CMS-PAS-HIG-20-006

CMS-PAS-HIG-20-006
Analysis of the CP structure of the Yukawa coupling between the Higgs boson and $\tau$ leptons in proton-proton collisions at $\sqrt{s}= $ 13 TeV
CMS Collaboration
July 2020

Abstract: The first measurement of the CP structure of the Yukawa coupling between the Higgs boson and $\tau$ leptons is presented. The measurement is based on data collected in proton-proton collisions at $\sqrt{s}= $ 13 TeV by the CMS experiment at the CERN LHC in 2016, 2017 and 2018, corresponding to an integrated luminosity of 137 fb$^{-1}$. Events are selected where one $\tau$ decays to a muon and the other hadronically, and where both $\tau$ leptons decay hadronically. These are the most sensitive decay modes for this analysis and together cover about 50% of all Higgs-to-tau decays. The analysis uses the angular correlation between the decay planes of $\tau$ leptons produced in Higgs boson decays. Machine learning techniques are deployed to distinguish between signal and background events, and dedicated analysis techniques are used to optimise the reconstruction of the $\tau$ decay planes. The mixing angle between CP-even and CP-odd $\tau$ Yukawa couplings was found to be 4 $\pm$ 17$^{\circ}$, compared to an expected uncertainty of $ \pm $ 23$^{\circ}$ at the 68% confidence level, while at the 95% confidence level the observed (expected) uncertainties were $ \pm $ 36 ($\pm$ 55)$^{\circ}$. The observed (expected) significance of the separation between the CP-even and CP-odd hypotheses is 3.2 (2.3) standard deviations. The results are compatible with predictions for the standard model Higgs boson.
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ; These preliminary results are superseded in this paper, Submitted to JHEP. The superseded preliminary plots can be found here.

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