Reconsidering the one leptoquark solution: flavor anomalies and neutrino mass

We reconsider a model introducing a scalar leptoquark phi similar to (3, 1, -1/3) to explain recent deviations from the standard model in semileptonic B decays. The leptoquark can accommodate the persistent tension in the decays (B) over bar -> D (*)(TV) as long as its mass is lower than approximately 10TeV, and we show that a sizeable Yukawa coupling to the right-chiral tau lepton is necessary for an acceptable explanation. A characteristic prediction of this scenario is a value of R-D* slightly smaller than the current world average. Agreement with the measured (B) over bar -> D (*)(TV) rates is mildly compromised for parameter choices addressing the tensions in b -> s mu mu, where the model can significantly reduce the discrepancies in angular observables, branching ratios and the lepton-flavor-universality observables R-K and R-K* . The leptoquark can also reconcile the predicted and measured value of the anomalous magnetic moment of the muon and appears naturally in models of radiative neutrino mass derived from lepton-number violating e ff ective operators. As a representative example, we incorporate the particle into an existing two-loop neutrino mass scenario derived from a dimension-nine operator. In this speci fi c model, the structure of the neutrino mass matrix provides enough freedom to explain the small masses of the neutrinos in the region of parameter space dictated by agreement with the anomalies in B -> D (*)(TV), but not the b -> s transition. This is achieved without excessive fi ne-tuning in the parameters important for neutrino mass.