Three-nucleon matrix elements for beta decays with quantum Monte Carlo methods

Precision measurements of beta decays provided stringent tests of the Standard Model and could uncover signals of new physics. However, nuclear theory is needed to interpret the results of these experiments and to extract physics paremeters. In the case of neutrinoless double beta decay, nuclear matrix elements are needed to constrain the effective Majorana mass, and in the case of superallowed beta decay, radiative corrections are needed to precisely determine the Cabibbo-Kobayashi-Maskawa matrix element V_ud. In this work, we derive three-nucleon operators for these transitions using delta-full chiral effective field theory and compute their matrix elements in light nuclei using quantum Monte Carlo methods. We compare to the contributions of the leading-order operators and discuss the impact on the extraction of physics parameters.