1. sin2  : Status & Perspectives Gerhard Raven NIKHEF & VU Amsterdam BaBar

2. CP from Interference of Mixing and Decay Time-dependent CP asymmetry: CP violation results from interference between decays with and without mixing mixing decay  Theoretically clean way (~1%) to measure sin2  B  J/  K S,L : dominated by single decay amplitude

3. Ingredients of the Measurements B-Flavor Tagging Exclusive B Meson Reconstruction PEP-2 (SLAC) Vertexing & Time Difference Determination f flav : determine  t resolution, mistag rates w, (  m d,  B, …) f CP : measure CP asymmetries

4. Available Samples before tagging and vertexing cuts B decays to flavor-specific final states B decays to CP-eigenstates with charmonium angular analysis (not shown) Add Belle D*lnu here BelleBaBar

5. Flavour Tagging Mistag rates measured using control samples Babar: –D ( * )  /  /a 1 –Simultaneous fit with CP sample Errors due to finite control sample size automatically included in statistical error Belle: –D*lv –Separate fit, propagate numbers to CP fit Belle: rank individual tags based on expected performance in 6 groups BaBar: rank according to ‘physics process’ (eg. Lepton tags, Kaon tags,…) with performance cuts (eg. Kaon I and Kaon II) Drop low performance tags, end up with 4 groups

6. Doubly CKM suppressed decays on tag side 1.Many B  DX modes have, at O(10 -4 ), intrinsic “mistagging” due to b  u transitions. Effect usually assumed to be Small Accounted for by measured mistag rates 2.On reco-side this b  u interference can be used for sin(2  +  ) measurement. Induces time-dependent effects of order |V ub V cd /V cb V ud |= 0.02 Lepton tags unaffected, but eg. Kaon based tags are For BaBar: Q lep ~0.1, Q nonlep ~0.2 Small effect on sin(2  ), larger on | |; last BaBar result:  DCSD (sin2  )= 0.008 (cmp to total syst: 0.034)  DCSD (| |) = 0.024 (cmp to total syst: 0.030)  b  u interference for tag-side B induces time-dependent effect, just like reco-side and thus not fully accounted for in measured mistag rates Long, Baak, Cahn, Kirkby hep-ex/0303030, submitted to PRD B0B0 B0B0 3.  (4s)  B 0 B 0 system is antisymmetric in two B mesons 4.System evolves coherently in time

7. Results Belle BaBar PRL 89 (2002) 201802 PRD 66 (2002) 071102 Note that the experiments also agree on color codes for B and B tags N(BB)= 88 10 6 N(BB)= 85 10 6

8. Belle/KEK-B Extrapolation: Luminosity SVD2 installation Belle/KEK-B Both experiments expect ~500/fb by 2006 BaBar/PEP II

9. Extrapolation: Some History… a)“Osaka 2000” measurement. (hep-ex/0008048). Only J/K S and (2s) K S. b)1 st Paper (PRL 86 (2001) 2515). Added J/K L. Simultaneous sin2 and mixing fit. c)2 nd Paper (PRL 87 (2001) 091801). Added J/K *0 and  c K S. Better vertexing. Better SVT alignment and higher K S efficiency for new data. d)Winter 2002 (hep-ex/0203007). Improved event selection. Reprocessed 1 st 20 fb -1. e) 3 rd Paper (PRL 89 (2002) 201802 ) Improved flavor tagging. One more CP mode:  c K S. a b c d e So far seem to do better than extrapolations predict Systematic Statistical sin 2  uncertainties BaBar

10. Extrapolation: Belle Expected errors in A CP ’s KEKB PEPII Next B factory Goals for July 2005: 315 /fb Stat. error ~0.04 Syst. error ~0.02 Goals for July 2007: 1000 /fb Stat. error ~0.02 Syst. error ~0.01 Will require a lot of hard work to get there!

