A New Clue In The Antimatter Mystery

TORONTO, May 20, 2010 — York University researchers have played a key role in a new finding that may help explain the imbalance of matter and antimatter in our universe. 

The DZero collaboration of scientists at the US Department of Energy’s Fermi National Accelerator Laboratory submitted a finding to the journal Physical Review D, reporting significant differences between matter and antimatter, which run up against current theories of particle physics. Their research indicates a one percent difference between the production of pairs of muons and pairs of antimuons in the decay of B mesons produced in high-energy collisions at Fermilab’s Tevatron particle collider. An independent DZero measurement carried out by York researchers and submitted to Physical Review last month further verifies these results. 

Scientists believe that during the Big Bang, matter and antimatter were created in equal proportions; they have been searching for minute differences between the two in the hopes it will help us understand why our universe is composed primarily of matter. 

Physicists theorize that a physical process preferentially consumes the antimatter in the universe, leaving only matter behind; they refer to this process as “CP violation.”  However, the Standard Model of Particle Physics predicts very small amounts of this phenomenon, insufficient to account for the dominance of matter in the universe. The findings of York University Professor Wendy Taylor and her colleagues put forth new evidence of CP violation as a key factor. 

“These results are very exciting,” says Taylor, Canada Research Chair in Experimental Particle Physics, and a member of the tight-knit DZero b-quark physics group, which led the research. “This puts us one step closer to answering the big questions about matter-antimatter asymmetry – where did the antimatter go, and how was it consumed?”

Taylor and York graduate student Steven Beale looked for another particle, called a D_s meson, which is often produced along with muons in b-quark decays.

“Muons also originate from the decays of other particles, so it was important to try and verify that the muons originated from the b-quark,” says Taylor. 

The two independent analyses are consistent: a combined result shows evidence of a source of CP violation in the decay of b-quarks.

DZero is an international experiment of about 500 physicists from 86 institutions in 19 countries. It is supported by the U.S. Department of Energy, the National Science Foundation and a number of international funding agencies.

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Ian Shalapata
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