Oscillation and Mixing Among the Three Neutrino Flavors

TL;DR

This paper provides an accessible overview of neutrino physics, focusing on neutrino oscillations, their quantum mechanical nature, and recent findings about neutrino mixing angles, highlighting ongoing challenges and theoretical models.

Contribution

It offers a comprehensive, non-technical summary of neutrino oscillation phenomena, recent experimental results, and theoretical approaches to neutrino masses and mixing.

Findings

Neutrino oscillations demonstrate quantum mechanics over large distances

The 2012 result shows the small neutrino mixing angle is larger than previously thought

Discussion of models explaining neutrino masses and mixing angles

Abstract

With the educated, interested non-specialist as the target audience, we overview what is known and not known about contemporary neutrino physics. Theory tells us that neutrinos are the second-most common particle in the Universe, behind only the quanta of radiation called photons. Almost a trillion neutrinos per second enter each human eyeball, and yet we do not see them; these neutrinos, in roughly equal numbers, are emanations from our Sun and relics of the hot "big bang" era of the early Universe. Much of what we know about neutrinos, and hope to learn in the future, is derived from a unique feature of neutrinos -- "oscillation" among neutrino "flavor" types. An initial neutrino flavor will in general oscillate into another flavor as the neutrino propagates in space and time. Oscillations are a quantum mechanical phenomenon. One of the wonders of neutrinos is that their quantum mechanics may be observed over large distances, even astronomically large. We begin this article with neutrino phenomenology in terms of masses and mixing angles, including the matter-antimatter asymmetric "phase" that appears with three neutrino types. Next we venture into neutrino oscillations. We conclude with a discussion of model-building for the neutrino masses and mixings. Throughout this article, attention is devoted to the 2012 result that the "small" neutrino mixing angle is not so small, after all.