Beta Decays from Lattice QCD
Beta decays, where nuclei emit electrons, have played an instrumental role in furthering our understanding of particle physics for almost 100 years. Even today they can play a crucial role in the discovery of new physics. But to separate effects of new physics from effects of the Standard Model requires precision understanding of the protons, neutrons, and other hadrons that participate in those decays. The quarks and gluons in those hadrons are governed by quantum chromodynamics, a strongly-interacting sector of the Standard Model. In the hadronic regime QCD requires a numerical approach.
I will review the history of beta decays, highlight some current mysteries and hopes, and explain how recent lattice QCD results have allowed us to narrow the gap between precision experiments and finding new physics by computing the neutron axial coupling which controls its coupling to the weak nuclear force responsible for beta decays and other hadronic matrix elements important for experimental searches for neutrinoless double beta decays.
