Measurements of the bb̄ production cross section and forward–backward asymmetry at centre-of-mass energies above the Z pole at LEP

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