Correlating lepton flavor universality violation in B decays with $\mu \to eγ$ using leptoquarks

Abstract

Motivated by the measurements of b→sℓ+ℓ− transitions, including R(K) and R(K∗), we examine lepton flavor (universality) violation in B decays and its connections to μ→eγ in generic leptoquark models. Considering all 10 representations of scalar and vector leptoquarks under the Standard Model gauge group we compute the tree-level matching for semileptonic b-quark operators as well as their loop effects in ℓ→ℓ′γ. In our phenomenological analysis, we correlate R(K), R(K∗) and the other b→sμ+μ− data to μ→eγ and b→sμe transitions for the three leptoquark representations that generate left-handed currents in b→sℓ+ℓ− transitions and, therefore, provide a good fit to data. We find that while new physics contributions to muons are required by the global fit, couplings to electrons can be sizeable without violating the stringent bounds from μ→eγ. In fact, if the effect in electrons in b→sℓ+ℓ− has the opposite sign from the effect in muons, the bound from μ→eγ can always be avoided. However, unavoidable effects in b→sμe transitions (i.e. Bs→μe, B→Kμe, etc.) appear that are within the reach of LHCb and BELLE II.