Enhancement of nucleon-nucleon cross section in sidewards flowing nuclear matter through zero sound mode excitation

We investigate the modification induced on the nucleon-nucleon cross section by screening of the interaction inside nuclear matter. The interaction is described by the relativistic one boson exchange of $\sigma$, $\omega$ and $\pi$ mesons. Medium effects enter as loop corrections to the meson propagators and are characterized not only by density, but also by temperature and velocity with respect to the center of mass of the collision. The cross section displays peaks for some specific values of the velocity, corresponding to the excitation of zero-sound modes of the longitudinal $\omega$ field. The enhancement factor amounts to about 1.5 under reasonable conditions. It increases with density and is reduced at finite temperature. These findings may have verifiable consequences on the angular dependence of the measurable secondary particle distributions.