Parity-violating Longitudinal Response

The parity-violating quasielastic electron scattering response is explored within the context of a model that builds antisymmetrized random phase approximation and Hartree-Fock correlations on a relativistic Fermi gas basis. Particular emphasis is put on the weak-neutral longitudinal response function, since this observable displays a strong sensitivity to isospin correlations: specifically, it is shown how, through a diagrammatic cancellation/filtration mechanism, this response acts as a magnifier of pionic correlations in the nuclear medium. The parity-violating longitudinal response function also displays appreciable sensitivity to the electric strangeness content of the nucleon, thus making quasielastic electron scattering a possible candidate to measure the nucleon electric strange form factor at relatively high momentum transfers. Finally, we discuss how observables, related to the asymmetry, can be constructed to disentangle the nuclear and nucleonic effects. 1 Introduction Parity-violating (pv) electron scattering is a promising tool to study the structure of the nucleon, a notable issue being, for instance, the strangeness content (for a general review of pv studies see Ref. 1). The proton alone, however, is not enough to extract sufficiently constrained information, because of the large number of poorly known form factors entering the game. One is thus led to consider the neutron as well, which in turn implies, generally, the use of nuclei as target. A natural first choice is then elastic scattering off very light nuclei, in order to minimize the nuclear structure uncertainties and to have a nuclear form factor that falls off not too rapidly with the momentum transfer. At intermediate energies also quasielastic scattering shows promising features , such as large cross sections (being proportional to the number of nucle-ons) and nuclear form factors slowly decreasing with the momentum transfer. 2 The issue here is, of course, whether one is able to control the nuclear dynamics sufficiently well to extract accurate information on the single nucleon form factors. This issue has been discussed at length in Ref. 3 , where it has been shown that observables can be constructed, which are selectively sensitive to the nuclear or nucleonic physics content (more on this in the last Section). In the following we focus on the pv (or weak-neutral) longitudinal response,