CP violation and the Belle Experiment

1. CP violation and the Belle Experiment Jin Li USTC 2010

2. What is a symmetry? • Invariants of the system. (Space, time, rotation) Momentum, Energy, Angular Momentum. • Discrete symmetry.

3. Parity violation Experiment Parity inversion C.S.Wu et. al., Phys. Rev. 105, 1413 (1957) Not observed Observed

4. Pion decay Weak interaction: C and P are violated maximally.

5. 1964: Discovery of CP violation Phys. Rev. Lett. 13, 138 (1964) 1999: Direct CP violation in kaon decay (KTeV and NA48) 2001: CP violation in B meson (Belle and Babar)

6. Matter and Antimatter in 1st 10−3s 10−3 second - NOW ~109 photons per quark 10−32-10−4 second Slight excess of quark 10−35 second #quark=#anti-quark Sakhalov’s 3 conditions (1967): 1. BothC andCP violation 2. baryon number violating process 3. existence of non-equiblium

7. Quark mixing Flavor is not conserved in the weak interaction. The weak eigenstates are not flavor eigenstates:

8. CKM matrix 6 quark phases − 1 overall phase 3x3 complex matrix # free parameters = 18 − 9 − 5 = 4 +1 complex phase 3 Euler angles (3-D rotation)

9. 2 Vud Vub* (a) Vtd Vtb* 3 1 (g) (b) Vcd Vcb* Unitary Triangle Wolfenstein’s parameterization d b r = r (1-l2/2) _ Vud Vub* +Vcd Vcb*+Vtd Vtb* = 0 h = h (1-l2/2) _ _ h (r,h) _ _ Normalized f2 (a) (1,0) f3 f1 (g) (b) r _

10. Feynman diagrams CP necessary for CP violation Two amplitudes needed to account for phase redefinition. Direct CP violation as an example.

11. Direct CP violation Define Changes sign under CP “weak” phase Does not change sign under CP “strong” phase CP

12. CP violation mechanism Two contributions to the amplitude • At least two interfering amplitudes with comparable size • Different weak phases. • Different strong phases.

13. An excellent example of direct CPV Tree Penguin (World Average) Interference between T & P

14. ¯ ¯¯ ¯ ¯ B0=d b , B0= b d, B+=u b, B−=b u • σ(e+e−→BB) ≈1nb • B0B0/B+B− = 50/50 • Coherent 1−− P-wave ¯ ¯ The B meson • Heaviest quark with bound states. • Long lifetime because of must decay outside of third family. • Decay through “b→c” dominant, |b→c|2/|b→u|2 ≈100 . • “penguin” in “b→s” transition. • Flavor oscillation through “b↔t” box diagram. In e+e− collider, can be produced by (4S) resonance.

15. Flavor Oscillation mass eigenstates:

16. Parameters in B0 mixing Define if final state f = CP eigenstate

17. Time-dependent CP violation B0 B0 B0 fcp B0 fcp B0 B0 Same “strong” phase Case |λf| = 1

18. B0→J/Ψ KS • Theoretically clean • Clear experimental signatures • Relatively large BF

19. 535M BB _ 465M BB Now: Precise measurement _ (cc)K(*)0 14000 signals 12000 signals BJ/yKs _ B0 tag B0 tag CP-odd BJ/yKL CP-even Av. 0.670 0.023: 3.4% error ! +y(2S)KS 0.687  0.028  0.012 sin2f1= 0.650  0.029  0.018 19 19 [PRL 98,031802(07)+PRD77 091103(08)] [PRD 79,072009(2009)]

20. Comparison to Kaon system CP violation in B0 system far greater than in K0 system. • In B physics, the physical states cannot be isolated. • One startes with pure B0 or B0 initial states. Parameter λfis natural. • In K physics, the physical states are well-isolated, • thanks to very different lifeimes. Parameter ε is natural.

21. Flavor-tag (B0 or B0 ?) Reconstruction J/ e fCP e t=0 z Vertexing KS B0 B0 B0-tag B0-tag Dt z/cbg CPV meas. at B-factories Inclusive info. (lepton, K etc.) eeff ~30% sDt~1.4ps fit Extract CPV Prob. bg=0.425 (KEKB) 0.56 (PEP-II) 21

22. Belle detector Ares RF cavity e+ source The KEKB Collider (Tsukuba, Japan) 8 x 3.5 GeV 22 mrad crossing angle SCC RF(HER) World record: L = 1.7 x 1034/cm2/sec ARES(LER)

23. The Belle Detector

24. Measuring the sub-picosecond time dependence of CPV 4 layers, radiation hard readout, r = 1.5 cm 50m Beam spot: 110 μm x 5 μm x 0.35 cm Belle uses double-sided silicon strip detectors to measure Δz. KEKB/Belle: βγ = 0.425 Decay distance increased by x 10 Vertex resolutions(Belle): (σ(zcp) = 75μm;σ(ztag) =140μm)

25. New Physics in CP violation • Selected topics: • Direct CP violation in B0 system. • The penguin b→sss process. • CP violation in exclusive b →sγ process.

