Constraining Lepton Flavor Violating Higgs Couplings at the HL-LHC in the Vector Boson Fusion Channel

TL;DR

This paper assesses the potential of the HL-LHC to detect or constrain lepton flavor violating Higgs couplings via vector boson fusion, providing projected sensitivities and limits for both the Standard Model Higgs and additional Higgs bosons.

Contribution

It offers the first detailed projection of HL-LHC sensitivities to LFV Higgs couplings in the VBF channel, including model-independent limits and a case study within two-Higgs doublet models.

Findings

Projected sensitivity for Br(h→μτ) at HL-LHC in VBF channel

Upper limits on H→μτ cross-section for Higgs masses 20-800 GeV

Comparison with low-energy LFV constraints and model interpretations

Abstract

We explore the parameter space of lepton flavor violating (LFV) neutral Higgs Yukawa couplings with the muon and tau leptons that can be probed at the high-luminosity Large Hadron Collider (HL-LHC) via the vector boson fusion~(VBF) Higgs production process. Our projected sensitivities for the Standard Model Higgs ($h$) LFV branching ratio ${\rm Br}(h \to \mu\tau)$ in the $pp \to h j j \to (h \to \mu \tau) jj$ channel at the HL-LHC are contrasted with the current and future low-energy constraints from the anomalous magnetic moment and electric dipole moment of the muon, as well as with other LFV observables, such as $\tau\to 3\mu$ and $\tau\to \mu\gamma$. We also study the LFV prospects of a generic beyond the Standard Model neutral Higgs boson ($H$) with a mass in the range of $m_{H}\in [20,800]~$GeV and give the projected model-independent upper limits on the VBF production cross-section of $Hjj$ times the branching ratio of $H\to \mu\tau$ at the HL-LHC. We interpret these results in the context of a two-Higgs doublet model as a case study.