The A dependence of the (e,e’p) reaction in the quasifree region has been measured at an average $Q^2$ of 0.33 (GeV/c${)}^2$ for targets of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$, ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$, and ${}_{}{}^{181}{}_{}{}^{}\mathrm{Ta}$. The outgoing proton kinetic energy was 180±30 MeV. By comparing the ratio of (e,e’p) coincidence to (e,e’) singles yields, average proton transmissions are obtained for each target. The resulting ‘‘mean free path’’ or, more precisely, the attenuation length for protons in the nucleus is significantly longer than expectations based on the free nucleon-nucleon cross section.

• Received 24 April 1989

DOI:https://doi.org/10.1103/PhysRevLett.63.734