A Measurement of the b-quark Mass from Hadronic Z Decays

TL;DR

This paper measures the b-quark mass at the Z boson energy scale using hadronic decay data from ALEPH at LEP1, analyzing event-shape variables and jet rates with next-to-leading order predictions.

Contribution

It provides a novel measurement of the b-quark mass from Z decays using ratios of observables and includes a test of the flavor independence of the strong coupling constant.

Findings

Measured mb(MZ) = 3.27 GeV/c^2 with uncertainties

Validated the flavor independence of the strong coupling constant

Used the first moment of the y3 distribution for minimal uncertainties

Abstract

Hadronic Z decay data taken with the ALEPH detector at LEP1 are used to measure the three-jet rate as well as moments of various event-shape variables. The ratios of the observables obtained from b-tagged events and from an inclusive sample are determined. The mass of the b quark is extracted from a fit to the measured ratios using a next-to-leading order prediction including mass effects. Taking the first moment of the y3 distribution, which is the observable with the smallest hadronization corrections and systematic uncertainties, the result is: mb(MZ) = [3.27+-0.22(stat) +-0.22(exp)+-0.38(had)+-0.16(theo)] GeV/c2. The measured ratio is alternatively employed to test the flavour independence of the strong coupling constant for b and light quarks.