The detector works by looking for flashes of light from particles that exceed the speed of light in the water. Credit: University of Tokyo
A step closer to solving one of the biggest mysteries in fundamental physics?
Experts may be on the cusp of an important breakthrough in the study of neutrinos following the exciting results released today (15 June 2011) of an international T2K neutrino experiment in Japan involving the University of Sheffield.
The question of where all the matter in the universe came from is one of the biggest mysteries in fundamental physics and the findings could mean an important step towards resolving this puzzle.
The intriguing results indicate a new property of the enigmatic particles known as neutrinos.
There are three types of neutrinos, called flavours one paired by particle interactions with the familiar electron, called the electron neutrino, and two more paired with the electron´s heavier cousins, the muon and tau leptons. Previous experiments around the world have shown that these different flavours of neutrinos can spontaneously change into each other, a phenomenon called 'eutrino oscillation'
Two types of oscillations have already been observed but in its first full period of operation, the T2K experiment has already seen evidence for a new type of oscillation (the appearance of electron neutrinos in a muon neutrino beam). This means that experts have now observed that neutrinos can oscillate in every way possible.
This level of complexity opens the possibility that the oscillations of neutrinos and their anti-particles (called anti-neutrinos) could be different. And if the oscillations of neutrinos and anti-neutrinos are different, it would be an example of what physicists call CP violation. This could be the key to explaining why there is more matter than anti-matter in the universe, an excess which could not happen within the known laws of physics.
The experiment ran from January 2010 until 11 March 2011, when it was dramatically interrupted by the Japanese earthquake. Fortunately, the multinational T2K team were unharmed and their highly sensitive detectors were largely undamaged. Six clean electron neutrino events are observed in the data from before the earthquake, while in the absence of oscillations there should only have been 1.5. Even though such an excess could only happen by chance about one time in a hundred, that is not good enough to confirm a new physics discovery, so this is called an 'indication'.
Dr Lee Thompson from the Department of Physics and Astronomy, said: "This is a great start to the T2K experiment. The emphasis now is on collecting more data to confirm this 'indication'. Following the earthquake there are lots of checks of the detector to make but we hope to have everything fully functional again by the end of this year."
Prof Takahashi Kobayashi of the KEK Laboratory in Japan and the spokesperson of the T2K experiment, said: "It shows the power of the experimental design that with only 2 per cent of our design data we are already the most sensitive experiment in the world for looking for this new type of oscillation."
Professor Dave Wark of STFC and Imperial College London, who served for four years as the International Co-Spokesperson of the experiment and is head of the UK group, explained: "People sometimes think that scientific discoveries are like light switches that click from 'off' to 'on', but in reality it goes from 'maybe' to 'probably' to 'almost certainly´ as you get more data. Right now we are somewhere between 'probably' and 'almost certainly'."
STFC is the UK sponsor of particle physics and supports the UK universities involved in the T2K experiment.