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Evidence for new form of matter-antimatter asymmetry observed

Lambda-b particle is first baryon to show signs of CP violation

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9:00am, October 4, 2016
LHCb

NOT SYMMETRIC The LHCb experiment, shown above, has detected hints of an asymmetry between matter and antimatter in decays of particles known as lambda-b baryons.

Like two siblings with divergent personalities, a type of particle has shown signs of behaving differently than its antimatter partner. It’s the first time evidence of matter-antimatter differences have been detected in decays of a baryon — a category of particle that includes protons and neutrons. Such matter-antimatter discrepancies are key to explaining how the universe came to be made mostly of matter, scientists believe.

The result is “the first measurement of its kind,” says theoretical physicist Yuval Grossman of Cornell University. “Wow, we can actually see something that we’ve never seen before.”  

Evidence of matter-antimatter differences in decays of baryons — particles which are composed of three smaller particles known as quarks — has eluded scientists until now. Previous experiments have found differences between matter and antimatter varieties of mesons, which are made up of one quark and one antiquark, but never in baryons.

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