Abstract
In recent years, experiments revealed intriguing hints for new physics (NP) in semi-leptonic B decays. Both in charged current processes, involving b → cτν transitions, and in the neutral currents b → sℓ+ℓ−, a preference for NP compared to the standard model (SM) of more that 3σ and 5σ was found, respectively. In addition, there is the long-standing tension between the theory prediction and the measurement of the anomalous magnetic moment (AMM) of the muon (aμ) of more than 3σ. Since all these observables are related to the violation of lepton flavor universality (LFU), a common NP explanation seems not only plausible but is even desirable. In this context, leptoquarks (LQs) are especially promising since they give tree-level effects in semi-leptonic B decays, but only loop-suppressed effects in other flavor observables that agree well with their SM predictions. Furthermore, LQs can lead to a mt/mμ enhanced effect in aμ, allowing for an explanation even with (multi) TeV particles. However, a single scalar LQ representation cannot provide a common solution to all three anomalies. In this article we therefore consider a model in which we combine two scalar LQs: the SU(2)L singlet and the SU(2)L triplet. Within this model we compute all relevant 1-loop effects and perform a comprehensive phenomenological analysis, pointing out various interesting correlations among the observables. Furthermore, we identify benchmark points which are in fact able to explain all three anomalies (b → cτν, b → sℓ+ℓ− and aμ), without violating bounds from other observables, and study their predictions for future measurements.
Highlights
Current b → s + −, point towards the violation of lepton flavor universality (LFU)
In recent years, experiments revealed intriguing hints for new physics (NP) in semi-leptonic B decays. Both in charged current processes, involving b → cτ ν transitions, and in the neutral currents b → s + −, a preference for NP compared to the standard model (SM) of more that 3σ and 5σ was found, respectively
There is the long-standing tension between the theory prediction and the measurement of the anomalous magnetic moment (AMM) of the muon of more than 3σ. Since all these observables are related to the violation of lepton flavor universality (LFU), a common NP explanation seems plausible but is even desirable
Summary
In order to illustrate the phenomenology of our model, we will limit ourselves to the case of one LQ singlet Φ1 and one LQ triplet Φ3 without mixing among them. QCD corrections to the matching of scalar LQs for semi-leptonic processes (both charged and neutral current) can be taken into account by applying the following shifts to the Wilson coefficients of vector (V ), scalar (S) and tensor (T ) operators [148]. Are in order: in principle, one has to integrate out only the LQ at the scale M but keep the quark as a dynamical degree of freedom In this way, the matching contribution to CL fi acquires an infrared divergence, which is cancelled by the corresponding UV divergence of the contribution of the tensor operator, obtained by integrating out the LQ at tree level. We can express the branching ratios of flavor changing radiative lepton decays in terms of the Wilson coefficients as αm.
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