Narrowing the window on sterile neutrinos

A major international collaboration between the MINOS experiment, which involves UCL scientists, and the Daya Bay experiment has today announced results which shed new light on one of the most pressing questions in particle physics - do sterile neutrinos exist?. Sterile neutrinos are a suggested fourth neutrino alongside the well-known electron, muon and tau neutrinos. They were first proposed in the 1990s following the LSND experiment at the Los Alamos National Laboratory when muon neutrinos seemed to turn into electron neutrinos. The oscillations which would have caused this neutrino metamorphosis were much faster than those discovered by Super-Kamiokande that led to the 2015 Nobel Prize in Physics. This suggested the existence of a new, fourth type of neutrino which would have to be much stranger than anything seen before - the sterile neutrino - with 'sterile' meaning that it does not interact with matter except through gravity. Over the last twenty years, a number of experiments have tried to confirm or refute the LSND findings, but the results have been inconclusive. The results published today in Physical Review Letters by the MINOS and Daya Bay experiments strongly suggest that ghost-like sterile neutrinos do not explain the LSND result after all.