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Compact Muon Solenoid
LHC, CERN

CMS-PAS-SMP-19-007
Studies of Z $ \to 4\ell $ decays in proton-proton collisions at $ \sqrt{s} = $ 8 and 13 TeV
Abstract: Decays of Z bosons to four charged leptons (electrons and muons) are studied in proton-proton collisions at $ \sqrt{s} = $ 8 and 13 TeV. The analysis is based on data collected with the CMS detector at the LHC corresponding to an integrated luminosity of 19.7 fb$ ^{-1} $ at 8 TeV and 138 fb$ ^{-1} $ at 13 TeV. The measured value of the inclusive branching fraction for all four-lepton decay modes, $ \mathcal{B}(\mathrm{Z} \rightarrow 4\ell) $, is ( 4.67 $ \pm $ 0.11 (stat) $ \pm $ 0.10 (sys) ) $ \times $ 10$^{-6} $ which has a precision of about 3%. Measurements of the individual branching fractions for the decays Z $ \to 4\mu $, Z $ \to 4\mathrm{e} $, and Z $ \to 2\mu2\mathrm{e} $ are also reported. Differential decay rates as functions of kinematic and angular quantities in the Z boson rest frame are presented. Measurements of triple-product asymmetries, which are sensitive to violations of charge conjugation and parity (CP) invariance, are performed for Z $ \to 4\ell $ decays. The results are compared to standard model predictions and used to set limits on the production of new gauge bosons.
CMS Publications
Compact Muon Solenoid
LHC, CERN