Electroweak Penguin decays at Belle

1
Electroweak Penguin decays at Belle

• Akimasa Ishikawa
• KEK

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Flavor Changing Neutral Current Decays

• Flavor Changing Neutral Current decays, b?sg,
  b?sll
• Forbidden at tree level
• induced through Penguin or Box diagrams at lowest
  order
• sensitive to heavy particles (SUSY, heavy Higgs)
• Observables
• Decay Width (Branching Fraction)
• Inclusive decay, theoretically clean,
  experimentally hard.
• Exclusive decays, large uncertainty due to form
  factor
• ?test of QCD in B decays
• Ratio of Decay Width
• Some theoretical and experimental uncertainties
  cancel
• Good probe also for exclusive decays!
• CP Asymmetry
• Isospin Asymmetry
• Up-Down Asymmetry
• BF ratio of electron mode to muon mode
• Forward-Backward Asymmetry

Penguin diagram in the SM
Beyond the SM diagram
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OPE and Wilson Coefficient

• Effective Hamiltonian is expressed in term of
  Operator Product Expansion.
• O1,2 current current operator
• O3-6 QCD penguin operator
• O7,8 electro- and chromo-magnetic operator
• O9,10 semileptonic operator
• Ci Wilson coefficient
• Wilson coefficient is a strength of corresponding
  short distance operator.
• Precise measurement of Wilson coefficients is one
  of the goals for B physics.
• For b?sg and b?ll case, only O7, O9 and O10
  appear in the Hamiltonian.

New Physics changes the Wilson Coefficients
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b?sg and b?sll decays
Decay widths for b?sg and b?sll can be described
with Wilson coefficients.

? Absolute value of can be measured.

Interference terms
?Relative signs can be also determined from
interference terms!!
can be extracted from B(b?sg), B(b?sll-) and
AFB (b?sll-) !
(sometimes we do not use Ci but Ai which is
leading coefficient)
In the SM
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Branching Fraction of B?Kg

• b?sg was observed at CLEO in Kg
• K is reconstructed from 4 modes
• Kp-, Ksp0, Kp0 , Ksp
• MK - MKp lt 75MeV
• Better than 10 accurary!
• Theoretical preduction
• QCD fact. (70 ? 25) ?10-6
• LEET (68 ? 23) ?10-6
• pQCD (35 ? 10) ?10-6
• Lattice (35 ? 16) ?10-6

B(B0 ? K0g) (40.9 ? 2.1 ? 1.9) ?10-6
B(B ? Kg) (44.0 ? 3.3 ? 2.4) ?10-6
K
K2(1430)
Theoretical uncertainties are large
80/fb data
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Asymmetry in B?Kg

• Isospin Asymmetry D0 is sensitive to sign of
  Wilson coefficients C6/C7
• D0 510 and C6/C7 gt0 in the SM
• If C6/C7lt0, D0 lt0.
• Direct CPV is less than 1 in the SM
• 5 CPV is allowed in new physics

A.Kagan and M.Neubert, PLB 539, 227 (2002)
B0
B0
D0 (3.4 ? 4.4(stat) ? 2.6(syst) ?
2.5(f-/f00))
ACP (-0.1 ? 4.4 ? 0.8)
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Time dependent CPV in B?Ksp0g

• Not only the K0g, but any Ksp0g can be used for
  TCPV measurement.
• In the SM, Slt0.1, Alt0.01.
• Right handed currents induce large value of S
• S corresponds to fraction of C7R to C7L
• MKsp0 lt 1.8GeV

Atwood, Gershon, Hazumi, Soni PRD71 (2005) 076003
First Measurement
250/fb data
K
K2(1430)
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Observation of B?Khg
First Observation

• Kshg can be used for time dep. CPV measurement to
  search for right handed currents.
• B?Khg, Kshg
• h is reconstructed from gg and ppp0
• MKh lt 2.4GeV

B0
B0
250/fb data
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Observation of B?K1(1270)g
M.Gronau et al. PRL88 051802 (2002)

• B?Kpp0g final state via K1g can be used for
  up-down Asymmetry to search for right handed
  currents.
• K1(1270) is reconstructed from Kpp- and Kspp-.
• 0.6lt Mpp lt 0.9GeV (r mass region) to enhance
  K1(1270)
• Resonance components are extracted by fitting to
  the hadronic mass distribution.

First Observation
140/fb data
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Observation of B? pLg

• Baryon production via weak decay of meson
• Near threshold enhancement of di-baryon system is
  observed in B?pLp (b?s process)
• Near threshold enhancement also observed
• Fragmentation?

