Particle production in central Pb+Pb collisions at 158 A GeV/c

The NA44 experiment has measured single particle inclusive spectra for charged pions, kaons, and protons as a function of transverse mass near mid-rapidity in 158 A GeV/$c$ Pb+Pb collisions. From the particle mass dependence of the observed $m_T$ distributions, we are able to deduce a value of about 120 MeV for the temperature at thermal freeze-out. From the observed ratios of the rapidity densities, we find values of the chemical potentials for light and strange quarks and a chemical freeze-out temperature of approximately 140 MeV.