Radiative and EW Penguin BDecays

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Radiative and EW Penguin B-Decays with the Belle
Detector
Tom Ziegler ? Beauty 2003 ? Pittsburgh,
Pennsylvania 13-18th Oct 2003

• Introduction
• Rare/Radiative Decays
• Purely Leptonic Decays
• Status Perspective

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Introduction and Motivation
b -gt sg and b -gt sll- decays proceed
via lflavour changing neutral current (FCNC) box
and penguin diagrams
b -gt sg penguin
BR(b-gtsg) ? 3.5 ? 10-4
Not so rare actually
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b -gt sll- penguin
b -gt sll- box

BR(b-gtsll-) ? aem?BR(b-gtsg) ? 10-6 !!!
New particles can/will contribute quite
significantly to the decay rates and various
asymmetries quite significantly via the
loops! gt Ideal testing ground for SM and
extensions (2HDM, MSSM, GUT, ?)
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The KEK-B collider
3.5 GeV e on 8 GeV e-
L gt (1.0 x 1034)/cm2/sec
? L dt 158 fb-1
Y(4S)
140 fb-1 on resonance!
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The Belle Detector
Aerogel Cherenkov Counter
? and KL detection system
3.5 GeV e
3 layer Silicon Vertex Detector
Electromagnetic. Cal.(CsI crystals)
8 GeV e-
Central Drift Chamber
1.5T SC solenoid
ToF counter
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Continuum suppression

• BB and qq have different topologies!
• Typical variables for Bkg suppression
• Modified Fox Wolfram moments
• Sphericity cos(qsph)
• Thrust, cos(qthr)
• gt Build Fisher discriminant F for correlated
  variables
• gt Form Likelihood for uncorrelated variables
  L(F,cosqB)
• gt Build Likelihood ratio LR LB / (LBLqq)

Kinematic Variables
DE EB Ebeam
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B -gt Kg

• Photon with 1.8 lt Eg lt 3.4 GeV, p0/h veto
• K(892) reconstructed in 4 final states
  Kp-, K0sp0, Kp0, K0sp with M(Kp)
  M(K)r lt 75 MeV/c2
• BKG suppression against ee- -gt qq(g) -gt
  LR(F,cos(qB))

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BR(B -gt Kg )
DE EB Ebeam
BR(B0 -gt K0g) (40.9 ? 2.1 ? 1.9) ?10-6 SM ?
(69 ? 21) ?10-6
BR(B -gt Kg) (44.0 ? 3.3 ? 2.4) ?10-6 SM ?
(74 ? 23 ) ?10-6
Based on 78 fb-1 ( ? 85 M BB-pairs)
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AIS(B -gt Kg )
Investigate Isospin asymmetry between B0 and B
BR(B0-gtK0g) BR(B-gtKg)
D0
BR(B0-gtK0g) BR(B-gtKg)
1.083 ? 0.017 PDG2002
Assumes f/f0 1! f/f0 1.072 ? 0.057
PDG2002
SM predicts (5-10)!
D0 (0.3 ? 4.5 ? 1.8)
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ACP(B -gt Kg )
In SM ACP should be smaller than 1 !
ACP 1/(1-2w) ? N(B-gtKg) - N(B-gtKg)
N(B-gtKg) N(B-gtKg)
ACP (-0.1 ? 4.4 ? 0.8)
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B -gt ? K g

• Photon with 2.0 lt Eg lt 2.7 GeV, p0/h veto
• Select 2 charged K charged/neutral K
• ? ID M(KK) M(?)r lt 10 MeV/c2
• BKG suppression against ee- -gt qq(g) -gt
  LR(F,cos(qB))

