Combined explanations of B-physics anomalies: the sterile neutrino solution

TL;DR

This paper proposes a combined explanation for B-physics anomalies using a light sterile neutrino and specific leptoquark models, showing that the vector leptoquark fits current data while scalar models face tensions, and discusses cosmological and collider constraints.

Contribution

It introduces a unified model with sterile neutrino and leptoquarks to explain B-physics anomalies, analyzing its viability and constraints from experiments and cosmology.

Findings

Vector leptoquark $U_1^mu$ can explain anomalies and fit all constraints.

Scalar leptoquark $S_1$ faces tension between $B_s$ mixing and anomalies.

Future LHC searches will test the entire parameter space.

Abstract

In this paper we provide a combined explanation of charged- and neutral-current $B$-physics anomalies assuming the presence of a light sterile neutrino $N_R$ which contributes to the $B \to D^{(*)} \tau \nu$ processes. We focus in particular on two simplified models, where the mediator of the flavour anomalies is either a vector leptoquark $U_1^\mu \sim ({\bf 3}, {\bf 1}, 2/3)$ or a scalar leptoquark $S_1 \sim ({\bf \bar 3}, {\bf 1}, 1/3)$. We find that $U_1^\mu$ can successfully reproduce the required deviations from the Standard Model while being at the same time compatible with all other flavour and precision observables. The scalar leptoquark instead induces a tension between $B_s$ mixing and the neutral-current anomalies. For both states we present the limits and future projections from direct searches at the LHC finding that, while at present both models are perfectly allowed, all the parameter space will be tested with more luminosity. Finally, we study in detail the cosmological constraints on the sterile neutrino $N_R$ and the conditions under which it can be a candidate for dark matter.