Exclusive Measurement Of Proton Quasifree Scattering And Density Dependence Of The Nucleon-Nucleon Interaction

Differential cross sections and analyzing powers (A(y)) have been measured for the proton knockout reaction from s(1/2) orbits of three kinds 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 found to depend on target. For the present setting, where the recoil momentum 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 function of the averaged density, which strongly suggests the existence of a nuclear medium effect on the nucleon-nucleon interaction.