Event recognition: multivariate analysis methods to tag b quark events in ALEPH

Two multivariate analysis methods: a linear discrimination method and a classification tree have been performed to get classifiers. These classifiers have been applied to tag b quark events in ALEPH. Two decays of the b quark have been considered : semi-leptonic decays involving an electron and purely hadronic decays. The ratios of number of classified events n(b→e)/n(e) and n(b→hadrons)/n(events) are computed with Monte Carlo events and ALEPH events. 5 figs