Systematic decomposition of dimension-11 short-range neutrinoless double beta decay operators

A bstract Neutrinoless double beta decay (0 νββ ) may receive sizable contributions from short-range physics beyond the Standard Model. We present a systematic classification of all tree-level ultraviolet completions of the dimension-11 short-range 0 νββ decay operators, renormalizable scenarios with scalar and fermion mediators are considered. We identify eight distinct topologies and twenty-eight viable diagrams, from which all consistent UV completions are generated by imposing Standard Model gauge invariance. All these models involve a total of 61 new fields beyond the Standard Model and they typically feature fractionally charged fermions and exotic bosons such as dileptons, diquarks, and leptoquarks. We further study a representative model without colored mediators and analyze its implications for the 0 νββ decay half-life and light neutrino masses. We find that current and future 0 νββ decay experiments impose stringent constraints. Our systematic decomposition provides a general framework for exploring exotic short-range contributions to 0 νββ decay in future experiments.