Matter, Antimatter, Other Matters

Diana Michele Yap Email 07.23.02

People who put together an international conference know that place is of the essence -- and the more resort-like and tropical that essence, the better.

But sometimes a cooler location, like a groovy European city, can prove romantically compelling to weary travelers wearing sweat-sticky, itchy suits (or jeans, if the well-funded scientist is determined to seem teeth-gleamingly Californian).

And if the conference itself is considered No. 1 in its rarefied field where everyone absolutely must go to compare notes, then despite the bad American doughnuts and bad American coffee that's typically dripping into teacups during the mid-morning break, as far as dependable attendance is concerned, it's golden. Golden as Gouda.

At the 31st International Conference on High Energy Physics, which opens Wednesday in Amsterdam, about 850 physicists representing more than 200 institutions from maybe 45 countries have signed up to attend, according to particle physicist Ger van Middelkoop, a longtime driving force in Dutch physics and chairman of the organizing committee. A quarter of the participants are American.

The new measurement of a parameter that expresses the degree of asymmetry between matter and antimatter in the universe is expected to be announced on Thursday by researchers from the BaBar experiment based at Stanford Linear Accelerator Center. That exact parameter happens to be sin 2b (pronounced sine two beta) = 0.74 +/- 0.07.

The fact of sin 2b being bigger than 0 is a mathematical expression that partially explains why the universe contains more matter than antimatter. You'd think, according to the big-bang theory that the universe began with equal amounts of matter and antimatter, that the two sides would have annihilated each other, leaving only energy. But matter won out. The world we see exists.

The explanation, a phenomenon called charge-parity violation, has been observed in disintegrations of mesons with bottom quarks by researchers at competing experiments on similar equipment at SLAC and at the High Energy Accelerator Research Organization (KEK) near Tokyo, BaBar spokesman and Princeton physicist A. J. Stewart Smith said. Mesons are subatomic particles far heavier than protons.

An earlier interpretation of the data was published last year in Physical Review Letters, the physics journal of record. The only other experiment to find charge-parity violation was a 1964 experiment at Brookhaven National Laboratory involving another type of meson. It led to a Nobel Prize in 1980, an SLAC representative said.

Many discoveries from the last two years that will be presented at the biennial conference, which occupies an auditorium and rooms at the RAI Exhibition and Congress Centre until July 31, have to do with computer calculations on atom-smasher data to see what the universe is made of.

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Science , Discoveries