The standard theory of electroweak interactions predicts a parity nonconserving asymmetry in the order of 1 × 10−5 for the quasi-elastic scattering of 300 MeV longitudinally polarized electrons from nuclei at backward angles. The experimental setup for the detection of such small effects is described, and the procedure of data taking and analysis is discussed with regard to systematic uncertainties. The experimental asymmetry is found to be Aexp = (−3.51 ± 0.68 ± 0.20) × 10−6, where the first quoted error specifies the statistical uncertainty, the second one, the systematical. Aexp is interpreted in terms of model-independent coupling constants between the weak neutral current and the nucleon.
Quasi-elastic scattering of polarized electrons on polarizedHe3