Nuclear ab initio calculations of 6He $beta$-decay for beyond the Standard Model studies

Precision measurements of $beta$-decay observables offer the possibility to search for deviations from the Standard Model. A possible discovery of such deviations requires accompanying first-principles calculations. Here we compute the nuclear structure recoil corrections for the $beta$-decay of $^6$He which is of central interest in several experimental efforts. We use the emph{ab~initio} no-core shell model in the impulse approximation with potentials based on chiral effective field theory, augmented with an analysis of relevant uncertainties. We find that nuclear corrections create a significant deviation from the pure Gamow--Teller predictions -- within the sensitivity of future experiments -- making them essential in searches for physics beyond the Standard Model.