Z⁰ parameters and M top from LEP 1990 data

Abstract

The four detectors ALEPH, DELPHI, L3 and OPAL have collected ≈550,000 Z⁰ decays during the LEP run in 1990. We have made model-independent simultaneous fits to the LEP data to determine the Z⁰ parameters. The mass and widths of Z⁰ are M_z=91.177± 0.006±0.02(LEP) GeV, Γ_z=2.481±0.010 GeV, Γ_had=1.734±0.010 GeV and Γ_lept=83.0 ± 0.4 MeV. The number of ν families is determined to be N_ν=3.01±0.05. Simultaneous fits are performed within the Standard Model framework to the LEP data and constraining the value of sin² θ_w from the P̅P colliders we get the following values for top mass, electroweak mixing angle sin² θ_w and the radiative correction Δr : M_top = 123⁺³³₋₃₈ ± 19 (Higgs) GeV, n² θ_w=0.230 ±0.004 and Δr=0.056 ±0.011.