Identified final states in the hadronic decays of the Z

Abstract

Abstract Two physics analyses performed with RICH detector identification are presented. Both refer to the hadronic decays of the Z recorded by the DELPHI experiment at LEP during the 1992 data taking. The first analysis is the measurement of the spectral composition of the hadronic events by a maximum likelihood technique using the average reconstructed Cherenkov angle. The inclusive fractions of kaons and protons as a function of momentum and related quantities such as the average multiplicities and the ξ ∗ peak position are reported. The differential production cross sections have also been measured. These quantities are compared with the JETSET predictions and with the MLLA+LPHD QCD theoretical predictions for the hadron mass spectra. The second analysis shows another way of using the RICH as an identification tool: an individual track-by-track hadronic flavour tagging is used, merging the Cherenkov information with that coming from the d E d x . In bb events selected by a lifetime tag, kaons and protons have been selected to measure for the first time the average multiplicity of kaons and protons in Z → b b events. Studying the rapidity distribution with respect to the thrust axis, the average multiplicity of kaons and protons in the decay of the B hadrons has been extracted.