Inclusive semileptonic branching ratios of b hadrons produced in Z decays

TL;DR

This paper measures the inclusive semileptonic branching ratios of b hadrons from Z decays using ALEPH data, employing two methods to distinguish decay contributions, resulting in precise branching ratio values.

Contribution

It introduces two complementary methods to separate direct and cascade b decays, reducing model dependence and improving measurement accuracy.

Findings

BR(b->l) = 0.1070 ± 0.0010 ± 0.0023 ± 0.0026

BR(b->c->l) = 0.0818 ± 0.0015 ± 0.0022 + 0.0022 -0.0014

Enhanced precision in semileptonic branching ratio measurements.

Abstract

A measurement of the inclusive semileptonic branching ratios of b hadrons produced in Z decay is presented, using four million hadronic events collected by the ALEPH detector from 1991 to 1995. Electrons and muons are selected opposite to b-tagged hemispheres. Two different methods are explored to distinguish the contributions from direct $\bl$ and cascade $\bcl$ decays to the total lepton yield. One is based on the lepton transverse momentum spectrum, the other makes use of the correlation between the charge of the lepton and charge estimators built from tracks in the opposite hemisphere of the event. The latter method reduces the dependence on the modelling of semileptonic b decays. The results obtained by averaging the two techniques are BR(b->l) = 0.1070 +- 0.0010 +- 0.0023 +- 0.0026 BR(b->c->l) = 0.0818 +- 0.0015 +- 0.0022 + 0.0022 -0.0014