Improved Direct Measurement of the Parity-Violation Parameter A_b Using a Mass Tag and Momentum-Weighted Track Charge

TL;DR

This paper reports an improved measurement of the parity-violation parameter A_b in Z boson decays to b quarks, using a novel track-charge technique and beam polarization to achieve a precise, independent result.

Contribution

It introduces a self-calibrating track-charge method combined with topological B hadron mass reconstruction for more accurate A_b measurement.

Findings

Measured A_b = 0.906 +/- 0.022(stat.) +/- 0.023(syst.)

Used a sample of 400,000 Z decays from 1996-98 with 73.4% beam polarization

Achieved an independent and improved determination of the parity-violation parameter.

Abstract

We present an improved direct measurement of the parity-violation parameter A_b in the Z boson-b quark coupling using a self-calibrating track-charge technique applied to a sample enriched in Z -> b b-bar events via the topological reconstruction of the B hadron mass. Manipulation of the SLC electron-beam polarization permits the measurement of A_b to be made independently of other Z-pole coupling parameters. From the 1996-98 sample of 400,000 hadronic Z decays, produced with an average beam polarization of 73.4%, we find A_b = 0.906 +/- 0.022(stat.) +/- 0.023(syst.).