| The E-158 experiment at the Stanford Linear Accelerator Center (SLAC) measures the parity-violating cross-section asymmetry in electron-electron (Moller) scattering at low Q2. This asymmetry, whose Standard Model prediction is roughly -150 parts per billion (ppb), is directly proportional to (1--4 sin2 qW ), where qW is the weak mixing angle. Measuring this asymmetry to within 10% provides an important test of the Standard Model at the quantum loop level and probes for new physics at the TeV scale.; The experiment employs the SLAC 50 GeV electron beam, scattering it off a liquid hydrogen target. A system of magnets and collimators is used to isolate and focus the Moller scattering events into an integrating calorimeter. The electron beam is generated at the source using a strained, gradient-doped GaAs photocathode, which produces roughly 5 x 1011 electrons/pulse (at a beam rate of 120 Hz) with ∼80% longitudinal polarization. The helicity of the beam can be rapidly switched, eliminating problems associated with slow drifts. Helicity-correlations in the beam parameters (charge, position, angle and energy) are minimized at the source and corrected for using precision beam monitoring devices.; The parity-violating cross-section asymmetry A PV in Moller scattering is measured to be A PV = -160 +/- 21(stat) +/- 16(syst) ppb, at an average Q2 of 0.026 GeV2. This represents the first observation of parity violation in Moller scattering, and corresponds to the following low-energy determination of the weak mixing angle: sin2q W&parl0;Q2=0.026GeV 2&parr0;MS=0.2381+/- 0.0015stat +/-0.0014syst . This agrees with the Standard Model prediction of 0.2385 +/- 0.0006. Roughly half of the experiment's total data set is represented here. This thesis provides a full description of the experimental method and analysis procedure used to obtain the above result. It also discusses the result's physical implications in terms of possible extensions to the Standard Model. |
