Modification of the φ-meson spectrum in nuclear matter

The vacuum spectrum of the φ-meson is characterized by its decay into KK. Modifications of the KK-loops in baryonic matter change this spectrum. We calculate these in-medium modifications taking both s- and p-wave kaon-nucleon interactions into account. We use results of the in-medium K and K spectra determined previously from a coupled channel approach based on a chiral effective Lagrangian. Altogether we find a very small shift of the φ meson mass, by less than 10 MeV at normal nuclear matter density ρ0. The in-medium decay width of the φ meson increases such that its life time at ρ=ρ0 is reduced to less than 5 fm/c. It should therefore be possible to observe medium effects in reactions such as π−p→φn in heavy nuclei, where the φ meson can be produced with small momentum.