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sin2f1 measurement with b?s penguin decays at
Belle

• Koji Hara (Nagoya University)
• for the Belle Collaboration

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• Introduction
• Measurement of time-dependent CP violation (tCPV)
  in B0?hK0
• tCPV result for B0?KSp0

3
Introduction

• tCPV measurements in B0 decays

_
w
J/?
s
?,f
B0
g
t
B0
s
_
s
K0
K0
d
Check if
/
Ssin2?1 , A 0
sin2?1 -?fS sin2?1, A 0
Extra CPV phase sin2f1?sin2f1 Hint of New
Physics
SM Anchor
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SM Contamination

• It is essential to estimate possible deviation
  from sin2f1within the SM to claim new physics.
• b?u Tree contamination
• Final state rescattering

color-allowed
color-suppresed
_ sdd penguin
_ sss penguin
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Theoretical Estimation

• hK0, fK0, KSKSKS are the Golden modes with
  the smallest expected difference from sin2f1 in
  SM
• Expected differences are mostly positive.
• For example,

Chua, talk at FPCP06, hep-ph/0605301
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(No Transcript)
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New tCPV result for B0?hKShKL
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Event Selection

• Dominant Background is ee- ? qq continuum
• ? Distinguished from signal by the Likelihood
  Ratio made with event shape variables.

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B0?hKS Signal

• Event-by-event signal fractions extracted from 3D
  Mbc-DE-LR fit.

LR?0.5
LRlt0.5
LR
h? rg Ks(pp-) 794 ? 36 ? h(2g)pp
Ks(pp-) 363 ? 21 ? h(3p)pp Ks(pp-) 100 ? 11
?rg Ks(p0p0) 103 ? 15 ?h(2g)pp
Ks(p0p0) 62 ? 9 Total 1421 ? 46
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B0?hKL Signal

• Signals are extracted from PB-LR 2D fit

Background subtracted
h?h(2g)pp KL 392 ? 37 ?h(3p)pp KL 62
? 13 Total 454 ? 39
LR
PB(GeV/c)
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B0?hK0 Result
Background subtracted
sin2f1 0.64 ? 0.10 ? 0.04 A - 0.01
? 0.07 ? 0.05

• Consistent with sin2f1
• 5.6s First observation of tCPV in b?sqq penguin

good tag
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CP Fit Results for B0?hKS, KL
hKS Background subtracted
sin2f1
good tag
hKL Background subtracted
good tag
A
errors are statistical only
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New tCPV result for B0?KSp0
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tCPV in KSp0

• b?s penguin dominant mode
• S ? sin2f1 (Possible deviation within SM
  O(0.1) )
• A Member of Kp Family
• A is important to check the sum rule
• A(Kp-)A(K0p)A(Kp0)A(K0p0)
• No primary tracks from B vertex
• Vertex reconstruction with KS trajectory

Gronau, Phys. Lett. B627, 82 (2005)
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B0?KSp0 Signal
LR?0.7
LRlt0.7

• Signal yield 515 ? 32

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Vertex Reconstruction with KS

• Extrapolate KS track to the Interaction Point
• Vertex reconstruction efficiency 33
• Events without the vertex can still be used for A
  measurement.

Ks track
p p-
IP profile
BCP vertex

• The validity is confirmed with the J/yKS as
  control sample.
• B0 Lifetime 1.503/-0.036 ps
• sin2f10.68/-0.06

J/yKS with the KS Vertexing
Raw asymmetry
good tag
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B0?KSp0 tCPV Result
sin2f1 0.33 ? 0.35 ? 0.08 A - 0.05
? 0.14 ? 0.05

• Consistent with
• sin2f1 from b?c
• the sum rule expectation
• A -0.15?0.06
• using Belle 532M A, Br and
• PDG2006 t/t0

good tag
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Summary

• tCPV in b?sqq modes are sensitive to the new
  physics
• Golden modes are fK0, hK0, KSKSKS
• New Results from Belle with 532 M BB
• Other tCPV results will be reported in the
  Plenary Talk by M. Hazumi.

B0?hK0
sin2f1 0.64 ? 0.10 ? 0.04 A - 0.01
? 0.07 ? 0.05
5.6s tCPV observation
B0?KSp0
sin2f1 0.33 ? 0.35 ? 0.08 A -
0.05 ? 0.14 ? 0.05
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(No Transcript)
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B0?hKS DE distribution
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B0?hKS,hKL Results
sin2f1 0.67 ? 0.11 A - 0.03 ?
0.07
sin2f1 0.46 ? 0.24 A 0.09 ?
0.16
errors are statistical only
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sin2f1
A
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Systematic Errors
hK0
KSp0

• dS dA dS dA
• Vertexing 0.013 0.021 0.011 0.020
• Flavor tagging 0.004 0.007 0.008 0.005
• Resolution 0.035 0.024 0.066 0.010
• Physics 0.001 0.007 0.007 0.001
• Possible Fit bias 0.007 0.005 0.009 0.004
• BG fraction 0.020 0.022 0.009 0.001
• BG dt shape 0.004 0.002 0.046 0.019
• Tag-side interference 0.001 0.024 0.001 0.043
• ----------------------------------------------
• Total 0.043 0.047 0.082 0.053