Observation of Parity Nonconservation in Moller Scattering

TL;DR

This paper reports the first direct measurement of parity nonconservation in Moller scattering, confirming the Standard Model prediction of the electron's weak charge at low energy with high precision.

Contribution

It provides the first direct observation of parity violation in Moller scattering and measures the electron's weak charge consistent with the Standard Model.

Findings

Parity-violating asymmetry A_PV = -175 ± 30 (stat.) ± 20 (syst.) ppb

Electron's weak charge Q^e_W = -0.053 ± 0.011

Weak mixing angle sin^2θ_W(M_Z)_MSbar = 0.2293 ± 0.0024 ± 0.0016 ± 0.0006

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^2\theta_W(M_Z)_MSbar = 0.2293 +/- 0.0024 (stat.) +/- 0.0016 (syst.) +/- 0.0006 (theory).