Data-driven study of the implications of anomalous magnetic moments and lepton flavor violating processes of $e$, $\mu$ and $\tau$

Abstract

We study anomalous magnetic moments and flavor violating processes of $e$, $\mu$ and $\tau$ leptons. We use a data driven approach to investigate the implications of the present data on the parameters of a class of models, which has spin-0 scalar and spin-1/2 fermion fields. We compare two different cases, which has or does not have a built-in cancelation mechanism. Our findings are as following. Chiral interactions are unable to generate large enough $\Delta a_e$ and $\Delta a_\mu$ to accommodate the experimental results. Sizable $\Delta a_e$ and $\Delta a_\mu$ can be generated from non-chiral interactions, but they are not contributed from the same source. The upper limit of $\mu\to e\gamma$ decay gives the most severe constraints on photonic penguin contributions in $\mu\to e$ transitions, but the situation may change in considering future experimental sensitivities. The $Z$-penguin diagrams can constrain chiral interaction better than photonic penguin diagrams in $\mu\to e$ transitions. In most of the parameter space, box contributions to $\mu\to 3e$ decay are subleading. In $\tau\to e$ $(\mu)$ transitions, the present $\tau\to e\gamma$ $(\mu \gamma)$ upper limit constrains the photonic penguin contribution better than the $\tau\to 3 e$ $(3\mu)$ upper limit, and $Z$-penguin amplitudes constrain chiral interaction better than photonic penguin amplitudes. Box contributions to $\tau\to 3e$ and $\tau\to 3\mu$ decays can sometime be comparable to $Z$-penguin contributions. The $\tau^-\to e^- \mu^+ e^-$ and $\tau^-\to \mu^- e^+ \mu^-$ rates are highly constrained by $\tau\to e\gamma$, $\mu\to e\gamma$ and $\tau\to \mu\gamma$, $\mu\to e\gamma$ upper limits, respectively. We compare the current experimental upper limits, future sensitivities and bounds from consistency on various muon and tau LFV processes.