CMS-PAS-HIG-25-012

CMS-PAS-HIG-25-012
Analysis of the $ CP $ structure of the Yukawa coupling between the Higgs boson and tau leptons in proton-proton collisions at $ \sqrt{s}= $ 13.6 TeV
CMS Collaboration
2026-03-21

Abstract: This note presents a measurement of the charge-parity ($ CP $) structure of the Yukawa coupling between the Higgs boson and tau leptons, using proton-proton collision data at $ \sqrt{s}= $ 13.6 TeV recorded by the CMS detector at the LHC, corresponding to an integrated luminosity of 62.4 fb$ ^{-1} $. Angular correlations between the decay products of tau leptons produced in $ \text{H}\to\tau\tau $ decays are exploited to constrain the effective $ CP $ mixing angle $ \alpha^{\text{H}\tau\tau} $, which parameterizes the admixture of scalar and pseudoscalar couplings. The mixing angle is measured to be $ \alpha^{\text{H}\tau\tau} = $ 36 $ ^{+33}_{-30} $ ^\circ, compared with an expected value of 0 $ \pm $ 19 $ ^\circ $ under the standard model hypothesis. When combined with the previous CMS measurement using data collected at $ \sqrt{s} = $ 13 TeV, corresponding to an integrated luminosity of 138 fb$ ^{-1} $, the mixing angle is determined to be 7 $ \pm $ 16 $ ^\circ $, compared with an expected value of 0 $ \pm $ 14 $ ^\circ $. This result represents the most precise measurement by CMS of the $ CP $ nature of the Higgs boson coupling to tau leptons, with an expected precision that is the best achieved by any experiment to date.
Links: CDS record (PDF) ; CADI line (restricted) ; These preliminary results are superseded in this paper, Submitted to JHEP. The superseded preliminary plots can be found here.

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