Fourth generation neutrinos and neutrino induced hadron production in the resonance region

Abstract

We investigate two aspects in neutrino physics. First, we consider the extension of the standard model by a fourth fermion generation. Allowing finite mixing of the additional neutrino, which is kept most general with a Majorana mass term, constraints on the size of its Majorana mass are derived by its contribution in neutrinoless double beta decay. This determines the neutrino to be a pseudo-Dirac particle and implications for lepton number violating processes are discussed. After constraining the mixing matrix elements by radiative charged lepton decays we present an extradimensional model for softening the horizontal neutrino mass hierarchy. Then we study the consequences of the neutrino in baryogenesis, where a similar bound on the Majorana mass is obtained by estimating the washout effect on any baryonor lepton-asymmetry. The second topic is the production of pions by neutrino-nucleon interactions via resonances. For this process various cross sections, including nuclear corrections and pion spectra, are calculated and possible applications to CP searches are proposed.