A μ-τ-philic scalar doublet under Zn flavor symmetry

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 Z n 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 Z 4 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.

Probing μτ flavor-violating solutions for the muon g − 2 anomaly at Belle II

“…Since the dipole operator requires the chirality flipping, one-loop correction involving a mediator with the µτ flavor violating couplings is enhanced by a factor of m τ /m µ O (10). Such µτ flavor violating scenarios are discussed to explain the muon g − 2 anomaly in the context of the axion like particles (ALPs) [11,12], in the general two Higgs doublet model (G2HDM) [13][14][15][16][17][18][19][20][21][22][23][24][25][26], and in the Z models [27][28][29][30]. Figure 1 shows the representative diagram to induce the δa µ contribution with a µτ flavor violating mediator particle X, which is either a scalar or vector boson, and the µτ flavor violating nature of X introduces the internal τ -propagator at one-loop level.…”

Combined Explanations of $(g-2)_\mu$, $(g-2)_e$ and Implications for a Large Muon EDM∗

“…Examples for such a chiral enhancement are tan β in the MSSM (see e.g. [36] for a review), m t /m in leptoquark (LQ) models [37,38], or m τ /m µ in two-Higgs-doublet (2HDM) models [39,40]. In general, in any model with chiral enhancement, c R can be complex with an a priori unconstrained phase, so that the resulting muon EDM can become sizable.…”

Muon $$g-2$$ anomaly and $$\mu $$–$$\tau $$-philic Higgs doublet with a light CP-even component

“…However, in the decay τ → μν ν, the tree-level diagram mediated by the charged Higgs gives negative contribution, which will lead to the deviation of the lepton flavor universality (LFU) in τ decays [13][14][15]. Besides, a scalar with the a e-mail: leiwang@ytu.edu.cn (corresponding author) μ-τ lepton flavor violation (LFV) interactions can accommodate the a μ discrepancy by the one-loop contribution [27][28][29][30][31][32][33][34][35][36][37][38][39][40]. Meanwhile, the extra Higgs doublet with the μτ LFV interactions can alleviate the discrepancy of LFU in τ decays [34].…”

“…Besides, a scalar with the a e-mail: leiwang@ytu.edu.cn (corresponding author) μ-τ lepton flavor violation (LFV) interactions can accommodate the a μ discrepancy by the one-loop contribution [27][28][29][30][31][32][33][34][35][36][37][38][39][40]. Meanwhile, the extra Higgs doublet with the μτ LFV interactions can alleviate the discrepancy of LFU in τ decays [34]. In this paper, we consider relevant theoretical and experimental constraints, including the lepton flavor universality (LFU) in the τ decays and multi-lepton event searches at the LHC, and examine the possibilities of explaining the a μ discrepancy reported by Fermilab in the 2HDM with a discrete Z 4 symmetry in which an inert Higgs doublet field (H, A, H ± ) has the lepton flavor violation μ-τ interactions.…”