Following up on yesterday’s intriguing antimatter results at Fermilab, a neutrino study called the Main Injector Neutrino Oscillation Search (MINOS) is providing independent confirmation of a critical idea: neutrinos have mass. This is significant news because it helps to illuminate earlier experiments that suggested neutrinos oscillate between three different types, something that could occur only if they do have mass, and an effect that, given the sheer abundance of neutrinos in the universe, may provide clues to why antimatter has disappeared and how galaxies originally formed.
Neutrinos are odd things indeed; they can pass through the entire Earth without interacting with matter. MINOS studies them by producing neutrinos at Fermilab using protons accelerated in a 4000 foot tunnel pointing toward a second detector some 450 miles away in Soudan, Minnesota. The neutrinos are measured first with a detector below the Fermilab site, with a second measurement being taken at a 6000-ton particle detector at Soudan. Researchers are examining how many muon neutrinos have disappeared along the way, presumably by turning into another type of neutrino and thus confirming that neutrinos have mass.
The result, based on only the first months of data: a signficant number of muon neutrinos are disappearing in ways consistent with the idea that neutrinos regularly transform themselves into different types. The mass difference between two of the types of neutrino is now found to be 0.056 eV, just 0.00001% of the mass of the electron. Further MINOS work should confirm whether actual neutrino oscillation is occurring, or whether we are observing some form of neutrino decay or, a more exotic possibility, the influence of extra dimensions.