University of Pennsylvania
Department of Physics and Astronomy
High Energy Physics Seminar

Abstract

SLAC E-158 is an experiment to measure the right-left cross-section asymmetry in the Moller scattering. We are scattering 45-GeV and 48-GeV longitudinally polarized electron beams off unpolarized electrons in a liquid hydrogen target at an average momentum transfer squared of Q^2 = 0.025 GeV^2. The asymmetry is proportional to (1/4 - sin^2 theta_W), where sin^2 theta_W is the weak mixing angle. This measurement tests electroweak theory at the one-loop level and probes for physics beyond the Standard Model, including additional heavy gauge bosons, electron compositeness, and extra spatial dimensions. E-158 had its first physics run in the Spring of 2002. I will present preliminary results from that run, including a blinded result for the Moller asymmetry. I will also briefly describe the Jefferson Lab Hall A Proton Parity Experiment (HAPPEX). HAPPEX measured the parity-violating asymmetry in elastic e-p scattering at Q^2 = 0.477 GeV^2 and set new constraints on the strange electric and magnetic form factors of the proton. The HAPPEX collaboration is planning two additional experiments on hydrogen and helium at Q^2 = 0.1 GeV^2 in the Spring of 2003.