Toward a Robust Confirmation or Refutation of the Sterile-Neutrino Explanation of Short-Baseline Anomalies

The sterile neutrino interpretation of the LSND and MiniBooNE neutrino anomalies is currently being tested at three liquid argon detectors: MicroBooNE, SBND, and ICARUS. It has been argued that a degeneracy between <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:msub><a:mrow><a:mi>ν</a:mi></a:mrow><a:mrow><a:mi>μ</a:mi></a:mrow></a:msub><a:mo stretchy="false">→</a:mo><a:msub><a:mrow><a:mi>ν</a:mi></a:mrow><a:mrow><a:mi>e</a:mi></a:mrow></a:msub></a:mrow></a:math> and <d:math xmlns:d="http://www.w3.org/1998/Math/MathML" display="inline"><d:mrow><d:msub><d:mrow><d:mi>ν</d:mi></d:mrow><d:mrow><d:mi>e</d:mi></d:mrow></d:msub><d:mo stretchy="false">→</d:mo><d:msub><d:mrow><d:mi>ν</d:mi></d:mrow><d:mrow><d:mi>e</d:mi></d:mrow></d:msub></d:mrow></d:math> oscillations significantly degrades their sensitivity to sterile neutrinos. Through an independent study, we show two methods to eliminate this concern. First, we resolve this degeneracy by including external constraints on <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:msub><g:mi>ν</g:mi><g:mi>e</g:mi></g:msub></g:math> disappearance from the PROSPECT reactor experiment. Second, by properly analyzing the full three-dimensional parameter space, we demonstrate that the stronger-than-sensitivity exclusion from MicroBooNE alone already covers the entire <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:mrow><i:mn>2</i:mn><i:mi>σ</i:mi></i:mrow></i:math> preferred regions of MiniBooNE at the level of <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"><k:mrow><k:mn>2</k:mn><k:mo>−</k:mo><k:mn>3</k:mn><k:mi>σ</k:mi></k:mrow></k:math>. We show that upcoming searches at SBND and ICARUS can improve on this beyond the <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:mn>4</m:mn><m:mi>σ</m:mi></m:math> level, thereby providing a rigorous test of short-baseline anomalies.