yield 21.6?5.6
DElt400MeV
B -gt fKg
B -gt fKg
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B -gt ? K g
BR(B -gt ? Kg) (3.4 ? 0.9 ? 0.4) ?10-6 -gt
5.5?
BR(B0 -gt ? K0g) (4.6 ? 2.4 ? 0.6) ?10-6 -gt
3.3? lt 8.3 ?10-6 (_at_90 C.L.)
BR(B -gt Kg) ? 10? BR(B -gt ? Kg)
B0 -gt ? K0 g is around the corner! and is a very
promising candidate for time-dependent CPV
analysis!
Based on 90fb-1 ( ? 96 M BB-pairs)
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Status of b-gtsg in Belle
Channel BR (?10-6) ?Ldt Ref.
B -gt Xs g 336 ?
53 ? 42 50/-54 6 fb-1 1 B0 -gt K0 g 40.9 ?
2.1 ? 1.9 78 fb-1 2 B -gt K g 44.0 ? 3.3 ?
2.4 78 fb-1 2 B -gt f K g 3.4 ? 0.9 ? 0.4 90
fb-1 3 B -gt Kpp- g 24 ? 5 4/-2 29 fb-1
3 B0 -gt K02(1430) g 13 ? 5 ? 1 29 fb-1 4
--------------------------------- B -gt
r g lt 2.7 (_at_ 90 C.L.) 78 fb-1 5 B0 -gt r0 g lt
2.6 (_at_ 90 C.L.) 78 fb-1 5 B0 -gt w(783) g lt
4.4 (_at_ 90 C.L.) 78 fb-1 5
Belle
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Status of b-gtsg
BaBar
Channel BR (?10-6) ?Ldt
B -gt Xs g 388 ? 36 ?
37 43/-23 54.6 fb-1 B0 -gt K0 g 42.3 ? 4.0 ?
2.2 20.7 fb-1 B -gt K g 38.3 ? 6.2 ? 2.2 20.7
fb-1 B0 -gt K02(1430) g 12.2 ? 2.5 ? 1.1 81.4
fb-1 B -gt K2(1430) g 14.4 ? 4.0 ? 1.3 81.4
fb-1
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Status of BR(b-gtsg )
B -gt K(892) g (12.5)
B -gt K2(1430) g (4)
B -gt Kp g (9)
B -gt K r g (9)
B -gt K f g (1)
Rest of b-gtsg (656)

• Kpng (ngt3)
• Baryons g (?13)
• Mode with resonances,e.g. h, h
• KKKpng (?Kfg)

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Future of b-gtsg

• Large theoretical uncertainties on BR!
• In ratios like ACP or Isospin asymmetries
  systematicuncertainties are expected to cancel
  (th./exp.)
• Current measurements are statistically
  limited!Also more modes accessible with more
  data!
• e.g. B0 -gt fK0Sg promising candidate for
  time-dependentCPV analysis!
• Energy spectrum analysis -gt transition dynamics
  (CKM)
• b-gtdg transitions not yet observed, large CPV
  effects could be expected!

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B -gt K ll- B -gt Kll-

• K charged or neutral
• K Kp-, K0sp, Kp0 with M(Kp)-M(K)rlt75
  MeV/c2
• Lepton pair e or mp(e)gt0.4 GeV/c, p(m)gt0.7
  GeV/cveto on J/Y, Y(2S)

7.61.3
yield 35.8
-6.9-1.2
7.60.9
yield 37.9
-6.9-1.1
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B -gt K ll- B -gt Kll-
BR(B -gt Kll-) (4.8 1.0/-0.9 ? 0.3 ? 0.1) ?10-7
BR(B -gt Kll-) (11.7 2.6/-2.4 ? 0.8 ? 0.4)
?10-7
Based on 140 fb-1 ( ? 152 M BB-pairs)
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Status of B -gt s ll-
Channel BR (?10-7) ?Ldt Ref.
B -gt Xsll 61 ? 14
14/-11 60 fb-1 6 B -gt Kll 4.8 1.0/-0.9 ? 0.3
? 0.1 140 fb-1 7 B -gt Kll 11.5 2.6/-2.4 ?
0.8 ? 0.2 140 fb-1 7
---------------------------------- B -gt Xsll 63
? 16 18/-15 82 fb-1 B -gt Kll 6.5 1.4/-1.3 ?
0.4 113 fb-1 B -gt Kll 8.8 3.3/-2.9 ? 1.0 113
fb-1 B -gt Knn lt 7.0 ? 10-5 (_at_90 C.L.) 51/80
fb-1
Belle
BaBar
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Status and Perspective B -gt s ll-

• Next target
• precise measurement of Xsll-
• increase precision in q2
• AFB measurement

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B0 ? ll-

gt Helicity suppressed 2-body decay in SM
BR in SM B-gtmm (1.00 ? 0.14) ? 10-10
B-gtee (2.34 ? 0.33) ? 10-15
Not observable, but enhancement by 2-3 orders of
magnitude in 2HDM or Z mediated FCNC models.
B-gtem forbidden in SM, but possible in SUSY or
Lepto-Quark models!
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B0 ? ll-

• Tight cut on leptons (e/m) L gt 0.9
• BKG suppression with LR(F,cos(qB))
• Signal box 5.27ltMbclt5.29 GeV/c2, DElt0.05GeV

