1. Selected Results on CP Violation From BaBar
Vivek Sharma
UC San Diego

2. Weak Interactions of Quarks & The CKM Matrix
Vpq=
p = u, c, t W±
gVpq
q = d, s, b q
W - p
gVqp
W +
gV*qp
quark decay
anti-quark
decay
Cabbibo-Kobayashi-Maskawa matrix
Complex matrix elements lead to different amplitudes for quarks and anti-quarks
 CP violation

3. CKM Matrix : Wolfenstein Parameterization
λ = ± 0.002
A = ± 0.05
É = ± 0.09
¿ = ± 0.05
CKM phases
relative
magnitudes =
Complex elements Vtd and Vub result in large CP asymmetries in B decays

4. Probing The Unitarity Triangle in B System
CKM phases
CKM Paradigm: All CP asymmetries related to single CKM phase   SM CP violation is very predictive
Experimentalist’s goal  Is this the full picture?
Overconstrain the Unitarity Triangle with Multiple Measurements

5. this talk is not targeted at the BaBarians in the audience
Outline of This Talk
BaBar detector and data samples
Common measurement techniques
Focus on :
sin2 from B  Charmonium
“sin2” from Penguin mediated decays
Paradigm Shift in Measurement
Chasing 
My apology that
this talk is not targeted at the BaBarians in the audience

6. The BaBar Detector e+ (3.1 GeV) e- (9 GeV)
Electromagnetic Calorimeter
6580 CsI(Tl) crystals
1.5 T solenoid
e+ (3.1 GeV)
Cerenkov Detector (DIRC)
144 quartz bars
11000 PMs
e- (9 GeV)
Drift Chamber
40 stereo layers
Instrumented Flux Return
iron / RPCs (muon / neutral hadrons)
Silicon Vertex Tracker
5 layers, double sided strips
SVT: 5 layers, 97% efficiency, 15 mm z hit resolution (inner layers, perp. tracks)
SVT+DCH: (pT)/pT = 0.13 %  pT %
DIRC: K- separation GeV/c  GeV/c
EMC: E/E = 2.3 %E-1/4  1.9 %

7. PEP-II Asymmetric Energy Collider at (4S) Resonance
Run1
Run2
Run3
Run4
227M BB
PEP-II top luminosity:
9.2 x 1033 cm-2s (design 3.0 x 1033 cm-2s-1 )
Top recorded L/8 h: 240 pb-1
Top recorded L/month:16 fb-1
BABAR logging efficiency: > 96%
trickle injection
w/o trickle injection top-off every min
Continuous filling with trickle injection
more stable machine, +35% more lumi

8. Time-Dependent CPV Measurements

9. Cartoon Of (4S) B0B0 Decay Along Beam Axis

10. Time Evolution And Decay
For B0 Decay to a CP eigenstate
(with single weak decay amplitude  and strong phase )
CP = CP of the decay final state

11. Time-dependent CPV Asymmetry
Phase of mixing
Amplitude ratio
With the C and S coefficients defined as :
(for single weak decay amplitude)

12. The Simple Case of B0 J/K0
CP = -1 (+1)
for J/y K0S(L)

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

14. Producing B Meson and “Junk” at (4S) Resonance
BB (spherical)
Continuum
(jet-structure)
e+e-  (4S)  B+B-
suppress continuum background noting event
topology
e+e-  (4S)  B0B0
Dominant background
for charmless B decays:
e+e-  qq (continuum)
Off On
PEP-II BABAR
BB threshold
B0B0 threshold

15. Signal and Background Event Topologies
Differences in the event topology in (4S) rest frame (Isotropic B Vs jet-like Continuum) and Energy flow structure in these events used to construct continuum background suppression tools. BB qq

16. B Meson Reconstruction
Unique kinematics at the (4S) for signal selection
Beam-energy substituted mass
Energy difference
Correctly
reconstructed
BB events
Combinatorial
background

17. 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]

18. B Flavor Tagging By examining decay product in recoiling Btag
Tagging performance
Category
e(%)
w(%)
Q(%)
Lepton
8.6 ±0.1
3.2 ±0.4
7.5 ±0.2
Kaon I
10.9 ±0.1
4.6 ±0.5
9.0 ±0.2
Kaon II
17.1 ±0.1
15.6 ±0.5
8.1 ±0.2
K-p
13.7 ±0.1
23.7 ±0.6
3.8 ±0.2
Pion
14.5 ±0.1
33.9 ±0.6
1.7 ±0.1
Other
10.0 ±0.1
41.1 ±0.8
0.3 ±0.1
Total
74.9 ±0.2
30.5 ±0.4

19. Effect of Vertex Resolution 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

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

21. Testing  Vs “”

22. Compare sin2 with “sin2” from CPV in Penguin decays of B0
Both decays dominated by single weak phase
Tree:
Penguin:
New Physics? 3 ?

