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

Abstract

Abstract We present a model of radiative neutrino masses which also resolves anomalies reported in B-meson decays, R D ∗ $$ {R}_{D^{\left(\ast \right)}} $$ and R K ∗ $$ {R}_{K^{\left(\ast \right)}} $$ , 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 ∗ $$ {R}_{D^{\left(\ast \right)}} $$ , R K ∗ $$ {R}_{K^{\left(\ast \right)}} $$ 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 s $$ \sqrt{s} $$ = 14 TeV high-luminosity LHC ( s $$ \sqrt{s} $$ = 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 ∗ $$ {R}_{D^{\left(\ast \right)}} $$ 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.

Keywords

• Beyond Standard Model
• Higgs Physics
• Neutrino Physics