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## B Decays to Open Charm (an experimental overview)

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### B Decays to Open Charm(an experimental overview)

Yury Kolomensky

LBNL/UC Berkeley

Flavor Physics and CP Violation

Philadelphia, May 18, 2002

Contents of This Talk

- Focus on recent results, in particular “rare” modes, accessible with high statistics samples at CLEO, Belle, and BaBar
- Due to time constraints, can’t cover the plethora of modes and measurements shown on the front page
- Topics:
- BgD(*)D(*) : Cabibbo-suppressed: BF, Angular analysis, CPV
- BgD(*)K : Cabibbo-suppressed: potential for g
- Color-suppressed open charm decays B0gD0(*)X0
- B0gDS+(*)p- : Vub-suppressed

Yury Kolomensky, Open Charm Decays

D(*)-

( )

B0

B0

D(*)+

D(*)+

_

CP

- Complementary to J/Y KS (bgccs)
- Potential sensitivity to New Physics
- But: Cabibbo-suppression, penguin
- pollution, angular structure

mixing

decay

bccd decays: BgD(*)D(*)( )

-ηeff sin2βsin(ΔmΔt)

Yury Kolomensky, Open Charm Decays

First Things First: Observation of BgD(*)D(*)

- First observation: CLEO, PRD 62, 032005 (2000)
- 9.7M B decays
- 8 signal events
- 6s observation

Yury Kolomensky, Open Charm Decays

Difficulties for CP Analysis

- D*D final states are not CP eigenstates:

D+

D*+

B0

D _

D*_

strong

phase

CP

conjugation

D*_

D _

B0

D+

D*+

- D*+D*-is not an eigenstate either: it is a combination of

CP-odd and CP-even amplitudes.

- Measure CP content through angular (transversity)

analysis for decay products

Yury Kolomensky, Open Charm Decays

Transversity Analysis for B0gD*+D*-

The angular distribution as

a function of one angle,qtr:

Where Rt is a fraction of P-wave (CP-odd)

component

BaBar Results:

Rt = 0.22 0.18 0.03

signal fit

background fit

Yury Kolomensky, Open Charm Decays

CP asymmetry in D*+D*- and D*+D-

- BaBar 1999-2001 data sample: 56fb-1 on U(4S)
- Fit forSfandCf
- SeparateSfandCfforD*+D-andD*-D+.

D*D*

Ntag = 76

Purity = 80%

D*D

Ntag = 85

Purity = 52%

D*D*

S = - 0.05 0.45 0.05

C = 0.12 0.30 0.05

D*D

S+- = - 0.43 1.41 0.20

C+- = 0.53 0.74 0.13

S-+ = 0.38 0.88 0.05

C-+ = 0.30 0.50 0.08

Expect 10-fold increase in statistics over the next 4 years

Yury Kolomensky, Open Charm Decays

B-gD(*)0K(*)- Decays: Motivation

Potential for measuring CKM angle g:

- Determine g through amplitude relationships (up to discrete ambiguities)

Gronau &Wiler; Dunietz (1991)

Yury Kolomensky, Open Charm Decays

Experimental Challenges

- Rate suppressed by about factor of 10 compared to favored mode B-gD0p-
- Small BF
- Need to reconstruct D0 into a CP eigenstate (another Cabibbo penalty)
- Particle identification crucial

(BaBar preliminary)

BgDh, DgKK

BgDh, DgKp

h=p

h=K

Yury Kolomensky, Open Charm Decays

BF Results

Yury Kolomensky, Open Charm Decays

Decays into D0CP

- Belle: 29.1fb-1 sample (preliminary, 2002)
- Measure amplitude asymmetries for 3 samples:
- Df : flavor eigenstate D0gK-p+ (control sample)
- D1(DCP=+1): CP eigenstates D0gK-K+ andD0gp-p+
- D2(DCP=-1): CP eigenstates D0gKSp0,KSh, KSh’,
- KSf, KSw
- BaBar: 55 fb-1 sample (preliminary, 2002)
- Df : flavor eigenstate D0gK-p+ (control sample)
- D+(DCP=+1): CP eigenstate D0gK-K+

