Bestimmung des schwachen Mischungswinkels sin"2#THETA#_e_f_f aus der Ladungsasymmetrie hadronischer Zerfaelle des Z-Bosons

Abstract

Final results are presented on the measurement of the charge asymmetry of hadronic decays of the Z using the full data samples of about 300.000 events collected with the DELPHI experiment at LEP in 1990 and 1991. The asymmetry has been obtained with two different approaches, which are based on a momentum weighted charge sum to determine the jet charge in the two hemispheres. From the observed asymmetry the Minimal Standard model parameter sin"2\Thetaeff has been derived to the sin"2\Thetaeff = 0.2335+0.0047-0.0035. Within the framework of the Minimal Standard model this result provides a determination of the top quark mass of mTop = 12990-...(exp.)+21-22 (mHiggs GeV. Alternatively, by including the measurement of the total hadronic width of the Z the effective vector and axial-vector couplings of the Z can be extracted to give ga = -0.4998#+-#0.0021 and g#upsilon# -0.0331+0.0094-0.0070. Comparisons with other experimental results and predictions of the standard model give no hint for necessary extensions of the Minimal Standard model. (orig.)SIGLEAvailable from TIB Hannover: RO 9740(92-10) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman