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CP Violation in Neutral K-Meson Decay

CP Violation in Neutral K-Meson Decay. [Secs 16.8 Dunlap]. CP Violation. James Cronin (1931- ). Val Fitch (1923- ).

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CP Violation in Neutral K-Meson Decay

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  1. CP Violation in Neutral K-Meson Decay [Secs 16.8 Dunlap]

  2. CP Violation James Cronin (1931- ) Val Fitch (1923- ) In 1980 Cronin and Fitch received the Nobel Prize in Physics for and experiment they completed in 1964: Cronin and Fitch were physicists from Princeton University, working at Brookhaven National Laboratory. What did they discover? The detection of CP violation in the decay of neutral K mesons (K0).

  3. Quark constituents of K0 and K0 From the quark model we know that the , K0 an K0 are : and which have strangeness S=+1 and S=-1 respectively. However, because strangeness is not conserved in weak interactions, these states can be converted into each other

  4. What is special about K0 – K0 system? This interchange is in marked contrast to most other particle-antiparticle systems, for which such transitions are forbidden due to some major conservation law. For example and have opposite charge, while n and have opposite Baryon no.

  5. K0 and K0 are not the free-space eingenstates of the K0 system K0 and K0 are the eigenstates of the (K0 system) when “molded” by the STRONG force – under production in a target However when the K0 or K0 are out in “free space” the WEAK force is also at work DETECTED by STRONG Interaction PRODUCTION by STRONG Interaction Out in Free Space

  6. What are “free space” eigenstates? Thus in free space the K0 system will be expected to be eigenstates of the WEAK interaction. That is they should have natural eigenstates with good CP eigenvalues: This is because we expect But K0 and K0 are not eigenstates of CP ! The CP operator just converts K0↔ K0

  7. What are “free space” eigenstates? No, The “Free Space” eigenstates are: CP=+1 CP= -1 Can you see why? What is the meaning of the “S” and the “L”. It stands for Short-lived and Long-lived. Thus we can conclude that when the weak interaction is operational the there are two natural eigen-states- KSand KL

  8. Why is the decay time different for KS and KL ? CP=+1 CP= -1 (0.89 × 10-11s) (5.2 × 10-8 s) It is a little difficult to prove (although you can find the proof in many books) that these are the CP values of these final states. Lets assume it to be the case. It is the difference in energy available (output phase space) for the products that causes the difference in lifetimes. These states also differ very slightly different in mass (3.5x10-12MeV/c2)

  9. How we detect the K0

  10. CP violation Cronin and Fitch in 1964 discovered CP violating decays have been observed at the 0.3% level indicating that CP is not perfectly conserved in the weak interaction. CPT invarience is expected though under relativistic quantum electrodynamics. This implies a breaking of T conservation too, which has implications with regard to why we live in a universe that is largely matter and not anti-matter!

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