Determination of the Higgs CP-mixing angle in the tau decay channels

TL;DR

This paper investigates the potential to measure CP-violation in the Higgs sector through tau decay channels at the LHC, focusing on a CP-sensitive observable and its distribution for signal and background, to estimate the precision of the CP-mixing angle.

Contribution

It introduces a method to analyze CP-violation in Higgs decays to tau pairs using a specific observable and background calibration, estimating measurement precision at the LHC.

Findings

Identified a CP-sensitive observable for Higgs to tau decays.

Analyzed the distribution of this observable for signal and background.

Estimated the measurement precision of the CP-mixing angle for future LHC runs.

Abstract

The measurement of possible Higgs sector CP-violation in the tau decay channels at the LHC is investigated. A CP-violating effect would manifest itself in these decay modes in characteristic spin-spin correlations of the tau lepton pairs which can be accessed using the momenta and impact parameters of the charged tau decay particles. We examine a CP-sensitive observable for a 125 GeV Higgs boson resonance in the gluon fusion channel at the LHC. Furthermore, we consider the distribution of this observable for the irreducible Drell-Yan background. By splitting these events into two categories we obtain two different distributions which can be used for calibration purposes. Finally, we estimate the achievable precision of the scalar-pseudo-scalar mixing angle of the tau decay channel for Run II and the high luminosity run of the LHC.