The semileptonic decay rates and fragmentation parameters of b and c states

From a fit to the p, pperpendicularto distribution of single electron and muon candidates in a sample of 127 083 hadronic Z decays, collected using the ALEPH detector at LEP, measurements of the average semileptonic branching ratios B(b → l) and B(c → l) are obtained. In the fit Standard Model values are assumed for the branching ratios Z → banti b/Z → qanti q = 0.217 and Z → canti c/Z → qanti q = 0.171. In the fit the heavy quarks are assumed fragment according to the model of Peterson at al. Within the framework of this model the mean values X = Ehadron are obtained for both b and c states. (orig.)