Clues About the ‘Antimatter Wars’

by Paul Gilster on March 30, 2006

With 700 physicists from 90 different institutions in 20 countries working on an experiment, you expect interesting results. And the DZero experiment at Fermi National Accelerator Laboratory is living up to the expectation. Scientists at Fermilab have been studying a subatomic particle known as the B_s meson (pronounced ‘B sub s’). Their work suggests that this particle actually oscillates between matter and antimatter more than 17 trillion times per second.

The data come from over 1 billion events at Fermilab’s Tevatron particle accelerator, and more precise results are expected soon from a different Fermilab collaboration. And the more we learn, the better: exactly how particles turn into their own antiparticles, and with what frequency, is a major issue that could point to answers in an even bigger one, the balance between matter and antimatter in the universe. For if matter and antimatter appeared in equal numbers at the time of the Big Bang, their mutual annihilation should have left nothing behind but energy.

So how did matter survive? One solution is that there was, for reasons unknown, an imbalance between matter and antimatter. Back in 1985, physicist John Cramer, in one of his engaging columns for Analog, said that the early universe could have had 100,000,001 protons for every 100,000,000 antiprotons, making the universe we see around us “…the few ragged survivors of the ‘antimatter wars’ of 16 billion years ago.” We’ve revised the date on that, knowing from the WMAP results that the universe’s birth occurred roughly 13.7 billion years ago. But the idea of an early imbalance remains, even if unsatisfying.

But the fluctuation of particles into their own antiparticles may be giving us clues about a more robust solution. The frequency of matter/antimatter oscillation has never been measured to this degree of confidence. Studies of such oscillations go back to the 1980s, when a different kind of meson (the B_d meson) was found to oscillate at a higher rate than predicted by theory. The current studies aim to firm up our knowledge of how B_s mesons fit into the picture, with an eye toward uncovering new interactions that any deviation from prediction might reveal. Out of such results could come ways to evaluate exotic supersymmetry theories, whose predictions may be put to the test.

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