A measurement of the partial hadronic widths of the Z grade using neural networks

From the data collected by the DELPHI detector at LEP during 1990, the hadronic branching fractions of the Z neutral boson into all five known quarks have been measured for the first time in the literature. A classifier based on a feed-forward neural network has been used for separating the handronic decays of the Z neutral into four classes, corresponding to (xxxxx) unresolved, ss, cc, bb. Data on the hard final-state photon radiation have been then used to resolve the decay rate into uu pairs from the decay rate into dd pairs. The preliminary results are consistent with the predictions from the Standard Model. Problems related to the estimate of systematics are discussed