DE EB Ebeam
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Status of B ? ll
Channel BR (_at_90 C.L.) ?Ldt
B-gtee lt 1.9 ?
10-7 78 fb-1 Belle B-gtmm lt 1.6 ? 10-7 78
fb-1 Belle B-gtem lt 1.7 ? 10-7 78 fb-1 Belle
Channel BR (_at_90 C.L.) ?Ldt
B-gtee lt 1.9 ?
10-7 78 fb-1 Belle B-gtmm lt 1.6 ? 10-7 78
fb-1 Belle B-gtem lt 1.7 ? 10-7 78
fb-1 Belle B-gtmm lt 2.5 ? 10-7 113
pb-1 CDF Bs-gtmm lt 9.5 ? 10-7 113
pb-1 CDF Bs-gtmm lt 16 ? 10-7 100 pb-1 D0
--------------------------------------------------
- B-gten lt 5.4 ? 10-6 60 fb-1 Belle B-gtmn lt 6.8 ?
10-6 60 fb-1 Belle B-gtmn lt 6.6 ? 10-6 81
fb-1 Babar B-gttn lt 4.1 ? 10-4 81 fb-1 Babar
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Future? B ? ll(g)
SM prediction for purely leptonic/radiative
B-decays B-gttt ? 3 ? 10-8 B-gtttg gt 3 ?
10-8 B-gtmm ? 1 ? 10-10 B-gtmmg ? few ?
10-10 B-gtee ? 3 ? 10-15 B-gteeg ? few ?
10-10 B-gttn ? 7 ? 10-5 B-gttng gt 7 ?
10-5 B-gtmn ? 3 ? 10-7 B-gtmng ? few ?
10-6 B-gten ? 7 ? 10-12 B-gteng ? few ?
10-6 Any significant increase in these BR might
give hint for new physics Some of these modes
should be accessible with the B-factories!
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What have we achieved?
Radiative B-Decays in PDG 2000 charged
modes neutral modes ------------------------------
----------------------- K(892) g (5.73.3)
10-5 (4.01.9) 10-5 K1(1270) g lt 7.3 10-3 lt
7.0 10-3 K2(1400) g lt 2.2 10-3 lt 4.3
10-3 K2(1430) g lt 1.4 10-3 lt 4.0
10-4 K(1680) g lt 1.9 10-3 lt 2.0
10-3 K3(1780) g lt 5.5 10-3 lt 1.0
10-2 K4(2045) g lt 9.9 10-3 lt 4.3 10-3 Quite
dramatic improvement in our knowledge of
radiative B-decays
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Summary

• Since last year new modes to B -gt Xsg and B -gt
  Xsll- added-gt first observation of B -gt fKg and
  B -gt Kll-
• BR and asymmetries are in good agreement with
  SM,but many results are statistically limited
• We are entering the exciting phase of precision
  measurements(e.g. AFB, q2 dependence in K()ll)
  just started
• Radiative Penguin decays are ideal testing ground
  for SM and new physics but you knew that
• Need more data to fix some of the important
  parameters inEW/radiative penguin transitions
• Many interesting discoveries are still ahead

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There are lots of them
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List of References
1 Phys.Lett. B511, 151 (2001) 2 Abs.537,
BELLE-CONF-0319 Preliminary 3 Phys.Rev.Lett 98,
231801 (2002) 4 Abs.542, BELLE-CONF-0322
Preliminary 5 Moriond 2003 Preliminary 6 PRL
90, 021801 (2003) 7 hep-ex/0309032, submitted
to PRL 8 hep-ex/0309069, submitted to PRD
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Low energy eff. Hamiltonian
Heff ? ?10i1 Ci(m)Oi(m)
G(b-gtsg) 1/32p4 G2F aem m5b VtsVtb2
(C7eff2 O(1/mb,1/mc)))
gt Access to C7
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Low energy eff. Hamiltonian
Heff ? ?10i1 Ci(m)Oi(m)
G(b-gtsg) ? VtsVtb2 C7eff2
gt Access to C7 Interesting observables BR,
ACP, g spectrum
G(b-gts??-)/ds ? VtsVtb2 O(s, C7eff2,
C8eff2 ,C10eff2 , C7effRRe(C9eff))
s q2/m2b (M(??-)/mb)2
gt Access to C7, C9, C10,
sgn(C7) Interesting observables BR, AFB, q2
distribution
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Particle ID Kinematic Variables

• K/p separation
• dE/dx from CDC
• light yield from ACC
• t from ToF
• e ID
• dE/dx from CDC
• light yield from ACC
• t from ToF
• CsI (ECL)
• m ID
• hits in KLM
• g ID
• 16X0 CsI (ECL)

Kinematic Variables
DE EB Ebeam
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