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In the standard model, the weak interaction is formulated with a purely vector-axial-vector (V-A) structure. Without restriction on the chirality of the neutrino, the most general limits on tensor currents from nuclear β decay are dominated by a single measurement of the β-ν¯ correlation in He6 β decay dating back over a half century. In the present work, the β-ν¯-α correlation in the β decay of Li8 and subsequent α-particle breakup of the Be8∗ daughter was measured. The results are consistent with a purely V-A interaction and in the case of couplings to right-handed neutrinos (CT=-CT′) limits the tensor fraction to |CT/CA|2<0.011 (95.5% C.L.). The measurement confirms the He6 result using a different nuclear system and employing modern ion-trapping techniques subject to different systematic uncertainties.

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Physical Review Letters