CP Violation Studies in B 0 D (*) in B A B A R and BELLE Dominique Boutigny LAPP-CNRS/IN2P3...
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Transcript of CP Violation Studies in B 0 D (*) in B A B A R and BELLE Dominique Boutigny LAPP-CNRS/IN2P3...
CP Violation Studies in CP Violation Studies in BB00DD(*)(*) in B in BAABBAAR and R and
BELLEBELLEDominique Boutigny
LAPP-CNRS/IN2P3
HEP2003 Europhysics Conference in Aachen, GermanyJuly 17-23, 2003
Dominique BoutignyHEP2003
2
Theoretical MotivationTheoretical Motivation
* *arg /ud ub cd cbV V V V
It is important to check the consistency of the CKM mechanism Over-constrain the Unitarity
Triangle Measure the angles
* *arg /cd cb td tbV V V V
W.A. Charmonium modes:sin(2) = 0.734 0.055
- CP Violation is now well established
Should measure other angles
This talk
*
*td tb
cd cb
V VV V
*
*ud ub
cd cb
V VV V
Dominique BoutignyHEP2003
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CP Violation in BCP Violation in B00DD(*) (*)
c0B
d
bu
d
*D
d
bc
d 0B
u
*D
Dominant diagram b c transition
Suppressed diagram b u transition
CP violation appearing in interference between 2 amplitudes • Final states are not CP
eigenstates• No penguin pollution
CP violation proportional to:* */ 0.020ub cd cb udr V V V V
0 (*) 3favored
0 (*) 6suppressed
BF 3.10
BF 10
B D
B D
• b u transition relative weak phase between the 2 amplitudes• Mixing 2• Relative strong phase between the 2 amplitudes
Measure sin(2+)
0B
b
d
Dominique BoutignyHEP2003
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Determination of Determination of sin(2sin(2++) from Time ) from Time Dependent EvolutionDependent Evolution
• Time evolution for D-+ final states:
0
0
--
--
cos
c
, 1B deca sin
sin
ys:
B decays: , 1- os -
td
d
d
dt
S m t
S
C m t
C m t
R D t Ne
R D t Ne m t
0
0
π ,Δ 1
π ,Δ 1
cos sin Δ Δ
sin Δ
B decays:
B dec Δ
Δ Δ
cos Δays: Δ
d d
dd
t
t
S m tR D C m t
C S m t
t N e
R mNe tD t
• Time evolution for D+- final states:
2
2
11
1rCr
2
2
2 sin 21
2 sin 20.04, 0.04
1
rSrrSr
• Similar equation for D*
Need to know both S andS to determine (2+) and There are four ambiguities in (2+) determination
Dominique BoutignyHEP2003
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Experimental Technique Experimental Technique (1)(1)
With fully reconstructed B0D(*)
– Advantages:• Small background
– But: relatively small number of events
N(D) = 5207 87Purity = 85 %
N(D*) = 4746 78Purity= 94 %
• Background mainly from combinatorics
• Peaking background mainly from B+ D(*)0+ (~1%)
BaBar
Dominique BoutignyHEP2003
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Experimental Technique Experimental Technique (2)(2)
With partially reconstructed B0D*+-
B0 +f D*-
D0 -s
X• Using:• Soft pion• Fast pion• Beam constraints
Reconstruct missing mass peaking at the D0 mass
D*
combinatoric
signal
Other peaking Continuu
m
BaBar BELLE
0B decays:
• Advantages:– More statistics:
– Lepton tag: 6406 129 events– Kaon tag: 25157 323 events
• But …– More background
Dominique BoutignyHEP2003
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Experimental Technique Experimental Technique (3)(3)
(4s)
Tag BReco B
K+
+z
K+
t z/c
= 0.56At time of BTAG decay,the 2 B’s are in opposite
flavor states
z
Coherent B0B0
production-
s
-
Fully reconstruct one Bin D or D*Vertex determined using all tracks
Or partially reconstruct one B in D*Vertex determined using the fast only and a beam spot constraint
Determine flavor of other B meson BTAG (“tagging”)Using Kaon or lepton charge correlation
Reconstruct vertex of BTAG and compute proper time difference t z/c
Dominique BoutignyHEP2003
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Difficulties (1)Difficulties (1)Determination of Amplitude Determination of Amplitude
Ratio: rRatio: r
• Simultaneous determination of sin(2+) and r(*) is not possible with the current statistics– Use B0 Ds
(*)+- (I. Dunietz, Phys. Lett. B 427, 179 (1998))
– and SU(3) symmetry
0 (*)(*)
(*) 0 (*)
( )( ) 0.02( )A B Dr D rA B D
0Bd
u
*SD
bc
0Bd
d
u
*D
bc
scsV cdVSU(3)
(*)
(*)
0 (*)
(*) 0 (*)
( )( )
S
s cd D
cs D
fBr B D VrBr B D V f
0.004 * 0.0050.005 0.007( ) 0.021 ( ) 0.017r D r D
Add another 30% systematic error for SU(3) breaking uncertainty and for missing W-exchange diagrams in calculation
