Short baseline neutrino oscillations: when entanglement suppresses coherence

TL;DR

This paper demonstrates that entanglement between neutrinos and charged leptons suppresses oscillation coherence in short-baseline experiments, affecting the interpretation of neutrino oscillation data especially for sterile neutrino searches.

Contribution

It introduces a non-perturbative Wigner-Weisskopf approach to accurately model entangled neutrino states and quantifies how source lifetime and disentanglement length suppress oscillations.

Findings

Suppression of oscillations depends on source lifetime and disentanglement length.

Short-baseline experiments and low energies are most affected.

Standard quantum mechanical models underestimate mixing parameters.

Abstract

For neutrino oscillations to take place the entangled quantum state of a neutrino and a charged lepton produced via charged current interactions must be disentangled. Implementing a non-perturbative Wigner-Weisskopf method we obtain the correct \emph{entangled} quantum state of neutrinos and charged leptons from the (two-body) decay of a parent particle. The source lifetime and disentanglement length scale lead to a suppression of the oscillation probabilities in short-baseline experiments. The suppression is determined by $\pi\, L_s/L_{osc}$ where $L_s$ is the \emph{smallest} of the decay length of the parent particle or the disentanglement length scale. For $L_s \geq L_{osc}$ coherence and oscillations are suppressed. These effects are more prominent in \emph{short base line experiments} and at low neutrino energy. We obtain the corrections to the appearance and disappearance probabilities modified by both the lifetime of the source and the disentanglement scale and discuss their implications for accelerator and reactor experiments. These effects imply that fits to the experimental data based on the usual quantum mechanical formulation \emph{underestimate} $\sin^2(2\theta)$ and $\delta m^2$, and are more dramatic for $\delta m^2\simeq \,\mathrm{eV}^2$, the mass range for new generations of sterile neutrinos that could explain the short-baseline anomalies.