A simple relation between the nucleon-nucleon scattering cross sections in vacuum and in nuclear matter is proposed. It consistently takes into account the velocity dependence of the nuclear mean field and Pauli blocking, and is shown to be fairly accurate. It is used to study the mean free path of nucleons in nuclear matter and the imaginary part of the optical potential. It is also used with the local density approximation and the correlated Glauber approximation to calculate the transparency of nuclei as measured by (e,e’p) reactions. The Pauli blocking, velocity dependence of the nuclear mean field, and the ground-state correlations increase the transparency, and all the three effects are necessary to explain the observed transparencies of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$, ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$, and ${}_{}{}^{181}{}_{}{}^{}\mathrm{Ta}$ for recoiling 180 MeV protons.

• Received 10 October 1991

DOI:https://doi.org/10.1103/PhysRevC.45.791