From Anna Phan US/LHC Blog via Quantum Diaries: “What exactly is CP violation?”

Hey, Anna, nice new picture!!

“When we look around us, everything is made up of matter – protons, neutrons and electrons. Even looking out into space, all the planets, stars and gas that we can observe is made up of these particles. There is a cosmological excess of matter over antimatter which is at odds with the theoretical symmetry between them.

The theoretical symmetry between matter and antimatter is more commonly known to particle physicists as CP. If nature treated matter and antimatter alike, then nature would be CP-symmetric. If not, CP is violated.

CP is the combination of two other more fundamental symmetries, Charge conjugation and Parity. C is the symmetry between positive and negative charge while the P is the symmetry of spatial coordinates.”

If we take a particle with positive charge, C reverses the charge, meaning the particle will now have negative charge, and vice versa. Note that if we start with a neutral particle, C will have no effect, since it has no charge.

P is a little harder to explain, though more intuitive, as we encounter a symmetry of spatial coordinates every time we look into a mirror. I am right handed, but when I look into a mirror, my reflection is left handed. This almost a perfect analogy to the P symmetry in particle physics, which transforms left handed particles to right handed ones.

So the combination of CP on a left handed, negatively charged particle would transform it into a right handed, positively charged particle.

For the full story, see Anna’s post here.

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