Measurement of the running b-quark mass using e+e−→bbg events

We have studied the determination of the running b-quark mass, mb(MZ), using Z0 decays into 3 or more hadronic jets. We calculated the ratio of ≥3-jet fractions in e+e−→bb̄ versus e+e−→qlql (ql = u or d or s) events at next-to-leading order in perturbative QCD using six different infra-red- and collinear-safe jet-finding algorithms. We compared with corresponding measurements from the SLD Collaboration and found a significant algorithm-dependence of the fitted mb(MZ) value. Our best estimate, taking correlations into account, is mb(MZ) = 2.56±0.27 (stat.) +0.28−0.38 (syst.) +0.49−1.48 (theor.) GeV/c2.