Quasielastic12C(e,e′p)reaction at high momentum transfer

We measured the ${}^{12}\mathrm{C}{(e,e}^{\prime }p)$ cross section as a function of missing energy in parallel kinematics for $(q,\omega )=(970\mathrm{}\hspace{0.5em}\mathrm{MeV}/c,\hspace{0.5em}330\hspace{0.5em}\mathrm{MeV})$ and $(990\mathrm{}\hspace{0.5em}\mathrm{MeV}/c,\hspace{0.5em}475\hspace{0.5em}\mathrm{MeV}).\mathrm{}$ At $\omega =475\mathrm{}\hspace{0.5em}\mathrm{MeV},$ at the maximum of the quasielastic peak, there is a large continuum ${(E}_m>50\mathrm{}\hspace{0.5em}\mathrm{MeV})$ cross section extending out to the deepest missing energy measured, amounting to almost 50% of the measured cross section. The ratio of data to distorted-wave impulse approximation (DWIA) calculation is 0.4 for both p and s shells. At $\omega =330\mathrm{}\hspace{0.5em}\mathrm{MeV},$ well below the maximum of the quasielastic peak, the continuum cross section is much smaller and the ratio of data to DWIA calculation is 0.85 for the p shell and 1.0 for the s shell. We infer that one or more mechanisms that increase with $\omega$ transform some of the single-nucleon knockouts into a multinucleon knockout, decreasing the valence knockout cross section and increasing the continuum cross section.