Strong phase

difference

Measure

Yury Kolomensky, Open Charm Decays

Direct CP Asymmetry in BgDK

Belle

Belle

Belle

B±gD1 K±

B±gD2 K±

B±gDf K±

Yury Kolomensky, Open Charm Decays

DE

DE

DE

Color-Suppressed Open Charm Decays

Test of factorization in Class II BgMcL0 decays

“Naïve” Factorization:

Class I (color-allowed)

a1 and a2 two phenomenological

(but mode-independent) real parameters that can be determined from data

(e.g. Neubert & Stech, hep-ph/9705292)

Class II (color-suppressed)

Yury Kolomensky, Open Charm Decays

Color-Suppressed Modes: the Data

B0gD0p0

- Recent measurements of color-suppressed and color-favored BgDXlight modes
- CLEO observation of B0gD(*)0p0 (2001)
- Belle observation of B0gD(*)0p0, B0gD(*)0w, B0gD(*)0h (2001)
- CLEO new measurements of color-allowed BgDp
- BaBar new measurement of B0gD(*)-a1+

B0gD0w

Yury Kolomensky, Open Charm Decays

Color-Suppressed Modes: Results

Yury Kolomensky, Open Charm Decays

Interpretations

2 independent isospin amplitudes:

and with non –zero phase

difference

CLEO analysis (2002, preliminary):

(CLEO data)

(CLEO and Belle data)

(similar analysis: Neubert & Petrov, hep-ph/0108103)

- Non-zero strong phase differences: violates the basic assumption
- of naïve factorization. Sizable final-state rescattering effects in
- Class II processes

Yury Kolomensky, Open Charm Decays

D(*) =

A(B0 D(*+) -)

~0.02

SU(3)

A(B0D(*-)+)

A(B0Ds(*-)+)

Vub-suppressed Decay B0gDS+(*)p-- Motivation: measurement of sin(2+) usingB0 D(*)
- Requires amplitude decomposition B0 D(*)+-andB0 D(*)-+
- Need to measure

Cabibbo-suppressed

BR not known

Cabibbo-allowed

BR=0.0030±0.0004

Yury Kolomensky, Open Charm Decays

Measurement of the parameterlDp

s

BF (B0 D- p+)

fDs2

BF (B0 Ds+ p-)

l2Dp

u

cos2qC

fD2

b

- Reconstructed Ds+ modes
- DS+ fp+ , K*0K+ , KSK+, DS*+gDS+g
- f K+K-, K*0 K-p+ , KS p+p-
- Background rejection
- helicity angle (for Ds+ fp+ , K*0 K+ modes)
- Fisher discriminant
- cosqthrust
- Dsp vertex probability
- (DE , mES) of the reconstructed B

BaBar, 2002, 56 fb-1

Ds+

c

p-

B0

d

d

Also: potential for measuring

Vub/Vcb through ratios

Kim et al, PRD 63, 094506 (2001)

(shaky theoretical grounds ?)

Yury Kolomensky, Open Charm Decays

D- r+

D- p+

Evidence for B0 Ds+ p-B0DS+*-

B0 Ds+p-:

significance of the signal = 3.5 s

B0 Ds*+p-:

significance of the signal = 2.2 s

BaBar Preliminary

BF( B0 Ds+p-) = ( 3.1 1.0 1.0 ) 10-5

BF( B0 Ds+p-) BF(Ds+ fp+ ) = ( 1.11 0.37 0.24 ) 10-6

BF(B0 Ds*+p- ) < 4.3 10-5 @ 90% CL

Belle (21.3 fb-1):BF( B0 Ds+p-) < 11 10-5, BF( B0 Ds+K-) < 7 10-5

Yury Kolomensky, Open Charm Decays

B0 Ds+ p- : Unofficial(*) Interpretation

(*)Riccardo Faccini, private communication

Assuming SU(3) symmetry:

- What is SU(3) uncertainty ?

Assuming naïve factorization (a la Kim et al) and using PDG value for BF(B0gDSD*):

- Experimental error 0.023: but is 15%theoretical uncertainty reliable ?
- Need theoretical guidance

Yury Kolomensky, Open Charm Decays

Outlook

- Interesting new data coming from (old and new) B factories
- Helicity structure and first CP asymmetries in BgD(*)D(*)
- First measurements of direct CP asymmetries in BgDK
- First observations of color-suppressed decays open charm decays
- First evidence for B0 Ds+ p-
- More on the way: ten times more data at both BaBar and Belle by 2005

Yury Kolomensky, Open Charm Decays

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