Chiral interactions, chiral states and "chiral neutrino oscillations"

TL;DR

This paper clarifies that chiral neutrino oscillations do not occur in vacuum due to the nature of neutrino states, but can occur in matter, with implications for neutrino behavior in cosmological contexts.

Contribution

The paper provides a detailed analysis showing that vacuum chiral neutrino oscillations are not possible and clarifies the conditions under which oscillations can occur, especially in matter.

Findings

Chiral neutrino oscillations do not occur in vacuum.

Oscillations are possible in matter with a length determined by the matter potential.

Relic neutrinos in the universe convert to equal left and right-handed components.

Abstract

In vacuum the ``chiral neutrino oscillations'', i.e. the periodic transitions between the left- and right-handed states do not occur. The produced state differs from the chiral component that appear in the Lagrangian of interactions and should be computed for each specific process. The phase difference between components of a produced neutrino is space-time independent. This neutrino state consists of only positive energy solutions of the Dirac equation and therefore the energy splitting $2E_\nu$ between the components with different helicities that would drive the chiral oscillations does not exist. Consideration in terms of neutrino propagators leads to the same conclusion. The situation is similar for the Majorana neutrinos and in the presence of flavor mixing. However, oscillations of the neutrino states produced in the chiral interactions are possible in matter with the length determined by the matter potential. Description of oscillations in terms of amplitudes of production and detection is elaborated that does not lead to any misconception. In the expanding Universe the relic neutrinos adiabatically convert to equal number densities of the left and right handed components.