Probing chirality structure in lepton-flavour-violating Higgs decay $h\to\tau\mu$ at the LHC

TL;DR

This study investigates the chirality structure of lepton-flavor-violating Higgs decays at the LHC, emphasizing the role of tau polarization and momentum ratios to distinguish scenarios and refine bounds on decay rates.

Contribution

It introduces a method to analyze tau polarization effects and momentum ratios in hLFV decays, providing improved sensitivity and bounds on the decay parameters at the LHC.

Findings

Sensitivity to BR(h→τμ) can be affected by 4-6%.

Distinguishes tau polarization scenarios at 2σ with 1000 fb⁻¹.

Potential for similar sensitivity with 139 fb⁻¹.

Abstract

A phenomenological study for determining the chirality structure in lepton-flavor-violating Higgs (hLFV) decays $h \to \tau\mu$ at the LHC is presented. We estimate the effects of the $\tau$ polarization in the analysis andthe importance of determining the relative visible momentum ratio $x$, and show the analysis with a collinear mass $m_{col1}$ by assuming one missing particle is appropriate. We find that the sensitivity would be generically affected up to $\pm$ $4-6$~\% in terms of the BR$(h\to \tau\mu)$ upper bound, and show the altered bounds on the $(|y_{\mu\tau}|, |y_{\tau\mu}|)$ plane. We further study the benchmark scenarios, and demonstrate the sensitivity study for the chirality structure using the relative visible momentum ratio. We find that the two fully polarized cases, the $\tau_R$ and $\tau_L$ scenarios consistent with the recently reported excess, are distinguishable at 2$\sigma$ level for 1000~fb$^{-1}$. We also show that a further improved study potentially provides a similar sensitivity already for 139~fb$^{-1}$.