Saturday, April 05, 2008

Matter-Antimatter Split Hints at Physics Breakdown

Very cool but geeky article from Scientific American.

MATTER AND ANTIMATTER annihilate each other on contact. Experiments hint at a subtle difference between them that may explain why antimatter is so rare.

Nature may have handed scientists a new clue in a longstanding mystery: how matter beat out antimatter for dominance of the universe. Early data from twin experiments at the Tevatron, the world's reigning particle accelerator at Fermi National Accelerator Laboratory (Fermilab) in Batavia, Ill., suggest an unexpected chink in the hugely successful standard model of particle physics.

The twist comes from odd behavior in a particle called the BS (pronounced "B-sub-S"), which flips back and forth between its matter and antimatter forms three trillions times per second. Researchers believe that such a breakdown, known as CP violation, is required to explain why matter is so abundant.

Researchers say the finding is well worth following up to make sure it is not a random clump in the data, as frequently happens in particle physics experiments. "This is exciting, definitely," says physicist Jacobo Konigsberg of the University of Florida in Gainesville, cospokesperson for CDF, one of two detectors that may have glimpsed the effect.

Antimatter is well-known to science fiction fans as the stuff that explodes on contact with regular particles such as protons and electrons, which have the same mass as their antiparticles but the opposite charge. The hot, early universe contained equal parts matter and antimatter. Yet somehow, as the cosmos cooled, matter was not completely annihilated.

Researchers strongly suspect that the key to this riddle lies in the weak nuclear force, which governs radioactive decay, along with more exotic reactions created in particle accelerators. In nearly all cases, matter obeys something called CP symmetry, which states that a particle ought to behave identically to the mirror image of its antiparticle. Not so when acted on by the weak nuclear force.

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