First Measurement of the Left-Right Charge Asymmetry in Hadronic Z Boson Decays and a New Determination of sin^2(theta_eff)

TL;DR

This paper reports the first measurement of the left-right charge asymmetry in hadronic Z decays, providing a new determination of the electroweak mixing angle, sin^2(theta_eff), using polarized electron beams at SLAC.

Contribution

It introduces the first measurement of A_Q^{obs} in hadronic Z decays and derives a new value for sin^2(theta_eff) from this asymmetry.

Findings

Measured A_Q^{obs} = 0.225 ± 0.056 ± 0.019

Determined A_e = 0.162 ± 0.041 ± 0.014

Calculated sin^2(theta_eff) = 0.2297 ± 0.0052 ± 0.0018

Abstract

We present the first measurement of the left-right charge asymmetry A_Q^{obs} in hadronic Z boson decays. This was performed at E_cm = 91.27 GeV with the SLD at the SLAC Linear Collider with a polarized electron beam. Using 89838 events, we obtain A_Q^{obs}=0.225+-0.056+-0.019 which leads to a measurement of the electron left-right asymmetry parameter, A_e=0.162+-0.041+-0.014, and sin^2(theta_eff)=0.2297+-0.0052 +-0.0018. Also, the A_Q^{obs} measurement combined with the left-right cross section asymmetry determines A_e independently of the value of the electron-beam polarization.