Constraining new physics with a novel measurement of the 23^{23}Ne β\beta-decay branching ratio

Jul 29, 2021
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2021202220232024310
Abstract: (arXiv)
Measurements of the beta-neutrino correlation coefficient (aβν_{\beta\nu}) in nuclear beta decay, together with the Fierz interference term (bF_F), provide a robust test for the existence of exotic interactions beyond the Standard Model of Particle Physics. The extraction of these quantities from the recoil ion spectra in β\beta-decay requires accurate knowledge, decay branching ratios, and high-precision calculations of higher order nuclear effects. Here, we report on a new measurement of the 23^{23}Ne β\beta-decay branching ratio, which allows a reanalysis of existing high-precision measurements. Together with new theoretical calculations of nuclear structure effects, augmented with robust theoretical uncertainty, this measurement improves on the current knowledge of aβν_{\beta\nu} in 23^{23}Ne by an order of magnitude, and strongly constrains the Fierz term in beta decays, making this one of the first extractions to constrain both terms simultaneously. Together, these results place bounds on the existence of exotic tensor interactions and pave the way for new, even higher precision, experiments.