Sigma decay at finite temperature and density

Sigma decay and its relation with chiral phase transition are discussed at finite temperature and density in the framework of the Nambu-Jona-Lasinio model. The decay rate for the process σ→2π to first order in 1/Nc (inverse number of colours) expansion is calculated as a function of temperature T and baryon density nb. In particular, only when the chiral phase transition happens around the tricritical point, the σ decay zone sandstonnon-thermal enhancement of pions in the final state distributions in relativistic heavy ion collisions