Measurement of R(b) in e+ e- collisions at 182-GeV - 209- GeV

Measurements of Rb, the ratio of the bbbar cross-section to the qqbar cross- section in e+e- collisions, are presented. The data were collected by the OPAL experiment at LEP at centre-of-mass energies between 182 GeV and 209 GeV. Lepton, lifetime and event shape information is used to tag events containing b quarks with high efficiency. The data are compatible with the Standard Modelexpectation. The mean ratio of the eight measurements reported here to the Standard Modelprediction is 1.055+-0.031+-0.037, where the first error is statistical and the second systematic.