In my thesis I study Majorana fermions from three different perspectives. The first one corresponds to non-interacting Majorana fermions that, however, pose non-trivial topological properties. The... Show moreIn my thesis I study Majorana fermions from three different perspectives. The first one corresponds to non-interacting Majorana fermions that, however, pose non-trivial topological properties. The second one corresponds to strongly interacting Majoranas and the third to relic neutrinos. No one knows for sure if they have Dirac or Majorana nature. Show less
Several different topics related to the CHORUS experiment at CERN are presented. CHORUS has searched for neutrino oscillation between νμand ντwith mixing probability down to 2⋅10-4 and ∆ m-2 >0... Show moreSeveral different topics related to the CHORUS experiment at CERN are presented. CHORUS has searched for neutrino oscillation between νμand ντwith mixing probability down to 2⋅10-4 and ∆ m-2 >0.5 eV2. Chapter 1 discusses the discovery of neutrino oscillations by several other experiments. Chapter 2 describes the experimental setup with 770 kg of emulsion followed by electronic detectors to measure energy and momentum. The emulsion records the tracks and decays of short-lived particles with very high resolution. It is scanned with computer-controlled microscopes. New developments in microscope hardware and associated tracking software are given in chapter 4. Several algorithms are described that reconstruct tracks from about 105hits in a few seconds. These algorithms are based on multi-dimensional search trees to quickly build a connection graph. To improve the suppression of background, a honeycomb drift-tube tracker was added to CHORUS. Its read-out stores a stream of over--threshold samples in four separate memory banks. This solution is very fault tolerant. More than 2000 charm decays were reconstructed in the emulsion. For identified D0 decays, the experiment has looked for associated π+particles from D*+->D0π+decays. From the number of found events, the cross-section for D*+production in νμcharged-current interactions is determined. Show less