26. + 0.006 -0.107± 0.016BaBar Revisit Direct CP violation in B→Kp Belle Results: Nature 452, 332 (2008) Recent Update { - 0.004 -0.094± 0.018 ± 0.008Belle Acp(K+p-) = -0.086± 0.023 ± 0.009CDF -0.04± 0.16 ± 0.02CLEO + 0.012  -0.098@ 8.1sAVG - 0.011 { +0.030± 0.039± 0.010BaBar Acp(K+p0) = +0.07± 0.03± 0.01 Belle -0.29± 0.23± 0.02CLEO  +0.050± 0.025 @2.0sAVG DAKp = Acp(K+p-) - Acp(K+p0)= -0.147± 0.028 @ 5.3s

27. The Kπ “puzzle” Expectation from current theory T & P are dominant  DAKp ~ 0 • Enhancement of C ? •  C＞T is needed (C/T = 0.3–0.6 in SM) •  breakdown of theoretical understanding • Enhancement of PEW ? •  Would indicate new physics. • Due to poor understanding of strong interactions? • C.-W.Chaing, et al., PRD 70, 034020 • H.-n.Li,et al., PRD 72, 114005 • Y.-Y.Charng, et al., PRD 71, 014036 • W.-S.Hou, et al., PRL 95, 141601 • S.Baek, et al., PRD 71, 057502 • Baek & London PLB 653, 249 • Feldmann, Jung & Mannel, JHEP 0808,066

28. Isospin sum rule for ACP in BKp M. Gronau, PLB 627, 82 (2005); D. Atwood & A. Soni, Phys. Rev. D 58,036005(1998). A(K0p0) B →Kp A(K0p+)=0.009 ±0.025 A(K+p0)=0.050 ±0.025 A(K+p-)=-0.098 ±0.012 A(K0p0)=-0.01 ±0.10 HFAG, ICHEP08 sum rule A(K0p+) measured (HFAG) expected (sum rule)

29. Non-KM CP violation in penguins Decay amplitude does not bring new phase. In SM: sin2Φ1eff=sin2Φ1 in B0→ J/ΨKS

30. New Physics may enter b→s loops O(1) effect allowed even if SUSY scale is above 2TeV. Many new phases are possible in SUSY Large effects, O(0.1-0.2), are also possible in extra dimensional models e.g.with a 3 TeV Kaluza-Klein (K.K) particle. e.g. K. Agashe, G. Perez, A. Soni, PRD 71, 016002 (2005)‏

31. Summary of sin2Φ1eff measurements sin2Φ1=0.67±0.02 0.17 0.18 0.44± 0.59±0.07 0.74±0.17 Need more data to clarify If there’s deviation.

32. mb ms ms mb Right-handed currents in exclusive bsγ processes D.Atwood, M.Gronau, A.Soni, PRL79, 185 (1997) D.Atwood, T.Gershon, M.Hazumi, A.Soni, PRD71, 076003 (2005) • Time dependent CPV in B0 (KS0)K*γ • SM: γis polarized, the final state almost flavor-specific. S(KS0γ) ~ -2ms/mbsin21 • mheavy/mb enhancement for right-handed currents in many new physics models (left-right symmetric, extra dimensions etc) • No need for a new CPV phase (right handed currents suffice)

33. Right handed currents ? e.g. new mode BKS 0γ Use the 0+ - decay for the vertex in the silicon. Does not require KS vertexing in the silicon c.f BKS0γ Good tags: BKS+-γ Effective CP parameters in the 0 region Require M() consistent with a 0 meson

34. SCP mesurement in exclusive b→sγ Opposite C

35. Crab crossing New IR b*y = σz = 3 mm 3.5 GeV SuperKEKB Crab cavities installed and undergoing testing in beam e+ 9.4 A e- 4.1 A 8 GeV Damping ring The superconducting cavities will be upgraded to absorb more higher-order mode power up to 50 kW. The state-of-art ARES copper cavities will be upgraded with higher energy storage ratio to support higher current. Higher current More RF New vacuum system + Linac upgrade The beam pipes and all vacuum components will be replaced with higher-current design. Aiming 8 × 1035 cm-2s-1 35 35

36. New Physics in Super B factory CKM UT triangle NP effect Now 50ab-1

37. Summary • CP violation is caused by two amplitudes and a common phase. • Mixing-induced CP violation in B0 system is much larger than in K0 system. • New Physics in CP violation will be probed by Belle-II.

38. BACKUP

39. Flavor Oscillations

40. Δm and ΔΓ

41. D0 mixing

42. NP in D0 mixing D0-mixing CPV in D system negligible in SM CPV in interf. mix./decay: Currently ~±200 50 ab-1 go below 20 1, 2, 3 s @ 50 ab-1 LFV, CPV in D/t : Clear Indication of New Physics !