THE ROLE OF CP AND T IN HIGH-ENERGY PHYSICS

1. THE ROLE OF CP AND TIN HIGH-ENERGY PHYSICS • Phenomenology of CP and T • Direct CP Violation Measurements NA48, KTEV • T Violation in rare Kaon decays KTEV • Direct checks of T Violation CPLEAR • Outlook L.Gatignon / CERN Symposium Marie Curie

2. PHENOMENOLGY OF CP AND T C: Charge conjugation Replace all particles by their anti-particles P: Parity Space inversion: x  -x T: Time reversal Invert the arrow of time t  - t CPT Theorem:within any quantum field theory, all interactions are invariant under the succession of the three operations C, P and T in any order. This theorem is based on very general assumptions. • Its experimental consequences are rather well verified, such as the • identity of masses of particles and anti-particles, e.g. • m Ko – mKo < 10-18

3. Actions of P and T operators Like r xp Like fors Magnetic dipole Electric dipole Long. polarization Transv. polarization We can now verify the behaviour of these quantities under the operators

4. Actions of P and T operators In High-Energy physics, direct checks of T-violation are not so easy to do. Here we will see 3 approaches: • Address T-related issues via CPe.g. CP experiments NA48 and KTEV • Transverse polarization measurementse.g. KTEV experiment • Direct measurements on time reversedprocessese.g. CPLEAR experiment

5. Parity violation • The angular distribution of e- isI(q) = 1 + as.p / E- s is a unit spin vecor alongJ- p and E are the e- momentum and energy • The first term, 1, is even parity • The second term,s.p, is odd parity Parity is violated

6. C Violation Left-handed neutrino Right-handed anti-neutrino J n n J But CP transforms a left-handed n into a right-handedn Is CP conserved ???

7. CP Violation • CP violation is (via CPT) one of the feasible experimental approaches to T‑violation in high-energy physics • Many of the T-violation studies have indeed been performed by experiments originally designed for CP-violation measurements (NA48, KTEV, CPLEAR,..) • The neutral kaon system provides an excellent laboratory for CP and T violation experiments • CP violation is considered to be one of the necessary elements to explain the matter dominance (over anti-matter) in the universe. This implies also that the matter/anti-matter ratio increases with time, thus giving a direction to time.

8. THE NEUTRAL KAON SYSTEM

10. Ko pp or ppp Ko W s W s d W d KoKo Mixing • Ko can mix withKo via virtual pp or ppp states: KoppKo orKop p pKo These are DS = 2 transitions

11. 1964: J.Cronin et al: Observation of KL 2p 1964: Christenson, Cronin, Fitch and Turlay observed an excess of  50 events with 490 < mpp < 510 MeV/c2 in the cosq distribution of the pp system w.r.t. the KL line of flight. The dashed line shows the expectation for 3p decays

12. CP is not a conserved quantity in the weak interaction

13. s d s d d d Direct and indirect CP Violation It is usually described by so-called Penguin diagrams: The relevant parameter is e’

18. Experiments in the 1980’s:

21. NA48 - HISTORY

23. SCHEMATIC LAYOUT OF NA48

24. The KS beam

28. THE KTEV REGENERATOR

30. RESULT FROM KTEV:

32. T VIOLATION STUDIES IN KLp+p-e+e- BY KTEV

34. The angular distributions and asymmetries

35. The sinF cosF distribution: