QCD Tests Using $b\bar{b}g$ Events and a New Measurement of the B-Hadron Energy Distribution

TL;DR

This paper presents new measurements of gluon and B-hadron energy distributions from Z^0 decays, confirming QCD predictions, testing electroweak and CP violation, and introducing a novel B-hadron energy reconstruction technique.

Contribution

It introduces a new method for reconstructing B-hadron energy and provides comprehensive measurements of gluon and B-hadron spectra in Z^0 decays, testing fundamental QCD and electroweak predictions.

Findings

Gluon energy spectrum consistent with QCD

Measured B-hadron average scaled energy = 0.719

Set limits on anomalous chromomagnetic bbg coupling

Abstract

We present new studies of 3-jet final states from hadronic $Z^0$ decays recorded by the SLD experiment, in which jets are identified as quark, antiquark or gluon. Our gluon energy spectrum, measured over the full kinematic range, is consistent with the predictions of QCD, and we derive a limit on an anomalous chromomagnetic $bbg$ coupling. We measure the parity violation in $Z^0$ decays into $b\bar{b}g$ to be consistent with the predictions of electroweak theory and QCD, and perform new tests of T- and CP-conservation at the $bbg$ vertex. We also present a new technique for reconstructing the energy of a $B$ hadron using the set of charged tracks attached to a secondary vertex. The $B$ hadron energy spectrum is measured over the full kinematic range, allowing improved tests of predictions for the shape of the spectrum. The average scaled energy is measured to be $ = 0.719 \pm 0.005 (stat.)$ (Preliminary).