Santanu Pal

Multiphase transport model for relativistic heavy ion collisions

We describe in detail how the different components of a multiphase transport (AMPT) model that uses the heavy ion jet interaction generator (HIJING) for generating the initial conditions, Zhangs parton cascade (ZPC) for modeling partonic scatterings, the Lund string fragmentation model or a quark coalescence model for hadronization, and a relativistic transport (ART) model for treating hadronic scatterings are improved and combined to give a coherent description of the dynamics of relativistic heavy ion collisions. We also explain the way parameters in the model are determined and discuss the sensitivity of predicted results to physical input in the model. Comparisons of these results to experimental data, mainly from heavy ion collisions at the BNL Relativistic Heavy Ion Collider, are then made in order to extract information on the properties of the hot dense matter formed in these collisions.

Dense Nuclear Matter in a Strong Magnetic Field

We investigate in a relativistic Hartree theory the gross properties of cold symmetric nuclear matter and nuclear matter in beta equilibrium under the influence of strong magnetic fields. If the field strengths are above the critical values for electrons and protons, the respective phase spaces are strongly modified. This results in additional binding of the systems with distinctively softer equations of state compared to the field free cases. For magnetic field {approximately}10{sup 20}G and beyond, the nuclear matter in beta equilibrium practically converts into a stable proton-rich matter. {copyright} {ital 1997} {ital The American Physical Society}

Partonic effects on pion interferometry at the Relativistic Heavy-Ion Collider

Using a multiphase transport model that includes both initial partonic and final hadronic interactions, we study the pion interferometry at the Relativistic Heavy-Ion Collider. We find that the two-pion correlation function is sensitive to the magnitude of the parton-scattering cross section, which controls the parton density at which the transition from the partonic to hadronic matter occurs. Also, the emission source of pions is non-Gaussian, leading to source radii that can be more than twice larger than the radius parameters extracted from a Gaussian fit to the correlation function.

Charged particle rapidity distributions at relativistic energies

PACS number~s!: 25.75.2q, 24.10.Lx Collisions of nuclei at high energies offer the possibility to subject nuclear matter to the extreme conditions of large compression and high excitation energies. Studies based on both nonequilibrium transport models @1# and equilibrium thermal models @2# have shown that the experimental data from heavy ion collisions at SIS, AGS, and SPS, where the center of mass collision energies are, respectively, about 3, 5, and 17 A GeV, are consistent with the formation of a hot dense nuclear matter in the initial stage of collisions. With the Relativistic Heavy Ion Collider ~RHIC! at Brookhaven National Laboratory, which can reach a center-of-mass energy of 200A GeV, the initial energy density is expected to exceed that for the transition from the hadronic matter to the quark-gluon plasma. Experiments at RHIC thus provide the opportunity to recreate the matter which is believed to have existed during the first microsecond after the big bang and to study its properties. Recently, charged particle multiplicity near midrapidity

Quantizing Magnetic Field and Quark-Hadron Phase Transition in a Neutron Star

We investigate the influence of a strong magnetic field on various properties of neutron stars with quark-hadron phase transition. The one-gluon exchange contribution in a magnetic field is calculated in a relativistic Dirac-Hartree-Fock approach. In a magnetic field of 5{times}10{sup 18} G in the center of the star, the overall equation of state is softer in comparison to the field-free case resulting in the reduction of maximum mass of the neutron star. {copyright} {ital 1997} {ital The American Physical Society}

Multiphase transport model for heavy ion collisions at RHIC

Using a multiphase transport model (AMPT) with both partonic and hadronic interactions, we study the multiplicity and transverse momentum distributions of charged particles such as pions, kaons and protons in central Au+Au collisions at RHIC energies. Effects due to nuclear shadowing and jet quenching on these observables are also studied. We further show preliminary results on the production of multistrange baryons from the strangeness-exchange reactions during the hadronic stage of heavy ion collisions.

Prescission neutron multiplicity and fission probability from Langevin dynamics of nuclear fission

A theoretical model of one-body nuclear friction, which was developed earlier, namely, the chaos-weighted wall formula, is applied to a dynamical description of compound nuclear decay in the framework of the Langevin equation coupled with statistical evaporation of light particles and photons. We have used both the usual wall formula friction and its chaos-weighted version in the Langevin equation to calculate the fission probability and prescission neutron multiplicity for the compound nuclei

Phi meson production in relativistic heavy ion collisions

{}^{178}\mathrm{W},

Rapid cooling of magnetized neutron stars

{}^{188}\mathrm{Pt},