This work presents a determination of potential short-distance contributions to the unphysical π−→π+e−e− decay through lattice QCD calculations. The hadronic contributions to the transition amplitude are described by the pion matrix elements of five Standard Model Effective Field Theory operators, which are computed on five ensembles of domain-wall fermions with Nf=2+1 quark flavors with a range of heavier-than-physical values of the light quark masses. The matrix elements are extrapolated to the continuum, physical light-quark mass, and infinite volume limit using a functional form derived in chiral Effective Field Theory (χEFT). This extrapolation also yields the relevant low-energy constants of χEFT, which are necessary input for χEFT calculations of neutrinoless double beta decay of nuclei.
@article{arxiv.2208.05322,
title = {Neutrinoless Double Beta Decay from Lattice QCD: The Short-Distance $\pi^-\rightarrow\pi^+ e^- e^-$ Amplitude},
author = {William Detmold and William I. Jay and David J. Murphy and Patrick R. Oare and Phiala E. Shanahan},
journal= {arXiv preprint arXiv:2208.05322},
year = {2023}
}