Neutrinos in Physics and Astrophysics

Abstract

The observed flavor oscillations of solar and atmospheric neutrinos determine several elements of the leptonic mixing matrix, but leave open the small mixing angle Theta_13, a possible CP-violating phase, the mass ordering, the absolute mass scale m_nu, and the Dirac vs. Majorana property. Progress will be made by long-baseline, tritium endpoint, and 2-beta decay experiments. The best constraint on m_nu obtains from cosmological precision observables, implying that neutrinos contribute very little to the dark matter. However, massive Majorana neutrinos may well be responsible for ordinary matter by virtue of the leptogenesis mechanism for creating the baryon asymmetry of the universe. In future, neutrinos could play an important role as astrophysical messengers if point sources are discovered in high-energy neutrino telescopes. In the low-energy range, a high-statistics observation of a galactic supernova would allow one to observe directly the dynamics of stellar collapse and perhaps to discriminate between certain mixing scenarios. An observation of the relic neutrinos from all past supernovae has come within reach.