Luminosity evaluation and fragmentation studies for the DELPHI experiment at LEP

Abstract: The first subject addressed in this thesis is the contribution of the VSAT luminosity to the lineshape analysis, i.e. to the extraction of the mass and width of the Z0 boson from LEP1 DELPHI data. The VSAT detector has contributed to the lineshape parameter determination by providing a relative luminosity measurement of high accuracy. The second subject of the thesis is the extraction of the helicity components of the fragmentation function. The analysis is performed on data collected by the DELPHI detector from 1992 to 1995 . The study concentrates on the correction required for the hadronization process. Hadronization mainly affects the longitudinal component of the fragmentation function. The corrected measurement is used for the extraction of the strong coupling constant.