Isotensor Axial Polarizability and Lattice QCD Input for Nuclear Double-β Decay Phenomenology

The potential importance of short-distance nuclear effects in double-beta decay is assessed using a lattice QCD calculation of the nn -> pp transition and effective field theory methods. At the unphysical quark masses used in the numerical computation, these effects, encoded in the isotensor axial polarizability, are found to be of similar magnitude to the nuclear modification of the single axial current, which phenomenologically is the quenching of the axial charge used in nuclear many-body calculations. This finding suggests that nuclear models for neutrinoful and neutrinoless double-beta decays should incorporate this previously neglected contribution if they are to provide reliable guidance for next-generation neutrinoless double-beta decay searches. The prospects of constraining the isotensor axial polarizabilities of nuclei using lattice QCD input into nuclear many-body calculations are discussed.