The T2K signal was small: just shy of of "3-sigma." But it was still statistically strong enough, given the rarity of the event, to be considered a genuine signal, not just background noise.The experiment detected 88 candidate events for the oscillation of muon neutrinos into electron neutrinos, based on data collected between January 2010 and March 11, 2011.
In contrast, MINOS recorded a total of 62 candidate events; if this particular type of quick change does not occur, they should have recorded only 49 such events. If the T2K analysis is correct, MINOS should have seen 71 events. The slight discrepancy enables physicists to further narrow the range of values for the rate at which this transformation occurs.
As always, more data is needed before an actual "discovery" can be claimed. The T2K data run was cut short because the major earthquake that devastated Japan also damage the experiment's muon neutrino source. But researchers expect to have the machine back online and taking more data by January 2012. With more data, the current 3-sigma signal should strengthen sufficiently to claim a solid discovery. MINOS will also continue collecting data until February 2012.
Physicists want to know more about neutrino oscillations, and their masses, because this provides a potential clue to why there is something in the universe, rather than nothing. Back when our universe was still in its infancy, matter and antimatter were colliding and annihilating each other out of existence constantly.
This process slowed down as our universe gradually cooled, but there should have been equal parts matter and antimatter. Instead, there were slightly more matter particles than antimatter, and that slight excess formed everything around us. Physicists think that neutrinos, with their teensy-tiny bits of mass, might have been the tipping point that tilted the scales to matter's favor.
Image credit: Fermilab