CP violation at B-factoris

1
CP violation at B-factoris
Pavel Krokovny KEK, Tsukuba, Japan

• Introduction
• f1/b
• f2/a
• f3/g
• Vub, D mixing, Bs
• Conclusion

KEK
2
Unitarity triangle
Using unitarity requirement
We need to measure all the angles to test SM.
3
CPV in Mixing
2
2
Af
Af
B0
fCP
fCP
B 0
B0
B 0
Af
Af
Difference in decay rate for B0 and B0 ? CP
Violation
4
Direct CPV in charged B Decays
CP violation through interference of decay
amplitudes

• One rate asymmetry is not sufficient to extract
  physical parameters
• measure A and A, but need A1, A2, fwk, dst

5
KEKB and Belle
KEKB Collider

• 3.5 GeV e 8 GeV e beams
• 3 km circ, 11 mrad crossing angle
• L 1.65 x 1034 cm2s1
• world record
• L dt 740 fb1 _at_ ?(4S)off(10)

6
Kinematics and event shape
Event shape
?(4S) rest frame
s(DE) mode dependent
s(mES) ? 3 MeV
Event shape variables examples
7
f1 from the golden b?ccs mode
-
8
Measuring cos2f1
B ? D()0 h0 with D0 ? KSpp-
(same weak phase as B0 ? J/?K0)
sin2f10.75 0.440.22
cos2f11.79 0.53 0.33
cos2f1gt0 _at_ 98.3 CL
cos2b consistently measured to be gt 0!
9
CPV in B0 ? DD-
10
sin2f1 from Penguin Decays
Standard Model
New Physics
new physics


NP weak phase
no weak phase from decay

• no weak phase in b?(qq)s penguin decays
• expect to measure S sin(2f1) just as in B ? ?
  KS
• contributions from suppressed diagrams expected
  to be small (Dsin(2f1) sin(2f1eff)- sin(2f1)
  0.01-0.1)
• if new physics introduces weak phase in decay, we
  could measure something different than sin(2f1)

11
sin2f1 in b?sqq Penguins
eff
sin2feff
1
No significant deviations from the WA from the
value from the b?ccs modes
sin2f1 0.680.03
HFAG advises extreme caution when interpreting
this average (assumption of Gaussian errors not
justified for all measurements)
sin2f1
12
Determination of f2(a)
Time-dependent CP asymmetry
Penguin
Tree
Including penguin
Without penguin
Use isospin relations to estimate the
penguin contribution
Gronau-London, PRL, 65, 3381 (1990) Lipkin et
al., PRD 44, 1454 (1991)
Neglecting EWP, h h0 (I2)pure tree
13
f2(a) Measurement using B g pp
Dt (ps)
PRL 78, 211801 (2007)
14
Sorting out penguin pollution
WA values
Triangle analysis 6 observables 6 unknowns
97 11
15
B?rr isospin analysis
B0?rr has 3 polarization states with different
CP eigenvalues
Fortunately, longitudinal polarization dominates
? pure CP-even state No significant ?0?0 signal ?
small penguin contribution
62lt f2lt 106
WA values
16
B?rr CP fit results
PRD 76, 011104 (2007)
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B ? rr
Large branching fraction !
Small penguins !
Dominantly longitudinally polarized !
B0 tag
BABAR
B0 tag
BaBar 383 MBB
Time-dependent CP asymmetries in B0 ? rr-
arXiv 0705.2157v2
18
a with B ? r0r0
arXiv0708.1630
With more data information on S00 and C00 will
allow to resolve discrete ambiguities
19
B0?(rp)0 Dalitz Analysis
r
p -
B0
r-
p
p p -p 0
Dt
r 0
Dalitz
p 0
Interference by B0B0 oscillation Interference
Between r, r-, r0
Various (24) Patterns of Interferences
? Information on
Relative Phases
20
B?pp-p0
Pentagon analysis
PRL 98, 221602 (2007)

