The discovery of neutrino mass and the observed baryon asymmetry in the Universe provide strong motivations to pursue the two neutrino physics research lines addressed by our group, namely the experimental test of the Majorana nature of the neutrino through neutrinoless double beta decay searches on the one hand, and the search for possible violations of the CP (charge and parity) symmetry in the lepton sector with long-baseline (LBL) neutrino oscillation experiments at particle accelerators on the other.
The discovery and precision measurements of neutrino oscillations during the last 20 years have triggered a critical examination of the Standard Model (SM) of particle physics. Neutrinos were proven to be massive and to change flavour in an oscillatory pattern as they propagate. According to theoretical prejudice, the most natural SM extension that accommodates massive neutrinos is the seesaw mechanism. This model would require neutrinos to be Majorana particles, i.e. identical to their antiparticles, and would imply that lepton number can be violated in certain physical processes.
Cosmological observations have unequivocally demonstrated that the Universe today is almost entirely made of matter, as a result of an asymmetry between matter and antimatter that would have developed in the early Universe, and of matter-antimatter annihilation. The theoretically preferred mechanism to generate matter dominance is through a lepton asymmetry that is then efficiently transferred into a baryon asymmetry (leptogenesis).
