Quasielastic electron scattering and Coulomb sum rule inHe4

Double differential cross sections for inelastic electron scattering from {sup 4}He have been measured at bombarding energies between 279 and 725 MeV. The longitudinal and transverse response functions were obtained for constant momentum transfer between 300 and 500 MeV/{ital c}. Plane-wave impulse approximation calculations overestimate the longitudinal response and produce fair agreement with the transverse part. The Coulomb sum is determined and compared with exact calculations. Within the experimental error the data exhaust the sum rule; this provides a first measurement of ground-state correlations.