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| CMS-PAS-HIN-24-011 | ||
| Measurement of the tau g$- factor in ultraperipheral PbPb collisions recorded by the CMS experiment | ||
| CMS Collaboration | ||
| 9 October 2024 | ||
| Abstract: Measurements of the anomalous magnetic moment of leptons provide stringent tests of the standard model and potential hints of physics beyond the standard model. These measurements for electrons and muons are among the most precisely measured quantities in physics. However, due to the short lifetime of the tau lepton, its anomalous magnetic moment cannot be determined through precession measurements. We report the latest measurement of the anomalous magnetic moment of the tau lepton based on a data sample of ultraperipheral PbPb collisions with an integrated luminosity of up to 1.70 nb$^{-1}$, depending on the decay channel, collected by the CMS experiment at a center-of-mass energy per nucleon pair of $ \sqrt{\smash[b]{s_{_{\mathrm{NN}}}}} = $ 5.02 TeV. The dependence on $ Z^4 $ ($ Z = $ 82 for lead) enhances the cross section for photoproduction with respect to proton-proton and electron-positron collisions. This measurement is improved with respect to the previous CMS measurement via the addition of three tau pair decay modes, a factor of four in luminosity, and the incorporation of both cross section and kinematic distributions in the determination of g$-$2. The measured value of the $ \gamma\gamma \to \tau^{+}\tau^{-} $ fiducial cross section is the most precise to date, while the g$-$2 measurement is one of the most precise both in PbPb and $ \mathrm{e^{+}e^{-}} $ collisions. | ||
| Links: CDS record (PDF) ; CADI line (restricted) ; | ||
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Compact Muon Solenoid LHC, CERN |
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