[en] The discovery of neutrino oscillations opened a new era in neutrino physics: an era of investigation of neutrino masses, mixing, magnetic moments and other neutrino properties. On the other hand small neutrino masses cannot be explained by the standard Higgs mechanism of mass generation. Thus, small neutrino masses are the first signature in particle physics of a new beyond the Standard Model physics. One of the most important challenges ahead is the problem of the very nature of neutrinos with definite masses: are they Dirac neutrinos possessing a conserved lepton number which distinguish neutrinos and antineutrinos or Majorana neutrinos with identical neutrinos and antineutrinos? Many experiments of the next generation and new neutrino facilities are now under preparation and investigation. This book is intended as an gentle but detailed introduction to the physics of massive and mixed neutrinos that will prepare graduate students and young researchers entering the field for the exciting years of neutrino physics to come. It is based on numerous lectures given by the author, one of the pioneers of modern neutrino physics (recipient of the Bruno Pontecorvo Prize 2002), at different institutions and schools. (orig.)

[en] We investigate possible tests of CPT invariance on the level of event rates at neutrino factories. We do not assume any specific model but phenomenological differences in the neutrino-antineutrino masses and mixing angles in a Lorentz invariance preserving context, such as could be induced by physics beyond the standard model. We especially focus on the muon neutrino and antineutrino disappearance channels in order to obtain constraints on the neutrino-antineutrino mass and mixing angle differences; we found, for example, that the sensitivity |m₃-m(bar sign)₃|(less-or-similar sign)1.9x10^-4 eV could be achieved

[en] From the standard seesaw mechanism of neutrino-mass generation, which is based on the assumption that the lepton number is violated at a large (∝10¹⁵ GeV) scale, it follows that the neutrinoless double-beta decay (0νββ-decay) is ruled by the Majorana neutrino-mass mechanism. With this notion, we derive for the inverted neutrino-mass hierarchy the allowed ranges of the half-lives of the 0νββ-decay for nuclei of experimental interest with different sets of nuclear matrix elements. The present-day results of the calculation of the 0νββ-decay nuclear matrix elements are briefly discussed. We argue that if 0νββ-decay will be observed in future experiments sensitive to the effective Majorana mass in the inverted mass hierarchy region, then a comparison of the derived ranges with measured half-lives will allow us to probe the standard seesaw mechanism assuming that future cosmological data will establish the sum of the neutrino masses to be about 0.2 eV. (orig.)

[en] Neutrinos play an exceptional role in particle or nuclear physics as well as in astrophysics. Postulated by Pauli in 1930, they were named by Fermi in 1933 and experimentally discovered by Reines and Cowan in 1956. A second family of neutrinos was discovered in 1962 and a third in 1975. The CERN collider LEP proved in 1989 that 3 types of interacting neutrinos are enough in the standard model of particle physics. They are named electron-neutrino (ν_e), muon-neutrino (ν_μ) and tau-neutrino (ν_τ), associated to the charged leptons electron, muon and tau. They have no charge, a very tiny mass and interact only weakly, so these elusive particles can cross large quantity of matter (like the Sun or the Earth) without interacting. Emitted in huge numbers (about 1020 per second) in nuclear reactors, they are also artificially produced in man-made accelerators which deliver intense neutrino beams. But the main source of neutrinos is the Universe itself: the relic neutrinos from the Big Bang have been wandering for more than 13.6 billion years, with a density of 330 per cm³ everywhere. Starting with the fusion of two protons, nuclear reactions in the core of the Sun produce about 2 10³⁸ electron-neutrinos per second, which means 65 billions of neutrinos per second per cm² on Earth. Supernova explosions emit about 10⁵⁸ neutrinos in a few seconds and the central engines of active galactic nuclei produce them abundantly. On Earth, many neutrinos are produced by the interaction of high energy cosmic rays in the upper atmosphere and are also emitted by radioactive elements in the crust and the mantle of the Earth. We are bathed in neutrinos which cross us continually and abundantly. Witnesses of the core of the Sun, solar electron-neutrinos have been observed since 1968, but their number is significantly less than what is predicted by solar models built by astrophysicists. It took more than 30 years to solve the problem of the deficit, when the SNO experiment showed in 2001 that part of the solar electron-neutrinos had been transformed into mu-neutrinos or tau-neutrinos. This was explained by the fact that neutrinos were oscillating between the three families, a mechanism invented by Pontecorvo in 1958 and authorized by quantum mechanics (mechanism completed by the MSW effect for solar neutrinos). In fact the oscillation mechanism was first observed in 1998 by the SuperKamiokande experiment via the study of atmospheric neutrinos: muon-neutrinos produced in the atmosphere at the antipodes were oscillating into tau-neutrinos during their travel through the Earth. Neutrino oscillation is possible only if neutrinos have a mass (which is not necessary in the minimal standard model of particle physics) and its discovery opens the door towards, at least, the completion of the standard model. Since 1970, neutrino beams have been used also to study neutrino properties but also to penetrate deep inside the nucleons and unveil their fine structure. This document is the compilation of all presentations given at the conference