Transverse electron scattering response function ofHe3

Abstract

The transverse response function ${R}_{T}(q,\ensuremath{\omega})$ for $^{3}\mathrm{He}$ is calculated using the configuration space BonnA nucleon-nucleon potential, the Tucson-Melbourne three-body force, and the Coulomb potential. Final states are completely taken into account via the Lorentz integral transform technique. Nonrelativistic one-body currents plus two-body \ensuremath{\pi} and \ensuremath{\rho} meson exchange currents (MECs) as well as the Siegert operator are included. The response ${R}_{T}$ is calculated for $q=174$, 250, 400, and 500 MeV/$c$ and in the threshold region at $q=174$, 324, and 487 MeV/$c$. Strong MEC effects are found in low- and high-energy tails, but due to MECs there are also moderate enhancements of the quasielastic peak (6--10%). The calculation is performed both directly and via transformation of electric multipoles to a form that involves the charge operator. The contribution of the latter operator is suppressed in and below the quasielastic peak, while at higher energies the charge operator represents almost the whole MEC contribution at the lowest $q$ value. The effect of the Coulomb force in the final state interaction is investigated for the threshold region at $q=174$ MeV/$c$. Its neglect enhances ${R}_{T}$ by more than 10% in the range up to 2 MeV above threshold. In a comparison with experimental data, one finds relatively good agreement at $q=250$ and 400 MeV/$c$, while at $q=500$ MeV/$c$, presumably due to relativistic effects, the theoretical quasielastic peak position is shifted to somewhat higher energies. The strong MEC contributions in the threshold region are nicely confirmed by data at $q=324$ and 487 MeV/$c$.