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Particle physics

A meson unmirrored

A fourth type of subatomic particle shows imperfect symmetry with its antiparticle.

Charge conjugation parity symmetry holds that an experiment should be indistinguishable from its reflection in a mirror if all particles are replaced with their antiparticles. Since the first exception to this was found in 1964, physicists have been hunting for more particles that violate the principle.

A major collaborative effort co-led by Vincenzo Vagnoni at the Large Hadron Collider at CERN, Europe's particle-physics laboratory near Geneva in Switzerland, identified an asymmetry by tracking decays of the subatomic particles B0s mesons, which are made up of elementary particles called strange quarks and antibottom quarks. The identification of 'CP violation' in these mesons confirmed a prediction of the standard model of particle physics. However, more-drastic violations are required to explain why matter dominates over antimatter in the universe.

Phys. Rev. Lett. 110, 221601 (2013)

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A meson unmirrored. Nature 498, 9 (2013). https://doi.org/10.1038/498009b

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