New results from the MicroBooNE experiment at Fermi National Accelerator Laboratory deal a blow to a theoretical particle known as the sterile neutrino. For more than two decades, this proposed fourth neutrino has remained a promising explanation for anomalies seen in earlier physics experiments. Finding a new particle would be a major discovery and a radical shift in our understanding of the universe.
However, four complementary analyses released by the international MicroBooNE collaboration and presented during a seminar today do not show signs of the sterile neutrino. Instead, the results align better with the Standard Model of Particle Physics, scientists’ best theory of how the universe works.
“MicroBooNE has made a very comprehensive exploration through multiple types of interactions, and multiple analysis and reconstruction techniques,” said Bonnie Fleming, physics professor at Yale University and co-spokesperson for MicroBooNE. “They all tell us the same thing, and that gives us very high confidence in our results that we are not seeing a hint of a sterile neutrino.”
MicroBooNE is a 170-ton neutrino detector roughly the size of a school bus that has operated since 2015. The international experiment has close to 200 collaborators from 36 institutions in five countries. They used cutting-edge technology to record spectacularly precise 3D images of neutrino events to examine particle interactions in detail.
Neutrinos are one of the fundamental particles in nature, but among the most mysterious; scientists don’t know why their masses are so vanishingly small and whether they are responsible for matter's dominance over antimatter in our universe. This makes neutrinos a unique window into exploring how the universe works at the smallest scales.
“The new MicroBooNE results are an exciting milestone in neutrino research and showcase the capabilities of this type of neutrino experiment,” said University of Chicago Assoc. Prof. David Schmitz, a MicroBooNE collaborator.
Additional detectors of the same kind will soon come online at Fermilab that will further boost the ability to test the sterile neutrino hypothesis and enable the exploration of other possible explanations for the past anomalies.