Observation of Parity Nonconservation in Moller Scattering

Abstract

We report a measurement of the parity-violating asymmetry in fixed target electron-electron (Moller) scattering: A_PV = -175 +/- 30 (stat.) +/- 20 (syst.) parts per billion. This first direct observation of parity nonconservation in Moller scattering leads to a measurement of the electron's weak charge at low energy Q^e_W = -0.053 +/- 0.011. This is consistent with the Standard Model expectation at the current level of precision: sin^2θ_W(M_Z)_MSbar = 0.2293 +/- 0.0024 (stat.) +/- 0.0016 (syst.) +/- 0.0006 (theory).

Version 3 is the same as version 2. These versions contain minor text changes from referee comments and a change in the extracted value of Q^e_W and sin^2θ_W due to a change in the theoretical calculation of the bremsstrahulung correction (ref. 16)