Measurement of Z0 lepton coupling asymmetries

Polarized Z0's from e+e- collisions at the SLAC Linear Collider (SLC) have been used to determine the asymmetry parameters Ae, Aμ and Aτ from the leptonic decay channels. This is the first direct measurement of Aμ. The data have been gathered by the SLC Large Detector (SLD) with the electron polarization averaging 63% during the 1993 data taking period and 77% in 1994-95. A maximum likelihood procedure as well as cross section asymmetries was used to measure the asymmetry parameters from the differential cross sections for equal luminosities of left- and right-handed electron beams. The polarization-dependent muon-pair distributions give Aμ = 0.102 ±0.034 and the tau-pairs give Aτ = 0.195 ±0.034. The initial state electronic couplings in all three leptonic channels as well as the final state angular distribution in the e+e- final state measure Ae to be Ae = 0.152±0.012. Assuming lepton universality and defining a global leptonic asymmetry parameter Ae-μ-τ = 0.151±0.011. This global leptonic asymmetry value translates directly into sin2θWeff=0.2310±0.0014 at the Z0 pole