Compact Muon Solenoid
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| CMS-PAS-SMP-18-010 | ||
| Measurement of the $ \tau $ lepton polarization in Z boson decays | ||
| CMS Collaboration | ||
| 10 February 2023 | ||
| Abstract: The polarization of $ \tau $ leptons is measured using leptonic and hadronic $ \tau $ lepton decays in $ \mathrm{Z}\rightarrow\tau\tau $ events. A sample of pp collisions of an integrated luminosity of 36.3 fb$ ^{-1} $ at $ \sqrt{s}= $ 13 TeV is used. The measured polarization at the Z pole is $ \mathcal{P}_{\tau}(\mathrm{Z}) = - $0.144 $ \pm $ 0.015 $ = - $0.144 $ \pm $ 0.006 (stat) $ \pm $ 0.014 (syst), in good agreement with the standard model value of the lepton asymmetry parameter of $ A_{\ell} = $ 0.1468 $ \pm $ 0.0003. The $ \tau $ polarization is used to determine the ratio of the vector to axial-vector coupling of the $ \tau $ leptons in the neutral current and thus the weak mixing angle independently of the production process of the Z resonance. The obtained value is $ \sin^2\theta^{\mathrm{eff}}_W = $ 0.2319 $ \pm $ 0.0019 $ = $ 0.2319 $ \pm $ 0.0008 (stat) $ \pm $ 0.0018 (syst). | ||
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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These preliminary results are superseded in this paper, Submitted to JHEP. The superseded preliminary plots can be found here.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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Compact Muon Solenoid LHC, CERN |
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