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CP Violation in B 0 Decays: Some Highlights

CP Violation in B 0 Decays: Some Highlights. Vivek Sharma University of California at San Diego. SheldonFest, May 20, 2006. 1987: Argus Discovers large B 0  B 0 Oscillation Rate. ARGUS. First time I heard the word CP violation and B mesons spoken together.

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CP Violation in B 0 Decays: Some Highlights

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  1. CP Violation in B0 Decays:Some Highlights Vivek Sharma University of California at San Diego SheldonFest, May 20, 2006

  2. 1987: Argus Discovers large B0B0 Oscillation Rate ARGUS First time I heard the word CP violation and B mesons spoken together Started a chain of activities which ultimately led to the construction & operation of the asymmetric energy B factories Much skepticism initially about how well these machines would perform

  3. PEP-II Asymmetric B Factory & BaBar

  4. 96% efficiency over the entire history of BABAR BABAR, Run 5 Machine Performance Exceeds Design (x3) KEK-B operation even more spectacular !

  5. BaBar Physics Productivity Publication Luminosity As of April 3 As of April 12 ‘06 BaBar papers by topic: BaBar papers by area: Plan to exceed 220 publications by summer 2006

  6. Direct CP Violation in B0 K T P • Loop diagrams from New Physics (e.g. SUSY) can modify • SM asymmetry via Penguin diagram • Need reliable knowledge of T/P and relative strong phase to • extract /3 • Clean mode with a “large” rate: • Measurement is a “Counting Experiment”

  7. B0K+ BABAR 4.2, syst. included BABAR B0K+ Direct CP Violation in B0 K : BaBar

  8. Direct CP Violation in B0 K : Belle (386M BB) Combined significance >> 6 Belle Rules out Superweak model Establishes CPV not just due to phase of B Mixing But hadronic uncertainties preclude determination of CKM angle   challenge to theory

  9. B0 B0 fcp fcp B0 B0 B0 B0 fcp fcp 2 2  + + CPV In Interference Between Mixing and Decay CP asymm. can be very large and “cleanly” related to CKM angles Requires time dependent measurement of CP Asymmetry

  10. Amplitude ratio Phase of mixing (for single weak decay amplitude) Time-dependent CP Asymmetry Due to Interference in Mixing and Decay (direct CPV) (indirect)

  11. The “Platinum” Mode : B0 J/K0 CP = -1 (+1) for J/y K0S(L)

  12. Visualizing Time-Dependent CPV Measurement

  13. Steps in Time-Dependent CPV Measurement z distinguish B0VsB0 m- bgU(4S) = 0.55 K- B0 B0 Coherent BB pair B0  J/y Ks Vivek Sharma , UCSD

  14. Effect of Mis-measurements on Dt Distribution perfect flavor tagging & time resolution realistic mis-tagging & finite time resolution CP PDF Determineflavor mis- tag rates w and Dt resolution function R from large control samples of B0  D(*)p/r/a1,J/K* BB Mixing PDF

  15. B Charmonium Data Samples MES [GeV] MES [GeV] BABAR J/ψ KL signal J/ψ X background Non-J/ψ background (ηCP = +1) ΔE [MeV]

  16. (cc) KSmodes (CP = -1) Sin(2b) Result From B Charmonium K0 Modes (2004) J/ψKLmode (CP = +1) background hep-ex/0408127 sin2β = 0.722  0.040 (stat)  0.023 (syst) (PRL 89, 201802 (2002): sin(2β) = 0.741 ± 0.067 ± 0.034)

  17. Belle 2005 (386M BB)

  18. The Unitarity Triangle Defined By CPV Measurements New B Factory milestone: Comparable UT precision from CPV in B decays alone

  19. UT With CPV & CP Conserving Measurements Incredible consistency between measurements ! Paradigm shift ! Look for NP as correction to the CKM picture

  20. Searching For NP << Testing  Vs “” >>

  21. Compare sin2 with “sin2” from CPV in Penguin decays of B0 Both decays dominated by single weak phase Tree: Penguin: New Physics? 3 ? Must be if one amplitude dominates

  22. Naïve Ranking Of Penguin Modes by SM “pollution” Naive (dimensional) uncertainties on sin2 Decay amplitude of interest SM Pollution f f SuperGold Gold Bronze Note that within QCD Factorization these uncertainties turn out to be much smaller !

  23. 140 fb-1 Belle 68±11 Penguin Lust ! CP Asymmetry in B φ KS : LP2003 Belle sin2φ1eff = -0.96 ±0.50 Then WA: sin(2φ1)ccs = 0.731±0.056 3.5σ different !

