The Delta(1232) at RHIC

H. van Hees, R. Rapp

Published 2004-09-13, updated 2005-01-26Version 3

We investigate properties of the Delta(1232) and nucleon spectral functions at finite temperature and baryon density within a hadronic model. The medium modifications of the Delta consist of a renormalization of its pion-nucleon cloud and resonant pi-Delta scattering. Underlying coupling constants and form factors are determined by the elastic \pi-N scattering phase shift in the isobar channel, as well as empirical partial decay widths of excited baryon resonances. For cold nuclear matter the model provides reasonable agreement with photoabsorption data on nuclei in the Delta-resonance region. In hot hadronic matter typical for late stages of central Au-Au collisions at RHIC we find the Delta-spectral function to be broadened by $\sim$65 MeV together with a slight upward mass shift of 5-10 MeV, in qualitative agreement with preliminary data from the STAR collaboration.