Charged lepton flavor violation in light of muon $$g-2$$
Wei-Shu Hou (Department of Physics, National Taiwan University, Taipei, 10617, Taiwan); Girish Kumar (Department of Physics, National Taiwan University, Taipei, 10617, Taiwan)
The recent confirmation of the muon $$g-2$$ anomaly by the Fermilab $$g-2$$ experiment may harbinger a new era in $$\mu $$ and $$\tau $$ physics. In the context of general two Higgs doublet model, the discrepancy can be explained via one-loop exchange of sub-TeV exotic scalar and pseudoscalars, namely H and A, that have flavor changing neutral couplings $$\rho _{\tau \mu }$$ and $$\rho _{\mu \tau }$$ at $$\sim 20$$ times the usual tau Yukawa coupling, $$\lambda _\tau $$ . Taking $$\rho _{\ell \ell ^\prime }\sim \lambda _{ \mathrm min(\ell , \ell ^\prime )}$$ , we show that the above solution to muon $$g-2$$ then predicts enhanced rates of various charged lepton flavor violating processes, which should be accessible at upcoming experiments. We cover muon related processes such as $$\mu \rightarrow e \gamma $$ , $$\mu \rightarrow eee$$ and $$\mu N \rightarrow e N$$ , and $$\tau $$ decays $$\tau \rightarrow \mu \gamma $$ and $$\tau \rightarrow \mu \mu \mu $$ . A similar one-loop diagram with $$\rho _{e\tau }= \rho _{\tau e} = \mathcal{O}(\lambda _e)$$ induces $$\mu \rightarrow e\gamma $$ , bringing the rate right into the sensitivity of the MEG II experiment. The $$\mu e\gamma $$ dipole can be probed further by $$\mu \rightarrow 3e$$ and $$\mu N \rightarrow eN$$ . With its promised sensitivity range and ability to use different nuclei, the $$\mu N \rightarrow eN$$ conversion experiments can not only make discovery, but access the extra diagonal quark Yukawa couplings $$\rho _{qq}$$ . For the $$\tau $$ lepton, we find that $$\tau \rightarrow \mu \gamma $$ would probe $$\rho _{\tau \tau }$$ down to $$\lambda _\tau $$ or lower, while $$\tau \rightarrow 3\mu $$ would probe $$\rho _{\mu \mu }$$ to $$\mathcal{O}(\lambda _{\mu })$$ .