Improved Tensor Current Limit from B8 β Decay Including New Recoil-Order Calculations

This is the authors' abstract. We don't add key points for this paper.

A precision measurement of the β⁺ decay of ⁸B was performed using the Beta-decay Paul Trap to determine the β-ν angular correlation coefficient a_βν. The experimental results were combined with new ab initio symmetry-adapted no-core shell-model calculations to yield the second-most precise measurement from Gamow-Teller decays, a_βν=-0.3345±0.0019ₛₜₐₜ±0.0021syst. This value agrees with the standard model value of -1/3 and improves uncertainties in ⁸B by nearly a factor of 2. By combining results from ⁸B and ⁸Li, a tight limit on tensor current coupling to right-handed neutrinos was obtained. A recent global evaluation of all other precision β decay studies suggested a nonzero value for right-handed neutrino coupling in contradiction with the standard model at just above 3σ. The present results are of comparable sensitivity and do not support this finding.