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Abstract:
Neutrinoless double beta decay is a very sensitive experimental probe for physics
beyond the Standard Model. In fact, this process is the only known possibility to
ascertain in the foreseeable future whether the neutrino is a Dirac or a Majorana
particle. Most theoretical results on this subject, however, have been known for many
years. In the advent of the next generation of experiments, it is worthwhile to reexamine
old results and provide some new theoretical contributions. This thesis deals
with various topics related to neutrinoless double beta decay. In particular, we focus
on a discussion of the famous Schechter–Valle (or Black Box) theorem, as well as on a
realization of neutrinoless double beta decay in universal extra dimensions, which has
not been considered in the literature so far. We find that the Schechter–Valle theorem,
although valid, is of merely academic interest, as it generates a neutrino mass which is
many orders of magnitude smaller than the one expected. Concerning universal extra
dimensions, we are able to give a new bound on their size, which is slightly weaker
but complementary to the existing constraints from electroweak precision data. Next
generation experiments are expected to improve upon the bounds we obtain.
