flow in relativistic heavy ion collisions including dissipative effects.

Effects of jet quenching on the hydrodynamical evolution of quark-gluon plasma.

We study the effects of jet quenching on the hydrodynamical evolution of the quark-gluon plasma (QGP) fluid created in a heavy-ion collision. In jet quenching, a hard QCD parton, before fragmenting into a jet of hadrons, deposits a fraction of its energy in the medium, leading to suppressed production of high-pT hadrons. Assuming that the deposited energy quickly thermalizes, we simulate the subsequent hydrodynamic evolution of the QGP fluid. For partons moving at supersonic speed, vp>cs, and sufficiently large energy loss, a shock wave forms leading to conical flow. The PHENIX Collaboration recently suggested that observed structures in the azimuthal angle distribution might be caused by conical flow. We show here that, for phenomenologically acceptable values of parton energy loss, conical flow effects are too weak to explain these structures.

A Density dependent interaction in the folded alpha nucleus potential

Abstract Assuming that the density dependence of the effective nulceon-nucleon interaction can be factorized into a target and a projectile term, an alpha-nucleus potential is obtained. It is shown that a complete energy-independent density dependence can give a satisfactory description of elastic alpha scattering data in the energy range of 104 MeV to 172 MeV.

Elliptic flow (v{sub 2}) in pp collisions at energies available at the CERN Large Hadron Collider: A hydrodynamical approach

At Large Hadron Collider energy, the expected large multiplicities suggest the presence of collective behavior even in pp collisions. A hydrodynamical approach has been applied to estimate the expected elliptic flow measured by the azimuthal asymmetry parameter v{sub 2} in pp collisions at {radical}(s)=14 TeV. v{sub 2} of {pi}{sup -} is found to be strongly dependent on the parton density profile inside a proton [e.g., surface diffuseness parameter ({xi})]. For {xi}=0.105 fm, v{sub 2} is found to be positive and larger compared to that at {xi}=0.25 fm. The centrality dependence of v{sub 2} has also been studied.

Centrality dependence of elliptic flow and QGP viscosity

In the Israel–Stewart theory of second-order hydrodynamics, we have analysed the recent PHENIX data on charged particles elliptic flow in Au+Au collisions. PHENIX data demand more viscous fluid in peripheral collisions than in central collisions. Over a broad range of collision centrality (0–10% to 50–60%), the viscosity-to-entropy ratio (η/s) varies between 0 and 0.17.

An α-nucleus optical potential using a realistic effective interaction

Abstract The real part of the α-nucleus optical potential has been computed, the direct part by folding in the two density distribution functions and the exchange part by folding in the two density matrices with the finite-range M3Y and Paris two-body effective interactions. The exchange part turns out to be both density and energy dependent. The potentials reproduce the elastic α-scattering data from 40 Ca, 50 Ti, 52 Cr, 58 Ni and 208 Pb successfully.

Hydrodynamical evolution of dissipative QGP fluid

In the framework of the Mueller-Israel-Stewart theory of dissipative fluid dynamics, we have studied the space-time evolution of a QGP fluid. For simplicity, we have considered shear viscosity only and neglected bulk viscosity and heat conductivity. Shear viscosity opposes the expansion and cooling of the fluid. As a result, the lifetime of the fluid is extended. We also find that the parton pTdistribution is considerably flattened.

A microscopic optical model analysis of heavy ion elastic scattering data using the realistic NN interaction

Abstract The real part of the nucleus-nucleus optical potential has been computed, the direct part by folding in the two density distribution functions with the direct parts of the finite range M3Y and Paris two-body effective interactions and the exchange part by folding in the two density matrices with the exchange parts of the same interactions. The magnitude of the potential as obtained by Satchler and Love at the strong absorption radius is reproduced with a normalisation of 0.92 ± 0.27. The quality of fits does not change appreciably however if the normalisation is changed by 20%.

Comparison of results from a 2+1D relativistic viscous hydrodynamic model to elliptic and hexadecapole flow of charged hadrons measured in Au-Au collisions at

Simulated results from a 2+1D relativistic viscous hydrodynamic model have been compared to the experimental data on the centrality dependence of invariant yield, elliptic flow (

\sqrt{s_{\rm {NN}}}

v_{2}