EXCLUSIVE MEASUREMENT OF PROTON QUASI-FREE SCATTERING AND DENSITY-DEPENDENCE OF THE NUCLEON-NUCLEON INTERACTION

Differential cross sections and analyzing powers (A(y)) have been meas ured for the proton knockout reaction from s(1/2) orbits of three kind s of target nuclei at E(p) = 392 MeV. The A(y) values are reduced from those of free proton-proton scattering and the reduction rate is foun d to depend on target. For the present setting, where the recoil momen tum is almost zero, an averaged density seen through this reaction can be estimated and it reaches almost half of the saturation density in some cases. The reduction of A(y) shows a monotonically decreasing fun ction of the averaged density, which strongly suggests the existence o f a nuclear medium effect on the nucleon-nucleon interaction.