Low Energy Measurements of the Weak Mixing Angle

TL;DR

This paper reviews low energy measurements of the weak mixing angle, highlighting their role in testing the Standard Model and probing new physics at energy scales beyond current colliders.

Contribution

It provides a comprehensive overview of recent and ongoing low $Q^2$ weak mixing angle measurements and discusses future experimental prospects and their implications for new physics.

Findings

Current measurements test electroweak theory at quantum loop level

Low $Q^2$ experiments can indirectly probe physics beyond the Standard Model

Future experiments aim for increased sensitivity to new physics effects

Abstract

We review the status of precision measurements of weak neutral current interactions, mediated by the $Z^0$ boson, at $Q^2\ll M_Z^2$. They can be used to extract values for the weak mixing angle $\sin^2\theta_W$, a fundamental parameter of the $SU(2)_L\times U(1)_Y$ electroweak sector of the Standard Model. Apart from providing a comprehensive test of the electroweak theory at the quantum loop level, such measurements allow indirect access to new physics effects at and beyond the TeV scale. After a theoretical introduction and a brief overview of the three most precise low $Q^2$ weak mixing angle determinations, we describe the ongoing experimental program and prospects for future more sensitive studies. We also compare sensitivities of planned and proposed measurements to physics beyond the Standard Model.