CP Violation Studies in B 0 D (*) in B A B A R and BELLE Dominique Boutigny LAPP-CNRS/IN2P3 HEP2003 Europhysics Conference in Aachen, Germany July

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


3

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


4

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


5

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


6


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


7


(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


8

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)


9

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


10

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:


11

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*


12

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


13

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


14

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


15

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


16

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


17

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


18

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…


19

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


21

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


22

Monte-Carlo ValidationMonte-Carlo ValidationPartially Reconstructed Partially Reconstructed

MethodMethod


23

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


24

Partial Reconstruction Partial Reconstruction Method Cross-Check – Mixing Method Cross-Check – Mixing

AsymmetriesAsymmetries


25

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

Documents

CP Violation Studies in B 0 D (*) in B A B A R and BELLE Dominique Boutigny LAPP-CNRS/IN2P3 HEP2003 Europhysics Conference in Aachen, Germany July