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Lecture 4

Italian Physical Society International School of Physics “Enrico Fermi”. Lecture 4. Lecture 4 Life times Regeneration Discovery of CP violation How can we measure the phase? Final state interaction phase Watson’s theorem Other possibilities Hyperon decays

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Lecture 4

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  1. Italian Physical Society International School of Physics “Enrico Fermi” Lecture 4

  2. Lecture 4 • Life times • Regeneration • Discovery of CP violation • How can we measure the phase? • Final state interaction phase • Watson’s theorem • Other possibilities • Hyperon decays • In this section, we refrain from deriving the expression for ε and ε' etc.

  3. Ｃ ＝ Ｐ ＝ ＣＰ｜ππ＞＝＋｜ππ＞

  4. Regeneration

  5. Measuring the sign of ΔM using regeneration

  6. Discovery of CP violation FCCT experiment

  7. A very good year 1964 (Pais) • The Higgs mechanism • The quark model • The first storage ring for e+e- collisions was built in Frascati. • Ω- baryon was found at Brookhaven National Laboratory. • CP violation was discovered at the same lab.

  8. First look at CP violation Partial width asymmetry CP violation physics is physics of phases So, if c is real CP is conserved

  9. Just because H is not invariant under CP, it does not mean that there is an observable effect.

  10. Within our formalism Eigenstate of H

  11. A tiny violation

  12. Remember Young's slit experiment Search for other effects How can experimentalists measure phases? They only countparticles!

  13. CP asymmetry If P had only one decay channel, F, then it is impossible to see CP violating effect CPT constraints CPT constraints is less for heavy particle

  14. Presence of the final state interaction phase is crucial in detecting CP violation Good news is that it is usually present Bad news is that it is hard to compute them reliably Can we do anything about the strong phase?

  15. π π K π π For K's, we have the Watson's theorem

  16. G-parity We want to find an operator for which the triplet of pions is an eignstate

  17. Time reversal in particle scattering S-matrix

  18. Can we do the same thing for B decays? Why or why not?

  19. Mystery of CP violation What if pion mass was zero?

  20. eiδ P f P One other possibility • Mixing exists • Common final state exists • There is large δ

  21. Remember?

  22. Within our formalism Eigenstate of H

  23. b d t W W b d t

  24. What about T odd correlations?

  25. T odd corelations

  26. T symmetry implies

  27. Correlation can arise not only from CP violation, but also from strong interaction So, is non-vanishing correlation a sign of T violation? Strong interaction can mimic T violation

  28. T changes the strong interacting state

  29. Look at T odd correlation in both particle and anti-particle

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