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

Abstract

We estimate the smallest branching ratio for the Higgs decay channel h→μτ, 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→μτ) as a purely phenomenological quantity, we find that this branching ratio can be probed down to ≈2.69×10^-3 and ≈5.83×10^-4, respectively, at the 250 GeV and 1000 GeV runs of an e⁺e^- collider.