BBC:
Researchers at Japan’s multinational T2K project say they
have seen indications that neutrinos—electrically neutral
elementary particles—can spontaneously change into any of
their types, or flavors: electron neutrinos, muon neutrinos, or
tau neutrinos, writes Jonathan Amos for the BBC. The T2K
project involves two facilities: The Japan Proton Accelerator
Research Complex (J-PARC), on the country’s east coast,
generates a beam of muon neutrinos that it fires under the
ground for 295 km to the Super-Kamiokande facility on the west
coast. In experiments run this year on T2K, researchers found
that an excess of electron neutrinos turned up at Super-K. They
believe the muon neutrinos sent from J-PARC changed flavor in
flight. The data could indicate that the oscillations of
neutrinos and their antiparticles (antineutrinos) could be
different—an example of
CP violation and a potential explanation for why
normal matter and antimatter created at the Big Bang did not
annihilate each other but left instead an excess of normal
matter. Although the statistics are not big enough to claim a
discovery, the T2K collaboration is excited. Experiments had to
be suspended in the wake of the Tohoku earthquake in March, but
the facility should be up and running again by the end of the
year.
