Transport coefficients for multi-component gas of hadrons using Chapman Enskog method

The transport coefficients of a multi-component hadronic gas at zero and non-zero baryon chemical potential are calculated using the Chapman-Enskog method. The calculations are done within the framework of an $S$-matrix based interacting hadron resonance gas model. In this model, the phase-shifts and cross-sections are calculated using $K$-matrix formalism and where required, by parameterizing the experimental phase-shifts. Using the energy dependence of cross-section, we find the temperature dependence of various transport coefficients such as shear viscosity, bulk viscosity, heat conductivity and diffusion coefficient. We finally compare our results regarding various transport coefficients with previous results in the literature

One particle distribution function and shear viscosity in magnetic field: a relaxation time approach

We calculate the $\delta f$ correction to the one particle distribution function in presence of magnetic field and non-zero shear viscosity within the relaxation time approximation. The $\delta f$ correction is found to be electric charge dependent. Subsequently, we also calculate one longitudinal and four transverse shear viscous coefficients as a function of dimensionless Hall parameter $\chi_{H}$ in presence of the magnetic field. We find that a proper linear combination of the shear viscous coefficients calculated in this work scales with the result obtained from Grad's moment method in \cite{Denicol:2018rbw}. Calculation of invariant yield of $\pi^{-}$ in a simple Bjorken expansion with cylindrical symmetry shows no noticeable change in spectra due to the $\delta f$ correction for realistic values of the magnetic field and relaxation time. However, when transverse expansion is taken into account using a blast wave type flow field we found noticeable change in spectra and elliptic flow coefficients due to the $\delta f$ correction. The $\delta f$ is also found to be very sensitive on the magnitude of magnetic field. Hence we think it is important to take into account the $\delta f$ correction in more realistic numerical magnetohydrodynamics simulations.Comment: 14 pages, 6 figures, revised version, new section added, new figures added, published in EPJ

Weibull Distribution and the multiplicity moments in pp (ppˉ)pp\,(p\bar{p}) collisions

A higher moment analysis of multiplicity distribution is performed using the Weibull description of particle production in $pp\,(p\bar{p})$ collisions at SPS and LHC energies. The calculated normalized moments and factorial moments of Weibull distribution are compared to the measured data. The calculated Weibull moments are found to be in good agreement with the measured higher moments (up to 5$^{\rm{th}}$ order) reproducing the observed breaking of KNO scaling in the data. The moments for $pp$ collisions at $\sqrt{s}$ = 13 TeV are also predicted.Comment: 5 pages, 3 figure

Charged participants and their electromagnetic fields in an expanding fluid

We investigate the space-time dependence of electromagnetic fields produced by charged participants in an expanding fluid. To address this problem, we need to solve the Maxwell's equations coupled to the hydrodynamics conservation equation, specifically the relativistic magnetohydrodynamics (RMHD) equations, since the charged participants move with the flow. To gain analytical insight, we approximate the problem by solving the equations in a fixed background Bjorken flow, onto which we solve Maxwell's equations. The dynamical electromagnetic fields interact with the fluid's kinematic quantities such as the shear tensor and the expansion scalar, leading to additional non-trivial coupling. We use mode decomposition of Green's function to solve the resulting non-linear coupled wave equations. We then use this function to calculate the electromagnetic field for two test cases: a point source and a transverse charge distribution. The results show that the resulting magnetic field vanishes at very early times, grows, and eventually falls at later times.Comment: 13 pages, 5 figures. Minor revisions and a new figure showing domain of influence adde