  24. New Physics ? Standard Model

  25. B0  K0 Since LP03 • Modes with KS and KLare both reconstructed hep-ex/0502019 BaBar: 222M BB (Opposite CP) full background continuum bkg 114 ± 12 signal events 98 ± 18 signal events Plots shown are ‘signal enhanced’ through a cut on the likelihood on thedimensions that are not shown, and have a lower signal event count

  26. CP analysis of ‘golden penguin mode’ B0  K0 BaBar (Opposite CP) S(fKS) = +0.29 ± 0.31(stat) S(fKL) = -1.05 ± 0.51(stat) Standard Model Prediction S(fK0) = sin2b = 0.69 ± 0.03 C(fK0) = 1-|l| = 0 Combined fit result 0.8s hfK0

  27. Large statistics mode Reconstruct many modes ’   + –, 0      ,  + –0 KS + – ,00 Other (More Prolific) Golden penguin mode: B0 h’K0 hep-ex/0502017,0507087 B0 h’KS B0 h’K0 BaBar hfK0  sin2 [cc] @ 2.7 ’KS 819 ± 38 signal events (Ks mode) 440 ± 54 signal events (KL mode)

  28. Taken individually, each decay mode in reasonable agreement with SM but (almost) all measurements are lower than sin2 from ccs Naïve b  s penguin average sin2eff = 0.50 0.06 Theory models predict SM pollution to increase sin2eff!!

  29. How good is the SM Theoretical Prediction? 2-body: Beneke, PLB 620 (2005) 143 Calculations within framework of QCD factorization 3-body: Cheng, Chua & Soni, hep-ph/0506268

  30. Direct CPV in s-Penguins ? No sign of direct CPV !

  31. 2.4s? discrepancy This could be one of the greatest discoveries of the century, depending, of course, on how far down it goes… What Are s-Penguins Telling Us ?

  32. Possible Evolution by Summer 2008 Luminosity expectations: K*g 2004=240 fb-1 2008=1.0 ab-1 f0KS KSp0 jKS h’KS KKKS 4s discovery region if non-SM physics is 0.19 effect 2004 2008 Individual modes reach 4-5 sigma level Projections are statistical errors only; but systematic errors at few percent level

  33. An Optimist’s Global CKM fit ? : 2008 (1 fb-1 each) 95%contours ?

  34. Backup Slides

  35. Double again from 2006 to 2008 ICHEP08 • PEP-II: IR-2 vacuum, 2xrf stations, BPM work, feedback systems • BABAR: LST installation Double from 2004 to 2006 ICHEP06 4-month down for LCLS, PEP-II & BABAR Projected data sample growth: BaBar Expectation 20 Integrated Luminosity [fb-1] 17 12 Lpeak = 9x1033

  36. 40% 30% 10% Factor 2! PEP-II overall parameters and goals

  37. BABAR 2008 BABAR+ Belle 2008 Only More Data Can Reveal The True Picture Possible evolution of deviations From SM average h’KS Assuming fluctuations aroundpresent central values KS Number of standard deviations Integrated luminosity (fb-1)

  38. _ f-+ f+- M(KSp-) M(KSp-) M(KSp+) M(KSp+) B0  D0h0Belle’s New Method for Direct measurement of f1 (D0KSp+p-) AB0D0h0(Dt) = cos(DMDt/2) -ei2f1hh0 sin(DMDt/2) Vivek Sharma , UCSD

  39. _ Reconstruction of B0  D[KSp+p-]h0 D0 p0 D0 w D0 h D*0 p0, h Nsig = 157 ±24 purity : 59% Nsig = 67 ±10 purity : 86% Nsig = 58 ±13 purity : 60% Nsig = 27 ±11 purity : 52% D*0 D0p0 D*  D0 pi0 D*pi0 : 22 +- 9 D*eta : 5+- 6 TOTAL Nsig = 309 ±31 purity : 63% Vivek Sharma , UCSD

  40. Time-Dependent Dalitz fit results Belle preliminary -30o < f1 < 62o (95% C.L.) Vivek Sharma , UCSD

  41. Implications of Time-dependent Dalitz analysis Consistent with B0J/yK* results cos2f1 = 0.87 ±0.75, hep-ex/0504046 ? f1~70o Disfavored >2s sin2f1 (^_^) ? f1~20o f1 2-fold ambiguity resolved ! Vivek Sharma , UCSD

  42. A Completely Reconstructed (4S) Event at BaBar All particles accounted for Nothing Missing !

  43. An (4S)B B Event : Along The Beam Line Z

  44. Close Up of a Reconstructed (4S) B0 B0 Event

  45. Sin2b BaBar 2004: Belle 2005: background

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