Measurements of $R_{\rm b}$ , $A_{\rm FB}^{\rm b}$ , and $A_{\rm FB}^{\rm c}$ in ${\rm e^+ e^-}$ collisions at 130 – 189 GeV

Abstract

The cross-section ratio $R_{\mathrm{b}} = \sigma( \rm e^+ e^- \to{\rm b\overline{\rm b}} )/\sigma(\rm e^+ e^-\to{\mathrm q\bar{\mathrm q}} )$ and the bottom and charm forward-backward asymmetries $A_{\mathrm{FB}}^{\mathrm{b}}$ and $A_{\mathrm{FB}}^{\mathrm c}$ are measured using event samples collected by the OPAL detector at centre-of-mass energies between 130 and 189 GeV. Events with bottom quark production are selected with a secondary vertex tag, and a hemisphere charge algorithm is used to extract $A_{\mathrm{FB}}^{\mathrm{b}}$ . In addition, the bottom and charm asymmetries are measured using leptons from semileptonic decays of heavy hadrons and pions from $\mathrm{D}^{*+}\to\rm D^0{\pi^+}$ decays. The results are in agreement with the Standard Model predictions.