$ϕ$ meson self-energy in nuclear matter from $ϕN$ resonant interactions

Abstract

The $ϕ$-meson properties in cold nuclear matter are investigated by implementing resonant $ϕN$ interactions as described in effective approaches including the unitarization of scattering amplitudes. Several $N^*$-like states are dynamically generated in these models around $2$ GeV, in the vicinity of the $ϕN$ threshold. We find that both these states and the non-resonant part of the amplitude contribute sizably to the $ϕ$ collisional self-energy at finite nuclear density. These contributions are of a similar strength as the widely studied medium effects from the $\bar K K$ cloud. Depending on model details (position of the resonances and strength of the coupling to $ϕN$) we report a $ϕ$ broadening up to about $40$-$50$ MeV, to be added to the $ϕ\to\bar K K$ in-medium decay width, and an attractive optical potential at threshold up to about $35$ MeV at normal matter density. The $ϕ$ spectral function develops a double peak structure as a consequence of the mixing of resonance-hole modes with the $ϕ$ quasi-particle peak. The former results point in the direction of making up for missing absorption as reported in $ϕ$ nuclear production experiments.

17 pages, 2 figures