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Published December 25, 1989 | Published
Journal Article Open

Measurement of Z Decays into Lepton Pairs


We present measurements by the Mark II experiment of the ratios of the leptonic partial widths of the Z boson to the hadronic partial width. The results are Γ_(ee)/Γ_(had)=0.037_(-0.012^()+0.016),Γ_(µµ)/Γ_(had)=0.053-_(0.015)^(+0.020), and Γ_(ττ)/Γ_(had)=0.066_(-0.017)^(+0.021), in good agreement with the standard-model prediction of 0.048. From the average leptonic width result, Γ_(ll)/Γ_(had)=0.053_(-0.009)^(+0.010), we derive Γ_(had)=1.56_(-0.24)^(+0.28) GeV. We find for the vector coupling constants of the tau and muon v_τ^2=0.31±0.31_(-0.30)^(+0.43) and v_μ^2=0.05±0.30_(-0.23)^(+0.34).

Additional Information

© 1989 The American Physical Society. Received 24 October 1989; published in the issue dated 25 December 1989. One of us (M. Kuhlen) wishes to acknowledge the Alexander von Humboldt Foundation for its support. This work was funded in part by Department of Energy, Contracts No. DE-AC03-81-ER40050 (California Institute of Technology), No. DE-AM03-76SF00010 (University of California, Santa Cruz), No. DE-AC02-86ER40253 (University of Colorado), No. DE-AC03-83ER40103 (University of Hawaii), No. DE-AC02-84ER40125 (Indiana University), No. DE-AC03- 76SF00098 (LBL), No. DE-AC02-76ER01112 (University of Michigan), and No. DE-AC03-76SF00515(SLAC), and by the National Science Foundation (Johns Hopkins University).

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