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A US-based physics experiment has found a clue as to why the world around us is composed of normal matter and not its shadowy opposite: anti-matter. Anti-matter is rare today; it can be produced in "atom smashers", in nuclear reactions or by cosmic rays.
But physicists think the Big Bang should have produced equal amounts of matter and its opposite. New results from the DZero exeriment at Fermilab in Illinois provide a clue to what happened to all the anti-matter.
This is regarded by many researchers as one of the biggest mysteries in cosmology. The data even offer hints of new physics beyond what can be explained by current theories. For each basic particle of matter, there exists an anti-particle with the same mass but the opposite electric charge. For example, the negatively charged electron has a positively charged anti-particle called the positron.
But when a particle and its anti-particle collide, they are "annihilated" in a flash of energy, yielding new particles and anti-particles. Similar processes occurring at the beginning of the Universe should have left us with equal amounts of matter and anti-matter. Yet, paradoxically, today we live in a Universe made up overwhelmingly of matter.
Unexplained result
Researchers working on the DZero experiment observed collisions of protons and anti-protons in Fermilab's Tevatron particle accelerator. They found that these collisions produced pairs of matter particles slightly more often than they yielded anti-matter particles.
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