Lepton flavor violation in Higgs boson decays at the HL-LHC

Abstract

We explore the discovery potential for lepton flavor-violating Higgs boson decays, $h \to \ell_i \ell_j$ ($\ell_i \neq \ell_j$; $\ell = e, \mu, \tau$), in proton-proton collisions. The analysis is performed within a Froggatt-Nielsen framework, which offers a well-motivated theoretical mechanism for such processes. By performing a systematic scan over the phenomenologically viable parameter space, we identify regions that can yield observable signatures at the High-Luminosity LHC (HL-LHC). For an integrated luminosity of $\mathcal{L}_{\rm int} \gtrsim 1000~\text{fb}^{-1}$, we project that the channels $h \to e\mu$ and $h \to \tau\mu$ (with $\tau^{\pm} \to \pi^{\pm} \nu_{\tau}$) could reach the $5\sigma$ discovery threshold, while $h \to \tau e$ remains inaccessible even at $3000~\text{fb}^{-1}$. Our results highlight the unique capability of the HL-LHC to probe new physics through searches for rare Higgs decays.