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

TL;DR

This paper explores how scalar leptoquarks influence neutrinoless double beta decay and their connection to neutrino mass, flavor physics, and recent anomalies, providing a comprehensive analysis of parameter constraints and experimental prospects.

Contribution

It presents a global analysis of scalar leptoquark effects on neutrinoless double beta decay, incorporating constraints from various flavor observables and collider searches, highlighting their impact on neutrino mass ordering.

Findings

Leptoquark contributions can alter the effective mass in neutrinoless double beta decay.

Constraints from muon-electron conversion and kaon decays are most restrictive.

Leptoquarks can bridge the gap between normal and inverted neutrino mass orderings.

Abstract

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 $S_1(\bar{3},1,1/3)$ and $\widetilde{R}_2(3,2,1/6)$. We carve out the parameter region consistent with constraints from neutrino mass and mixing, collider searches, as well as measurements of several flavor observables, such as muon and electron anomalous magnetic moments, charged lepton flavor violation and rare (semi)leptonic kaon and $B$-meson decays, including the recent anomalies in $R_{D^{(*)}}$ and $B\to K\nu\bar{\nu}$ observables. 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 $\mu \to e$ conversion in nuclei and $K^{+} \rightarrow\, \pi^{+}\nu \bar{\nu}$ decay. We also point out a tension between the muon and electron $(g-2)$ anomalies in this context. Taking benchmark values from the combined allowed regions, we study the implications for neutrinoless double beta decay including both 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.