Recent results on
BÆ X(s)γ and B ÆX(s)l+lMeasurements with Belle
M. Iwasaki
University of Tokyo
For the Belle Collaboration
特定領域「質量起源と超対称性物理の研究」

Introduction (I)•bÆsγ, bÆsll : FCNC processes
In SM, FCNC are forbidden at tree level•Lowest order diagram : One-loop Penguin or Box
bÆsγ in the SMbÆsll in the SM

Introduction (II)•Sensitive to New Physics
Æ Branching fraction, Acp,
Kinematical distributions q2, AFB-----------------------------In this talk, we’ll show1) Exclusive BÆK*(892)γ(Br, ∆0+ , Acp)
2) Inclusive BÆXsγ(Br, Eγ spectrum)3) Exclusive BÆK(*)l+l(Br, q2 spectrum)4) Semi-inclusive BÆXsl+l- (Br, Mll and Mxs spectrum)

Belle Detector

γ energy resolution σE/E = 1.5% (at E=2.5GeV)Electron ID P>500MeV, ε=91%, fake rate = 0.2%
Muon ID
P>1.0GeV, ε=83%, fake rate = 1.5%

Belle Luminosity>200fb-1!!

Record : 818.8pb-1/day

peak 1.20x1034/cm2/sec

Exclusive BÆK*(892)γAnalysis of BÆ K*γ
 Reconstruct K* from K+π0 ,Ks0π+,K+π-,Ks0π0 Main Background … continuum Used data sample

Æ 78 fb-1 (submitted to PRD) Theoretical prediction by
S.W.Bosch and G.Buchalla (2002).7−6Br ( B → K * γ ) = [70.9 +−24]×1022.7BÆK*(892)γ results (I)Belle 78fb-1Br(B0ÆK*0γ) = (40.1 ± 2.1 ± 1.7) x 10-6
Br(B+ÆK*+γ) = (42.5 ± 3.1 ± 2.4) x 10-6
Isospin asymmetry∆0+ = [(τB+/τB0)Br(B0) – Br(B+)] / [(τB+/τB0)Br(B0) + Br(B+)]= +0.012 ± 0.044 ± 0.026

BÆK*(892)γ results (II)Partial rate asymmetry
Acp = 1/(1-2ω) x[N(B)-N(B)]/[N(B)+N(B)]ω: wrong-tag fraction
0.9% for the neutral mode
negligible for the charged

Acp (BÆK*γ) = -0.015 ± 0.044 ± 0.012

Belle 78fb-1

BÆK*(892)γ results (III)Inclusive BÆXsγ
Analysis of BÆ K*γ

 Fully inclusive reconstruction: see only the γ spectrum

1) Measure Eγ spectrum (single high-energy photon)
2) Continuum suppression based on the event shape3) π0/η veto

 Huge BG … Subtract BG Eγ spectrum

γ from Continuum estimated by off-resonance dataγ from π0/η in BB estimate the Eγ spectrum by on- andoff-resonance data Eγ > 1.8 GeV(CLEO… 2.0GeV BaBar … 2.1GeV)
Æ reduce theoretical model error
 Used data sample Æ 140 fb-1 (submitted to PRL)BÆXsγ results (I)Belle 140fb-1

Subtract BG
ε correction

Br (b → sγ ) = (3.59 ± 0.32+0.30 +0.11− 0.31 − 0.07) × 10 −4Eγ = 2.289 ± 0.026 ± 0.034(GeV )Eγ2− Eγ

2= 0.0311 ± 0.073 ± 0.063(GeV 2 )BÆXsγ results (II)bÆsll measurements•b->sγ vs b->sll
bÆsγ

bÆsll

Br is low (bÆsγ: 10-4 bÆsll: 10-6)
Exists the contribution from Z0
Have Additional operator
with q2(=mll2) dependenceÆ q2 distribution, AFB(q2).. Sensitive to the New Physics

AFB (K* l+ l- )SMSUSY(C7>0)

Ali et al. PRD61 (2000) 074024

()+Exclusive BÆK * l l
Analysis of BÆ K(*)l+l- (l=e,µ) Reconstructed hadron system… K+, Ks0, K*+(K+π0 ,Ks0π+), K*0 (K+π-) Backgrounds

J/ψeliminated by J/ψ vetol+νX, l-νX
dominant source
Single lepton misID small
Double lepton misID small but peaked BG source
studied with Kh+h- data

 Used data sample … 140 fb-1 (PRL91(2004)012002)BÆK(*)ll Results (1) PRL90(2003)021801
3.6σ

4.6σ

4.4σ

5.6σ

5.9σ

7.4σ

Belle (140 fb-1)
Fits to Mbc after ∆E cutBÆK(*)ll Results (2)Combining Modes (Average Branching Fractions)

Isospin symmetry for K+ vs. K0
Lepton universality is assumed for Kll
B(BÆK*ee)/B(BÆK*µµ) = 1.33 (Ali et al. 2002) (due to the photon pole)Br ( B → Kll ) = 4 .8 +−10..09 ± 0 .3 ± 0 .1 × 10 −7
Br ( B → K *ll ) = 11 .5 +− 22..46 ± 0 .7 ± 0 .4 × 10 − 7 First measurement!

q2(=mll2)distributions : consistent with SM

Results BÆK(*)ll

Consistent with the predictions.
Kll : Error is already comparable to the theoretical error.
K*ll : First measurement!!

Semi-inclusive BÆXsl+lAnalysis of BÆ Xsl+l- (l=e,µ) Reconstructed Xs system…1 (K+ or Ks0) + 0-4π (at most 1π0)
 Backgrounds
Dominant sources … 1) continuum 2) BBÆl+νX + l-νX Best candidate selection: LR(∆E, cosθB) Used data sample … 60.1 fb-1 (PRL90(2003)021801)
 Ali et al.

SM prediction (Mll>0.2GeV)
Br(BÆXsll) = (4.2 ± 0.7) x 10-6

Belle (60.1 fb-1)
Mbc unbinned likelihood
fits, after all cutsBÆXsll results ( PRL90 (2003)021801 )60.1 net signal, significance 5.4σ, Ave. of e+e-, µ+µ−

Br ( B → Xsll ) = [6.1 ± 1.4 +−11..14 ] ×10 −6

The result is in agreement with SMBÆXsll results (II)Both Belle and BaBar results are consistent with SM

Summary

With the world highest luminosity provided by KEKB,
Belle is continually updating the results.

Exclusive BÆ K*γ (78pb-1)

Measure partial-rate asymmetry ACP andsubmitted to PRD
isospin asymmetry ∆0+Inclusive BÆXsγ (140pb-1)
Fully inclusive method Eγ>1.8GeV
submitted to PRL

Exclusive BÆK(*)ll (140pb-1)
First observation of K*llpublished in PRL

Semi-inclusive BÆXsll (60fb-1)
First observation of inclusive BÆ Xsll
published in PRL & updat with 140fb-1 soon