Fundamental properties of neutrinos: masses and mixings

Sammanfattning: Neutrino physics is one of the fastest growing topic in phenomenological high energy physics. Neutrinos are elementary neutral particles and participate only in the weak interactions. For this reason it is very difficult to detect them experimentally. Nevertheless, much experimental progress has been obtained in the recent years. In particular our knowledge of the neutrino masses and mixing angles have increased, though there are still ambiguities. There are three experimental hints that neutrinos are massive. The most solid evidence come from studies of atmospheric neutrinos. Furthermore investigations of solar neutrinos as well as the accelerator experiment LSND gives hints of massive neutrinos. These three so-called anomalies cannot be reconciled with the standard scenario of three light neutrinos and it is conventional to disbelieve the LSND data. Therefore at present we are very certain that neutrinos are indeed massive and do mix, but more experimental information is needed. The first part of the thesis provides a general introduction to both the standard model of particle physics as well as neutrino physics. The second part concerns the research and are a collection of articles. The research deals in part with model building for generating neutrino masses through quantum corrections. Furthermore the atmospheric data from the Super-Kamiokande experiment in Japan are studies in detail in connection with the controversial LSND data and another non-standard scenario with CPT violation in the neutrino sector.