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

24. The « Golden » Penguin mode B0   K0
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

25. CP analysis of ‘golden penguin mode’ B0   K0
(Opposite CP)
S(fKS) = ± 0.31(stat)
S(fKL) = ± 0.51(stat)
Combined fit result (assuming fKL and fKS have opposite CP)
Standard Model Prediction
S(fK0) = sin2b = 0.72 ± 0.05
C(fK0) = 1-|l| = 0
0.9s
hfK0

26. The Silver penguin modes: B0  h’KS & B0  f0KS
hep-ex/
hep-ex/
B0  h’KS
B0  f0(980)KS
Large statistics mode
Reconstruct many modes
’   + –, 0 
    ,  + –0
KS  + – ,00
Modest statistics mode
CP analysis more difficult
Requires thorough estimate of CP dilution due to interference in B0   + –KS Dalitz plot
Fit finds 819 ± 38 events
Fit finds 152 ± 19 events

27. The Silver penguin modes: B0  h’KS & B0  f0KS
hfK0
hfK0
sin2 3.0
sin2 0.6

28. Sin2b from bs penguins – summary of BaBar results
None of the individual results (except perhaps h’KS) has a sizeable discrepancy with SM
But penguin average 2.8s away from Charmonium result
Note that new physics will generally have different effect on modes – so averaging not necessarily sensible…

29. sin2 from bs Penguins: World averages
BaBar/Belle agree on results. Discrepancy is 3.7s if averaged
Caveat: uncertainty due to sub-leading SM contributions are ignored in this view of the discrepancy
Theory needs to refine SM prediction for sin(2b) various penguin modes (conversations in progress!)
-hf×S (‘sin2b’)=0.43 ± 0.07
C (‘direct CPV’)= ± 0.05

30. All Penguin Measurements Are Luminosity Limited
Expect double BABAR luminosity in summer 2006:
2004: 246 fb-1
2006: 500 fb-1
f0KS
KSp0
jKS
KKKS
h’KS
K*g
5s discovery region if non-SM
physics is a 30% effect
2004
2006

31. Time Dependent CPV and Angle : Plan “B” Works Better !

32. CPV in b u u d Process : B0 +-
Neglecting Penguin diagram

33. Reality in B0 +-, + -
Tree
Penguin
Ratio of amplitudes |P/T| and
strong phase difference 
can not be reliably calculated!
If no penguins  Spp ~ -0.34
Gronau& London: Estimate dapeng = eff - using isospin relations

34. Estimating Penguin Pollution in B0 +-, + -

35. Rates and Asymmetries in B+ 0 , B0 0

36. Angle  From B+ - : Bottomline
B+ - TD CPV
Very weak constraint on  [67o -131o]
Needs more precise C00 measurements

37. B System As Probe of 
This system seems to have had
the Pope’s blessings !
Two years ago few would
have bet that this system
would play a defining role
in  measurement !

38. B0 + - System As Probe of 
Blessing # 1
Likelihood projection
Although 2 0’s make efficiency small

39. B0 + - System As Probe of 
Blessing # 2
Blessing # 3
68%C.L.
bkgd
total
 Helicity angle

40. TD CPV Measurement in B0 + -
Shown here are events from the Lepton and Kaon1 tagging categories only
total likelihood
total background
In total 617 52 signal events
Preliminary

41. Systematic Uncertainties in TD analysis

42. Discerning  No result from Belle on + - yet B0 + - Br(r+r-)
(30±6) 10-6
Br(r+r0)
(26±6) 10-6
Br(r0r0)
<
B0 + -
No result from Belle on + - yet

43. Chasing Gamma ! (Not a Pretty Picture With Current Dataset)

44. Towards The Angle : The phase in Vub
Look for B decays with 2 amplitudes with relative weak phase 
Direct CP Asymmetry
 Angle 

45. Angle  from B±DK±: Critical Requirement
Relative size of the 2 B decay amplitudes matters for interference
Want rb to be large to get more interference  Large CP asymmetry
Diff. between rb=0.1 and rb=0.2 substantial for precision on 
Theory cannot calculate r reliably must measure experimentally
Color suppression: Fcs  [0.2,0.5]
Left side U.T.: Ru  0.4
Expected range

