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 C.S.Wu et. al., Phys. Rev. 105, 1413 (1957) ObservedNot observed Experiment Parity inversion

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

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

6 Matter and Antimatter in 1 st 10 −3 s 10 −35 second #quark=#anti-quark 10 − −4 second Slight excess of quark 10 −3 second - NOW ~10 9 photons per quark Sakhalov’s 3 conditions (1967): 1. Both C and CP 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 # free parameters = 18 − 9 − 5 = 4 3x3 complex matrix 6 quark phases − 1 overall phase +1 complex phase 3 Euler angles (3-D rotation)

9 Unitary Triangle Wolfenstein’s parameterization V cd V cb * 11 22 33 ()() ()() ()() V td V tb * V ud V ub * V ud V ub * +V cd V cb * +V td V tb * = 0 db  (1,0)    (  )  ()() ()() ()() __ _ _  =  (1  2 /2)  =  (1  2 /2) _ _ Normalized

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 At least two interfering amplitudes with comparable size Different weak phases. Different strong phases. Two contributions to the amplitude

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

14 The B meson B 0 =d b, B 0 = b d, B + =u b, B − =b u ¯ ¯ ¯ ¯ ¯  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. σ(e + e − →BB) ≈1nb B 0 B 0 /B + B − = 50/50 Coherent 1 − − P-wave ¯ ¯

15 Flavor Oscillation mass eigenstates:

16 Parameters in B 0 mixing Define if final state f = CP eigenstate

17 B0B0 B0B0 B0B0 B0B0 Time-dependent CP violation f cp B0B0 B0B0 Same “strong” phase Case |λ f | = 1

18 B 0 →J/Ψ K S  Theoretically clean  Clear experimental signatures  Relatively large BF

19 Now: Precise measurement 1919 B 0 tag _ _ 465M BB 535M BB B  J/  Ks B  J/  K L _ (cc)K (*)0 [PRD 79,072009(2009)] CP-odd CP-even   sin2   =   [PRL 98,031802(07)+PRD (08)] Av  0.023: 3.4% error ! +  (2S)K S signals signals

20 Comparison to Kaon system CP violation in B 0 system far greater than in K 0 system. In B physics, the physical states cannot be isolated. One startes with pure B 0 or B 0 initial states. Parameter λ f is natural. In K physics, the physical states are well-isolated, thanks to very different lifeimes. Parameter ε is natural.

21 CPV meas. at B-factories 21 Flavor-tag (B 0 or B 0 ?) J/  KSKS ee ee zz t=0 f CP Vertexing Reconstruction Extract CPV fit B0B0 B0B0 B 0 -tag  t   z/c   eff ~30%   t ~1.4ps  =0.425 (KEKB)  0.56 (PEP-II) Inclusive info. (lepton, K etc.) Prob.

22 e + source Ares RF cavity Belle detector World record: L = 1.7 x /cm 2 /sec SCC RF(HER) ARES(LER) The KEKB Collider (Tsukuba, Japan) 8 x 3.5 GeV 22 mrad crossing angle

23 The Belle Detector

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

25 New Physics in CP violation Selected topics: Direct CP violation in B 0 system. The penguin b→sss process. CP violation in exclusive b →sγ process.

26 Revisit Direct CP violation in B→K  Belle Results: Nature 452, 332 (2008) A cp (K    ) = {  Belle  BaBar    CDF  CLEO A cp (K    ) = {  BaBar  Belle  CLEO  AVG  AVG  A K  =  cp (K   -  A cp (K    ) = 5.3    Recent Update

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

28 Isospin sum rule for A CP in B  K  M. Gronau, PLB 627, 82 (2005); D. Atwood & A. Soni, Phys. Rev. D 58, (1998). B →K  A(K 0  + )=0.009 ±0.025 A(K +  0 )=0.050 ±0.025 A(K +  - )= ±0.012 A(K 0  0 )=-0.01 ±0.10 HFAG, ICHEP08 A(K 0  0 ) A(K 0  + ) sum rule measured (HFAG) expected (sum rule)

29 Non-KM CP violation in penguins Decay amplitude does not bring new phase. In SM: sin2Φ 1 eff =sin2Φ 1 in B 0 → J/ΨK S

30 New Physics may enter b→s loops Many new phases are possible in SUSY O(1) effect allowed even if SUSY scale is above 2TeV. Large effects, O( ), 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, (2005)‏

31 Summary of sin2Φ 1 eff measurements 0.44± ± ±0.17 sin2Φ 1 =0.67±0.02 Need more data to clarify If there’s deviation.

32 Right-handed currents in exclusive b  sγ processes Time dependent CPV in B 0  (K S  0 ) K* γ –SM: γis polarized, the final state almost flavor-specific. S(K S  0 γ) ~ -2m s /m b sin2  1 –m heavy /m b 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) mbmb mbmb msms msms D.Atwood, M.Gronau, A.Soni, PRL79, 185 (1997) D.Atwood, T.Gershon, M.Hazumi, A.Soni, PRD71, (2005)

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

34 S CP mesurement in exclusive b→sγ Opposite C

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

36 New Physics in Super B factory 50ab -1 CKM UT triangle Now NP effect sin2φ1 = {Lunghi+Soni,hep-ph/ }

37 Summary CP violation is caused by two amplitudes and a common phase. Mixing-induced CP violation in B 0 system is much larger than in K 0 system. New Physics in CP violation will be probed by Belle-II.

38 BACKUP

39 Flavor Oscillations

40 Δm and ΔΓ

41 D 0 mixing

42 NP in D 0 mixing 1, 2, 3 50 ab -1 D 0 -mixing LFV, CPV in D/  : Clear Indication of New Physics ! CPV in D system negligible in SM CPV in interf. mix./decay: Currently ~± ab -1 go below 2 0