How charm data may help for f3 measurement at B-factories

1
How charm data may help for f3 measurement at
B-factories

• Alex Bondar (BINP, Novosibirsk)
• BELLE collaboration

1. Short description of the method
2. First results from Belle
3. Model uncertainties of the method
4. Model-independent approach using CP-tagged data
   from Charm Factories
5. Conclusion

2
KEKB BELLE
KEKB Collider
3
The Weak Decays of Quarks

• Coupling strength at decay vertex GFVij
• universal Fermi weak coupling GF
• Vij quark-mixing matrix elements
• CKM matrix
• unitarity VjiVjkdik
• explicit parametrization (Wolfenstein)
• complex phase leads to different b?u and t?d
  amplitudes for quarks and anti-quarks.

4
The B Unitarity Triangle
Using relation
-
-
(r,h)
5
f3 measurements

• b?u(cs) b?c(us) interference B-?DK- decays
• GLW method use CP eigenstates of D0 meson (DCP)
• ADS method use Kp- mode as common final states
  of D0 and D0
• b?u(cd) b?c(ud) interference ( B0 -B0 Mixing
  )
• sin(2f1f3) measurement via B0?D()p-

• Dalitz analysis of B- ? DK- (D ? KS p- p) decays
  to get f3 directly. (A.Giri, et. Al
  hep-ph/0303187) Independently by Belle
  (unpublished) http//belle.kek.jp/secured/dcpvrare
  /meetings/binp/020926/bondar.pdf First Belle
  measurement hep-ex/0308043

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B? D0K decay


If both D0 and D0 decay into the same final
states B? D0K and B? D0K amplitudes
interfere. Mixed state is produced Total phase
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B? D0K decay
in the case of no interference between and
Color suppression factor a2/a10.35 is estimated
from the ratio of B0? D0K0 and B? D0K
branching fractions (measured by Belle)
Use 3 body D0 decay, analyze Dalitz plot (fit
relative amplitude a and phase ?)
for B
can obtain both f3 and d separately
for B-
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D0?Kspp- decay model

• Use D0 3-body final state B?D0(D0)K?KSpp-K
• 3-body decay is parameterized by
  2-variablesm2(Ksp) m-2(Ksp-)
• Determine each D0 decay amplitudes by fitting
  relative amplitudes and relative phases.

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Effect of D0-D0 interference
10
Statistical accuracy (MC study)
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B? D0K signal with 142 fb-1

• ?Elt22 MeV
• 5.272ltMbclt5.288 GeV
• MD-1.86 GeVlt11 MeV
• cosTthrlt0.8
• Fisher discriminant Fgt-0.7
• PID(K/p)gt0.7

138 events 10712 signal 323 background
Signal selection cuts
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B? D0K, D0?Kspp- Dalitz plot
K(892) bands
68 events
70 events
D0 from B? D0K
D0 from B-? D0K- (p and p - interchanged)
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Backgrounds

• combinatorics (14)
• Fraction (together with D0) from ?E distribution
• Dalitz plot from continuum data (off-?(4S) or
  on-resonance)
• D0 from (3)
• Fraction (relative to combinatorial) from
  MD distribution
• Dalitz plot equal mixture of D0 and D0
• B decays (2 neutral, 4 charged)
• Fraction and Dalitz plot from generic MC
• Wrong particles in D0 decay (0.5)
• Fraction and Dalitz plot from B?D0K MC
• B?D0p with K/p misidentification (0.5)
• Fraction from signal ?E distribution
• Dalitz plot D0
• Flavour tagging K from combinatorics (lt0.4 at 95
  C.L. from MC)

14
Extracting f3

• Fit D0 Dalitz plots from B?D0K and B-?D0K-
  processes simultaneously with three (a, f3 and d)
  free parameters.

f3
f3
d
d
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Model uncertainty (MC study)
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Source of model uncertainty
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Model-independent approach
Preliminary
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CP-tagged events at Charm Factories
CP properties of the D states produced in the
Y(3700) are anticorrelated. If one D decaying as
CP1 other state is CP-tagged as CP-1
CP1
32,000 CP-tagged Kp- decays are expected for one
year run at CLEO-c (G.Burdman, I.Shipsey
hep-ph/0310076)
Based on this number we can estimate 8,000
KSpp- 6,000 p p- p0 1,500 KSKK-
CP-1
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Comparison with indirect measurements
Our result (68 CL)
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Conclusion

Data from Charm Factory are necessary!
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CLEO D0?Kspp- Dalitz plot analysis
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CLEO D0?Kspp- data and fit
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Event selection D? D0 p,D0?Kspp-
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Belle D0?Kspp- data and fit
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Close look to D0?Kspp- plot projections
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CLEO/Belle fit results
Preliminary
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B? D0KDalitz plot fit results (fixed a)
For fixed a0.125
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B? D0K Dalitz plot and projections
Fit result
Zero relative amplitude
68 events
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B-? D0K- Dalitz plot and projections
Fit result
Zero relative amplitude
70 events
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B? D0p signal with 142 fb-1

• ?Elt22 MeV
• 5.272ltMbclt5.288 GeV
• MD-1.86 GeVlt11 MeV
• cosTthrlt0.8
• Fisher discriminant Fgt-0.7
• PID(p/K)gt0.5

1752 events 165552 signal 1085 background
Signal selection cuts
Used as a test sample for Dalitz plot fit
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B? D0p, D0?Kspp- Dalitz plot
1752 events
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Test sample fits
Fit complex relative amplitude
Expect a 0
B? D0p (1750 events)
B? D0p (350 events)
a0.0650.020 (1-2 probability for a0),
however no CP asymmetry Need further
investigation. Stat. fluctuation can not be
excluded
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Constraints on complex D0-D0 amplitude
-
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B? D0K Dalitz plot fit results
-2 log L vs. f3
CL vs. (a, f3)
CL vs. (d, f3)
For a, f3 and d as free parameters
Two solutions (f3, d) and (f3p, dp)
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Toy MC study
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Strong phase value
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Strong phase value