BaBar – hep-ex/0207053 (2002)
Dominique BoutignyHEP2003
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Difficulties (2)Difficulties (2)b b u interference effects in u interference effects in
the tag sidethe tag side• We use b u interference
effects on the reco side to measure sin(2+)
• The same kind of interference effects exist in the tag side
(Long, Baak, Cahn, Kirkbyhep-ex/0303030, accepted by PRD)
• Induces time-dependent effect– Change the time-dependent PDFs– r and r' can be of the same order
of magnitude
• Lepton tags have no problem
• Kaon tags are affected
( , ) 1 cos( )
sin( 2 'sin(2) 2 sin(2 ) ')
td
d
R D t Ne m t
t rm r
No sine termsReco-side onlyReco-side and
tag-side
For r = r' = 0.1 ( 5 the expected value):
signal side
tag side
Dominique BoutignyHEP2003
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Re-ParameterizationRe-Parameterization• Due to the tag side b u interference effect,
one needs to change the parameters in the time dependent decay rate formulas
• a: Independent of tag side effects• b and c: absorb the tag side interferences
• For lepton tags:
2 sin(2 )cos2 'sin(2 )cos '2cos(2 )( sin 'sin ')
a rb rc r r
2 sin(2 )cos
2 cos(2 )si0
nlep
ba r
c r
Handle on phase
Define:
Dominique BoutignyHEP2003
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Fit is performed in 4 steps in order to determine the signal yield, the background contributions and the CP parameters
Time Dependent Fits in Time Dependent Fits in BaBarBaBar
Lepton tags
Lepton tags
D(*)- +
B0
D(*)- + D(*)+ -
D(*)+ -
B0
B0
B0
D*- +D*+ -
D*- + D*+ -
B0 B0
B0B0
Unbinned ML fit to t spectra: 48 parameters – 13 parameters for the a,b and c coefficients (D, D* , Kaon tags, lepton tag)
Fully reconstructed B D(*)
Partially reconstructed B D*
Dominique BoutignyHEP2003
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Results for Fully Results for Fully Reconstructed Reconstructed B B D D(*)(*)
in BaBar (1)in BaBar (1)From the fit to t spectra
From BaBar measurement of B0
DS(*)
Based on 81.9 fb-1 on-resonance events
* **
**
[ ] 2 sin(2 )cos [ ] 0.022 0.038 (stat) 0.021 (sys)[ ] 2 sin(2 )cos [ ] 0.068 0.038 (stat) 0.021 (sys)
[ ] 2 cos(2 )sin [ ] 0.025 0.068 (stat) 0.035 (sys)
[ ] 2 cos(2lep
lep
a D r D
a D r Dc D r D
c D r
*)sin [ ] 0.031 0.070 (stat) 0.035 (sys)D
* *
Vertexing 0.015 0.026Tagging 0.004 0.003Background 0.001 0.003Fit 0.014 0.0Total
23 ( ) 0.021 0
Sour
. 35
ce
0
a ca
tot
c
Systematic uncertainties
0.0040.005
0.005* 0.007
0.021
0.017
r
r
30% additional theoretical error assigned to r and r* values
Dominique BoutignyHEP2003
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Results for Fully Results for Fully Reconstructed Reconstructed B B D D(*)(*)
in BaBar (2)in BaBar (2)
Minimum at |sin (2+)| = 0.98
2 is highly non-parabolic Use a toy Monte-Carlo approach to interpret results in terms of confidence levels for |sin (2+)|
sin(2 ) 0.69@ 68.3% CL
sin(2 ) 0 excluded @ 83% CL
BaBar
BaBar
Minimize a 2 with respect to (2+), [D], [D*], r and r*
2 2
2 2 2min
C.L. sin(2 ) 1 frac( )
sin(2 )toy data
Dominique BoutignyHEP2003
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Results for Partially Results for Partially Reconstructed Reconstructed B B D D** in in
BaBar (1)BaBar (1)
*
*
[ ] 2 sin(2 )cos 0.063 0.024 (stat) 0.017 (sys)[ ] 2 cos(2 )sin 0.004 0.037 (stat) 0.020 (sys)lep
a D r
c D r
Combining lepton and Kaon results:
Deviates from 0 by 2.1
-3
Background 3.0 8.0 5.0 4.0 6.0Bkg CP content 10.0 10.0 13.0 7.0 13.0Fit 5.0 7.0 5.0 2.0 1.0Detector 10.0 10.0 10.0 6.0 10.0MC stat 13.0 13.0 8
Erro
.0 4.
r ( 10 )
Source
Total 20.0 21.00 9.0
S S a b c
19.0 11.0 20.0
Systematic uncertainties
• Lepton tag fit S andS• Kaon tag fit a, b and c
Based on 76,4 fb-1 on resonance events
Dominique BoutignyHEP2003
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Results for Partially Results for Partially Reconstructed Reconstructed B B D D** in in
BaBar(2)BaBar(2)• Interpretation in terms of C.L. using a toy Monte-Carlo approach
• Minimize a 2 to determine |sin (2+)| and
SourceKin. Var.Sideband fit
sin(2 ) 0.88 at 68.3% C.L.
sin(2 ) 0.75 at 90% C.L.
sin(
sin(2
2 ) 0.62 at 95% C.L
) 0 excluded at 98.3% L
.
