THE difference between matter and antimatter has been measured more accurately than ever before, an international team of physicists announced last week. But the question is far from resolved. The latest result simply highlights the fact that the only other team making the same measurement is churning out a completely different answer.
鈥淚t really does look like one of us is wrong,鈥� says Daniel Marlow, a physicist at Princeton University in New Jersey and a member of Belle, the team that announced its new finding. Belle鈥檚 latest result not only disagrees with the rival group, BaBar, but is also dangerously close to being 鈥渢heoretically impossible鈥�, he says.
Both Belle and BaBar are measuring the rates at which subatomic particles called B-mesons decay into particles called pions. If there were no difference between matter and antimatter, both the B and its antimatter counterpart, the anti-B, would decay at exactly the same rate. But theories that help explain why the universe has come to be dominated by matter suggest the antimatter particle should decay slightly faster. To look for this effect, Belle and BaBar have produced millions of B and anti-B pairs in particle accelerators.
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Belle鈥檚 measurement of the difference is the first to confidently rule out the possibility that the particles have the same decay rate 鈥� a step forward. But Belle鈥檚 answer is still much bigger than BaBar鈥檚.
Has someone blundered? The discrepancy between the two measurements is not so huge that it can鈥檛 be statistical chance, says Andreas Kronfeld, a theorist at Fermilab in Batavia, Illinois. He expects the two results will converge as more data is collected: 鈥淏ut we don鈥檛 know whether we鈥檒l end up more BaBar-like or more Belle-like or somewhere in the middle.鈥�
This matters because the Belle result is right on the edge of what current theories can cope with. 鈥淚f future data vindicate the Belle result,鈥� says Ulrich Nierste, another theorist at Fermilab, 鈥渋t will put us back to square zero.鈥