Pions from resonance decay in Brookhaven relativistic heavy-ion collisions

Because of possible effects from flow, it has proved difficult to unambiguously determine the freeze-out temperatures reached in relativistic heavy-ion collisions. We show that pions from the decay of the Π(33) resonance have a very different pperpendicularto distribution than primary pions. Since the ratio of Δ(33) resonances to nucleons depends, through Boltzmann factors, sensitively on the temperature, these pions can be utilized as a thermometer in AGS experiments. We find the temperature for 14.6 GeV/nucleon Si+Au central collisions to be T > or approx. 150 MeV. (orig.)