A search for lepton avour number violating Z 0 decays in the channels Z 0 ! , Z 0 ! e , Z 0 ! e , using the DELPHI detector with data collected during the 1991{94 LEP runs, is described. No signal was found. Upper limits at 95% con dence level for the respective branching fractions of 1:2 10 5 , 2 : 2 10 5 , and 0:25 10 5 , w ere obtained.
The probability P (c → D * + ) that a charm quark fragments into a D * + meson and the c → l + semileptonic branching fraction were measured in Z 0 decay into cc events.From the analysis of 3.5 Million Z 0 events collected from 1992 to 1995, a sample of charm meson decays with 81% cc purity was selected. The product of the c → D * + fragmentation probability times the D * + → D 0 π + branching fraction was measured to be:
The polarisation has been studied with the e + e ! + data collected by the DELPHI detector at LEP in 1993, 1994 and 1995 around the Z resonance rstly through the exclusive decay c hannels e , , , and a 1 and secondly with an inclusive hadronic analysis which benets from a higher eciency and a better systematic precision. The results have been combined with those previously published on 1990 to 1992 DELPHI data, to produce results which reect the full LEP-1 statistics. The t of the polarisation dependence on the
During 1993 and 1995 LEP was run at 3 energies near the Z 0 peak in order to give improved measurements of the mass and width of the resonance. During 1994, LEP operated only at the Z 0 peak. In total DELPHI accumulated data corresponding to an integrated luminosity of approximately 116 pb ,1 . Analyses of the hadronic cross-sections and of the cross-sections and forward-backward asymmetries in the leptonic channels used the most precise evaluations of the LEP energies. In the dimuon channel, events with a photon radiated from the initial state have been used to probe the cross-sections and asymmetries down to PETRA energies. Model independent ts to all DELPHI lineshape and asymmetry data from 1990 to 1995 have been carried out giving values of the resonance parameters:M Accepted by E . P h ys. J. C ii
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