Precision Measurement of the Weak Mixing Angle in Moller Scattering

TL;DR

This paper presents a highly precise measurement of the weak mixing angle via Moller scattering, confirming its energy dependence and constraining potential new physics beyond the Standard Model.

Contribution

It provides the most precise low-energy measurement of _W^eff and demonstrates the running of the weak mixing angle with over 6 sigma significance.

Findings

Measured _W^eff at low energy with high precision.

Confirmed the energy dependence of _W^eff consistent with the Standard Model.

Set constraints on new physics at the TeV scale.

Abstract

We report on a precision measurement of the parity-violating asymmetry in fixed target electron-electron (Moller) scattering: A_PV = -131 +/- 14 (stat.) +/- 10 (syst.) parts per billion, leading to the determination of the weak mixing angle \sin^2\theta_W^eff = 0.2397 +/- 0.0010 (stat.) +/- 0.0008 (syst.), evaluated at Q^2 = 0.026 GeV^2. Combining this result with the measurements of \sin^2\theta_W^eff at the Z^0 pole, the running of the weak mixing angle is observed with over 6 sigma significance. The measurement sets constraints on new physics effects at the TeV scale.