Full Simulation Study of the Higgs Branching Ratio into Tau Lepton Pairs at the ILC with $\sqrt{s} = 500$ GeV

TL;DR

This study uses full simulation to estimate how accurately the Higgs boson's decay into tau pairs can be measured at the ILC with 500 GeV energy, focusing on key production channels and analysis techniques.

Contribution

It provides the first detailed simulation-based estimate of the measurement precision of Higgs to tau pairs at the ILC, including multivariate analysis methods.

Findings

Estimated measurement accuracy of 4.7% for q q̄ h channel.

Estimated measurement accuracy of 7.4% for ν ν̄ h channel.

Cross-validated results with cut-based analysis.

Abstract

We evaluate the expected measurement accuracy of the branching ratio of the Standard Model Higgs boson decaying into tau lepton pairs $h \to \tau ^+ \tau ^-$ at the ILC with a center-of-mass energy of $\sqrt{s} = 500$ GeV with a full simulation of the ILD detector. We assume a Higgs mass of $M_h = 125$ GeV, a branching ratio of $\mathrm{BR}(h \to \tau ^+ \tau ^-) = 6.32 \%$, beam polarizations of $P(e^+, e^-) = (-0.8,+0.3)$, and an integrated luminosity of $\int L dt = 500 \mathrm{fb^{-1}}$. The Higgs-strahlung process $e^+ e^- \to Zh$ with $Z \to q \overline{q}$ and the $WW$-fusion process $e^+ e^- \to \nu \overline{\nu} h$ are expected to be the most sensitive channels at $\sqrt{s} = 500$ GeV. Using a multivariate analysis technique, we estimate the expected relative measurement accuracy of the branching ratio $\Delta(\sigma \cdot \mathrm{BR}) / (\sigma \cdot \mathrm{BR})$ to be 4.7% and 7.4% for the $q \overline{q} h$ and $\nu \overline{\nu} h$ final states, respectively. The results are cross-checked using a cut-based analysis.