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Date: August 05, 2004

New Clues to Altered Universe Discovered

New clues as to how the make-up of the Universe has shifted significantly since the Big Bang were announced this week by Stanford University following experiments that involved a team of physicists from UVic. The team is part of the BaBar experiment at the Stanford Linear Accelerator Center (SLAC), at Stanford University in California.

At the birth of the universe, both matter and antimatter were present in equal amounts. Now, only matter exists, although anti-matter can be created and occurs naturally in radio-active decay. SLAC’s accelerator caused collisions between electrons and their antimatter counterparts, positrons, creating B and anti-B mesons—rare forms of matter and anti-matter. They are short-lived, decaying quickly into lighter subatomic particles such as kaons and pions. The new observations at BaBar revealed that B mesons were 13 per cent more likely to decay to a kaon and pion than anti-B mesons.

“We’ve never observed this asymmetry with B-mesons before,” says Dr. Michael Roney, principal investigator of the UVic team. “A previous observation with kaons measured a similar effect, but only at the level of a few parts per million.” The discovery sheds new light onto a key mechanism underlying the structure and behaviour of matter.

He’s also excited about how physicists arrived at the latest observations. “We simply counted the number of decays. This is the first time such an effect—called direct charge parity violation—has been observed in this way.”

From a total sample of 227 million pairs of B and anti-B mesons, BaBar measured 1,606 examples of this rare decay. “The result was due to the ability of SLAC’s accelerator to deliver three times the rate of electron-positron collisions than required in its design and that BaBar reliably records the details of 98 per cent of these collisions,” says Roney.

The UVic team also includes Drs. Robert Kowalewski and Randall Sobie, seven graduate students and three post-doctorate students. It creates computer simulations of 25 per cent of the data generated by BaBar. The team is among 600 scientists and engineers from 75 institutions throughout the world working on the project. SLAC is funded by the U.S. Department of Energy’s Office of Science. Canadian physicists are funded through Canada’s Natural Sciences and Engineering Research Council (NSERC).

Media contacts:
Dr. Michael Roney (Physics and Astronomy) at (250) 721-7698 or mroney@uvic.ca
Patty Pitts (UVic Communications) at (250) 721-7656 or ppitts@uvic.ca
Downloadable images of the BaBar detector are available at www.interactions.org/slaccp/

UVic media releases and other resources for journalists are available on the World Wide Web at http://communications.uvic.ca/media

(image: fern)