Measurements of the $b\overline{b}$ production cross section and forward-backward asymmetry at centre-of-mass energies above the Z pole at LEP

Abstract The measurements of R b =σ( e + e − → b b )/σ( e + e − → q q ) and of the b quark forward–backward charge asymmetry, A fb b , at centre-of-mass energies above the Z pole are described. The measurement of R b is performed at s between 130 and 189 GeV using a b-tagging method that exploits the relatively large decay length of b-hadrons. The measurement of A fb b is performed using the large statistics event sample collected at s =189 GeV with a lepton-tag analysis based on the selection of prompt muons and electrons. The results at s =189 GeV are R b =0.163±0.013 (stat.) ±0.005 (syst.) , A fb b =0.61±0.18 (stat.) ±0.09 (syst.) .