Neutrino masses and mixings and...

TL;DR

The paper surveys experimental results and theoretical frameworks for neutrino masses and mixings, emphasizing oscillation evidence from solar and atmospheric data and the implications for physics beyond the Standard Model. It presents the main mass-generation mechanisms, notably the see-saw variants (Type I, II, III) and loop-mediated scenarios, and discusses the distinction between Majorana and Dirac neutrinos, parameter counting, and connections to grand unification, SUSY, and leptogenesis. The work also catalogs current experimental constraints, known mass-squared splittings and mixing angles, and outlines a comprehensive roadmap of future experiments—oscillation tests, direct mass measurements, $0\nu2\beta$ searches, and cosmological probes—that could elucidate the underlying scale and nature of neutrino masses. By integrating particle physics with astrophysics and cosmology, the paper highlights the potential of neutrino physics to reveal high-scale dynamics and to inform the origin of matter via leptogenesis, with broad implications for fundamental theory and observational programs.

Abstract

We review the main experimental and theoretical results related to neutrino physics and outline possible lines of developement. The main topics covered are: neutrino masses, oscillations, solar and atmospheric evidences, the LSND/MiniBoone, HM, NuTeV anomalies, future oscillation experiments, beta and 0nu2beta decays, leptogenesis, supernovae, astrophysics, cosmology, flavour models, RGE corrections, violations of lepton flavor in charged leptons, statistics.

Figures (7)

• Figure 1: Regions explored using natural (blue) or artificial (red) neutrino sources. Solar and atmospheric oscillations occur below the black lines.
• Figure 2: Location of main neutrino-related observatories.
• Figure 3: Bounds on the scale $\Lambda$ that suppresses non-renormalizable operators that violate $B,L,{\rm CP},L_f, B_f$ and affect precision data. Maybe the 'hierarchy problem' suggests new-physics around few hundred GeV.
• Figure 4: The neutrino Majorana mass operator $(LH)^2$ can be mediated by tree level exchange of: I) a fermion singlet ('see-saw'); II) a fermion triplet; III) a scalar triplet.
• Figure 5: The neutrino Majorana mass operator $(LH)^2$ can be mediated by one-loop exchange of various kinds of fermions (red thick continuous line) and scalars (red thick dashed line).