An improved direct measurement of leptonic coupling asymmetries with polarized Z bosons

TL;DR

This paper reports precise measurements of leptonic Z boson coupling asymmetries using polarized Z bosons, leading to an improved determination of the weak mixing angle, crucial for testing the Standard Model.

Contribution

It provides the most accurate measurements of leptonic Z coupling asymmetries and the effective weak mixing angle using polarized Z bosons, enhancing previous precision.

Findings

Measured asymmetry parameters Ae, Amu, Atau with high precision.

Combined asymmetry results yield a refined value of sin^2 θ_W^{eff}.

Results support the Standard Model predictions.

Abstract

We present final measurements of the Z boson-lepton coupling asymmetry parameters Ae, Amu, and Atau with the complete sample of polarized Z bosons collected by the SLD detector at the SLAC Linear Collider. From the left-right production and decay polar angle asymmetries in leptonic Z decays we measure Ae = 0.1544 +- 0.0060, Amu = 0.142 +- 0.015, and Atau = 0.136 +- 0.015. Combined with our left-right asymmetry measured from hadronic decays, we find Ae = 0.1516 +- 0.0021. Assuming lepton universality, we obtain a combined effective weak mixing angle of sin**2 theta^{eff}_W = 0.23098 +- 0.00026.