Measurement of the polarized forward-backward asymmetry of b quarks at SLD

Abstract

This thesis presents a direct measurement of the parity-violating parameter A{sub b} using the Left-Right Forward-Backward asymmetry of b{anti b} pair production at the Z{sup 0} pole. The measurement was done at the Stanford Linear Accelerator Center (SLAC) using data from the SLAC Large Detector (SLD). The authors take advantage of the high polarization of the SLAC Linear Collider (SLC) electron beam. To identify heavy flavor decays of the Z{sup 0}, they use a b-tag based on the topological reconstruction of the mass of the B vertex. Discrimination between the b and {anti b} quark directions is provided by a self-calibrating jet-charge technique. This technique allows calibration of the analyzing power from data and gives a much reduced model dependence. Based on the 1994--95 (1993) sample of 100,000 (50,000) Z{sup 0} decays recorded with an electron beam polarization of <P{sub e}> = 77% (63%), they have obtained A{sub b} = 0.911 {+-} 0.045(stat) {+-} 0.045(syst). This value is in goo d agreement with the Standard Model.