Direct Measurements of A_b and A_c using Vertex/Kaon Charge Tags at SLD

TL;DR

This paper reports precise direct measurements of the parity violation parameters A_c and A_b in Z boson decays to charm and bottom quarks, using vertex charge and kaon charge tagging techniques at SLD.

Contribution

It introduces a novel algorithm leveraging vertex charge and kaon charge to discriminate quark flavors, enabling direct measurement of A_c and A_b with high precision.

Findings

Measured A_c = 0.673 +/- 0.029 (stat.) +/- 0.023 (syst.)

Measured A_b = 0.919 +/- 0.018 (stat.) +/- 0.017 (syst.)

Utilized 400,000 Z decays with 73.4% beam polarization.

Abstract

Exploiting the manipulation of the SLC electron-beam polarization, we present precise direct measurements of the parity violation parameters A_c and A_b in the Z boson - c quark and Z boson - b quark coupling. Quark/antiquark discrimination is accomplished via a unique algorithm that takes advantage of the precise SLD CCD vertex detector, employing the net charge of displaced vertices as well as the charge of kaons that emanate from those vertices. From the 1996-98 sample of 400,000 Z decays, produced with an average beam polarization of 73.4%, we find A_c = 0.673 +/- 0.029 (stat.) +/- 0.023 (syst.) and A_b = 0.919 +/- 0.018 (stat.) +/- 0.017 (syst.).