Neutral Current Couplings of Leptons to Polarized Z 0 ' s in the SLD Experiment

We study neutral current couplings of leptons to polarized Z 0 's in the SLD experiment in terms of the leptonic asymmetry parameters A e , A and A. W e discuss in detail e , L;R + e + ! Z 0 ! , + and , + , with leftL-or rightR-handed polarized electron beams. SLD's most precise measurement o f A e is shown to result from the left-right cross section asymmetry, A LR , where the dependence on initial state electronic couplings enable use of essentially all of the data. Comparing A and A with A e tests the universality of leptonic couplings. from these two leptonic channels. If lepton universality is assumed, a combined asymmetry parameter A e = 0 : 1470:013 results, which directly corresponds to an eeective v alue of the weak mixing angle sin 2 eff W = 0 : 2315 0:0017.