Abstract
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, ∆aμ. Neutrino masses arise in the model through loop diagrams involving TeV-scale leptoquark (LQ) scalars R2 and S3. 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 ∆aμ 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 S3 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 νe or νμ in the final state. We also find that the same Yukawa couplings responsible for the chirally-enhanced contribution to ∆aμ 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.
Highlights
Among the many reasons to consider physics beyond the Standard Model (SM), an understanding of the origin of neutrino masses stands out, as neutrino oscillations have been firmly established [1] which require nonzero neutrino masses, in contradiction with the SM
We present a model of radiative neutrino masses which resolves anomalies reported in B-meson decays, RD( ) and RK( ), as well as in muon g − 2 measurement, ∆aμ
We find that the same Yukawa couplings responsible for the chirally-enhanced contribution to ∆aμ 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
Summary
Among the many reasons to consider physics beyond the Standard Model (SM), an understanding of the origin of neutrino masses stands out, as neutrino oscillations have been firmly established [1] which require nonzero neutrino masses, in contradiction with the SM. The ratio of branching ratios for the neutral-current decay RK( ) = BR(B → K( )μ+μ−)/BR(B → K( )e+e−) [36, 37] differs from the SM predictions [39,40,41,42] by 2.6 (2.4) σ in the high-momentum range, while the discrepancy is 2.2 σ in the lower-momentum range for RK These anomalies, while taken together, appear to suggest some lepton-flavor-universality violating new physics beyond the SM.
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