Effects of the modified Δ spectral function and of the coulomb interaction on the charged pions in Au + Au collisions at 1A GeV

We present the results of thermal model calculations including both a modification of the Δ (1232) spectral function and the Coulomb interaction. The model calculations are compared with the published pion spectra for central Au + Au collisions at 1A GeV. The freeze-out radius of the fireball is deduced to be about 6.3 fm by using an est mated Coulomb potential. The percentage of participant nucleons which are excited to the Δ(1232) resonance in large collision systems is reduced compared to that in small collision systems.