Thermal and nonthermal pion enhancements with chiral symmetry restoration - art. no. 016004

The pion production by sigma decay and its relation with chiral symmetry re storation in hot and dense matter are investigated in the framework of the Nambu-Jona-Lasinio model. The decay rate for the process sigma-->2 pi to th e lowest order in a 1/N-c expansion is calculated as a function of temperat ure T and chemical potential mu. The thermal and nonthermal enhancements of pions generated by the decay before and after the freeze-out are present o nly in the crossover region of the chiral symmetry transition. The stronges t nonthermal enhancement is located in the vicinity of the end point of the first-order transition.