Vivek Sharma University of California at San Diego CP Violation in B 0 Decays: Some Highlights SheldonFest, May 20, 2006

2 1987: Argus Discovers large B 0   B 0 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 Machine Performance Exceeds Design (x3) 96% efficiency over the entire history of BABAR BABAR, Run 5 Peak luminosity (cm -2 s -1 ) x Best shift247.2 pb -1 Best day710.5 pb -1 Best week4.464 fb -1 Best month fb -1 BABAR logged343 fb -1 KEK-B operation even more spectacular !

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

6 Direct CP Violation in B 0  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 Direct CP Violation in B 0  K  : BaBar B0K+B0K+ B0K+B0K+ BABAR 4.2 , syst. included BABAR

8 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 Combined significance >> 6  Direct CP Violation in B 0  K  : Belle (386M BB) Belle

9 CPV In Interference Between Mixing and Decay  B0B0 B0B0 B0B0 f cp B0B0 B0B0 B0B0 CP asymm. can be very large and “cleanly” related to CKM angles Requires time dependent measurement of CP Asymmetry

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

11 The “Platinum” Mode : B 0  J/  K 0  CP = -1 (+1) for J/  K 0 S(L)

12 Visualizing Time-Dependent CPV Measurement

Vivek Sharma, UCSD13 B 0  J/  K s z   (4S) = 0.55 Coherent BB pair B0B0 B0B0   distinguish B 0 Vs B 0 distinguish B 0 Vs B 0 Steps in Time-Dependent CPV Measurement

14 Effect of Mis-measurements on  t Distribution Determine flavor mis- tag rates w and  t resolution function R from large control samples of B 0  D (*)  /  /a 1, J/  K* BB Mixing PDF CP PDF perfect flavor tagging & time resolution realistic mis-tagging & finite time resolution

15 B  Charmonium Data Samples CP sampleN TAG purityη CP J/ψ K S (K S →π + π - )275196%  J/ψ K S (K S →π 0 π 0 )65388%  ψ(2S) K S (K S →π + π - )48587%  χ c1 K S (K S →π + π - )19485%  η c K S (K S →π + π - )28774%  Total for η CP = %  J/ψ K *0 (K *0 → K S π 0 )57277%  J/ψ K L %  Total773078% M ES [GeV] ΔE [MeV] J/ψ K L signal J/ψ X background Non-J/ψ background B A B AR (η CP = +1)

16 Sin(2  Result From B  Charmonium K 0 Modes (2004) sin2β =  (stat)  (syst) (cc) K S modes (CP =  1) (PRL 89, (2002): sin(2β) = ± ± 0.034) J/ψ K L mode (CP = +1) hep-ex/ background

17 Belle 2005 (386M B B )

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

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

21 Searching For NP >

22 Compare sin2  with “sin2  ” from CPV in Penguin decays of B 0 Both decays dominated by single weak phase Penguin: Tree: New Physics? 33 ? Must be if one amplitude dominates

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

24 Penguin Lust ! Belle 140 fb -1 68±11 CP Asymmetry in B  φ K S : LP2003 sin2φ 1eff = ± σ different ! Then WA: sin(2φ 1 ) c c s = 0.731±0.056 Belle

25 New Physics ? Standard Model

26 B 0   K 0 Since LP03 Modes with K S and K L are both reconstructed 114 ± 12 signal events98 ± 18 signal events full background continuum bkg (Opposite CP) Plots shown are ‘signal enhanced’ through a cut on the likelihood on the dimensions that are not shown, and have a lower signal event count hep-ex/ BaBar: 222M B B

27 CP analysis of ‘golden penguin mode’ B 0   K 0 S(K S ) = ± 0.31(stat)S(K L ) = ± 0.51(stat) Combined fit result Standard Model Prediction S(K 0 ) = sin2 = 0.69 ± 0.03 C(K 0 ) = 1-|| = 0 0.8 (Opposite CP)  K0  BaBar

28 Other (More Prolific) Golden penguin mode: B 0   ’K 0 Large statistics mode Reconstruct many modes –  ’   +  –,  0  –    ,  +  –  0 –K S  +  –,  0  0 B 0  ’K S 819 ± 38 signal events (K s mode) 440 ± 54 signal events (K L mode) hep-ex/ , B 0  ’K 0  sin2 2.7  K0  BaBar  ’K S

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

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

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

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

35 Possible Evolution by Summer 2008 K*K* 4  discovery region if non-SM physics is 0.19 effect 2004=240 fb =1.0 ab -1 Individual modes reach 4-5 sigma level Projections are statistical errors only; but systematic errors at few percent level Luminosity expectations : f 0 K S K S  0  K S  ’K S KKK S

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

Backup Slides

38 Projected data sample growth: BaBar Expectation Integrated Luminosity [fb -1 ] L peak = 9x10 33 oPEP-II: IR-2 vacuum, 2xrf stations, BPM work, feedback systems oBABAR: LST installation 4-month down for LCLS, PEP-II & BABAR Double from 2004 to 2006 ICHEP06 Double again from 2006 to 2008 ICHEP08

39 ParameterUnitsDesignOct goal I+mA I-mA Number of bunches y*y* mm Bunch lengthmm yy Luminosityx Int lumi / daypb PEP-II overall parameters and goals 30%40% 10% Factor 2!

40 Only More Data Can Reveal The True Picture Number of standard deviations Integrated luminosity (fb -1 ) KSKS  ’K S average Assuming fluctuations around present central values BABAR 2008 BABAR+ Belle 2008 Possible evolution of deviations From SM

Vivek Sharma, UCSD41 B 0  D 0 h 0 Belle’s New Method for Direct measurement of  1 _ (D 0  K S      M(K S   ) M(K S   ) f -+ M(K S   ) M(K S   ) f +- A B0  D0h0 (  t) = cos(  M  t/2) sin(  M  t/2) -e i2  1  h0

Vivek Sharma, UCSD42 Reconstruction of B 0  D[K S  +  - ]h 0 D 0  0 D 0  D 0  D *0  0,  Nsig = 157 ±24 purity : 59% Nsig = 67 ±10 purity : 86% Nsig = 58 ±13 purity : 60% Nsig = 27 ±11 purity : 52% D *0  D 0  0 TOTAL Nsig = 309 ±31 purity : 63% _ D*  D0 pi0 D*pi0 : D*eta : 5+- 6

Vivek Sharma, UCSD43 Time-Dependent Dalitz fit results Final state  1 ( o ) D 0  0 11 ± 26 D 0  28 ± 32 D *0  0,  25 ± 35 combined 16 ±21(stat) ±11(syst) -30 o <  1 < 62 o (95% C.L.) Belle preliminary

Vivek Sharma, UCSD44 Implications of Time-dependent Dalitz analysis  1 ~20 o  1 ~70 o sin2  1 11 ? ? (^_^) 2-fold ambiguity resolved ! Consistent with B 0  J/  K* results cos2  1 = 0.87 ±0.75, hep-ex/ Disfavored >2 

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

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

49 Close Up of a Reconstructed  (4S)  B 0 B 0 Event

50 Sin2b background BaBar 2004:Belle 2005:

51 Three Kinds of CP Violation in B 0 Meson System Indirect CPV Direct CPV