Density and expansion effects on pion spectra in relativistic heavy-ion collisions - art. no. 014904

We compute the pion inclusive momentum distribution in heavy-ion collisions at AGS energies, assuming thermal equilibrium and accounting for density a nd expansion effects at the time of decoupling. We compare to data on midra pidity charged pions produced in central Au+Au collisions and find very goo d agreement. The shape of the distribution at low m(t)-m is explained in pa rt as an effect arising from the high mean pion density achieved in these r eactions. The difference between the positive and negative pion distributio ns in the same region is attributed in part to the different average yields of each kind of charged pions. [S0556-2813(99)02607-2].