The three types of neutrino - Clockwise from top left - electron neutrino (red), muon neutrino (green) and electron (blue) - The directional arrows indicate how each can morph into different types. (T2K Experiment)

The three types of neutrino: electron neutrino (red), muon neutrino (green) and electron (blue). The directional arrows indicate how each can morph into different types. (T2K Experiment)

Scientists meeting in Stockholm say they’ve confirmed that subatomic particles known as neutrinos have the ability to morph from one type of the particle into another. The finding could one day help scientists explain why the universe contains matter but very little antimatter.

Neutrinos, one of the fundamental building blocks of matter, come in three distinct types or flavors: electron, muon or tau.  These particles have no electrical charge but their mass can vary by flavor.  An electron neutrino has a mass no greater than 2.2 eV (electron volts). The muon neutrino can have a mass that is less than 170 KeV (kilo-electron volts).  The tau neutrino, which has a mass of less than 15.5 MeV (mega-electron volts), was discovered in 2000 at the US Department of Energy’s Fermilab near Chicago.

Scientists produced a beam of muon neutrinos at the Japan Proton Accelerator Research Complex (J-PARC) near Japan’s east coast and aimed it at the gigantic Super-Kamiokande underground detector in Kamioka, 295 km away, near Japan’s west coast.  They discovered that some of the muon neutrinos had morphed into electron neutrinos somewhere along the journey.

Physicists know these three different neutrino flavors have the ability to freely change from one type into another through a phenomenon called neutrino oscillations. However, the new findings made by the T2K (Tokai to Kamioka) team, mark the first discovery of electron neutrinos showing up in a beam of muon neutrinos.

Illustration of the Super Kamiokande detector. It's the world’s largest underground neutrino detector that found electron neutrinos within a beam of muon neutrinos. (T2K experiment)

Illustration of the Super Kamiokande detector, the world’s largest underground neutrino detector, that found electron neutrinos within a beam of muon neutrinos. (T2K experiment)

“Understanding the properties of neutrinos in more detail would give an important clue to solving the riddle of how the universe has come to exist,” Takashi Kobayashi, a member of the T2K team, told the Japan News.

This new way of observing neutrino oscillation is the key for scientists to be able to make measurements that would allow them to distinguish the different oscillations of neutrinos and its anti-particle counterpart anti-neutrinos.  This is something that could help in better understanding the physical processes that involve matter and antimatter.

“We have seen a new way for neutrinos to change, and now we have to find out if neutrinos and anti-neutrinos do it the same way,” said Professor Dave Wark, who helped lead the international T2K experiment. “If they don’t, it may be a clue to help solve the mystery of where the matter in the universe came from in the first place. Surely answering that is worth a couple of decades of work.”