Unlocking the mysteries of anti-matter

T2K particle detector Image copyright Other
Image caption The T2K particle detector

We're back to the question of the preponderance of matter over anti-matter this morning.

Scientists working on the giant T2K particle detector in Japan believe they have made a breakthrough which could help to explain why the universe is made of matter, not anti-matter, and it's all to do with neutrino oscillations.

Neutrinos are fundamental particles of matter spat out when the nuclei of atoms fuse into heavier elements in stars like our sun.

They're hard to study because they only interact very weakly with other particles, but it turns out that there are three types, or flavours, of neutrino - and that they can spontaneously transform from one flavour into another: a process known as neutrino oscillation.

To date scientists have only seen two types of oscillation, but now researchers working at the massive T2K particle detector beneath Japan believe they have succeeded in observing the third, muon-electron neutrino oscillation.

The experiment has involved directing a beam of neutrinos 185 miles through the earth's crust from the J-PARC accelerator at Tokai on one side of Japan, to the giant Super-KamioKande underground detector on the other - a massive (40 metre by 40 metre) canister filled with 50,000 tons of ultra-pure water surrounded by photosensitive rods and buried in the ground.

The experiment ran from January 2010 to March this year - when operations were interrupted by the Fukushima quake. During that time, however, the researchers observed 121 oscillations including 6 muon-electron neutrino oscillations.

Image copyright Other
Image caption The giant Super-KamioKande underground detector

The significance of the discovery is that it opens up the mathematical possibility that neutrinos may have fundamentally different properties from their anti-neutrino counterparts: that they are not just simple mirror-image opposites of each other.

That raises the prospect of explaining the difference between matter and anti-matter, and ultimately solving the question of why the universe around us appears to be made almost exclusively of matter.

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