Open system approach to neutrinos propagating in an ultralight scalar background

Abstract

We examine decoherence in neutrino oscillations induced by an ultralight scalar field coupled to neutrinos. The scalar induces time- and position-dependent shifts in the neutrino mass matrix. Neutrinos sample different field configurations throughout an experimental data-taking period, which leads to damping effects in the oscillation pattern in the form of decoherence. By recasting the neutrino-scalar dynamics within the open quantum systems framework, we establish a mapping between a complete model and phenomenological decoherence approaches. We find that the parameter driving decoherence scales as $L^2/E^2$, where $L$ is the baseline and $E$ is the neutrino energy, as opposed to $L/E$ typically assumed in phenomenological studies of open system approaches to neutrino oscillations.

Figures (1)

• Figure 1: Contours of $\eta_\phi^{31}$ in the plane of the scalar parameters $g \phi_0$ and the lightest neutrino mass $m_1$, assuming normal ordering. The shaded region indicates the parameter space constrained by JUNO at 90% confidence level Delgadillo:2025wxw.