The $ρ$ Spectral Function in a Relativistic Resonance Model

Abstract

We calculate the spectral function $A_ρ$ of the $ρ$ meson in nuclear matter. The calculation is performed in the {\it low density} approximation, where the in-medium self energy $Σ_{med}$ is completely determined by the vacuum $ρN$ forward scattering amplitude. This amplitude is derived from a relativistic resonance model. In comparison to previous non-relativistic calculations we find a much weaker momentum dependence of $Σ_{med}$, especially in the transverse channel. Special attention is paid to uncertainties in the model. Thus, we compare the impact of different coupling schemes for the $RNρ$ interaction on the results and discuss various resonance parameter sets.