Baryonic B Meson DecaysBaryonic B Meson Decays

IntroductionCharmless decaysCharmed decays Summary

Min-Zu Wang (王名儒 )National Taiwan University

2006/07/03 BEACH2006

1997: first exclusive measurement of BcpX (X= , ) by CLEO

2001: first observation of charmless B+ppK+ by Belle

2002: observation of cpX (X=,) by Belle, CLEO, D(*)0pp by Belle

2003: first observation of 2-body decay: B0cp (Belle), first

evidence of J/p (BaBar)

2004: first observation of b→s penguin in baryonic B decays

by Belle: B+p

2005: doubly charmed baryon modes Bcc, BccK by Belle

Introduction - Review

2006/07/03 BEACH2006

First Observation of Charmless Baryonic B Decays B+ ppK+

First Observation of Charmless Baryonic B Decays B+ ppK+

PRL 88, 181803 (2002)

BF(3-body) >> BF(2-body)

With charmonium veto

PRD 65091103(2002)

( )

2006/07/03 BEACH2006

New type of B Decays:New type of B Decays:

Peak at Low Mass

Possible explanations Baryon form factor? Quasi 2-body Decay? glueball baryonium Fragmentation?

KppB

fJ(2220)?

Phase-space MC

2006/07/03 BEACH2006

Threshold EnhancementThreshold Enhancement

PLB 617, 141-149, 2005

ppK+ ppK0S

p-

Glueball is ruled out

2006/07/03 BEACH2006

Angular distribution: ppK+

bs dominant processFragmentation picture

p

p

K+ӨpX

Proton against K- (p against K

+) : flavor dependence!

ppK signal

2006/07/03 BEACH2006

Information from the ppK+Dalitz plot Information from the ppK+Dalitz plot

•The lower bands shown in the plots are J/psi and eta_c.

•Asymmetry near threshold of ppbar indicates flavor dependence

•Anti-proton moves slower in parallel with proton

PRD72 051101 (2005)

2006/07/03 BEACH2006

dominant decay diagram

Decay diagrams of Decay diagrams of J/ΨJ/Ψ to baryon pair to baryon pair

042.0036.0676.0 Latest BES result :

θαθd

dN 2cos1cos

< λ1 λ2|U|JM> = AJ λ1 λ2 links DJM λ1- λ2 (θ,φ)

2006/07/03 BEACH2006

Fit cosθ ( J/Fit cosθ ( J/ → p p) → p p)Fit cosθ ( J/Fit cosθ ( J/ → p p) → p p)

Likelihood fit

B= -0.60 ± 0.13 (stat) ± 0.14 (syst)

pp

= 0.43 ± 0.13 (stat) ± 0.14 (syst)

L = e-(Ns+Nb)/N! [NsPs(Mbci , Ei)(cos)P(cos)+NbPb(Mbci , Ei)]

(cos) - normalized efficiency, P(cos) =

(1+cos2)/(2+2/3)

signal

χ2 fit

2006/07/03 BEACH2006

Pentaquark search in ppKsPentaquark search in ppKs

Θ+(1540) : uuddsΘ+ K+n Θ+ K0 p

B0 Θ+ pB0 ppK0, B ppKsSearch for B signal with a 20 MeV pKs mass window cut at 1540MeV

dduu s

Θ+ K+ n

d du

uud

p

ds

K0

Θ+

uudsd

2006/07/03 BEACH2006

Pentaquark search in ppKsPentaquark search in ppKs

Fixed background shape from sideband data

Count the events in signal region and compare with background estimation

BF product upper limit < 2.3 x10-7 at 90% C.L.

