Density dependence of single-proton and two-proton knockout reactions under quasifree conditions

Abstract

We consider high-energy quasifree single- and two-proton knockout reactions induced by electrons and protons and address the question of what target-nucleus densities can be effectively probed after correcting for nuclear attenuation (initial- and final-state interactions). Our calculations refer to ejected proton kinetic energies of 1.5 GeV, the reactions $(e,{e}^{'}p)$, $(\ensuremath{\gamma},\mathit{pp})$, and $(p,2p)$, and a carbon target. It is shown that each of the three reactions is characterized by a distinctive sensitivity to the density of the target nucleus. The bulk of the $(\ensuremath{\gamma},\mathit{pp})$ strength stems from the high-density regions in the deep nuclear interior. Despite the strong attenuation, sizable densities can be probed by $(p,2p)$ reactions provided that the energy resolution allows one to pick nucleons from $s$ orbits. The effective mean densities that can be probed in high-energy $(e,{e}^{'}p)$ reactions is of the order of 30%--50% of the nuclear saturation density.