Parity violating measurements of neutron densities

TLDR

Parity‑violating electron–nucleus scattering offers a clean, highly accurate probe of neutron spatial distributions, exploiting interference between electromagnetic and weak neutral amplitudes where the Z⁰ couples mainly to neutrons at low Q², enabling data interpretation with confidence comparable to electromagnetic scattering. The study aims to review current knowledge of neutron densities and explore feasible parity‑violation measurements, their theoretical interpretation, and applications. The authors analyze potential parity‑violation experiments, detailing their theoretical frameworks and practical applications. They conclude that such experiments are feasible at existing facilities, that theoretical corrections are minimal or well understood, and that electron‑scattering asymmetries can be directly applied to atomic parity‑nonconservation studies due to similar nuclear‑shape dependence.

Abstract

Parity violating electron nucleus scattering is a clean and powerful tool for measuring the spatial distributions of neutrons in nuclei with unprecedented accuracy. Parity violation arises from the interference of electromagnetic and weak neutral amplitudes, and the ${Z}^{0}$ of the standard model couples primarily to neutrons at low ${Q}^{2}.$ The data can be interpreted with as much confidence as electromagnetic scattering. After briefly reviewing the present theoretical and experimental knowledge of neutron densities, we discuss possible parity violation measurements, their theoretical interpretation, and applications. The experiments are feasible at existing facilities. We show that theoretical corrections are either small or well understood, which makes the interpretation clean. The quantitative relationship to atomic parity nonconservation observables is examined, and we show that the electron scattering asymmetries can be directly applied to atomic parity nonconservation because the observables have approximately the same dependence on nuclear shape.