Exact Oscillation Probabilities of Neutrinos in Three generations derived from Relativistic Equation

TL;DR

This paper derives exact relativistic oscillation probabilities for three-generation neutrinos, including Dirac and Majorana types, revealing new CP phases and mass effects absent in previous simplified models.

Contribution

It provides a comprehensive derivation of neutrino oscillation probabilities from the Dirac equation, incorporating finite mass, helicity components, and new CP phases, extending beyond prior approximations.

Findings

Probabilities depend on absolute neutrino masses.

New CP phases appear in oscillation formulas.

Zero-distance effect is absent in this formulation.

Abstract

In three generations or more, we derive the oscillation probabilities of both Dirac and Majorana neutrinos relativistically by using the Dirac equation. We present various oscillation probabilities for including wrong-helicity neutrinos, right-handed neutrinos, and anti-neutrinos. We summarize the relations between these probabilities. As neutrinos have finite mass, there are two components for each chirality corresponding to positive and negative helicities. We show that the probability is different for each component even if neutrinos have the same chirality. The probabilities derived by the relativistic equation depend on not only the mass squared differences but also the absolute masses of neutrinos. Besides, the new CP phases appear in the probabilities of oscillations with chirality-flip. These new CP phases are equivalent to the Majorana CP phases in the case of Majorana neutrinos. We investigate the CP dependence of oscillation probabilities in vacuum. There are no direct CP violation in $\nu_{\alpha}\leftrightarrow \nu_{\beta}^c$ oscillations even if the flavors, $\alpha$ and $\beta$, are different as in the same as two generations. In other words, the difference between the CP-conjugate probabilities vanishes. However, in three generations or more, the sine terms of new CP phases appear in the probabilities in addition to the cosine terms. This is different from the result obtained in two generations. Furthermore, the zero-distance effect does not appear in our formulation.