Precision measurements of parity violation and the weak mixing angle in Moller scattering

摘要

We report an observation of a parity-violating asymmetry in fixed target electron-electron (Moller) scattering at a four-momentum transfer Q(2) = 0.03 (GeV/c)(2). This is a most precise measurement of parity nonconservation to date, and leads to a determination of the electron's weak charge and of the value of the effective weak mixing angle sin(2) theta(W)(eff) = 0.2403 +/- 0.0014, which is consistent with the Standard Model expectation at the current level of precision. The comparison between the measurements of the weak mixing angle at Q(2) = 0.03 (GeV/c)(2) and at the Z(0) pole establishes the running of sin(2) theta(W) with 6.5 sigma significance.