Status and prospects of Rn measurements at Mainz

Abstract

Parity-violating electron scattering is particularly sensitive to the neutron density. The recent PREX experiment at the Jefferson Laboratory (JLab) has demonstrated the feasibility of this method meanwhile outlining its major experimental challenges. On the other side intermediate energy photons are an ideal probe for studying the properties of strongly interacting matter from the nuclear scale down to the sub-nuclear components of the nucleus. Among others, coherent pion photoproduction on nuclei is an attractive approach to obtain information on the existence and nature of neutron skins in nuclei. The simultaneous combination of different techniques allows a systematic determination of the neutron skin of nuclei across the periodic table thus benchmarking modern calculations.Recently a systematic investigation of the latter method has been exploited at the MAMI accelerator. With the future accelerator MESA, the same experimental setup as in the measurement of the weak mixing angle will allow for a measurement of the parity violating asymmetry for longitudinally polarized electrons scattered on heavy nuclei with an accuracy of order 1% such that the neutron radius can be determined with precision competitive with the future PREX measurements.