68lt f2lt 95
21
f2 results pp,rp,rr
B?pp
90o10o
B?rp
B?rr
22
Determination of f3(g)
B? D0K B? D0K
If D0 and D0 decay into the same final state,
Relative phase (B? DK),
(B? DK) includes weak (?/f3) and
strong (d) phase.
Amplitude ratio
Possible D0 / D 0 final states CP eigenstates
(pp, KK) Flavor eigenstates (Kp) Three-body
decays (KSpp)
Gronau London, PLB 253, 483 (1991)
Gronau Wyler, PLB 265, 172
(1991) Atwood, Dunietz, Soni, PRL 78, 3257
(1997), Atwood, Dunietz, Soni, PRD 63, 036005
(2001) Giri, Grossman, Soffer, Zupan, PRD 68,
054018 (2003) Bondar, PRD 70, 072003 (2004)
23
Dalitz analysis method
A.Giri, Yu. Grossman, A. Soffer, J. Zupan, PRD
68, 054018 (2003) A.Bondar, Proceedings of the
Belle Workshop, September (2002)
Using 3-body final state, identical for D0 and
D0 Kspp-. Dalitz distribution density
(assuming ??-conservation in D0 decays)
is determined from D? D0p, D0 ? Kspp decay ?
model uncertainty of the result
Parameters are obtained from the
fit to Dalitz distributions of D? Kspp from
B?DK decays
24
Dalitz analysis sensitivity to the phase
25
Belle/Babar results on ?

• Fit parameters are x? r cos(?f3d) and y? r
  sin(?f3d)
• (better behaved statistically than r, f3 and d)
• Belle/Babar measurements in good agreement
• Note s? depends significantly on the value of rB

Contours do not include Dalitz model errors
Contours do not include Dalitz model errors
26
Dalitz analysis (Belle)
B??DK?
B??DK?
B??DK?
f386 -93(stat)
f311 -57(stat)
f366 -20 (stat)
23
37
19
Combined for 3 modes f35315 ?3 (syst)?9
(model)
8ltf3lt111 (2s interval)
rDK 0.1590.054
?0.012(syst)?0.049(model) CPV significance 78
rDK0.1750.108 ?0.013(syst)?0.049(model)
rDK0.5640.216
?0.041(syst)?0.084(model)
-18
-0.050
-0.099
-0.155
27
? from B?D()0K, D0?KS?? (Babar)
Dalitz distribution of selected B candidates
g(92411112)
B-? DK-
B ? DK
Stat Syst Model
2s
1s
28
Constraints of the Unitarity Triangle
80o30o
Estimated average with GLW, ADS, Dalitz and
sin(2f1f3)
29
Model-independent approach
A.Bondar, A.Poluektov hep-ph/0510246
A.Giri, Yu. Grossman, A. Soffer, J. Zupan,
PRD 68, 054018 (2003)
rB0.2
50 ab-1 at SuperB factory should be enough for
model-independent ?/f3 Measurement with
accuracy below 2 10 fb-1 at ?(3770) needed to
accompany this measurement.
30
Summary in pictures
CPV angles
CP-conserving quantities
31
Summary in pictures
32
Summary
f1 is measured with 1º accuracy. Still there is
room for improvement. Remarkable progress in f2
measurement accuracy of O(10º) is achieved using
rr and rp. Still limited by statistic -
improvements in the future. The f3 remains the
most difficult angle of the Unitarity Triangle to
measure. Good perspectives with higher statistics
since the theoretical uncertainties are very low.
Model error can be eliminated using charm data
CLEOc/BES. No indication for a New Physics is
found so far... Much more data is necessary ?
LHCb, Super B factory.
33
PEP-II and BaBar
Silicon Vertex Tracker (SVT)
1.5T magnet
Drift Chamber (DCH)
Detector of Internally Reflected Cherenkov Light
(DIRC)
Electromagnetic Calorimeter (EMC)
Instrumented Flux Return (IFR)

• 3.1 GeV e 9 GeV e beams
• L 1.12 x 1034 cm2s1 (June 28, 2006)
• L dt 380 fb1 _at_ ?(4S)off (10)

34
Future plans of KEKB

• Next milestone
• Accumulation of 1000 fb-1 (740 fb-1 at present)
• Near term plans
• L 2 x 1034cm-2s-1
• Benefits of crab crossing
• Higher beam current (HER) 1400 -gt 1500mA
• with several reinforcements of vacuum
  components
• Search for better machine parameters
• Beam emittance, ?x, ?x etc.
• Long-term future plan
• SuperKEKB
• Major upgrade plan of KEKB
• Design luminosity 1036cm-2s-1
• Not yet approved (Construction hope to start in
  FY 2009)