46. Angle  from B±D0 K±: Current Status
Even with ~250 fb-1 data in hand for each experiment, reconstructed samples of B±DK± events are too few for a meaningful measurement of the angle  (and r, and strong phase )
E.g: Effective Br. Ratio for (B±D0 K±)(D0K+-) 10-7
The exception is the case when B±D0 K± and D0KS+ - , a decay accessible to both D0 and D0. Entire resonant substructure can be used with Cabbibo-allowed and suppressed modes in D0KS + - interfering directly

47.  from B±D0 K±: D0 KS + - Dalitz Analysis

48.  from B±D0 K±: D0 KS + - Dalitz Analysis2
Schematic view of the interference

49. Modelling D0 KS + - Dalitz Distribution
D Decay amplitudes etc obtained from fit to 81K D*D0 sample
Use 16 2-body modes

50. Sensitivity to  : Not all events are Equal

51. Event Samples and  Sensitivity Vs rB
Event samples (from 227M BB ) are clean but small (when divided into B )
Further, error on  depends on rB value, poor sensitivity at low rB
448
28220
9011

52. (Poor) Constraints on 
Bayesian C.L.s
68%
95%
D*K DK g
180° 0°
-180°
0.1
0.3 rB
g = 70°±26°±10°±10°(Dalitz)
PRELIMINARY
DK : rB < 0.19
(90% C.L.)
dB = 114°±41°±8°±10°(Dalitz)
D*K : rB = 0.155
+0.070
± ± 0.020
-0.077
dB = 303°±34°±14°±10° (Dalitz)

53. (Poor) Constraints on  : Need More Statistics

54. Summary: In Pictures All interesting measurements are
data starved; need multiple times
current data samples for a precision
probe of the CKM paradigm
Waiting impatiently for more data !

55. Good News: Email (Sunday) From BaBar Counting Room
Dear colleagues,
yesterday afternoon our colleagues from the machine have been able to inject the first electrons into PEP. After only a few hours, they were able to store a 100 mA beam. Positrons are expected within a few days. This means that collisions and physics data taking should resume very soon.
This is really great news. Our PEP/Linac colleagues have done an outstanding work taking into account that they restarted the machine 10 days ago.
One hopes that BaBar doubles its dataset by mid 2006
and doubles it again by end of 2008
In the future LHC-b not enough, need SuperBFactory

56. See http://ckm2005.ucsd.edu for detailed presentation of topics discussed here

57.  from B±D0 K±: D0 KS + - Dalitz Analysis
BELLE’05

58. B Mixing Phenomenology

59. B0 B0 – Mixing: the Formalism
Generic neutral B-meson state
Time evolution governed by Schroedinger Equation
Hamiltonian is diagonal in basis of heavy and light mass eigenstates (G=GH=GL and |q/p|=1)

60. B0 Decay Amplitudes Time evolution of physical states Decay amplitudes
weak phase , strong phase d

61. (Time-dependent) Decay Rates
General case:

62. Decay Rates to Final States with specific Flavor (BB Mixing)
No CP asymmetry, if
“unmixed”
“mixed”

63. B0B0 Oscillation Measurements
Di-Leptons
B0  D*ln
D(*) p/r/a1, J/K*
B0B0 oscillation frequency
precisely determined from
flavor specific final states:
Dm = ± ps-1
(world average)
B0  D*ln

64. CP Eigenstate: 2 interfering Amplitudes
Vcb b c
Without mixing  W - c B0 s
Vcs K0 KS d d
Vcb b b c
With mixing  + c W B0 B0
BB mixing s
Vcs K0 KS d d d

65. Interference of 2 Amplitudes
Consider pure B0 initial state (B0 is the same)
ΔmΔt = 0: P(B0B0) = 0  no mixing, no interference
ΔmΔt = p: P(B0B0) = 1  full mixing, no interference
ΔmΔt = p/2: P(B0B0) = 1/2  maximal interference, resulting in CP violation !
only B0
final state f
BB mixing
only B0

66. CPV: B Decays With 2 Amplitudes With Relative Weak Phase : Need to Reorganize this

67. Some Relevant B Decay Diagrams
Color Suppressed
Spectator
Tree Diagrams
Gluonic Penguin
W-Exchange

68. Penguin Lust !

69. CPV: B Decays With 2 Amplitudes With Relative Weak Phase : Need to Reorganize this

70. Golden Decay Modes: (cc)K0 decays
B0 mixing
B0 decay
K0 mixing c d b s b d c t W+ s t d b d s d d
CP = -1 (+1)
for J/y K0S(L)

71. Example: Time Dependent CPV In B0 J/K0
B0 mixing
B0 decay
K0 mixing c d b s b d c t W+ s t d b d s d d
CP = -1 (+1)
for J/y K0S(L)