Measurement of the $\textit{CP}$ structure of the Higgs-tau Yukawa coupling

TL;DR

This paper reports the first measurement of the CP structure of the Higgs-tau Yukawa coupling at the LHC, using angular correlations in tau decays to determine the CP mixing angle with high precision.

Contribution

It introduces novel analysis techniques for reconstructing tau decay planes and measures the CP mixing angle of the Higgs-tau coupling with unprecedented accuracy.

Findings

CP mixing angle measured as 4±17 degrees

Pure CP-odd hypothesis excluded at 3.2 sigma

Analysis techniques optimize tau decay plane reconstruction

Abstract

The CMS experiment at the LHC has performed the first measurement of the CP structure of the Yukawa coupling between the Higgs boson and tau leptons. The measurement is based on data collected in proton-proton collisions at $\sqrt{s} = 13$ TeV during 2016-18, corresponding to an integrated luminosity of $137\text{ fb}^{-1}$. The analysis utilizes the angular correlation between the decay planes of tau leptons produced in Higgs boson decays, where dedicated analysis techniques are used to optimise the reconstruction of tau decay planes. The measured value of the CP mixing angle is $4\pm17^{\circ}$, at $68\%$ confidence level. The pure $\textit{CP-}$odd hypothesis is excluded by $3.2$ standard deviations. The analysis strategies and the results of the measurement are presented.