Accurate Four-Body Response Function with Full Final State Interaction: Application to Electron Scattering off4He

The longitudinal $\left({e,e}^{\prime }\right)$ response function of ${}^4\mathrm{He}$ is calculated precisely with full final state interaction. The explicit calculation of the four-body continuum states is avoided by the method of integral transforms. Precision tests of the response show the high level of accuracy. Nonrelativistic nuclear dynamics are used. The agreement with experimental data is very good over a large energy range for all considered momentum transfers ( $q=300\mathrm{}$, 400, $500\mathrm{MeV}/c$). Only at higher $q$ the theoretical response overestimates the experimental one beyond the quasielastic peak.