Precision Beta-Decay Studies of ⁸Li and ⁸B to Constrain Tensor Currents in the Weak Interaction

The weak interaction of the Standard Model is well-described by a vector-axial vector, or ‘V-A’, structure, which reproduces both maximal parity violation and left-handed neutrinos in beta-decay. However, there is no first-principles reason that other the interactions, such as scalar (S) or tensor (T), may not be present. The existence of these exotic S and T currents can then be probed through their effect on various β-decay correlations, such as the β-ν angular correlation coefficient a_βν and the Fierz interference term b_F. The Gamow-Teller β-decays of ⁸Li and ⁸B are ideal to probes to measure a_βν due to their large Q-values and the delayed alpha emission from the excited state ⁸Be, allowing for a detailed measurement of the kinematic shift between the two fragments which can be used to determine a_βν. These measurements were performed with the Beta decay Paul Trap (BPT) at Argonne National Lab. The BPT is surrounded on 4 sides with double-sided silicon strip detectors backed by plastic scintillator detectors, which allow the kinematics of decay products from the trapped mass-8 ions to be over-constrained. In this presentation we will present the recent results from our work in ⁸Li and first results from the decay of ⁸B.