First Results from E158 Measuring Parity Violation in Moller Scattering.

SLAC E158 is an experiment to measure the parity nonconserving asymmetry in Moller scattering. Longitudinally polarized 48 GeV electrons are scattered off unpolarized (atomic) electrons in a liquid hydrogen target with an average Q2 of 0.027 GeV2. The asymmetry in this process is proportional to (1/4 - sin2 θW), where sin2 θW gives the weak mixing angle. The preliminary results give APV = -151.9 ± 29.0(stat) ± 32.5(syst) parts per billion. This in turn gives sin2 θWeff = 0.2371 ± 0.0025 ± 0.0027, which is consistant with the standard model prediction (0.2386 ± 0.0006). © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]