ReactionCa40(e, e′p)and Observation of the1sProton State

The distorted spectral function of the protons in the reaction ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}(e, e^{\prime }p)$ is measured. For the $2s-1d$ region the distorted-wave impulse-approximation calculation using the Elton-Swift wave functions explains the data within 20%. The $1p$ occupation number is 1.7 times that of the shell-model prediction. After correcting for the radiative effects and for the multiple-collision background the $1s$ state is clearly observed at $E_S\simeq 58$ MeV with a reasonable occupation number.