Meson Spectra — What We Learn from Single Particle Distributions

Abstract

The dynamics of nucleus-nucleus collisions determine where the hadrons are observed in experiments. The distributions of different hadronic species in rapidity, y, transverse momentum, p t, and transverse mass, m t provide insights into the reaction dynamics. They shed light on the extent of thermalization, 1 the possibility and magnitude of collective flow, 2 and the effects of reinteractions of the produced particles. We use single particle spectra to look for evidence of formation of an extended strongly interacting system in heavy ion collisions. Formation of such a system allows study of the properties of highly excited matter, and enhances any signals over the “background” of normal hadronic interactions. It is in this region of high energy density that we can look for evidence of formation of a quark gluon plasma, as described theoretically in several lectures at this school.