Revisiting the vector leptoquark explanation of the B-physics anomalies

Abstract

We present a thorough investigation of the vector leptoquark hypothesis for a combined explanation of the $B$-physics anomalies. We analyze this hypothesis from a twofold perspective, taking into account recent results from $B$-physics observables and high-$p_T$ searches. First, using a simplified model, we determine the general conditions for a successful low-energy fit in presence of right-handed leptoquark couplings (neglected in previous analyses). Second, we show how these conditions, in particular a sizable 2-3 family mixing, can be achieved in a motivated ultraviolet completion. Our analysis reinforces the phenomenological success of the vector leptoquark hypothesis in addressing the anomalies, and its compatibility with motivated extensions of the Standard Model based on the idea of flavor non-universal gauge interactions. The implications of right-handed leptoquark couplings for a series of key low-energy observables, namely $B_s \to \tau\tau$ and $\tau\to\mu$ lepton flavor violating processes, both in $\tau$ and in $B$ decays, are discussed in detail. The role of the ultraviolet completion in precisely estimating other low-energy observables, most notably $\Delta F=2$ amplitudes, is also addressed.