A study on thermodynamical properties of hot and dense hadron gas using event generator - Hadro - molecular - dynamical calculation -

We investigate the equilibration and the equation of state of the hot hadron gas at finite baryon density using an event generator which is so designed to satisfy detailed balance at finite temperatures and finite baryon densities of the hadronic scale (80 MeV < T < 170 MeV, 0.157 fm−3 < nB < 0.315 fm −3). Molecular-dynamical-simulations are performed to the system of hadrons in the box with periodic boundary conditions. Starting from an initial state composed of only nucleons with uniform phase-space distribution, the evolution takes place through interactions such as collisions, productions and absorptions. The system approaches to the stationary state of baryons, mesons and their resonances, which is characterized by the value of the exponent in the energy distribution common to the different particles, i.e., temperature. After the equilibration, thermodynamical quantities such as energy density, particle density, entropy and pressure are calculated. Above T ∼ mπ, obtained equation of state shows a remarkable deviation from the naive mixed free gas model. Large values of entropy per baryon are also notable. In our 1 system, the excitation of heavy baryon resonances and meson productions are enhanced simultaneously, and rising of the temperature becomes moderate, but Hagedorn type artificial temperature saturation does not occur. Pressure shows linear dependence on the energy density, and sound velocity is smaller than √ 1 3 . 25.75.-q, 24.10.Lx, 05.70.-a Typeset using REVTEX 2