Neutrino Properties Probed by Lepton Number Violating Processes

Abstract

Study of neutrino properties is nowadays one of the most active domains of research in physics. On the one hand, fundamental properties of the neutrinos like their absolute mass, their character (are they Dirac or Majorana particles?) and the number of neutrino flavors, are still unknown. On the other hand, the knowledge of these properties are of great importance since the neutrinos are very abundant in nature and play a key role in nuclear and particle physics, astrophysics and cosmology. In addition, the results of the neutrino oscillation experiments have convincingly showed that neutrinos have mass and mix, in contradiction to the initial assumptions of the Standard Model. In this context there is an increased interest in the study of the Lepton Number Violating (LNV) processes, since they are capable to decide on the above mentioned neutrino properties. Since recently, the neutrinoless double beta (0nββ) decay was considered the only process able to distinguish between Dirac or Majorana neutrinos and to give a hint on the absolute mass of the electron neutrino. At present, the increased luminosity of the LHC experiments at CERN makes it feasable the search for LNV processes at LHC as well. Besides the neutrino character, these studies can also shed light on the existence of other types of neutrinos (the sterile neutrinos), than the three known ones. In this paper, I make a brief review on our present knowledge about the neutrino properties and on the way they can be probed by LNV processes at low- and high-energies. Particularly, I refer to the 0nββ decay process and to the first attempts of searching of LNV processes in hadron collider experiments, particularly in LHC experiments at CERN-Geneva.