Neutrinoless Double Beta Decay from Scalar Leptoquarks: Interplay with Neutrino Mass and Flavor Physics

We perform a comprehensive analysis of neutrinoless double beta decay and its interplay with low-energy flavor observables in a radiative neutrino mass model with scalar leptoquarks S₁ (3, 1, 1/3) and R₂ (3, 2, 1/6). We carve out the parameter region consistent with constraints from neutrino mass and mixing, from collider searches, as well as from measurements of several flavor observables, including muon and electron anomalous magnetic moments, charged lepton flavor violation and rare (semi) leptonic kaon and B-meson decays. We perform a global analysis to all existing constraints and show the (anti) correlations between all relevant Yukawa couplings satisfying these restrictions. We find that the most stringent constraint on the parameter space comes from e conversion in nuclei. We also point out a tension between the R₃^ (*) and muon (g-2) anomalies in this context. Taking benchmark points from these combined allowed regions, we study the implications for neutrinoless double beta decay including the canonical light neutrino and the leptoquark contributions. We find that for normal ordering of neutrino masses, the leptoquark contribution removes the cancellation region that occurs for the canonical case. The effective mass in presence of leptoquarks can lie in the desert region between the standard normal and inverted ordering cases, and this can be probed in future ton-scale experiments like LEGEND-1000 and nEXO. Taking suitable representative values of Yukawa couplings, we also obtain stringent constraints on leptoquark masses from different observables.