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Register a new userMuon g-2 explanation in a modular $A_4$ symmetry
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We construct a model to explain the muon anomalous magnetic moment, without considering any lepton flavor violations, in the modular $A_4$ symmetry. We have investigated a predictive radiative seesaw model including dark matter candidate at favorable fixed point of $tau=omega$ obtained by recent analysis of the stabilized moduli values from the possible configurations of the flux compactifications. In the result, we show our predictions on the Dirac CP and Majorana phases, the neutrino masses, the mass range of dark matter as well as the muon anomalous magnetic moment through the $chi^2$ analysis.
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We discuss the recent results on the muon anomalous magnetic moment in the context of new physics models with light scalars. We propose a model in which the one-loop contributions to g-2 of a scalar and a pseudoscalar naturally cancel in the massless limit due to the symmetry structure of the model. This model allows to interpolate between two possible interpretations. In the first interpretation, the results provide a strong evidence of the existence of new physics, dominated by the positive contribution of a CP-even scalar. In the second one, supported by the recent lattice result, the data provides a strong upper bound on new physics, specifically in the case of (negative) pseudoscalar contributions. We emphasize that tree-level signatures of the new degrees of freedom of the model are enhanced relative to conventional explanations of the discrepancy. As a result, this model can be tested in the near future with accelerator-based experiments and possibly also at the precision frontier.
We combine $SO(10)$ Grand Unified Theories (GUTs) with $A_4$ modular symmetry and present a comprehensive analysis of the resulting quark and lepton mass matrices for all the simplest cases. We focus on the case where the three fermion families in the 16 dimensional spinor representation form a triplet of $Gamma_3simeq A_4$, with a Higgs sector comprising a single Higgs multiplet $H$ in the ${mathbf{10}}$ fundamental representation and one Higgs field $overline{Delta}$ in the ${mathbf{overline{126}}}$ for the minimal models, plus and one Higgs field $Sigma$ in the ${mathbf{120}}$ for the non-minimal models, all with specified modular weights. The neutrino masses are generated by the type-I and/or type II seesaw mechanisms and results are presented for each model following an intensive numerical analysis where we have optimized the free parameters of the models in order to match the experimental data. For the phenomenologically successful models, we present the best fit results in numerical tabular form as well as showing the most interesting graphical correlations between parameters, including leptonic CP phases and neutrinoless double beta decay, which have yet to be measured, leading to definite predictions for each of the models.
We consider lepton flavor violating Higgs decay, specifically $h to mutau$, in a leptoquark model. We introduce two scalar leptoquarks with the $SU(3)_c times SU(2)_L times U(1)_Y$ quantum numbers, $(3,2,7/6)$ and $(3,2,1/6)$, which do not generate the proton decay within renormalizable level. They can mix with each other by interactions with the standard model Higgs. The constraint from the charged lepton flavor violating process, $tau^{-} to mu^{-} gamma$, is very strong when only one leptoquark contribution is considered. However, we demonstrate that significant cancellation is possible between the two leptoquark contributions. We show that we can explain the CMS (ATLAS) excess in $h to mu tau$. We also show that muon $(g-2)$ anomaly can also be accommodated.
We discuss an inverse seesaw model based on right-handed fermion specific $U(1)$ gauge symmetry and $A_4$-modular symmetry. These symmetries forbid unnecessary terms and restrict structures of Yukawa interactions which are relevant to inverse seesaw mechanism. Then we can obtain some predictions in neutrino sector such as Dirac-CP phase and sum of neutrino mass, which are shown by our numerical analysis. Besides the relation among masses of heavy pseudo-Dirac neutrino can be obtained since it is also restricted by the modular symmetry. We also discuss implications to lepton flavor violation and collider physics in our model.
We discuss type-II seesaw models adopting modular $A_4$ symmetry in supersymmetric framework. In our approach, the models are classified by the assignment of $A_4$ representations and modular weights for leptons and triplet Higgs fields. Then neutrino mass matrix is characterized by modulus $tau$ and two free parameters. Carrying out numerical analysis, we find allowed parameter sets which can fit the neutrino oscillation data. For the allowed parameter sets, we obtain the predictions in neutrino sector such as CP violating phases and the lightest neutrino mass. Finally we also show the predictions for the branching ratios of doubly charged scalar boson focusing on the case where the doubly charged scalar boson dominantly decays into charged leptons.
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