Effective Matter Flavor Conversion Mediated by Pseudo-Sterile States as the Possible Origin of Neutrino Oscillation Anomalies

TL;DR

This paper proposes a 3+1 neutrino oscillation model with a novel matter potential involving sterile neutrinos, explaining multiple anomalies across different experiments and energy ranges, and making testable predictions.

Contribution

It introduces a new matter potential for sterile neutrinos that unifies explanations for diverse neutrino anomalies and predicts resonant behaviors at high energies.

Findings

Explains NOvA and T2K tension with negative sterile potential.

Accounts for Super-Kamiokande excess via modified 3-flavor resonance.

Predicts a 10 TeV resonance consistent with IceCube observations.

Abstract

Neutrino oscillation experiments present anomalous results across a vast range of baselines and energies. Here we show that a 3+1 scenario in which sterile neutrinos feel a novel matter potential $V_s$ proportional to background density of ordinary or (asymmetric) dark matter is able to explain several anomalies. At low-energies ($E\lesssim$ 1 TeV) the model behaves as an effective 3-flavor NSI-like scheme among active flavors and eliminates the tension between the two LBL experiments NOvA and T2K provided that the potential is negative and the two sterile mixing angles $\theta_{14}$ and $\theta_{24}$ are non-zero. A further indication in favor of a negative non-zero potential comes from the anomalous excess of $\nu_e$-like events observed in Super-Kamiokande atmospheric neutrinos, which, in the new scenario is explained by a modification of the 3-flavor resonance at few GeV. A high energies ($E\gtrsim $ 1 TeV) the new framework reveals its 4-flavor nature and produces a resonant behavior at $E \simeq$ 10 TeV as hinted at by IceCube. We identify an irreducible 3-level dynamics generating a new resonance in the $(\nu_e, \nu_\mu)$ sector intertwined with two conventional resonances in the $(\nu_e, \nu_s$) and $(\nu_\mu, \nu_s)$ systems. The novel amplification mechanism manifests with the emergence of effective mixing angles in matter ($\theta_{12}^m$ or $\theta_{13}^m$) involving active neutrinos. The scenario requires values of $f = V_s/|V_{NC}| \sim -20 $, $\Delta m^2_{41} \sim 60 $ eV$^2$, $|U_{e4}|^2\simeq \sin^2\theta_{14} \simeq 0.01-0.03$ and $|U_{\mu4}|^2 \simeq \sin^2\theta_{24}\simeq 10^{-4}-10^{-3}$. Such a very small size of $|U_{\mu4}|^2$ eliminates the tension between IceCube and the other $\nu_\mu$ disappearance searches. The model can be directly probed by KATRIN, which is very sensitive to the electron-sterile neutrino admixture in the region of high $\Delta m^2_{41}$.