Pion Properties in a Hot $\Pi N\Delta$ Gas

Abstract

Based on a recent meson-exchange model for the vacuum $\pi \pi$ interaction we compute selfconsistently the in-medium $\pi \pi$ scattering amplitude and pion selfenergy in a hot $\pi N\Delta$ gas. The contributions to the pion selfenergy are calculated from the $\pi \pi$ T-matrix as well as from p-wave interaction with nucleons and thermally abundant $\Delta$'s. Results are presented for two scenarios believed to be realized in the relativistic heavy ion collisions performed at the GSI-SIS and the CERN-SpS. Possible implications for the observed soft pion enhancement at both SIS and SpS are indicated.

Comments: 20 pages in Latex, 5 figures available on request from the authors, UIUC preprint P-93-11-096