35
B???
B0?rr has 3 polarization states with different
CP eigenvalues
Fortunately, longitudinal polarization dominates,
therefore, pure CP-even state
Belle
of Events
BaBar (PRL 95, 041805, (2005))
Belle (hep-ex/0601024)
cosq
No significant ?0?0 signal ? small penguin
contribution
BaBar (PRL, 98, 111801 (2007))
36
ADS method
D. Atwood, I. Dunietz and A. Soni, PRL 78, 3357
(1997)
PRD 63, 036005 (2001)
Enhancement of ??-violation due to use of
Cabibbo-suppressed D decays
37
ADS method
Suppressed channel not visible yet
Belle results (357 fb-1)
Using rD0.0600.003, for maximum mixing (f30,
d180) rBlt0.18 (90 CL)
BaBar results (211 fb-1)
rBlt0.23 (90 CL) for B?DK rBlt0.16
for B?DK
38
GLW method
M. Gronau and D. London, PLB 253, 483 (1991) M.
Gronau and D. Wyler, PLB 265, 172 (1991)
?? eigenstate of D-meson is used (DCP). CP-even
D1 ?KK, p p CP-odd D2 ? KS p0, KS
?, KS f, KS?
??-asymmetry
for D1
? A1,2 of different signs
for D2
Additional constraint
4 equations (3 independent
), 3 unknowns
39
GLW averages
DCP K
DCP K
DCP K
40
GLW method
First evidence (3.4s) for direct CP violation in
B ? DK decays
41
Dalitz analysis (Belle)
Belle result (357 fb-1)
PRD73,112009
B??DK?
B??DK?
B??DK?
818 events
548 events
33117 events
B-
B
B-
B-
B
B
42
Dalitz analysis D0 ? Kspp decay
Statistical sensitivity of the method depends on
the properties of the 3-body decay involved
(For M2Const there is no sensitivity to the
phase ?) Large variations of D0 decay strong
phase are essential
Use the model-dependent fit to experimental data
from flavor-tagged D ?D0p sample ( gt2x105
events) Model is described by the set of
two-body amplitudes flat nonresonant term
As a result, model uncertainty in the ?/f3
measurement
43
D0 ? Kspp decay model
Doubly Cabibbo suppressed K
?-? interference
44
Dalitz analysis (Belle)
Fit parameters are x? r cos(?f3d) and y? r
sin(?f3d) (better behaved statistically than
) are obtained from
frequentist statistical treatment based on PDFs
from toy MC simulation.
easier to combine results
B??DK?
B??DK?
B??DK?
x 0.025 -0.080 y 0.170 -0.117 x 0.135
-0.070 y 0.085 -0.086
x- 0.128 -0.146 y- 0.339 -0.158 x 0.032
-0.116 y 0.008 -0.136
x 0.784 -0.295 y 0.281 -0.335 x 0.105
-0.167 y 0.004 -0.156
0.072
0.167
0.249
0.093
0.172
0.440
0.069
0.120
0.177
0.090
0.137
0.164
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sin(2f1f3) from B0? Dp decay
Decay

Use B flavor tag, measure time-dependent decay
rates
Btag ? B0
B ? D-?
Btag ? B0
CP violation
where
46
sin(2f1f3)
result (211 fb-1) hep-ex/0601018
result (357 fb-1) hep-ex/0604013
Lepton tags, D? final state
New
New
47
sin(2f1f3)
Combine partial and fully reco results and use
the R parameters from SU(3) symmetry
sin(2??) gt 0.64 _at_ 68 C.L. sin(2??) gt 0.42
_at_ 90 C.L.
30 theoretical error on rf
Frequentist confidence level
New
68 CL
sin(2f1f3)gt 0.52
sin(2f1f3)gt 0.44
90 CL
New
R0.02 from
Br(B?DS()p)/Br(B?D()p)
2?? 90o ? 43o
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D0-D0 mixing
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D0-D0 mixing
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D0-D0 mixing
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