C. .
0.0050.0070.017r
BaBar
Dominique BoutignyHEP2003
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Combined BaBar ResultsCombined BaBar Results• Assuming 30% theoretical
error on r(D) and r(D* )• One can also plot the lower limit on |
sin((2+)| as a function of r• In this case, r(D) = r(D* ) is assumed
sin(2 ) 0.89 @ 68.3% C.L.
sin(2 ) 0.76 @ 90% C.L.
sin(2 ) 0 excluded @ 99.5% No error on r assumed
BaBar
BaBar
Dominique BoutignyHEP2003
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Status of BStatus of B DD(*)(*) in BELLE in BELLE• Similar studies on B D(*) are being performed
by BELLE:
• For the partial reconstruction technique:– With 78 fb-1BELLE is expecting a statistical error of:
(2r.sin(21+3)) = 0.029 • For the full reconstruction technique• With the full data sample available this summer, BELLE
is expecting: (2r.sin(21+3)) =0.028
• Computed from the data• Includes background effects
• Estimated from the MC• Does not include background effects
Dominique BoutignyHEP2003
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SummarySummary• A study of time dependent CP asymmetry in B0D(*)+- has
been performed by BaBar using both partial and full reconstruction techniques
• With full reconstruction:– A limit is set at: |sin (2+)|>0.69 @ 68.3% C.L.– No limit is set at 90% CL
• With partial reconstruction:– A limit is set at: |sin (2+)|>0.75 (0.62) @ 90 % (95 %) C.L.
• Combining both methods:– |sin (2+)|>0.89 (0.76) @ 68.3 % (90%) C.L.– |sin (2+)| = 0 is excluded @ 99.5% C.L.– Limits are also set as a function of the ratio between
favored and suppressed amplitudes: r
• Similar studies are going on in BELLE, results will come soon…
Dominique BoutignyHEP2003
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Constraints in the Constraints in the , , Plane from BaBar Plane from BaBar
MeasurementsMeasurementsConstraint from sin(2+) assuming a given value of r with 30% theoretical error
Backup SlidesBackup Slides
Dominique BoutignyHEP2003
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Monte-Carlo ValidationMonte-Carlo ValidationFully Reconstructed Fully Reconstructed
MethodMethod
MC a[D] a[D*] cLEP[D] cLEP[D*]no asym.
+0.009 0.011
+0.003 0.014
-0.027 0.019
-0.029 0.024
No generated asymmetry: a=b=c=09.4x data statistics for B D and 6.9x data statistics for B D*
Generated asymmetry: a=0.04 b=c=04.6x data statistics for B D and 3.8x data statistics for B D*
No significant biases observed
MC a[D] a[D*] cLEP[D] cLEP[D*]with asym.
+0.058 0.016
+0.055 0.020
-0.006 0.028
-0.009 0.033
Dominique BoutignyHEP2003
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Monte-Carlo ValidationMonte-Carlo ValidationPartially Reconstructed Partially Reconstructed
MethodMethod
Dominique BoutignyHEP2003
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CP Asymmetry with CP Asymmetry with Partial Reconstruction Partial Reconstruction
Method in BaBarMethod in BaBarCP asymmetry
leptons
Kaons
0 0
0 0
tag tag
tag tag
B BCP
B B
N N
N N
A
Dominique BoutignyHEP2003
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Partial Reconstruction Partial Reconstruction Method Cross-Check – Mixing Method Cross-Check – Mixing
AsymmetriesAsymmetries
Dominique BoutignyHEP2003
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Measurement of BMeasurement of B00 Lifetime with Lifetime withPartially Reconstructed Partially Reconstructed B B D D** in in
BaBarBaBar • B0 lifetime has been measured in BaBar with
partially reconstructed B D* events– hep-ex/0212012 -
Phys.Rev.D67:091101,2003
B0 = 1.533 0.034 (stat) 0.038 (sys) ps
• In good agreement with World Average:B0 = 1.542 0.016 ps
Impact of a Impact of a t biast biasThe problem: if we get t wrong by t (<<1/Md)
cos(Mdt)+S sin(Mdt) cos(Mdt)+(S-Mdt)sin(Mdt)
A bias of 10m would cause a shift sin(2)=0.75
NOTE: given the sign combinations only the “c” parameters are biased
The answer: we let the t biases free in the fit and we are therefore insensitive to t
The objection: can you prove that you are insensitive to it also if the resolution function is different from your model (3 Gaussians)
The proofs:
• SVT misalignment tests: we include in the systematic error the variation due to using different misalignments in MC. They represent very different resolution function. They correspond to t<4m the scale of the possible bias is sin(2)=0.3 and it is anyhow accounted for in the error
•Toy MC test: since in our model biases are proportional to t toys have been generated with flat 10m biases. Fit results show biases c<0.005, 15% of the systematic error assigned to these parameters