- International team led by Rutgers challenges sterile neutrino existence after 10 years
- MicroBooNE experiment used liquid-argon detector and two neutrino beams for study
- Researchers ruled out single sterile neutrino with 95% certainty in Nature publication
After ten years of careful study, an international team of physicists, including researchers from Rutgers University, has challenged a long-standing idea about a mysterious particle called the sterile neutrino. The results were published in Nature and come from the MicroBooNE experiment at the US Department of Energy's Fermi National Accelerator Laboratory (Fermilab) in Batavia, Illinois, reported the Science Daily.com.
MicroBooNE uses a large liquid-argon detector and data from two different neutrino beams. By tracking how neutrinos behave, the scientists were able to rule out the existence of a single sterile neutrino with 95% certainty.
Andrew Mastbaum, associate professor in the Department of Physics and Astronomy at Rutgers University and leader of the MicroBooN team, said this discovery represents a significant change in the field. He explained that this result removes a major doubt, although it does not completely solve the mystery. He also said that this discovery will inspire new thinking and direction in neutrino research.
The Importance Of Neutrinos
Neutrinos are extremely tiny particles that rarely react with most matter and can pass unhindered through entire planets, including Earth. According to the Standard Model of particle physics, three types of neutrinos are known: electron, muon, and tau neutrinos. These neutrinos can change from one type to another, a phenomenon called oscillation.
Neutrin behaviour in earlier experiments did not fully match the Standard Model's predictions. To explain this, scientists proposed a fourth type of neutrino, called sterile neutrinos. Unlike known types, sterile neutrinos only interact with gravity and are extremely difficult to capture.
The MicroBoone team measured the behaviour of neutrinos from two different beams and observed how they changed as they travelled. After ten years of data collection and analysis, they found no evidence of sterile neutrinos. This ruled out a key explanation for unusual neutrino behaviour.
Mastbom led the analysis, which focused on converting raw detector signals into scientific conclusions. He also studied potential measurement errors, or systematic uncertainties, involving the neutrino's interactions with atomic nuclei, the number of neutrinos in the beam, and the detector's response. Properly handling these uncertainties was essential for accurate conclusions.
Undergraduate students at Rutgers also played a key role in this project. Panagiotis Angelezos designed the simulations that supported the data processing and analysis, while Keng Lin worked on validating the neutrino flux from Fermilab's NuMI beam. Their efforts ensured the accuracy and reliability of the final results.
Impact On Physics
This discovery is important because it ruled out a major possibility for new physics beyond the Standard Model. While the Standard Model explains many phenomena, it is unable to fully explain dark matter, dark energy, or gravity. Eliminating one possibility allows scientists to focus on other possibilities.
Rutgers scientists also studied how neutrinos interact with liquid argon. These techniques will prove useful in future experiments, such as the Deep Underground Neutrino Experiment (DUNE).
Mastbom said the MicroBoone team obtained a tremendous amount of information from the detector. With new experiments like DUNE, scientists will continue to explore more questions about the fundamental nature of matter and the universe.
