Tensor interaction constraints from beta decay recoil spin asymmetry of trapped atoms

TL;DR

This study measures recoil spin asymmetry in beta decay of polarized $^{80}$Rb to search for new tensor interactions, finding results consistent with the Standard Model and setting constraints on beyond-Standard Model physics.

Contribution

It provides the first experimental constraint on tensor interactions from recoil asymmetry measurements in trapped atoms, refining limits on new physics beyond the Standard Model.

Findings

Measured recoil asymmetry consistent with SM predictions

Set new limits on tensor interactions in beta decay

Identified dominant uncertainties from higher-order SM corrections

Abstract

We have measured the angular distribution of recoiling daughter nuclei emitted from the Gamow-Teller $\beta$ decay of spin-polarized $^{80}$Rb. The asymmetry of this distribution vanishes to lowest order in the Standard Model (SM) in pure Gamow-Teller decays, producing an observable very sensitive to new interactions. We measure the non-SM contribution to the asymmetry to be $A_{T}$= 0.015 $\pm$ 0.029 (stat) $\pm$ 0.019 (syst), consistent with the SM prediction. We constrain higher-order SM corrections using the measured momentum dependence of the asymmetry, and their remaining uncertainty dominates the systematic error. Future progress in determining the weak magnetism term theoretically or experimentally would reduce the final errors. We describe the resulting constraints on fundamental 4-Fermi tensor interactions.