Data-driven study of the implications of anomalous magnetic moments and lepton flavor violating processes of $e$, $μ$ and $τ$

Abstract

We study anomalous magnetic moments and flavor violating processes of $e$, $μ$ and $τ$ 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 $Δa_e$ and $Δa_μ$ to accommodate the experimental results. Sizable $Δa_e$ and $Δa_μ$ can be generated from non-chiral interactions, but they are not contributed from the same source. The upper limit of $μ\to eγ$ decay gives the most severe constraints on photonic penguin contributions in $μ\to e$ 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 $μ\to e$ transitions. In most of the parameter space, box contributions to $μ\to 3e$ decay are subleading. In $τ\to e$ $(μ)$ transitions, the present $τ\to eγ$ $(μγ)$ upper limit constrains the photonic penguin contribution better than the $τ\to 3 e$ $(3μ)$ upper limit, and $Z$-penguin amplitudes constrain chiral interaction better than photonic penguin amplitudes. Box contributions to $τ\to 3e$ and $τ\to 3μ$ decays can sometime be comparable to $Z$-penguin contributions. The $τ^-\to e^- μ^+ e^-$ and $τ^-\to μ^- e^+ μ^-$ rates are highly constrained by $τ\to eγ$, $μ\to eγ$ and $τ\to μγ$, $μ\to eγ$ upper limits, respectively. We compare the current experimental upper limits, future sensitivities and bounds from consistency on various muon and tau LFV processes.