Studies of the strong and electroweak interactions at the Z<sup>0</sup> pole

Abstract

This thesis presents studies of the strong and electroweak forces, two of the fundamental interactions that govern the behavior of matter at high energies. The authors have used the hadronic decays of Z{sup 0} bosons produced with the unique experimental apparatus of the e{sup +}e{sup {minus}} Linear Collider at the Stanford Linear Accelerator Center (SLAC) and the SLAC Large Detector (SLD) for these measurements. Employing the precision tracking capabilities of the SLD, they isolated samples of Z{sup 0} events containing primarily the decays of the Z{sup 0} to a chosen quark type. With an inclusive selection technique, they have tested the flavor independence of the strong coupling, {alpha}{sub s} by measuring the rates of multi-jet production in isolated samples of light (uds), c, and b quark events. They find: {alpha}{sub s}{sup uds}/{alpha}{sub s}{sup all} 0.987 {+-} 0.027(stat) {+-} 0.022(syst) {+-} 0.022(theory), {alpha}{sub s}{sup c}/{alpha}{sub s}{sup all} = 1.012 {+-} 0.104(stat) {+-} 0.102(syst) {+-} 0.096(theory), {alpha}{sub s}{sup b}/{alpha}{sub s}{sup all} = 1.026 {+-} 0.041(stat) {+-} 0.030(theory), which implies that the strong interaction is independent of quark flavor within the present experimental sensitivity. They have also measured the extent of parity-violation in the Z{sup 0} c{bar c} coupling, given by the parametermore » A{sub c}{sup 0}, using a sample of fully and partially reconstructed D* and D{sup +} meson decays and the longitudinal polarization of the SLC electron beam. This sample of charm quark events was derived with selection techniques based on their kinematic properties and decay topologies. They find A{sub c}{sup 0} = 0.73 {+-} 0.22(stat) {+-} 0.10(syst). This value is consistent with that expected in the electroweak standard model of particle interactions.« less