Constraint on CKM angle f2 from B decays

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Constraint on CKM angle f2 from B decays
PANIC05 Particles and Nuclei International
Conference Oct. 24-28, 2005, Santa Fe, NM, USA

• A. Kusaka (University of Tokyo),
• on behalf of Belle collaboration

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So, why f2 ?
Essential to check the standard KM model.
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Contents

• Principle
• CP violation measurement
• Event selection
• CPV measurement of B0?pp
• CPV measurement of B0?rr
• Polarization
• Time dependent fit
• Constraint on f2
• Penguin pollution
• Isospin analysis

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CKM triangle and f2
f2
VtdVtb
VudVub
f1
f3
VcdVcb
Vtb
Vtd
Vud
B0 ? pp-
Vub
B0 ? rr-
Vtb
Vtd
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CP violation measurement
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Data used
253/fb

253/fb (275M BB) until 2004 summer is used.
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Event selection

• Event reconstruction
• p0, r reconstruction (rr)
• PID (K/p separation)
• Continuum suppression (modified SFW, flavor
  tagging information)

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CPV measurement of B0?pp
Spp ?0.67 ?0.16?0.06
App 0.56 ?0.12?0.06
good tag
4s evidence of Direct CPV!
Will be published as PRL 95, 101801
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CPV measurement of B0?rr

• Differences from B0?pp
• Good point
• Small branching fraction of B0?r0r0 (lt1/20)
  compared with B0?rr- and B?rr0.
• ?small penguin pollution
• Bad (difficult) points
• Decay product contains two p0
• ?lower efficiency, larger BG
• Consists of three polarization states
• ?polarization measurement is essential

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Polarization

• B0?rr has 3 polarization states with different
  CP eigenvalues

Transverse
Longitudinal
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Time dependent fit
Good tag
q1
q-1
Number of events
MBC (GeV)
DE (GeV)
poor tag
good tag
No CP violation
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Comparison with BaBar
Belle 275M BB
BaBar 227M BB
232M BB
Difference from Belle is 2.3s
Results are consistent with each other.
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Constraint on f2
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Penguin pollution

Mixing diagram

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Isospin analysis (how to get k)

• BF and asymmetries World average (HFAG)
• Ahh and Shh Belle measurement above.

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Situation of B?pp
Due to the large App, one of the triangles
are squeezed.
at 1s
at 90 C.L.
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Situation of B?rr
Due to the small Br of B0?r0r0, both of
two triangles are squeezed.
at 1s
Good determination of f2 (with only two mirror
solutions)
at 90 C.L.
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Combined result from Belle
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Summary

• This summer, we released new CPV measurement of
  B?rr.
• Combining B?pp and B?rr, we constrain
  f29312-11? for 1s.
• The value from direct measurements is consistent
  with that from indirect measurements.

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(No Transcript)
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Isospin analysis

• With the amplitudes and asymmetries of three
  charged modes, f2eff-f2 can be measured.
• Branching fraction and asymmetries World average
  (HFAG)
• Ahh and Shh Belle measurement above.

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• chi2 of isospin analysis.
• pp 0.35
• rr 0.60
• combined 1.15