Abstract
We propose a minimal model which accommodates the long-standing anomaly of muon magnetic moment based on abelian discrete flavor symmetries. The standard model is extended by scalar doublets charged under a Zn lepton flavor symmetry. In these models, a large contribution to the muon magnetic moment can be obtained by the chirality enhancement from new scalar mediated diagrams without conflicting with the flavor symmetry. Thanks to the lepton flavor symmetry, these models automatically forbid lepton flavor violation. The minimal model is based on Z4 symmetry with only one extra scalar doublet. In this model, we show that the parameter space favored by the muon g − 2 can easily be consistent with experimental constraints and theoretical bounds such as the electroweak precision tests, lepton universality, potential stability condition and triviality bound as well as the LHC direct search mass bound. The new contributions to the muon electric dipole moment and the Higgs decay into γγ can be indirect signals of the model.
Highlights
SM prediction.1 Note that there is a non-negligible large theoretical uncertainties in the hadronic contribution due to the light-by-light scattering [3]
We show that the parameter space favored by the muon g − 2 can be consistent with experimental constraints and theoretical bounds such as the electroweak precision tests, lepton universality, potential stability condition and triviality bound as well as the LHC direct search mass bound
We propose a minimal model explaining the discrepancy of the muon anomalous magnetic moment between the SM prediction and the measurement based on abelian discrete symmetries
Summary
Let us discuss a simple extension of the SM with a pair of scalar doublets (Φ, Φ ) whose global U(1)Lμ−Lτ flavor charge is (2, −2), where Lμ and Lτ represent the muon and tau lepton flavor numbers, respectively. Detailed quantum charge assignments are given in table 1 Under this flavor symmetry, the following new Yukawa interactions are allowed,. A similar contribution to the muon g − 2 from the scalar doublets are discussed in the model based on the SU(2)μτ symmetry, which contains the U(1)Lμ−Lτ symmetry as a subgroup [17]. In such cases, a pair of scalar doublets plays the primary role in explaining the muon g − 2 anomaly instead of Z bosons. A pair of scalar doublets plays the primary role in explaining the muon g − 2 anomaly instead of Z bosons We noted that this new contribution remains even with the unbroken U(1)Lμ−Lτ flavor symmetry limit.
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