Unified framework for B-anomalies, muon g − 2 and neutrino masses

A bstract

We present a model of radiative neutrino masses which also resolves anomalies reported in B-meson decays, \[ {R}_{D^{\left(\ast \right)}} \] and \[ {R}_{K^{\left(\ast \right)}} \] , as well as in muon g − 2 measurement, ∆ a _μ . Neutrino masses arise in the model through loop diagrams involving TeV-scale leptoquark (LQ) scalars R ₂ and S ₃. Fits to neutrino oscillation parameters are obtained satisfying all flavor constraints which also explain the anomalies in \[ {R}_{D^{\left(\ast \right)}} \] , \[ {R}_{K^{\left(\ast \right)}} \] and ∆ a _μ within 1 σ. An isospin-3/2 Higgs quadruplet plays a crucial role in generating neutrino masses; we point out that the doubly-charged scalar contained therein can be produced in the decays of the S ₃ LQ, which enhances its reach to 1.1 (6.2) TeV at \[ \sqrt{s} \] = 14 TeV high-luminosity LHC ( \[ \sqrt{s} \] = 100 TeV FCC-hh). We also present flavor-dependent upper limits on the Yukawa couplings of the LQs to the first two family fermions, arising from non-resonant dilepton ( pp → ℓ ⁺ ℓ ⁻ ) processes mediated by t-channel LQ exchange, which for 1 TeV LQ mass, are found to be in the range (0 .15 − 0 .36). These limits preclude any explanation of \[ {R}_{D^{\left(\ast \right)}} \] through LQ-mediated B-meson decays involving ν _e or ν _μ in the final state. We also find that the same Yukawa couplings responsible for the chirally-enhanced contribution to ∆ a _μ give rise to new contributions to the SM Higgs decays to muon and tau pairs, with the modifications to the corresponding branching ratios being at (2–6)% level, which could be tested at future hadron colliders, such as HL-LHC and FCC-hh.