Prospects of Light Sterile Neutrino Oscillation and CP Violation Searches at the Fermilab Short Baseline Neutrino Facility

TL;DR

This paper assesses the Fermilab SBN program's potential to test sterile neutrino oscillations and CP violation, showing it can probe most of the allowed parameter space and possibly observe hints of CP violation.

Contribution

It provides a detailed sensitivity analysis of the SBN experiment for (3+1), (3+2), and (3+3) sterile neutrino models, including CP violation effects and potential for direct observation.

Findings

SBN can probe over 85% of the (3+1) parameter space at 5σ

SBN can test up to 95% of the (3+2) parameter space at 5σ

Potential to observe ~2σ hints of CP violation with antineutrino running

Abstract

We investigate the ability of the Short Baseline Neutrino (SBN) experimental program at Fermilab to test the globally-allowed (3+$N$) sterile neutrino oscillation parameter space. We explicitly consider the globally-allowed parameter space for the (3+1), (3+2), and (3+3) sterile neutrino oscillation scenarios. We find that SBN can probe with $5\sigma$ sensitivity more than 85\%, 95\% and 55\% of the parameter space currently allowed at 99\% confidence level for the (3+1), (3+2) and (3+3) scenarios, respectively. In the case of the (3+2) and (3+3) scenarios, CP-violating phases appear in the oscillation probability terms, leading to observable differences in the appearance probabilities of neutrinos and antineutrinos. We explore SBN's sensitivity to those phases for the (3+2) scenario through the currently planned neutrino beam running, and investigate potential improvements through additional antineutrino beam running. We show that, if antineutrino exposure is considered, for maximal values of the (3+2) CP-violating phase $\phi_{54}$, SBN could be the first experiment to directly observe $\sim 2\sigma$ hints of CP violation associated with an extended lepton sector.