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
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)
Peak luminosity
(cm-2 s-1)
x 1034
Best shift
247.2 pb-1
Best day
710.5 pb-1
Best week
4.464 fb-1
Best month
fb-1
BABAR logged
343 fb-1
96% efficiency over the entire history of BABAR
BABAR, Run 5
KEK-B operation even more spectacular !

5. BaBar Physics Productivity
Publication Luminosity
Submitted
BABAR
Belle
Journal Papers
201
163
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
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 B0 K : BaBar
4.2, syst. included
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. CPV In Interference Between Mixing and Decay+ 2  B0
fcp
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 : B0 J/K0
CP = -1 (+1)
for J/y K0S(L)

12. Visualizing Time-Dependent CPV Measurement

13. Steps in Time-Dependent CPV Measurementz
distinguish
B0 Vs B0 m- K-
bgU(4S) = 0.55
Coherent BB pair B0
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
Determine flavor 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]
CP sample
NTAG
purity
ηCP
J/ψ KS (KS→π+π-)
2751
96% -1
J/ψ KS (KS→π0π0)
653
88%
ψ(2S) KS (KS→π+π-)
485
87%
χc1 KS (KS→π+π-)
194
85%
ηc KS (KS→π+π-)
287
74%
Total for ηCP=-1
4370
92%
J/ψ K*0(K*0→ KSπ0)
572
77%
+0.51
J/ψ KL
2788
56% +1
Total
7730
78%
BABAR
J/ψ KL signal
J/ψ X background
Non-J/ψ background
(ηCP = +1)
ΔE [MeV]

16. Sin(2b) Result From B Charmonium K0 Modes (2004)
(cc) KS modes (CP = -1)
J/ψ KL mode (CP = +1)
background
hep-ex/
sin2β =  (stat)  (syst)
(PRL 89, (2002): sin(2β) = ± ± 0.034)

17. Belle 2005 (386M BB)

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

22. Must be if one amplitude dominates
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

23. 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 !

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

25. New Physics ?
Standard Model

26. B0   K0 Since LP03 BaBar: 222M BB
hep-ex/
Modes with KS and KL are both reconstructed
(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 the dimensions that are not shown, and have a lower signal event count

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

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

31. 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 !!

32. 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/

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…
2.4s?
discrepancy

35. 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

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

37. Backup Slides

38. Projected data sample growth: BaBar Expectation20
Double again from 2006 to 2008
ICHEP08
Integrated Luminosity [fb-1]
PEP-II: IR-2 vacuum, 2xrf stations, BPM work, feedback systems
BABAR: LST installation
4-month down for LCLS, PEP-II & BABAR 17
Double from 2004 to 2006
ICHEP06 12
Lpeak = 9x1033

39. PEP-II overall parameters and goals
Units
Design
Oct 2005
2007 goal I+ mA
2140
2940
4000 I-
750
1740
2200
Number of bunches
1658
1732
by* mm
15-20 11
8-8.5
Bunch length 15
11-12
8.5-9 xy
0.03
Luminosity
x1033
3.0
10.0 20
Int lumi / day
pb-1
130
727.8
1300
40%
30%
10%
Factor 2!

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

41. B0  D0h0 Belle’s New Method for Direct measurement of f1_
B0  D0h0 Belle’s New Method for Direct measurement of f1
(D0  KSp+p-)
AB0D0h0(Dt) =
M(KSp-)
M(KSp+)
f-+
cos(DMDt/2)
M(KSp+)
M(KSp-)
f+-
-ei2f1 hh0
sin(DMDt/2)
Vivek Sharma , UCSD

42. Reconstruction of B0  D[KSp+p-]h0_
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  D0 p0
D*  D0 pi0
D*pi0 :
D*eta :
TOTAL
Nsig = 309 ±31
purity : 63%
Vivek Sharma , UCSD

43. Time-Dependent Dalitz fit results
Belle preliminary
Final state
f1 (o)
D0 p0
11 ± 26
D0 w, h
28 ± 32
D*0 p0, h
25 ± 35
combined
16 ±21(stat) ±11(syst)
-30o < f1 < 62o
(95% C.L.)
Vivek Sharma , UCSD

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

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

48. An (4S)B B Event : Along The Beam LineZ

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

50. Sin2b
BaBar 2004:
Belle 2005:
background

51. Three Kinds of CP Violation in B0 Meson System
Indirect CPV Direct CPV