Light-Neutrino Exchange and Long-Distance Contributions to $0\nu 2\beta$ Decays: An Exploratory Study on $\pi \pi \to ee$

Xu Feng, Lu-Chang Jin, Xin-Yu Tuo +1

We present an exploratory lattice QCD calculation of the neutrinoless double beta decay $\pi \pi \to ee$. Under the mechanism of light-neutrino exchange, the decay amplitude involves sig…