出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：In a search for physics beyond the Standard Model (SM) one can use different types of guidelines.
A possible strategy is to attempt to explain the phenomena that cannot be t to the SM by minimal
means, that is by introducing the smallest possible number of new particles without adding
any new physical principles (such as supersymmetry or extra dimensions) or new energy scales
(like the Grand Unied scale). An example of such a theory is the renormalizable extension of
the SM, the nMSM (neutrino Minimal Standard Model) [2, 3], where three light singlet righthanded
fermions (sterile neutrinos) are introduced. The leptonic sector of the theory has the same
structure as the quark sector, i.e. every left-handed fermion has its right-handed counterpart. This
model is consistent with the data on neutrino oscillations, provides a candidate for dark matter
particle . the lightest singlet fermion (sterile neutrino), and can explain the baryon asymmetry
of the Universe [3]. A crucial feature of this theory is the relatively small mass scale of the new
neutral leptonic states, which opens a possibility for a direct search of these particles.
We discuss here the properties of neutral leptons in this model and the ways they can be searched
for in particle physics experiments. In particular, if sterile neutrinos are lighter than kaons, they
can be produced in leptonic and semileptonic kaon decays with branching ratios only one-two
orders of magnitude below the current experimental limits from direct searches. This gives a
unique possibility to either prove or rule out nMSM with light sterile neutrinos.
