Improved Limit on Tensor Currents in the Weak Interaction from ${}^8$Li ${\hat{I}}^2$ Decay

Abstract

The electroweak interaction in the Standard Model (SM) is described by a pure vector-axial-vector structure, though any Lorentz-invariant component could contribute. In this work, we present the most precise measurement of tensor currents in the low-energy regime by examining the ${\hat{I}}^2$-$\bar{\hat{I}}½$ correlation of trapped ${}^8$Li ions with the Beta-decay Paul Trap. We find $a_{{\hat{I}}^2\hat{I}½}=-0.3325\pm 0.0013_{stat}\pm 0.0019_{syst}$ at $1\ddot{I}ƒ$ for the case of coupling to right-handed neutrinos $(C_T=-C_T^{\prime })$, which is consistent with the SM prediction.

6 pages, 3 figures, 1 table