11. Extrapolation: BaBar Current analysis Clean modes Only lepton tags Current analysisClean modes, Lep. tag Integrated L (fb -1 )815002000815002000 Statistical error0.0670.0280.0130.1130.0470.022 Systematic error0.0340.0240.0220.0250.0150.012 Total error0.0750.0370.0260.1160.0490.025 “Probably somewhat conservative…”

12. The assumptions… Mixing Decay

13. Back to basics: Flavour Mixing Eigenstates: With mass & lifetime differences:, with Assumptions made: 1.CPT conserved 2.no CP in mixing  =0 Effective Hamiltonian: Note: if CPT and DG=0 => q/p is pure phase

14. CP in mixing: experiment Measure a SL using dileptons a SL =0.5  1.2(stat)  1.4(syst) New analysis: Simultaneous fit to time- dependence of both fully reconstructed CP and flavour eigenstates, tagged and untagged Include Detector charge asymmetries Doubly-CKM suppressed decays Started testing the assumptions that 1.CPT is conserved  is negligible 3.q/p is a pure phase Nothing unexpected seen, will need MUCH more data to approach SM prediction preliminary PRL 88 (2002) 231808

15. Back to basics: CP in decay Leading penguin contribution has same weak phase as tree  Expect very little direct CP Phys. Rev. D-RC 65 (2001) (20/fb) KEK Preprint 2002-9 (29/fb)) Experiment: Look for direct CP in J/  K + BaBar

16. Are (sin2  ) J/  K s and (sin2  ) J/  K L the same? Need K 0 —K 0 bar mixing for interference in J/  K S and J/  K L CP violation in K 0 —K 0 bar mixing: negligible Following Grossman, Kagan & Ligeti Phys. Lett. B538 (2002) 327 Very much consistent with SM expectation of 0 BaBar Measure “wrong flavour” amplitude in B  J/  K* 0 (K +  - ) ? For B  J/  K* 0 (K -  + ) : C  C, S  S,

17. Other Modes Angular analysis, cos(2  ) Color+Cabibbo suppressed tree + penguin b  s penguin b  s penguin + CKM suppressed tree b  d Cabibbo suppressed tree + penguin, angular analysis Cabibbo suppressed tree + non-CP eigenstate

18. O 1D: Treat R  as dilution  2D: Use  tr  4D: Full angular analysis J/  K*(K S  0 ) and cos(2  ) Vector-Vector mode; Angular components: A ||,A 0 : CP = +1 A  : CP = -1 (define R  = |A  | 2 )  Simplest method:  CP asymmetry diluted by D  = (1 - 2R  )  R  = (16.0 ± 3.2 ± 1.4) % BaBar, PRL87 (2001) 241801 BaBar, PRL87 (2001) 241801  R  = (19 ± 2 ± 3) % Belle, PLB538 (2002) 11-20 Belle, PLB538 (2002) 11-20 Full angular distribution is given by: So at first sight should be able to determine cos(2  ) and resolve some of the ambiguities in  Unfortunately there is an ambiguity: ±0.7 (syst) BaBar Belle

19. B  J/  0 In the absence of penguins, S=-sin(2  ) and C=0 penguin: competing weak phase? tree: color- and Cabibbo-suppressed hep-ex/0207058 hep-ex/0207098 N sig =40  7

20. Penguin Modes: B   K S Same CKM factors enter as J/  K S. –u-penguin CKM suppressed by ~0.02. Unlike J/  K S, the leading and u- penguin amplitudes are both penguins. Can use SU(3) related modes  + and K * K + to experimentally bound u-penguin amplitude. –Grossman et al, hep-ph/9708305. Current estimate of SM “pollution” on the assumption is <5 % internal penguin flavor-singlet penguin BaBar Belle Add Br, # of signal events PRD 67, 031102(R) (2003)

21. Penguin Modes: B  ’K S  Very similar to  K S except for one additional complication – a tree- level b  u contribution. London and Soni estimate the relative size of the b  u tree to be |T/P|<0.02 (hep-ph/9704277) Beneke and Neubert estimate |T/P|  (8  3)% (hep-ph/0210085) Rough estimate for SM pollution is same as  K S although this is probably somewhat less conservative. Add Br, # of signal events PRD 67, 031102(R) (2003) Belle BaBar

22. Penguin Modes: -  CP S=sin(2  ) ? ’K s BaBar 0.02  0.34  0.03 Belle0.71  0.37 ( +0.05 ) Ave0.34  0.25 K s BaBar –0.19 ( +0.52 )  0.09 Belle –0.73  0.64  0.22 Ave–0.39  0.41 K + K - K s non-resonant Belle 0.49  0.43  0.11 ( +0.33 ) ’ –0.00 –0.06 –0.50 “b  s penguin” average Babar and Belle 0.18  0.20 About 2.5  below golden modes!  2 /N dof = 4.8 / 4 Caveat: averaging  K S and  ’K S assumes the b->u tree contribution in  ’K S is negligible

