Inclusive electron scattering and pion degrees of freedom in light nuclei

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Abstract
We demonstrate that realistic models of nuclear interactions and currents quantitatively reproduce the α-particle longitudinal and transverse responses as measured in inclusive electron scattering at intermediate energies. Pion degrees of freedom in both the nuclear interactions and currents play a crucial role in reproducing the experimental data. The charge-exchange character of the pion-exchange interaction leads to shifts of both longitudinal and transverse strength to higher excitation energies, thus producing a significant quenching of the response in the region of the quasielastic peak. However, in the transverse channel this mechanism is more than offset by the two-body pion-exchange currents required by gauge invariance, and hence the response is enhanced over the entire quasielastic spectrum. We relate these results to responses to idealized single-nucleon couplings and to quasielastic data from hadronic reactions on nuclei.