Beta-decay Paul Trap Mk. IV Commissioning

The Beta-decay Paul Trap (BPT) at Argonne National Lab measures the beta-neutrino angular correlation coefficient a_βν in the decay of Li-8 and B-8 to search for a tensor contribution to the weak interaction, a beyond-Standard Model possibility. The BPT has an ultimate measurement goal of 0.1% uncertainty in a_βν. A new BPT Mk. IV has been built and will be commissioned in winter 2022 with Li-8. This new trap reduces systematic uncertainties associated with electron scattering and features other improvements. This talk will present the final design of the trap and results of the commissioning experiment, with preliminary expectations for new limits from a Li-8 data run in spring 2022.