Scaling of hadron masses and widths in thermal models for ultrarelativistic heavy-ion collisions

By means of a simple rescaling, modifications of hadron masses and widths a re incorporated into the thermal analysis of particle ratios in ultrarelati vistic heavy-ion collisions. We find that moderate, up to 20%, changes of h adron masses do not spoil the quality of the fits, which remain as good as those obtained without modifications. Larger changes are not likely. The fi ts with the modified masses yield modified values of the optimal temperatur e and baryon chemical potential. In particular, with decreasing masses of a ll hadrons (except for pseudo-Goldstone bosons) the fitted values-of the te mperature and the baryon chemical potential are lowered, with the change ap proximately proportional to the scaling of masses. In addition, we find tha t the broadening of the hadron widths by less than a factor of two practica lly does not affect the fits. (C) 2001 Elsevier Science B.V. All rights res erved.