First Observation
Theoretical prediction 10-6
140/fb data
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Inclusive B?Xsg

• Full inclusive b?g
• Photon with Egt1.8GeV
• Veto photons from p0 and h
• Subtract continuum with off-resonance data
• Moment analysis to extract HQET parameter

ltEggt 2.289 0.026 0.035 GeV
ltEg2gt - ltEggt2 0.0311 0.0073 0.0063 GeV

• HQET parameter

used to extract Vcb and Vub
140/fb data
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BF of Inclusive B?Xsg

• Subtract b?dg assuming B(b?dg)/B(b?sg) 3.8
  0.6
• Measured BF is consistent with theoretical
  predictions.
• MH gt200GeV 95CL (M.Neubert CKM2005)
• Limit on Wilson coefficient A7
• -0.36 lt A7 lt -0.17 or 0.21lt A7 lt 0.42
• In the SM A7 -0.33 at m 2.5GeV

G.Hiller and F.Krueger PRD 69 (2004) 074020
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Exclusive B?Xsg / Inclusive b?s
K
K1(1270)
59 6.0 missing
K2(1420)
Isospin symmetry for B and K decay is assumed
Kp
Kr
Kh
Kf
Lp

• 40 of b?sg are measured exclusively.
• Next step B0?K0S0g for TCPV analysis.
• Kh, Kf0, Ka0..

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Search for B?rg wg

• b?dg process has not been observed
• Simultaneous fit to B-?r-g, B0?r0g and B0?wg
• From isospin relations
• constrain Vtd/Vts

B(B- ? r-g) 2 (t(B-)/t(B0)) ? B(B0 ? r0g)
2 (t(B-)/t(B0)) B(B0 ? wg)
B(B?(r,w)g) B(B?r-g) lt 1.4 ? 10-6
SM predictions B(B-?r-g) (0.90 0.34) ?
10-6 (Ali-Parkhomenko) B(B-?r-g) (1.50
0.50) ? 10-6 (Bosch-Buchalla)
Just above the SM prediction!!
DR form factor ratio z SU(3) breaking effect
250/fb data
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Inclusive B?Xsll

• Semi-inclusive technique
• Electron or muon pair
• Mllgt0.2GeV
• Charmonium veto
• Xs is reconstructed from K or Ks 0-4p (at most
  one p0 is allowed)
• MXs lt 2.0 GeV

Wrong flavor
MXs
q2
Theoretical preduction by Ali et al.
140/fb data
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Limit on Wilson Coefficients
P.Gambino, U.Haisch and M.Misiak PRL 94 061803
(2005)

• Clean prediction of BF of B(B?Xsll) for
  1ltq2lt6GeV2 is available.
• Combine Belle and Babar results
• Sign of C7 flipped case with SM C9 and C10 value
  is unlikely.

BF Belle Babar WA SM C7 -C7SM
q2gt(2mm)2 4.111.1 5.62.0 4.51.0 4.40.7 8.80.7
1ltq2lt6GeV2 1.50.6 1.80.9 1.600.5 1.570.16 3.300.25
C10NP
C10NP
C7 -C7SM
C7SM
MXs
q2
C9NP
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Branching Fraction of B?K() ll

• K, Ks or K(Kp-, Ksp, Kp0) ee- or mm-
• Mllgt0.14GeV
• A ratio of BF of K()mm to K()ee is sensitive to
  neutral heavy Higgs in 2HDM with large tanb. In
  the SM, the ratio is 1.00 and 0.75 for Kll and
  Kll

Prediction by Ali et al.
G.Hiller and F.Krueger PRD 69 (2004) 074020
250/fb data
Y. Wang and D. Atwood PRD68 (2003) 094016
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First look at AFB in Kll
SM

• Sign of C7C10 can be determined from
  Forward-Backward Asymmetry in Kll.
• Raw AFB in each q2 region is extracted from Mbc
  fit.
• Kll has no asymmetry, so it is a good control
  sample.
• Curves show theoretical distributions including
  experimental efficiency effect (not fitted lines!
  ).
• Both curves are in agreement with data, so far.

AFB K l l-
q2
Ali et al. Phys.Rev. D61 (2000) 074024
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Summary

• Many results for BF are consistent with the SM
• Precision of BF(b?sg) is 15 level.
• Negative A7 solution is consistent with the SM A7
  value
• Upper limit on B(B?(r,w)g) is just above the
  predictions
• Constrain Vtd/Vts
• Improved measurement of inclusive B?Xsll decay
• Sign of C7 flipped case with SM C9 and C10 values
  is unlikely
• stringent limits on C9 and C10
• Many measurements of Ratio
• Precisions of D0 (B?Kg ) are 5 level
• Towards sign of (C6/C7).
• Time dep. CPV in B?Ksp0g is measured for the
  first time
• Search for right handed component in C7
• First look at Forward-Backward Asymmetry in
  B?Kll
• Will be used for measurement of A9 and A10
• New results will be presented at Lepton Photon
  05.
• Stay tuned

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Backup Slides
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AFB at Super Belle

• 1 year running at 5x1035/nb/sec
• ? 5/ab integrated luminosity, 10 billion B
  mesons!!
• We have accumulated 0.46/ab, about x10
• DA9/A911, DA10/A1013
• A7 fixed to SM value
• systematic error is not included

AFB Kll with 5/ab
Donut B(B?Xsll) with140/fb
C10NP
Belle Toy MC with 5/ab
C9NP