Physicists Observe Matter-Antimatter Asymmetry in Charm Particle Decays

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Physicists from the Large Hadron Collider beauty (LHCb) Collaboration at CERN have observed, for the first time,the matter-antimatter asymmetry known as charge-parity (CP) violation in the decays of a D0 meson, a subatomic particle made up of a charm quark and an up antiquark.

Key Facts:

  • The term CP refers to the transformation that swaps a particle with the mirror image of its antiparticle.
  • The weak interactions of the Standard Model of particle physics are known to induce a difference in the behavior of some particles and of their CP counterparts, an asymmetry known as CP violation.
  • This asymmetry is one of the key ingredients required to explain why today’s Universe is only composed of matter particles, with essentially no residual presence of antimatter.
  • It was first observed in 1964 in the decays of particles called neutral K mesons, which contain a strange quark, and the two physicists who made the discovery, James Cronin and Val Fitch, were awarded the Nobel Prize in physics in 1980.
  • The universe consists of a massive imbalance between matter and antimatter. Antimatter and matter are actually the same, but have opposite charges, but there’s hardly any antimatter in the observable universe, including the stars and other galaxies. In theory, there should be large amounts of antimatter, but the observable universe is mostly matters.
  • When antimatter and matter meet, they annihilate, and the result is light and nothing else. Given equal amounts of matter and antimatter, nothing would remain once the reaction was completed. As long as we don’t know why more matter exists, we can’t know why the building blocks of anything else exist, either.


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