Sensitivity of parity-violating A((e)over-right-arrow, e ')A scattering and atomic parity nonconservation to neutron distributions in nuclei

Parity-violating electron scattering (PVES) could provide a unique means to determine spatial neutron distributions and their moments in heavy nuclei. Knowledge of the neutron distribution is of fundamental interest for nucle ar structure models, and the first moment is of special interest for atomic parity experiments. We have examined what could be learned from a hypothet ical measurement of the parity-violating asymmetry in elastic electron scat tering on barium and lead nuclei (both spin-0 and N not equal Z). We find t hat a single measurement of this quantity could determine the rms neutron r adius to within a couple of percent, to be compared with the 5-10% existing uncertainties. We also compute the quantitative connection to atomic parit y nonconservation, and the resulting limits on possible low energy Standard Model tests which could be achieved.