Abstract:
The decay of the free neutron provides a sensitive tool to measure parameters of the Standard Model of particle physics with high precision.
The retardation spectrometer aSPECT was designed to determine the electron antrineutrino angular correlation coefficient a from the shape of the proton recoil spectrum.
a is sensitive to the ratio of the weak axialvector and vector coupling constants of the nucleon. Together with a second observable and the Fermi coupling constant from Muon decay, it allows us to measure the upper left element Vud, and therefore to test the unitarity, of the Cabbibo-Kobayashi-Maskawa (CKM) matrix.
In this thesis, a description of aSPECT and its detector and data acquisition system is given. Preliminary results of data taken at the research reactor FRM II in Garching are presented, as well as a study of the background caused by decay electrons.