A measurement of the $\alpha \mathrm{\text{−}}\beta \mathrm{\text{−}}\overline{\nu }$ angular correlation in the Gamow-Teller decay ${}^8\mathrm{Li}\to {}^8\mathrm{Be}^{*}+\overline{\nu }+\beta$, ${}^8\mathrm{Be}^{*}\to \alpha +\alpha$ has been performed using ions confined in a linear Paul trap surrounded by silicon detectors. The energy difference spectrum of the $\alpha$ particles emitted along and opposite the direction of the $\beta$ particle is consistent with the standard model prediction and places a limit of 3.1% (95.5% confidence level) on any tensor contribution to the decay. From this result, the amplitude of any tensor component $C_T$ relative to that of the dominant axial-vector component $C_A$ of the electroweak interaction is limited to $|C_T/C_A|<0.18$ (95.5% confidence level). This experimental approach is facilitated by several favorable features of the ${}^8\mathrm{Li}$ $\beta$ decay and has different systematic effects than the previous $\beta \mathrm{\text{−}}\overline{\nu }$ correlation results for a pure Gamow-Teller transition obtained from studying ${}^6\mathrm{He}$ $\beta$ decay.

• Received 22 October 2012

DOI:https://doi.org/10.1103/PhysRevLett.110.092502