A nonzero theta 13 is good news for physicists hoping to explore the differences between neutrinos and antineutrinos, should any such differences exist. (In fact, in another bit of neutrino slipperiness, it may be that neutrinos are their own antiparticles.) Any such differences may bear on the lingering question of why there is so much matter around, and so little antimatter, when both should have come out of the big bang on equal footing. One kind of matter–antimatter bias, a phenomenon known as CP violation, has been observed in other particles, and the new findings indicate that it might be demonstrable in neutrinos as well. "Theta 13 is the key parameter governing whether we can explore CP violation or not," says physicist Kam-Biu Luk of Lawrence Berkeley National Laboratory and the University of California, Berkeley, who serves as co-spokesperson for the experiment. "Now, with theta 13 being nonzero, there's a chance that we may find CP violation in the neutrino sector."
Future experiments, Luk says, should be able to investigate that possibility by sending neutrinos and antineutrinos from one lab to another, across hundreds of kilometers, to compare how they oscillate. "Certainly now, with our first result, it should give them a lot of the ammunition to push ahead," he says.
Fermilab physicist Rob Plunkett, co-spokesperson of the MINOS neutrino experiment, agrees that having a firm grasp on theta 13 is important to the field. "The number actually controls how much of other phenomena you may get," he says. "A large theta 13 is good, because it causes a lot of these other phenomena." Plunkett notes that other research groups, including his own, have been closing in on theta 13 and will continue to publish their findings to help improve the consensus estimate of its value. "I think that things are converging, but rather more quickly than people had anticipated," he says.