Proton propagation in nuclei studied in the (e,e'p) reaction.

Abstract

Proton propagation in nuclei was studied using the (e,e'p) reaction in the quasifree region. The coincidence (e,e'p) cross sections were measured at an electron angle of 50.4\ifmmode^\circ\else\textdegree\fi{} and proton angles of 50.1\ifmmode^\circ\else\textdegree\fi{}, 58.2\ifmmode^\circ\else\textdegree\fi{}, 67.9\ifmmode^\circ\else\textdegree\fi{}, and 72.9\ifmmode^\circ\else\textdegree\fi{} for $^{12}\mathrm{C}$, $^{27}\mathrm{Al}$, $^{58}\mathrm{Ni}$, and $^{181}\mathrm{Ta}$ targets at a beam energy of 779.5 MeV. The average outgoing proton energy was 180 MeV. The ratio of the (e,e'p) yield to the simultaneously measured (e,e') yield was compared to that calculated in the plane-wave impulse approximation and an experimental transmission defined. These experimental transmissions are considerably larger (a factor of \ensuremath{\sim}2 for $^{181}\mathrm{Ta}$) than those one would calculate from the free N-N cross sections folded into the nuclear density distribution. A new calculation that includes medium effects (N-N correlations, density dependence of the N-N cross sections and Pauli suppression) accounts for this increase.