Measurement of the branching ratios of the Z0 into heavy quarks

TL;DR

This paper reports precise measurements of the Z0 boson's decay probabilities into bottom and charm quarks using a large dataset and advanced vertex detection techniques, providing important tests of the Standard Model.

Contribution

The study introduces a multi-tag technique with CCD vertex detectors to accurately measure heavy quark branching ratios at the Z0 resonance.

Findings

Measured Rb with high precision, Rb=0.21604 +- 0.00098 (stat.) +- 0.00073 (syst.)

Measured Rc with high precision, Rc=0.1744 +- 0.0031 (stat.) +- 0.0020 (syst.)

Results are consistent with Standard Model predictions.

Abstract

We measure the hadronic branching ratios of the Z0 boson into heavy quarks: Rb=Gamma(Z0->bb)/Gamma(Z0->hadrons) and Rc=Gamma(Z0->cc/Gamma(Z0->hadrons) using a multi-tag technique. The measurement was performed using about 400,000 hadronic Z0 events recorded in the SLD experiment at SLAC between 1996 and 1998. The small and stable SLC beam spot and the CCD-based vertex detector were used to reconstruct bottom and charm hadron decay vertices with high efficiency and purity, which enables us to measure most efficiencies from data. We obtain, Rb=0.21604 +- 0.00098(stat.) +- 0.00073(syst.) -+ 0.00012(Rc) and, Rc= 0.1744 +- 0.0031(stat.) +- 0.0020(syst.) -+ 0.0006(Rb)