M ay 1 99 7 Medium effects in K + nuclear interactions ∗

Total (σ T) and reaction (σ R) cross sections are derived self consistently from the attenuation cross sections measured in transmission experiments at the AGS for K + on 6 Li, C, Si and Ca in the momentum range of 500-700 MeV/c by using a V opt = t ef f (ρ)ρ optical potential. Self consistency requires, for the KN in-medium t matrix, that Im t ef f (ρ) increases linearly with the average nuclear density in excess of a threshold value of 0.088±0.004 fm −3. The density dependence of Re t ef f (ρ) is studied phenomenologically, and also applying a relativistic mean field approach, by fitting to the σ T and σ R values. The real part of the optical potential is found to be systematically less repulsive with increasing energy than expected from the free-space repulsive KN interaction. When the elastic scatttering data for 6 Li and C at 715 MeV/c are included in the analysis, a tendency of Re V opt to generate an attractive pocket at the nuclear surface is observed.