Dual-Baseline Search for Active-to-Sterile Neutrino Oscillations in NOvA

TL;DR

This paper reports a search for sterile neutrinos using NOvA data, finding no evidence for oscillations but setting new limits that constrain the parameter space of active-to-sterile neutrino models.

Contribution

First analysis to combine neutrino and neutral-current interactions in NOvA for sterile neutrino search, extending sensitivity over a broad Δm² range.

Findings

No evidence for active-to-sterile neutrino oscillations at 90% CL.

Set the most stringent limits on ν_τ appearance for Δm²₄₁ ≤ 3 eV².

Excluded some parameter regions allowed by IceCube.

Abstract

We report a search for neutrino oscillations to sterile neutrinos under a model with three active and one sterile neutrinos (3+1 model). This analysis uses the NOvA detectors exposed to the NuMI beam, running in neutrino mode. The data exposure, 13.6e20 protons on target, doubles that previously analyzed by NOvA, and the analysis is the first to use $\nu_{\mu}$ charged-current interactions in conjunction with neutral-current interactions. Neutrino samples in the Near and Far detectors are fitted simultaneously, enabling the search to be carried out over a $\Delta m^2_{41}$ range extending 2 (3) orders of magnitude above (below) 1 eV$^2$. NOvA finds no evidence for active-to-sterile neutrino oscillations under the 3+1 model at 90% confidence level. New limits are reported in multiple regions of parameter space, excluding some regions currently allowed by IceCube at 90% confidence level. We additionally set the most stringent limits for anomalous $\nu_{\tau}$ appearance for $\Delta m^{2}_{41} \le 3$ eV$^2$.