Absolute spectroscopic factors from nuclear knockout reactions

Experimental cross sections at high energies for the ${}^{12}\mathrm{C}{(}^{16}\mathrm{O}{,}^{15}\mathrm{N}/\mathrm{O})X$ and ${}^{12}\mathrm{C}{(}^{12}\mathrm{C}{,}^{11}\mathrm{B}/\mathrm{C})X$ nucleon removal reactions are reduced by factors $R_s=0.49\mathrm{}–0.68$ relative to calculations in the shell model and eikonal reaction theory. For protons, this is exactly what has been found in the ${(e,e}^{\prime }p)$ reaction. We suggest that nuclear knockout has potential for extending the measurement of precise orbital occupancies to neutron states and to a wide range of nuclei including rare radioactive species. The halo proton in radioactive ${}^8\mathrm{B}$ turns out to have a stronger presence in the wave function with $R_s=0.88\mathrm{}\left(4\right).$