A Precise measurement of the left-right cross-section asymmetry in Z boson production,”. SLAC-0454

This thesis presents a measurement of the left-right asymmetry, ALR, in the production cross section of Z Bosons produced by e+e- annihilations, using polarized electrons, at a center of mass energy of 91.26 Gev. The data presented was recorded by the SLD detector at the SLAC Linear Collider during the 1993 run. The mean luminosity-weighted polarization of the electron beam was plutn = (63.0 i 1.1)%. Using a sample of 49,392 Z events, we measure ALR to be 0.1626±0.0071(stat.)±0.0030(sys.), which determines the effective weak mixing angle to be sin 2 ef =0.2292±0.0009(stat.)±0.0004(sys.). This result differs from that expected by the Standard Model of Particles and Fields by 2.5 standard deviations