Electroweak Precision Measurements with Leptons

TL;DR

This paper reviews precision measurements of lepton electroweak parameters at SLD and LEP, highlighting updated results for the weak mixing angle and their implications for the Standard Model.

Contribution

It provides the latest combined measurements of the effective weak mixing angle from leptonic asymmetries, emphasizing the discrepancy with quark-based measurements.

Findings

SLD weak mixing angle: 0.23099 ± 0.00026

Combined lepton-based value: 0.23119 ± 0.00020

Over 3σ difference from quark-based value

Abstract

The precision measurements of lepton electroweak parameters at SLD and LEP are reviewed and discussed. The updated SLD weak mixing angle measurement from $A_{LR}$ and the lepton left-right forward-backward asymmetries is $\sin^2\theta_W^{eff} = 0.23099 \pm 0.00026$, and the combined SLD/LEP lepton-based value is $0.23119 \pm 0.00020$. This value differs by over $3\sigma$ from the comparable quark-based value.