Abstract
The quartic scalar coupling λ5 term, which violates the lepton-number by two units in the Ma-model, is phenomenologically small when the model is applied to the lepton-flavor violation (LFV) processes. In order to dynamically generate the λ5 parameter through quantum loop effects and retain the dark matter (DM) candidate, we extend the Ma-model by adding a Z2-odd vector-like lepton doublet and a Z2-even Majorana singlet. With the new couplings to the Higgs and gauge bosons, the observed DM relic density can be explained when the upper limits from the DM-nucleon scattering cross sections are satisfied. In addition to the neutrino data and LFV constraints, it is found that the DM relic density can significantly exclude the free parameter space. Nevertheless, the resulting muon g − 2 mediated by the inert charged-Higgs can fit the 4.2σ deviation between the experimental measurement and the SM result, and the branching ratio for τ → μγ can be as large as the current upper limit when the rare μ → (eγ, 3e) decays are suppressed. In addition, it is found that the resulting BR(τ → μρ) can reach the sensitivity of Belle II with an integrated luminosity of 50 ab−1.
Highlights
The E989 experiment at Fermilab recently reports the first measurement with run-1 data as [8]: aFμNAL = 116592040(54) × 10−11
In order to determine if χ5 can be dark matter, we examine whether the associated couplings can produce the observed DM relic density (ΩDM), in which the observed value is given as [47]: ΩoDbMs h2 = 0.11933 ± 0.00091
When the neutrino data are satisfied, it is found that the λ5 quartic scalar coupling in the scalar potential has to be small when the lepton-flavor violation processes are required to fit the upper limits, and the resulting muon anomalous magnetic dipole moment cannot explain the inconsistency between the experimental results and the SM prediction
Summary
In order to dynamically generate the λ5 parameter in Ma-model, we introduce a global U(1)χ symmetry to suppress the tree-level λ5 term in the scalar potential, where the SM particles do not carry the U(1)χ charge. Since the λ5(H†HI ) term breaks the leptonnumber by two units, it is natural to extend the model by introducing new particles to the lepton sector. New couplings are introduced, such as XLHI R, the lepton-number symmetry is still retained. The lepton-number violation can be achieved if a right-handed Majorana. Fermion (N0) is added to the Ma-model, where N0 carries the lepton-number. The lepton-number can be broken by the Majorana mass term. We will demonstrate that U(1)χ is softly broken to a Z2 symmetry by the dimension-3 Majorana mass term. HI , N1,2,3, and X are Z2-odd, and N0 is a Z2-even
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