Study of the structure of e+e- -> b bbar g events and improved limits on the anomalous chromomagnetic coupling of the b-quark

TL;DR

This study analyzes e+e- -> b bbar g events from Z0 decays to test QCD predictions and set limits on the b-quark's anomalous chromomagnetic moment, finding results consistent with the Standard Model.

Contribution

It provides the first measurement of the b-quark's chromomagnetic moment using three-jet events and improves limits on its possible anomalous value.

Findings

Measured the b-quark's chromomagnetic moment to be consistent with zero.

Set limits on the anomalous chromomagnetic coupling: -0.11 < kappa < 0.08.

Compared gluon energy and angle distributions with perturbative QCD predictions.

Abstract

The structure of e+e- -> bbg events was studied using Z0 decays recorded in the SLD experiment at SLAC. Three-jet final states were selected and the CCD-based vertex detector was used to identify two of the jets as b or bbar. Distributions of the gluon energy and polar angle were measured over the full kinematic range, and compared with perturbative QCD predictions. The energy distribution is potentially sensitive to an anomalous b chromomagnetic moment kappa. We measured kappa to be consistent with zero and set limits on its value, -0.11 < kappa < 0.08 at 95% c.l. (preliminary).