Characterisation, optimisation and performance studies of pixel vertex detector modules for the Belle II experiment
von Philipp Wieduwilt
Datum der mündl. Prüfung:2021-05-03
Betreuer:Prof. Dr. Ariane Frey
Gutachter:Prof. Dr. Ariane Frey
Gutachter:PD Dr. Jörn Große-Knetter
EnglischThe Standard Model of particle physics is very successful in describing the fundamental particles and their interactions. Still, some questions regarding the details and input parameters of the theory, as well as regarding to date unsatisfactorily described phenomena are to be answered. Today’s high-energy physics experiments probe this new physics. The Belle II experiment at the SuperKEKB e+e−-collider in Japan explores the precision frontier, measuring the properties of particle interactions at great detail. The precise and abundant study of decays of B-mesons is a particularly good window to seek answers to the open questions of electro-weak interactions. Precise measurements in Belle II are possible in particular with a silicon pixel detector located very close to the interaction region of the electrons and positrons. The pixel detector is based on the depleted field-effect transistor (DEPFET) technology, which is employed for the first time in a high-energy physics experiment. Modules for the Belle II pixel detector were produced. A characterisation and optimisation procedure for these modules was developed in the scope of this thesis. A number of 17 modules have been processed according to this program, and the qualification criteria for the installation in Belle II have been determined. In addition, the performance of detector modules has been evaluated in beam tests. It is demonstrated that the optimisation procedure yields consistent characteristics among the tested modules. Signal-to-noise ratios of 20 to 40 are achieved at an in-pixel amplification factor of about 500 pA/electron in the DEPFET cell. The intrinsic spatial resolution is measured to be in the order of 10 μm, depending on pixel pitch and incidence angles, with a hit efficiency of 99.6 %. The module performance is in good agreement with the design goals and the requirements for the Belle II pixel detector are met.
Keywords: Belle II; DEPFET; Particle tracking detectors; Intrinsic spatial resolution; Detection efficiency