A joint Fermilab/SLAC publication

LHCb uses charm to find asymmetry


Photo from 2004 showing the two almost 30-ton magnets in the LHCb detector, which was under construction at the time. Image: CERN

According to theory, matter and antimatter should have been created in equal parts during the big bang. But somehow, the balance of the two skewed in the universe’s first moments. Now, matter dominates nature.

Scientists from the LHCb collaboration at CERN recently saw curious possible evidence of this asymmetry: The difference between the decay rates of certain particles in their detector, D and anti-D charm mesons, was higher than expected.

This anomaly is evidence of charge-parity violation, a more precise descriptor of nature’s preference for matter. Other LHC experiments have seen such symmetry breaking, but this is a first sighting in these charm particles.

“CP violation is expected to be very small in charm physics,” LHCb member Bolek Pietrzyk said. “This is a really surprising result.”

The preliminary findings, which the collaboration presented Monday night in Paris, have a significance measured at 3.5 sigma. Statistically speaking, this indicates an interesting observation. But scientists will need more certainty before they can declare a discovery.

In this study, the group used data they collected in the first half of 2011. LHCb’s next steps will be to look at the rest of the 2011 data and see whether they can make sense of the observations within the Standard Model theory, or if they’ll need a new explanation.

View the presentation about the LHCb result

Read the CERN Bulletin article

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