Title: Searching for Tensor Currents in the Weak Interaction Using Lithium-8 Beta Decay

Abstract: Not all searches for New Physics require 13 TeV of energy. Nuclear physics remains a powerful tool for probing the Standard Model’s limits. The electroweak interaction is well-predicted by a pure vector-axial vector structure. However, high-precision measurements of the beta-neutrino correlation coefficient (“little a”) have long been used as a “broad-band” test for New Physics because of the term’s sensitivity to tensor and scalar currents. The beta decay of Lithium-8 is an ideal reaction for probing “little a” due to its high Q-value and delayed alpha emission of the daughter nucleus. We utilize stopped Lithium-8 ions in a Paul Trap surrounded with silicon strip detectors and backing plastic scintillators to measure and fully reconstruct the decay’s kinematics. Upon completing the analysis of a high-statistics dataset obtained in 2016, we are poised to constrain tensor contributions in the weak interaction to ~0.2%, the most stringent limit yet achieved in the low energy regime.