The Lepton Flavor Changing Decays and One-loop Muon Anomalous Magnetic Moment in the Extended Mirror Twin Higgs Models

TL;DR

The paper investigates lepton flavor violation in extended Mirror Twin Higgs (MTH) models that include heavy gauge bosons, extra Higgs sectors, and heavy neutrinos. LFV couplings arise from mixing with twin neutrinos and right-handed neutrinos, enabling processes such as $\ell_i\to\ell_j\gamma$ and $\ell_i\to\ell_j\ell_k\ell_l$, and the authors compute the one-loop contributions to the muon anomalous magnetic moment $a_\mu$ within this framework. They derive the dipole amplitudes combining twin-neutrino–gauge and RH-neutrino–charged-Higgs loops, and quantify the branching ratios against current experimental bounds, finding that $\mathrm{BR}(\mu\to e\gamma)$ can reach detectable levels for $V_{\tilde{\nu}}$ or $y_{\nu_R}$ beyond certain thresholds, while $\tau$-channel LFV typically remains below present limits. Tree-level $\mu\to 3e$ decays mediated by new neutral gauge bosons show strong sensitivity to the couplings and mediator mass, with clear prospects to constrain the model; one-loop charged-Higgs–RH-neutrino contributions to $\mu\to 3e$ are generally too small to be observed. Overall, the results constrain the parameter space of TH extensions and illustrate how LFV processes complement collider probes in testing these models, while the muon g-2 contribution does not fully resolve the SM discrepancy.

Abstract

Mirror Twin Higgs(MTH) models always contain heavy gauge bosons and extra Higgses. Besides, to accommodate tiny neutrino masses via seesaw mechanism, new heavy neutrinos can also be introduced in MTH extension models. Such new particles and interactions may lead to new contributions to the lepton flavor violating (LFV) processes, including $\ell_i \to \ell_jγ$ and $\ell_i \to \ell_j\ell_k\ell_l$. We find that current experimental data can stringently constrain the parameter spaces and certain LFV processes can possibly be tested by the next generation colliders. One-loop contributions of the new particles to the muon anomalous magnetic momentumare also calculated. Such contributions can still not solve the discrepancy between the experiments and the prediction of the standard model.

Figures (7)

• Figure 1: Fenyman diagrams for $\ell_i \to \ell_j \gamma$ decays. The solid lines, wavy lines and dash lines denote the fermions, the gauge bosons and the charged Higgs, respectively, which are the same as those in Fig.\ref{['loop-3e']}.
• Figure 2: With other parameters shown in the figures, the branching ratios of $\mu\to e \gamma$ versus parameters $V_{\tilde{\nu}},~y_{\nu_R},~m_{H^\pm},~m_{\tilde{\nu}},~m_{\nu_R}$, respectively.
• Figure 3: With $m_{\tilde{\nu}}=1~GeV,~m_{\nu_R}=1000~GeV,~m_{H^\pm}=300~GeV$, the allowed points of $V_{\tilde{\nu}}$ and $y_{\nu_R}$ to be larger than the experimental upper bound for the $\mu\to e \gamma$ branching ratios.
• Figure 4: With $m_{\tilde{\nu}}=1~GeV,~m_{\nu_R}=1000~GeV,~m_{H^\pm}=300~GeV$, the branching ratios of $\tau\to e \gamma$ versus parameters $V_{\tilde{\nu}}$ (for $y_{\nu_R} =0.0001$) and $y_{\nu_R}$ (for $V_{\tilde{\nu}} =0.0001$), respectively.
• Figure 5: The branching ratios of $\mu\to 3e$(left) and $\tau\to 3e$(right) versus parameters $\tilde{g}$ for $m_{Z_0^\prime}=1000,~2000,~5000$ GeV, respectively.