2006/07/03 BEACH2006

B+pΛγ (b sγ) B+pΛγ (b sγ)

PRL 95, 061802, 2005Simultaneous fit on BpΛγ and BpΣ0γSignal Yield for BpΛγ with MpΛ<2.4GeV/c2: 34.1

Statistical Significance: 8.6σ

BF(BpΛγ )(2.16 ± 0.20)x10-6

BF(BpΣ0γ):<4.6 x 10-6

140fb-1

pΛγSignal

+7.1- 6.6

+0.58- 0.53

bsγ MC

Not bremstrahlung

2006/07/03 BEACH2006

Photon energy and Angular distributionPhoton energy and Angular distribution

Fit results in bins of cosθX with MpΛ<4.0GeV/c2

(Assuming XpΛ, calculated in X rest frame.) Λ

γ

p

θx

bsγ MCSignal Yield

qq backgroundSignal Yield

Lab frame X frame

2006/07/03 BEACH2006

ggb b s s

s s s s B+ΛΛK+B+ΛΛK+

PRL 93,211801, 2004PRL 93,211801, 2004

+6.5- 5.1

+0.90- 0.70

First observation of bs s s baryonic decay

Signal Yield in 2D fit: 19.9Efficiency: 4.0%-6.9%Statistical Significance: 7.4σ

BF:(2.91 ± 0.38) x 10-6

1.1. First Charmless B decay First Charmless B decay with two with two ΛΛ! !

2.2. Threshold enhancement Threshold enhancement again.again.

3.3. Compliment to BCompliment to BφφKK(*)(*)

(b(bsss penguin)sss penguin)

1.1. First Charmless B decay First Charmless B decay with two with two ΛΛ! !

2.2. Threshold enhancement Threshold enhancement again.again.

3.3. Compliment to BCompliment to BφφKK(*)(*)

(b(bsss penguin)sss penguin)

140fb-1

threshold peaking

2006/07/03 BEACH2006

Observation of ηηcc Λ Λ Λ Λ Observation of ηηcc Λ Λ Λ Λ

new

Ratio for baryon quark-diquark model check

hep-ex/0606022

2006/07/03 BEACH2006

Observation of B+c+c

-K+ Observation of B+c+c

-K+

Unexpected large rate considering the limited phase sapce

Threshold effect?

Hep-ex/0508015

c+ pK-π+ signal

BF(B+c+c

-K+ ) = (6.5 ± 1.1 ± 3.4) × 10-4+1.0-0.9

2006/07/03 BEACH2006

CKM(cc)=VcbVcs* <-> CKM(cp)=VcbVud*

cc 10-3 >> cp 10-5

Observation of B cc

Enhancement for smaller Q ?

Hep-ex/0510074

B+ c0c

+ B0 c-c

+

c π 1%

2006/07/03 BEACH2006

Observation of J/p Observation of J/p

J/p J/ppPRD72 051105 (2005)

2006/07/03 BEACH2006

Search for inclusive Λc+ production in

tagged B sample

Search for inclusive Λc+ production in

tagged B sample

N(B+) = 200359± 705

N(B0) = 110735± 424

2006/07/03 BEACH2006

Determination of BF(B Λc+ X)Determination of BF(B Λc

+ X)

hep-ex/0606026Useful for the understanding ofthe charm counting problem in b decays

BF(B- -> Λc+ X) =(2.8±0.5±0.3 )%

BF(B0 -> Λc+ X) =(5.0±1.0±0.5 )%

BF(B- -> Λc+ X) =(2.1±0.5±0.2 )%

BF(B0 -> Λc+ X) =(1.6±0.9±0.2 )%

+1.0-0.6+1.8-1.0+0.8-0.4+0.6-0.3

2006/07/03 BEACH2006

2006/07/03 BEACH2006

2006/07/03 BEACH2006

SummarySummary

Exclusive baryonic B decays: Well established after few years of B-factory running

BF(2-body) < BF(3-body) < BF(4-body) BF(2-body) < BF(3-body) < BF(4-body)

Threshold enhancement in the baryon-Threshold enhancement in the baryon-antibaryon systemantibaryon system

Searching ground for exotic statesSearching ground for exotic states

Good crosscheck for baryonic Good crosscheck for baryonic charmonium decayscharmonium decays

More results will be shown this summerMore results will be shown this summer