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Abstract:
Sterile neutrino with a mass of O(keV) is a well-motivated candidate to play the role
of dark matter (DM), one of the most abundant constituents of our Universe whose
nature remains still unknown. It arises as a natural and straightforward extension of
the particle content of the standard model (SM), it is neutral under all SM charges, it
can be stable over cosmological time scales, and it can be produced in adequate amount
in the early Universe to account for today’s DM abundance. In this thesis, we study
sterile neutrinos as DM candidates produced in the early Universe through oscillation
and collisions induced by their mixing with one of the active neutrino species, i.e. in the
framework of the Dodelson-Widrow and the Shi-Fuller mechanisms. In particular, we
investigate the parameter space of sterile neutrinos in two non-standard scenarios. The
first scenario studied is a non-standard cosmological scenario in which the production
of sterile neutrinos is delayed and starts at a critical temperature associated with a
low reheating temperature of the Universe or with a dynamical change in the sterile
neutrino mass. Here, we show that the discovery potential in terrestrial experiments is
considerably enhanced. In the second scenario, the production through the Dodelson-
Widrow mechanism is modified by non-standard interactions among active neutrinos.
An effective formalism to include such neutrino non-standard self-interactions in the
DM production is developed, and the sensitivity of the HUNTER experiment to this
specific model is highlighted. At the same time, we demonstrate that the stringent
limit on sterile neutrino DM coming from observations in the X-ray band should be
considered model-dependent and can be relaxed in different ways, thereby letting open
a window in the parameter space of utmost interest for experimental searches.
