Neutrinos: past, present, future

We review some fundamental aspects of the theory of neutrino masses and mixing. The results of neutrino oscillation experiments are interpreted as evidence of three-neutrino mixing. Implications for the mixing parameters and the neutrino masses are discussed, with emphasis on the connection with the measurements of the absolute values of neutrino masses in beta decay and neutrinoless double-beta decay experiments and cosmological observations.

The theoretical basics of neutrino mass and mixing are reviewed. Dirac and Majorana masses are explained, and added together to produce the see-saw picture of the lightness of neutrinos. This picture predicts that neutrinos are Majorana particles. The character, and an apparent paradox, of Majorana neutrinos are examined. The physics of neutrino flavor change (oscillation), in vacuo and in matter, is reviewed.

The status of the problem of neutrino masses and mixing is shortly reviewed. Different schemes of mixing of (Dirac or Majorana) massive neutrinos are considered. The theory of neutrino oscillations in vacuum and in matter is presented. Existing indications in favor of neutrino mixing are shortly discussed.

This book chapter presents an overview of the historical experimental and theoretical developments in neutrino physics and astrophysics and also the physical properties of neutrinos, as well as the physical processes involving neutrinos. It also discusses the role of neutrinos in astrophysics and cosmology. Correction to tex file made.

As in Greek mythology, the neutrino was born in the mind of Wolfgang Pauli to salvage a fundamental principle. Its existence met with universal skepticism by a scientific community used to infer particles from experiment. Its detection in 1956 brought particle physics acceptance; its chirality explained maximal parity violation in $\beta$ decay; its (apparent) masslessness led theorists to imagine new symmetries. Neutrinos are pioneers of mutli-messenger astronomy, from the S...

Neutrino physics is going through a revolutionary progress. In this talk I review what we have learned and why neutrino mass is so important. Neutrino masses and mixings are already shedding new insight into the origin of flavor. Given the evidences for neutrino mass, leptogenesis is gaining momentum as the origin of cosmic baryon asymmetry. Best of all, we will learn a lot more in the coming years.

In this brief review, I discuss the new physics unveiled by neutrino oscillation experiments over the past several years, and discuss several attempts at understanding the mechanism behind neutrino masses and lepton mixing. It is fair to say that, while significant theoretical progress has been made, we are yet to construct a coherent picture that naturally explains non-zero, yet tiny, neutrino masses and the newly revealed, puzzling patterns of lepton mixing. I discuss what ...

A brief sketch is made of the present observational status of neutrino physics, with emphasis on the hints that follow from solar and atmospheric neutrino observations, as well as cosmological data on the amplitude of primordial density fluctuations. I also briefly review the ways to account for the observed anomalies and some of their implications.

Theoretical aspects of neutrino physics are reviewed, with emphasis on possible explanations of the smallness of neutrino masses and of the peculiar mixing pattern observed in the lepton sector. Some theoretically motivated frameworks, such as those based on spontaneously broken discrete flavour symmetries, are discussed, stressing the importance of low-energy observables, like anomalous magnetic moments, electric dipole moments and lepton flavour violating transitions, to te...

This article presents an overview of neutrino physics research, with highlights on the physics goals, results and interpretations of the current neutrino experiments and future directions and program. It is not meant to be a comprehensive account or detailed review article. Interested readers can pursue the details via the listed references.