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

Understand

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.