Measurement of using impact parameters and leptons

A measurement of$$\Gamma _{b\bar b} /\Gamma _{had} \equiv \Gamma (Z^0 \to b\bar b)/\Gamma (Z^0 \to hadrons)$$ is presented using a “mixed tag” method involving the identification of$$Z^0 \to b\bar b$$ events by two different techniques. The first uses the large impact parameter of tracks emerging from the decay ofb-flavoured hadrons and the second their semi-leptonic decay. The identification efficiencies are measured from the data using …