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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

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b decays to open charm an experimental overview

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
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

b ccd decays b g d d

D(*)-

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

bccd decays: BgD(*)D(*)

( )

-ηeff sin2βsin(ΔmΔt)

Yury Kolomensky, Open Charm Decays

first things first observation of b g d d
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

summary of bf measurements
Summary of BF Measurements

BaBar

Belle

Yury Kolomensky, Open Charm Decays

difficulties for cp analysis
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 b 0 g d d
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
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 g d 0 k decays motivation
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
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
BF Results

Yury Kolomensky, Open Charm Decays

decays into d 0 cp
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 b g dk
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
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
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
Color-Suppressed Modes: Results

Yury Kolomensky, Open Charm Decays

interpretations
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

v ub suppressed decay b 0 g d s p

A(B0D(*-) +)

D(*) =

A(B0 D(*+) -)

~0.02

SU(3)

A(B0D(*-)+)

A(B0Ds(*-)+)

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

evidence for b 0 d s p

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
Evidence for B0 Ds(*)+ p-

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

evidence for b 0 d s p1

14.9  4.1 events

D- r+

D- p+

Evidence for B0 Ds+ p-

B0DS+*-

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

b 0 d s p unofficial interpretation
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
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