Article révisé par les pairs
Résumé : A classifier based on a feed-forward neural network has been used for separating a sample of about 123 500 selected hadronic decays of the Z0, collected by DELPHI during 1991, into three classes according to the flavour of the original quark pair: uū + dd̄ + ss̄ (unresolved), cc̄ and bb̄. The classification has been used to compute the partial widths of the Z0 into b and c quark pairs. This gave Γcc̄/Γh = 0.151 ± 0.008 (stat.) ± 0.041 (syst.), Γbb̄/Γh = 0.232 ± 0.005 (stat.) ± 0.017 (syst.).