Etudes des proprietes des neutrinos dans les contextes ...

tel-00450051, version 1 - 25 Jan 2010
the MSW framework. We establish with exact analytical formulas under which
conditions there might be CP effects in supernova. We then explore its consequences
on the neutrino fluxes, the electron fraction which is a key element in
the r-process for the heavy elements nucleosynthesis. We also observe the effects
of such a phase on the neutrino events that could be detected on Earth. Such
numerical calculations have required the development of numerical codes in 3
flavours to describe neutrino propagation in matter. In a second work, we added
the neutrino-neutrino interaction, and investigated the validity of the analytical
formula found in the previous work, we also modify our existing code to include
this non-linear interaction and study the consequences on the CP effects. Recent
developments in the past three years have shown that its inclusion deeply
changes our comprehension of neutrino propagation in matter and engenders new
collective phenomena. In the third work, we have studied an even more realistic
case by including a dynamical density of matter inside the star. The presence of
a shock wave, created during the rebound of the collapsing matter on the protoneutron
core of the star, in addition with the neutrino-neutrino interaction can
induce particular effects on the neutrino propagation, and can let a characteristic
imprint on the neutrino fluxes on Earth depending on the neutrino hierarchy and
on the third mixing angle. In a final work we explore the consequence of the
CP-violating phase on the neutrino degeneracy parameter, in the early Universe
environment, before Big Bang Nucleosynthesis (BBN) and neutrino decoupling.
The thesis is structured as follows. The first chapter gives the theoretical
framework for neutrino oscillations. The second chapter presents historically the
main experiments performed as well as those to come and the results they brought
in neutrino physics. The third chapter introduces the core-collapse supernovae
model we use. The fourth chapter tackles the impact of including a CP-violating
phase in the neutrino propagation in a supernova and the implications on the
main observables. Because of the recent and impressive developments, we give a
description of the neutrino-neutrino interaction and the change it implies for the
neutrino propagation in a supernova environment. The following chapter shows
the effect of CP-violation when the neutrino self-interaction is included. The
sixth chapter uses an even more realistic description of the supernova media by
adding a dynamic density profile and investigate the consequences on a neutrino
flux on Earth. The seventh chapter studies the effect of the CP-violating phase
before BBN. The last chapter is the conclusion.
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