# Sukanya Mitra

## Publications Authored By Sukanya Mitra

We estimate the shear and the bulk viscous coefficients for a hot hadronic gas mixture constituting of pions and nucleons. The viscosities are evaluated in the relativistic kinetic theory approach by solving the transport equation in the relaxation time approximation for binary collisions ($\pi\pi$,$\pi N$ and $NN$). Instead of vacuum cross-sections usually used in the literature we employ in-medium scattering amplitudes in the estimation of the relaxation times. Read More

The main focus of this article is to obtain various transport coefficients for a hot QCD medium that is produced while colliding two heavy nuclei ultra-relativistically. As the hot QCD medium follows dissipative hydrodynamics while undergoing space-time evolution, the knowledge of the transport coefficients such as thermal conductivity, electrical conductivity, shear and bulk viscosities are essential to understand the underlying physics there. The approach adopted here is semi-classical transport theory. Read More

Collective excitations of a hot QCD medium are the main focus of the present article. The analysis is performed within semi-classical transport theory with isotropic and anisotropic momentum distribution functions for the gluonic and quark-antiquark degrees of freedom that constitutes the hot QCD plasma. The isotropic/equilibrium momentum distributions for gluons and quarks are based on a recent quasi-particle description of hot QCD equations of state. Read More

The response of electromagnetic (EM) fields that are produced in non-central heavy-ion collisions to electromagnetically charged quark gluon plasma can be understood in terms of charge transport and charge diffusion in the hot QCD medium. This article presents a perspective on these processes by investigating the temperature behavior of the related transport coefficients, {\it viz.} electrical conductivity and the charge diffusion coefficients along with charge susceptibility. Read More

The self energy of $\Delta$-baryon is evaluated at finite temperature and density using the real time formalism of thermal field theory. The Dyson-Schwinger equation is used to get the exact thermal propagator followed by the spectral function of $\Delta$. The $\pi N$ scattering cross section obtained using explicit $\Delta$ exchange is normalized to the experimental data in vacuum and its medium modification is implemented by means of the exact thermal propagator. Read More

The relaxation times over which dissipative fluxes restore their steady state values have been evaluated for a pion gas using the 14-moment method. The effect of the medium has been implemented through a temperature dependent pi-pi cross-section in the collision integral which is obtained by including one-loop self-energies in the propagators of the exchanged rho and sigma mesons. To account for chemical freeze out in heavy ion collisions, a temperature dependent pion chemical potential has been introduced in the distribution function. Read More

The drag and diffusion coefficients of a hot hadronic medium have been evaluated by using hidden charm mesons as probes. The matrix elements for the evaluation of these coefficients are calculated using an effective theory as well as from scattering lengths. Although the transport coefficients show a significant rise with temperature its effects on the suppression of $J/\psi$ in hadronic matter is not significant. Read More

We investigate the effect of the medium on the thermal conductivity of a pion gas out of chemical equilibrium by solving the relativistic transport equation in the Chapman-Enskog and relaxation time approximations. Using an effective model for the pi-pi cross-section involving rho and sigma meson exchange, medium effects are incorporated through thermal one-loop self-energies. The temperature dependence of the thermal conductivity is observed to be significantly affected. Read More

The one-loop self-energy of the $D$ and $D^*$ mesons in a hot hadronic medium is evaluated using the real time formalism of thermal field theory. The interaction of the heavy open-charm mesons with the thermalized constituents $(\pi,K,\eta)$ of the hadronic matter is treated in the covariant formalism of heavy meson chiral perturbation theory. The imaginary parts are extracted from the discontinuities of the self-energy function across the unitary and the Landau cuts. Read More

The bulk and shear viscosities of a pion gas is obtained by solving the relativistic transport equation in the Chapman-Enskog approximation. In-medium effects are introduced in the $\pi\pi$ cross-section through one-loop self-energies in the propagator of the exchanged $\rho$ and $\sigma$ mesons. The effect of early chemical freeze-out in heavy ion collisions is implemented through a temperature dependent pion chemical potential. Read More

The photon spectra measured by the ALICE collaboration in Pb+Pb collisions at Large Hadron Collider (LHC) energies has been analyzed with a view of extracting the properties of thermal system formed in these collisions. The results of the analysis are compared with the previously studied spectra measured at Super Proton Synchrotron (SPS) and Relativistic Heavy Ion Collider (RHIC) energies. The thermal dilepton spectra from the Pb+Pb collision at LHC energy has been predicted for the initial conditions constrained by the thermal photon spectra at the same collision conditions. Read More

We discuss the role of running coupling on the thermal photon yield from quark gluon plasma. It is shown that the photon production rate from the partonic phase is considerably enhanced when running coupling is considered with respect to a fixed value. However, we show by explicit evaluation that although this difference survives the space-time evolution the experimental data cannot distinguish between the two once the hard contribution, which is an essential component of photon production mechanism, is added. Read More

We evaluate the shear viscosity of a pion gas in the relativistic kinetic theory approach. The in-medium propagator of the $\rho$ meson at finite temperature is used to evaluate the $\pi-\pi$ scattering amplitude in the medium. The real and imaginary parts of the self-energy calculated from one-loop diagrams are seen to have noticeable effects on the scattering cross-section. Read More

The effects of viscosity on the space time evolution of QGP produced in nuclear collisions at RHIC energies have been studied. The entropy generated due to the viscous motion of the fluid has been taken into account in constraining the initial temperature by the final multiplicity (measured at the freeze-out point). The viscous effects on the photon spectra has been introduced consistently through the evolution dynamics and phase space factors of the particles participating in the production process. Read More