Improved transverse (e,e-prime) response function of He-3 at intermediate momentum transfers

The transverse electron scattering response function of $^{3}\mathrm{He}$ is studied in the quasielastic peak region for momentum transfers between 500 and 700 MeV/$c$. A conventional description of the process leads to results that vary substantially from experiment. To improve the results, the present calculation is done in a reference frame [the active nucleon Breit (ANB) frame] that diminishes the influence of relativistic effects on nuclear states. The laboratory frame response function is then obtained via a kinematics transformation. In addition, a one-body nuclear current operator is employed that includes all leading-order relativistic corrections. Multipoles of this operator are listed. It is shown that the use of the ANB frame leads to a sizable shift in the quasielastic peak to lower energy and, contrary to the relativistic current, also to an increase in the peak height. The additionally considered meson exchange current contribution is quite small in the peak region. In comparison with experiment, there is excellent agreement of the peak positions. The peak height agrees well with experiment for the lowest considered momentum transfer (500 MeV/$c$) but tends to be too high for higher momentum transfer (10% at 700 MeV/$c$).