Neutrino scattering rates in neutron star matter with Delta isobars

Abstract

We take the Delta-isobar degrees of freedom into account in neutron star matter and evaluate their contributions to neutrino scattering cross sections and mean free paths. The neutron star matter is described by means of an effective hadronic model in the relativistic mean-field approximation. It is found that Delta isobars may be present in neutron stars. The electron chemical potential does not decrease and the neutrino abundance does not increase with the increase of the density when neutrinos are trapped in the matter with Delta isobars. The large vector coupling constant between the Delta(-) and neutrino and the high spin of the Delta influence significantly the neutrino scattering cross section and lead the contribution of the Delta(-) to the dominance of the scattering rates. In neutrino-trapped case, the presence of Delta s causes the neutrino mean free path to decrease drastically compared to that in the matter in which baryons are only nucleons.