Lepton flavor violating Higgs decay at $e^+ e^-$ colliders

TL;DR

This paper estimates the minimum detectable branching ratio of the lepton flavor violating Higgs decay $h ightarrow $ at future $e^+e^-$ colliders, comparing it with the LHC's projected sensitivity, using a model-independent approach.

Contribution

It introduces a model-independent analysis of Higgs flavor-violating decays at $e^+e^-$ colliders, considering scaled couplings and effective operators to determine detection thresholds.

Findings

Branching ratio can be probed down to approximately 2.69 x 10^{-3} at 250 GeV.

Branching ratio can be probed down to approximately 5.83 x 10^{-4} at 1000 GeV.

Comparison with LHC reach shows potential for improved sensitivity.

Abstract

We estimate the smallest branching ratio for the Higgs decay channel $h \rightarrow \mu \tau$, which can be probed at an $e^+e^-$ collider and compare it with the projected reach at the high-luminosity run of the LHC. Using a model-independent approach, Higgs production is considered in two separate cases. In the first case, $hWW$ and $hZZ$ couplings are allowed to be scaled by a factor allowed by the latest experimental limits on $hWW$ and $hZZ$ couplings. In the second case, we have introduced higher-dimensional effective operators for these interaction vertices. Keeping BR($h\to\mu\tau$) as a purely phenomenological quantity, we find that this branching ratio can be probed down to $\approx 2.69\times 10^{-3}$ and $\approx 5.83\times 10^{-4}$ respectively, at the 250 GeV and 1000 GeV run of an $e^+e^-$ collider.