Neutrino physics contributed in a fundamental way to the progress of science, opening important windows of knowledge in elementary particle physics, as well in astrophysics and cosmology. Substantial experimental efforts are presently dedicated to improve our knowledge on neutrino properties as, in fact, we do not know yet some of the basic ones. Although very significant steps forward have been made, neutrino masses and mixings still remain largely unknown and constitute an important field for future research. Are neutrinos Majorana or Dirac particles? Have they a magnetic moment? Historically, studies on weak processes and, therefore, on neutrino physics, provided first the Fermi theory of weak interactions and then the V – A theory. Finally, the observation of weak neutral currents provided the first experimental evidence for unification of weak and electromagnetic interactions by the so-called “Standard Model” of elementary particles.

In addition to the results obtained from the measurement of the solar neutrino flux, the study of atmospheric neutrinos (i.e. neutrinos produced in the hadronic cascades induced by high-energy cosmic rays interacting in the Earth's atmosphere) strongly supports the hypothesis of neutrino oscillation among different flavours. This phenomenon implies that neutrinos have mass different from zero and that the so-called family lepton number (electron, muon and tau) is not conserved in this type of process. The observation of the atmospheric neutrino interactions provides an indication, that has become more and more convincing with time, for muon neutrino transmutation (“oscillation”) in tau neutrinos, giving information on their masses and mixings. So, we are facing experimental facts not predicted by the Standard Model and opening a window, based on reliable experimental facts, on the so-called “Physics beyond the Standard Model”.

At the same time, the detection of neutrinos emitted by our Sun gave an important confirmation that the Sun (and therefore all the stars) produce energy via a chain of nuclear reactions; in particular in our Sun a specific cycle —the hydrogen cycle— is responsible for practically all the produced energy. Another very important neutrino contribution to the knowledge of astrophysical phenomena came from the observation of neutrinos emitted in conjunction with the explosion of the SN1987 supernova.

The lectures covered essentially all the aspects of the phenomenology of neutrinos, through the combination of lectures on basic theory, phenomenological interpretations and experimental results and problems. Some of the lectures have been dedicated to the far future of neutrino physics, by means of new accelerator concepts or by newly designed large detectors to investigate astrophysical phenomena involving neutrinos. After the charming introductory lecture by V.L. Telegdi on the “Ingenuity of the experimental physics”, lectures have been given by: E. Bellotti, C. Bemporad, A. Blondel, V. Berezinskii, L. L. Camilleri, E. Fiorini, G. Fogli, K. Hübner, M. Junker, W. Louis, S. Pokorski, G. Raffelt, S. Ragazzi, A. Suzuki, C. Weinheimer.

It is a pity that some of the speakers were unable to send their written contribution; all of them had serious reasons for that. Their papers would have certainly made this book more complete. In short, the subjects of their lectures covered the topics of future accelerators and detectors for neutrino beams (A. Blondel), high energy neutrino astronomy (V. Berezinskii), atmospheric neutrinos (S. Ragazzi), the physics at KamLand and non-accelerator physics in Japan (A. Suzuki).

The students participated in an active and very brilliant way, contributing to the School also through seminars illustrating aspects of their activity.

We are grateful to the President of the Italian Physical Society for having given the opportunity to provide a “state-of-the-art” summary on Neutrino Physics with the participation of highly motivated young scientists. It was a pleasant coincidence that we could discuss the recent and probably conclusive results on the flavour of solar neutrinos by the SNO collaboration shortly after their release. The first results from the KamLand experiment, presented and widely discussed at the School, have been published shortly after the School and constrain in a conclusive way the oscillation parameters in the solar sector.

Finally, we want to express our warmest thank to the Staff of the School, headed by Barbara Alzani, who made our stay in Villa Monastero pleasant and efficient, to Carmen Vasini for her remarkable effort in collecting the contributions and to Marcella Missiroli for producing this volume.

E. Bellotti, Y. Declais, P. Strolin and L. Zanotti