B Decays to Open Charm (an experimental overview)

1
B Decays to Open Charm(an experimental overview)

• Yury Kolomensky
• LBNL/UC Berkeley
• Flavor Physics and CP Violation
• Philadelphia, May 18, 2002

2
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, cant 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

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b?ccd decays BgD()D()
( )
? -?eff sin2ßsin(?m?t)
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First Things First Observation of BgD()D()

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

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Summary of BF Measurements
BaBar
Significance BF (?10-4)
CLEO (9 fb-1) BaBar (20 fb-1) Belle (20 fb-1) 6s gt6s 5s
CLEO (10 fb-1) BaBar (20 fb-1) Belle (30 fb-1, new) Belle (partial reco) 3s 4.3s 7s
CLEO (9 fb-1) 2s
Belle
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Difficulties for CP Analysis

• DD final states are not CP eigenstates

D
D
B0
D _
D _
strong phase
CP conjugation
D _
D _
B0
D
D

• DD- 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

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Transversity Analysis for B0gDD-
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
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CP asymmetry in DD- and DD-

• BaBar 1999-2001 data sample 56fb-1 on U(4S)
• Fit for Sf and Cf
• Separate Sf and Cf for DD- and D-D.

DD Ntag 76 Purity 80
DD Ntag 85 Purity 52
DD S - 0.05 ? 0.45 ? 0.05 C
0.12 ? 0.30 ? 0.05 DD 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
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B-gD()0K()- Decays Motivation
Potential for measuring CKM angle g

• Determine g through amplitude relationships (up
  to discrete ambiguities)
• Gronau Wiler Dunietz (1991)

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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
hp
hK
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BF Results
CLEO (3 fb-1) BaBar (55 fb-1, non-CP modes, new) BaBar (55 fb-1, CP modes, new) Belle (10 fb-1) (5.51.40.5) (8.310.350.13) (8.42.00.8) (7.90.90.6)
Belle (10 fb-1) (6.81.50.7)
Belle (10 fb-1) (7.81.90.9)
Belle (10 fb-1) BaBar (20 fb-1, partial reco) (7.41.50.6) (6.61.30.6)
CLEO (9 fb-1) (6.11.61.7)10-4
CLEO (9 fb-1) (3.71.51.0)10-4
CLEO (9 fb-1) (7.72.22.6)10-4
CLEO (9 fb-1) (3.81.30.8)10-4
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Decays into D0CP

• Belle 29.1fb-1 sample (preliminary, 2002)
• Measure amplitude asymmetries for 3 samples
• Df flavor eigenstate D0gK-p (control sample)
• D1(DCP1) CP eigenstates D0gK-K and D0gp-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(DCP1) CP eigenstate D0gK-K

Strong phase difference
Measure
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Direct CP Asymmetry in BgDK
Mode Expt ACP
BgDf K Belle (new) BaBar (new)
BgD1 K Belle (new) BaBar (new)
BgD2 K Belle (new)
Belle
Belle
Belle
BgD1 K
BgD2 K
BgDf K
DE
DE
DE
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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)
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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
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Color-Suppressed Modes Results
Mode Experiment Significance BF (?10-4) Prediction() (?10-4)
B0gD0p0 CLEO (9 fb-1) Belle (21 fb-1) 12.1 7.9 0.7
B0gD0p0 CLEO (9 fb-1) Belle (21 fb-1) 5.9 3.2 1.0
B0gD0w Belle (21 fb-1) 4.7 0.7
B0gD0w Belle (21 fb-1) 4.3 1.7
B0gD0h Belle (21 fb-1) 3.8 0.5
B0gD0h Belle (21 fb-1) 3.6 0.6
B-gD0p- CLEO (9 fb-1) 48
B0gD-p CLEO(9 fb-1) 30
B0gD()-a1 BaBar (21 fb-1), partial reco 116
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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

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Vub-suppressed Decay B0gDS()p-

• Motivation measurement of sin(2??) using B0
  ? D()?
• Requires amplitude decomposition B0 ? D()?-
  and B0 ? D()-?
• Need to measure

Cabibbo-suppressed BR not known
Cabibbo-allowed BR0.00300.0004
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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 ?)
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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 ? f p ) (
1.11 ? 0.37 ? 0.24 ) ? 10-6 BF(B0 ? Ds p- ) lt
4.3 ? 10-5 _at_ 90 CL
Belle (21.3 fb-1) BF( B0 ? Ds p- ) lt 11 ? 10-5,
BF( B0 ? Ds K- ) lt 7 ? 10-5
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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

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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