# A near-minimal leptoquark model for reconciling flavour anomalies and generating radiative neutrino masses

## TL;DR

This paper proposes a minimal scalar leptoquark model that explains flavour anomalies in B-meson decays and simultaneously accounts for neutrino masses through radiative mechanisms, with testable predictions for upcoming experiments.

## Contribution

It introduces a simplified leptoquark model with specific scalar particles and a vector-like quark, unifying explanations for flavour anomalies and neutrino masses in a testable framework.

## Key findings

- Model fits flavour anomaly data within parameter space.
- Neutrino masses generated radiatively without fine-tuning.
- Predictions include muon-electron conversion rates and collider signatures.

## Abstract

We introduce two scalar leptoquarks, the SU$(2)_L$ isosinglet denoted $\phi\sim(\mathbf{3}, \mathbf{1}, -1/3)$ and the isotriplet $\varphi\sim(\mathbf{3}, \mathbf{3}, -1/3)$, to explain observed deviations from the standard model in semi-leptonic $B$-meson decays. We explore the regions of parameter space in which this model accommodates the persistent tensions in the decay observables $R_{D^{(*)}}$, $R_{K^{(*)}}$, and angular observables in $b\to s \mu\mu$ transitions. Additionally, we exploit the role of these exotics in existing models for one-loop neutrino mass generation derived from $\Delta L=2$ effective operators. Introducing the vector-like quark $\chi \sim (\mathbf{3}, \mathbf{2}, -5/6)$ necessary for lepton-number violation, we consider the contribution of both leptoquarks to the generation of radiative neutrino mass. We find that constraints permit simultaneously accommodating the flavour anomalies while also explaining the relative smallness of neutrino mass without the need for cancellation between leptoquark contributions. A characteristic prediction of our model is a rate of muon--electron conversion in nuclei fixed by the anomalies in $b \to s \mu \mu$ and neutrino mass; the COMET experiment will thus test and potentially falsify our scenario. The model also predicts signatures that will be tested at the LHC and Belle II.