Nucleon size effects in the parity violating electron scattering asymmetry

We investigate isospin mixing effects in the asymmetry as obtained in parity-violating electron scattering from ⁴He, ¹²C, ⁴⁸Ca, ⁹⁰Zr and ²⁰⁸Pb nuclei. The scattering analysis is developed within the distorted wave Born approximation (DWBA) accounting for nucleon form factors. We use a relativistic mean field model, including the σ, ω, ρ and δ mesons, with density dependent couplings, as well as the electromagnetic interaction. Numerical results are presented for the asymmetry, charge and weak charge radius. We conclude nucleon size effects in parity-violating elastic electron scattering for N = Z nuclei affects very little the isospin mixing function for small q values but can be relevant for medium q experiments, where the extraction of the strangeness content of the nucleus is aimed. As for highly asymmetric nuclei, where the measurement of the neutron radius is of great interest, we have shown that the effect is less than 1% for ²⁰⁸Pb, but is bigger for ⁴⁸Ca (nearly 1% for the charge and 2% for the weak charge radius). For ⁹⁰Zr the figures are 0.8% and 1.6% respectively