Temperature dependence of hadron masses: I. Results from an extended linear σ model

The temperature dependence of hadron masses has been calculated from the linear σ-model, extended to include ρ and a1 mesons. In the symmetric matter approximation, the baryon propagator has been obtained which has then been used to calculate the free energy of the nuclear matter. The temperature dependence of the baryon mass has been obtained in the relativistic Hartree approximation (RHA). The meson masses have been calculated in the random phase approximation (RPA) self-consistently. It has been found that the baryon mass decreases with temperature. The π mass and the ω mass increase with temperature. The ρ mass increases while the a1 mass decreases with temperature and matches with the ρ mass, indicating the restoration of the broken chiral symmetry. (author)