Effects of a neutrino-dark energy coupling on oscillations of high-energy neutrinos

TL;DR

This paper investigates how a potential interaction between dark energy and neutrinos could alter high-energy neutrino oscillations, leading to observable CP violation and Lorentz-violating effects detectable by neutrino observatories.

Contribution

It introduces a new framework for understanding dark energy-neutrino coupling effects on neutrino oscillations, highlighting their energy dependence and potential observability in experiments.

Findings

DE-induced effects become significant at high neutrino energies.

CP violation can occur over a wide energy range due to DE coupling.

Current experiments can detect some anomalous effects but not the small directional changes.

Abstract

If dark energy (DE) is a dynamical field rather than a cosmological constant, an interaction between DE and the neutrino sector could exist, modifying the neutrino oscillation phenomenology and causing CP and apparent Lorentz violating effects. The terms in the Hamiltonian for flavor propagation induced by the DE-neutrino coupling do not depend on the neutrino energy, while the ordinary components decrease as $\Delta m^2/E_{\nu}$. Therefore, the DE-induced effects are absent at lower neutrino energies, but become significant at higher energies, allowing to be searched for by neutrino observatories. We explore the impact of the DE-neutrino coupling on the oscillation probability and the flavor transition in the three-flavor framework, and investigate the CP-violating and apparent Lorentz violating effects. We find that DE-induced effects become observable for $E_{\nu}m_{\text{eff}} \sim 10^{-20}~ \text{GeV}^2$, where $m_{\rm eff}$ is the effective mass parameter in the DE-induced oscillation probability, and CP is violated over a wide energy range. We also show that current and future experiments have the sensitivity to detect anomalous effects induced by a DE-neutrino coupling and probe the new mixing parameters. The DE-induced effects on neutrino oscillation can be distinguished from other new physics possibilities with similar effects, through the detection of the directional dependence of the interaction, which is specific to this interaction with DE. However, current experiments will not yet be able to measure the small changes of $\sim 0.03\%$ in the flavor composition due to this directional effect.