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Antimatter Finding Has Cosmological Implications.

One of cosmology's greatest mysteries is why we're here at all. One reason is that scientists have yet to explain how matter particles came to outnumber antimatter ones in the ultrahot inferno of the early Big Bang. Had they been present in equal numbers, as the simplest theories predict, matter and antimatter particles would have annihilated one another completely, leaving a sea of pure radiation. And in fact this nearly happened; particles exceeded their antiparticle counterparts by only one part in a billion.

It remains a mystery what caused this slight imbalance. But a recently published study may bring scientists a small step closer to a solution. Sited at the Fermi National Accelerator Laboratory in Illinois, the so-called KTeV experiment generates short-lived particles called neutral K mesons, or kaons. Neutral kaons and antikaons both can decay to form the same end product: a pair of p mesons, or pions. In some cases these pions are electrically charged; in others they are neutral. If the laws of physics treat matter and antimatter alike, there should be no difference in the rates with which kaons and antikaons make each kind of pion pair.

However, the rates indeed differ, albeit by a minuscule amount, roughly one part in 100,000. The international KTeV research team came to this conclusion after analyzing millions of kaon-decay events. Details appear in Physical Review Letters for July 5th.

The finding constitutes the first fundamentally new manifestation of matter-antimatter asymmetry since a famous 1964 experiment highlighted a different kind of kaon-antikaon imbalance. As such, "it's important to cosmology," says Fermilab's Edward W. Kolb. But the discovery falls several steps short of solving the matter-antimatter mystery. Nevertheless, says KTeV collaborator Edward Blucher (University of Chicago), "the only other place where matter and antimatter [are known to behave differently] is in these neutral kaon systems." At least that's how things stand at present; accelerators in California and Japan are currently generating even more ephemeral particles, called B mesons, in the hopes of shedding new light on this outstanding cosmic puzzle.

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Publication:Sky & Telescope
Article Type:Brief Article
Date:Oct 1, 1999
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