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A study of neutrino propagation and oscillations both in vacuum and in dense media

University of British Columbia

The phenomenon of neutrino oscillations has been studied for many years and is quite well understood. There remain, however, several issues related to the localization of neutrinos in space and time which have not been entirely resolved. In this thesis we present a detailed study of several of these issues and we present some novel approaches which are useful in their resolution. We begin by examining the effects of coherent and incoherent broadening on the oscillations of relativistic neutrinos. Such effects are due to distinct physical processes which could in principle be controlled at the source. We show under very general assumptions that these two types of broadening cannot be distinguished at the detector. The consequences of these issues for the oscillations of solar neutrinos is also discussed. We then present a novel approach to account for the localization in space and time of neutrinos in a typical neutrino oscillation experiment. This is accomplished by modelling the source and detector as spatially and temporally localized oscillators. This simple model allows us to study the effects due to the mass of the exchanged neutrinos and due to the time resolution of the detector. We then study the propagation of neutrinos in dense media. It is shown that the asymmetry of the dispersion relation as a function of the neutrino's momentum leads to several interesting and amusing effects. The dispersion relation has a minimum at a non-zero value of the momentum p~ρG[sub F], where ρ is the number density of particles in the medium. We show that as a result of this minimum a Dirac (but not Majorana) neutrino may be "trapped" by the medium provided its momentum is less than a critical value which is of order ρG[sub F].

Thesis/Dissertation

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2009-03-17

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http://hdl.handle.net/2429/6148

Physics

University of British Columbia

UBCV

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