Chiral oscillations in the non-relativistic regime

TL;DR

This paper investigates chiral oscillations in non-relativistic particles, especially neutrinos, revealing significant effects on their survival probabilities and potential implications for future cosmic neutrino background experiments.

Contribution

It provides a quantitative analysis of chiral oscillations in the non-relativistic regime and explores their impact on neutrino flavor oscillations, a novel extension of previous relativistic studies.

Findings

Chiral oscillations can cause up to 40% depletion in neutrino survival probability.

Non-relativistic regime enhances the significance of chiral oscillations compared to relativistic cases.

Results suggest potential observable effects in upcoming cosmic neutrino background experiments.

Abstract

Massive Dirac particles are a superposition of left and right chiral components. Since chirality is not a conserved quantity, the free Dirac Hamiltonian evolution induces chiral quantum oscillations, a phenomenon related to the \textit{Zitterbewegung}, the trembling motion of free propagating particles. While not observable for particles in relativistic dynamical regimes, chiral oscillations become relevant when the particle's rest energy is comparable to its momentum. In this paper, we quantify the effect of chiral oscillations on the non-relativistic evolution of a particle state described as a Dirac bispinor and specialize our results to describe the interplay between chiral and flavor oscillations of non-relativistic neutrinos: we compute the time-averaged survival probability and observe an energy-dependent depletion of the quantity when compared to the standard oscillation formula. In the non-relativistic regime, this depletion due to chiral oscillations can be as large as 40$\%$. Finally, we discuss the relevance of chiral oscillations in upcoming experiments which will probe the cosmic neutrino background.