23. Penguin Modes: C = 0 ? ’K s BaBar 0.10  0.22  0.03 Belle–0.26  0.22  0.03 Ave–0.08  0.16 K s BaBar –0.80  0.38  0.12 Belle 0.56  0.41  0.16 Ave –0.19  0.30 K + K - K s non-resonant Belle 0.40  0.33  0.10 ( +0.26 ) “b  s penguin” average “C” Babar and Belle –0.03  0.13

24. Tree vs. Penguin: B  D* + D - Cabibbo-suppressed tree b  d penguin Gronau PRL 63, 1451 (’89) PLB 233, 479 (’89) PRL 89, 122001 (2002) If penguins negligible, C=0, S=-sin(2  ) BaBar Note: not a CP eigenstate Belle BaBar

25. B  D*D* Mostly CP-even Belle BaBar Vector-Vector mode. since R T ~ 0 angular analysis not really needed

26. Summary See also http://www.slac.stanford.edu/xorg/hfag/triangle/winter2003/index.shtml Thanks to: Riccardo Faccini Yoshi Sakai Owen Long Gautier Hamel de Monchenault Andreas Hoecker Time dependent CP fits @ B factories have reached maturity sin(2  ) measurement with charmonium K S,L well established, Starting to explore other (rare) modes, but …need more data!

27. Summary See also http://www.slac.stanford.edu/xorg/hfag/triangle/winter2003/index.shtml Thanks to: Riccardo Faccini Yoshi Sakai Owen Long Gautier Hamel de Monchenault Andreas Hoecker Time dependent CP fits @ B factories have reached maturity sin(2  ) measurement with charmonium well established, Consistent with constraint from indirect measurement no longer limiting factor on CKM analysis Starting to explore other (rare) modes, but …need more data!

28. BACKUP SLIDES

30. Details: from  z to  t Proper time difference: Boost Approximation Improved Boost Approximation 0.2% effect Average  B Approximation 1.Improves resolution by 5% in quadrature 2.If not used, resolution depends on |  t|

31. Penguin Modes: the data… BaBar hep-ex/0207070 Belle hep-ex/0212062 Submitted to PRD

33. Yields (BaBar) BaBar

34. Tagging Performance CategoryEfficiency (  )Mistag Fr. (  )  MistagQ=  (1-2  ) 2 Lepton9.1  0.23.3  0.6-1.4  1.17.9  0.3 Kaon I16.7  0.29.9  0.7-1.1  1.110.7  0.4 Kaon II19.8  0.320.9  0.8-4.2  1.16.7  0.4 Inclusive20.0  0.331.6  0.9-2.0  1.22.7  0.3 Total 65.6  0.528.1  0.7

35. Control Samples No asymmetry observed as expected

36. Systematic Errors for sin(2b) Source  sin2  CP and Mix BG0.017 Klong BG0.015  t meas. and RF0.017 Signal Dilutions0.012 Fit bias correction0.010 B lifetime0.004 mdmd 0.003 Total0.033 Total from winter 2002 result (56 fb -1 ) was 0.035 Largest source comes from backgrounds CP of Argus BG is zero in default fit. Attempt to fit for it in SB. Difference is systematic (very conservative). Klong BG contributions Composition of J/X BG : 0.007 Shape/reslution of E : 0.007 Some improvements over last iteration Switched from PDG 2000 to PDG 2002 for B lifetime and m d. PDG uncertainties down by x2 (thanks to us). Both were 0.010 last time. Peaking BG now split by mode. J/K s has the lowest (0.3%, others >1.2%). Was 0.013, now 0.007. MC bias correction (or MC statistics). Used x7 more MC this time. We understand part of the bias. Was 0.014, now 0.010.

37.  t reconstruction Reconstruct B rec vertex from charged B rec daughters Determine B Tag vertex from All charged tracks not in B rec Constrain with B rec vertex, beam spot, and  (4S) momentum Remove high  2 tracks (to reject charm decays) High efficiency: 95% Average  z resolution ~ 180  m (dominated by B Tag ) ( ~ 260  m)  t resolution function measured from data Beam spot Interaction Point B REC Vertex B REC daughters B REC direction B TAG direction TAG Vertex TAG tracks, V 0 s z

38. Lepton tag only (cc)K S with lepton tag N tagged = 220 Purity = 98% Mistag fraction 3.3%    t 20% better than other tag categories sin2 = 0.79  0.11

40. Belle b->s penguin