Particle-hole calculation of the longitudinal response function ofC12

The longitudinal response function of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ in the range of momentum transfers 200 MeV/c≤q≤550 MeV/c is calculated in the Tamm-Dancoff approximation. The particle-hole Green’s function is evaluated by means of a doorway-state expansion. This method allows us to take into account finite-range residual interactions in the continuum, including exchange processes. At low momentum transfers, calculations agree qualitatively with the data. The data cannot be reproduced at momentum transfers around 450 MeV/c. This discrepancy can be accounted for neither by uncertainties in the residual interaction, nor by more complicated processes in the nuclear final states.