Linking lepton number violation with $B$ anomalies

TL;DR

This paper explores a specific leptoquark scenario that explains B decay anomalies, violates lepton number, and naturally generates neutrino masses, while analyzing related lepton number violating processes.

Contribution

It identifies a unique leptoquark model compatible with B anomalies that also accounts for neutrino masses and predicts lepton number violation effects.

Findings

A single leptoquark scenario explains B anomalies and violates lepton number.

Neutrino masses are radiatively generated with correct order of magnitude.

Estimated lepton number violating process rates are consistent with current bounds.

Abstract

Hints of violation of lepton flavor universality in semileptonic $B$ decays have prompted a renewed interest in leptoquarks at the low TeV scale. Among the different scenarios suggested, some happen to violate also lepton number, yet not much attention has been paid to the expected size of the associated lepton number violating processes. In this note we examine this issue. We find that there is a single leptoquark scenario compatible with the current size of the anomalies which also violates lepton number. In this scenario (Majorana) neutrino masses are radiatively generated. With the leptoquark parameters extracted from fitting the flavor anomalies, one actually gets the right order of magnitude for neutrino masses. We examine the associated effective field theories both at the electroweak scale and at the hadronic scale and estimate the size of the most relevant lepton number violating processes.