Analytical Theory of Neutrino Oscillations in Matter with CP violation

TL;DR

This paper provides an exact analytical formulation for neutrino oscillations in matter, incorporating CP violation, and explores how small parameter expansions behave near resonances.

Contribution

It introduces a novel exact analytical framework for neutrino oscillations in matter with CP violation, including explicit formulas and analysis of small-parameter expansions.

Findings

Exact closed-form expressions for all partial oscillation probabilities.

Identification of branch points causing singularities in small-parameter expansions.

Numerical insights into the practical use of these expansions near resonances.

Abstract

We develop an exact analytical formulation of neutrino oscillations in matter within the framework of the Standard Neutrino Model assuming 3 Dirac Neutrinos. Our Hamiltonian formulation, which includes CP violation, leads to expressions for the partial oscillation probabilities that are linear combinations of spherical Bessel functions in the eigenvalue differences. The coefficients of these Bessel functions are polynomials in the neutrino CKM matrix elements, the neutrino mass differences squared, the strength of the neutrino interaction with matter, and the neutrino mass eigenvalues in matter. We give exact closed-form expressions for all partial oscillation probabilities in terms of these basic quantities. Adopting the Standard Neutrino Model, we then examine how the exact expressions for the partial oscillation probabilities might simplify by expanding in one of the small parameters {\alpha} and sin{\theta}13 of this model. We show explicitly that for small {\alpha} and sin{\theta}13 there are branch points in the analytic structure of the eigenvalues that lead to singular behavior of expansions near the solar and atmospheric resonances. We present numerical calculations that indicate how to use the small-parameter expansions in practice.