Baryonic b meson decays
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Baryonic B Meson Decays. Min-Zu Wang ( 王名儒 ) National Taiwan University. Introduction Charmless decays Charmed decays Summary. Introduction - Review. 1997: first exclusive measurement of B   c pX (X=  ,  ) by CLEO 2001: first observation of charmless B + ppK + by Belle

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Baryonic B Meson Decays

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Baryonic b meson decays

Baryonic B Meson Decays

Min-Zu Wang (王名儒)

National Taiwan University

Introduction

Charmless decays

Charmed decays

Summary


Baryonic b meson decays

Introduction - Review

  • 1997: first exclusive measurement of BcpX (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: B0cp (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 Bcc, BccK by Belle

BEACH2006


First observation of charmless baryonic b decays b ppk

First Observation of Charmless Baryonic B Decays B+ ppK+

With charmonium veto

PRL 88, 181803 (2002)

)

(

PRD 65

091103

(2002)

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

BEACH2006


New type of b decays

Peak at Low Mass

Possible explanations

Baryon form factor?

Quasi 2-body Decay?

glueball

baryonium

Fragmentation?

New type of B Decays:

fJ(2220)?

Phase-space MC

BEACH2006


Threshold enhancement

Threshold Enhancement

  • PLB 617, 141-149, 2005

p-

ppK+

ppK0S

Glueball is ruled out

BEACH2006


Baryonic b meson decays

p

Өp

X

K+

p

Angular distribution: ppK+

ppK signal

bs dominant process

Fragmentation picture

Proton against K- (p against K+) : flavor dependence!

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)

BEACH2006


Baryonic b meson decays

Decay diagrams of J/Ψ to baryon pair

dominant decay diagram

< λ1 λ2|U|JM> = AJλ1 λ2 linksDJMλ1- λ2 (θ,φ)

Latest BES result :

BEACH2006


Fit cos j p p

Fit cosθ ( J/→ p p)

L = e-(Ns+Nb)/N!   [NsPs(Mbci , Ei)(cos)P(cos)+NbPb(Mbci , Ei)]

(cos) - normalized efficiency,P(cos) = (1+cos2)/(2+2/3)

χ2 fit

Likelihood fit

pp

signal

B= -0.60 ± 0.13 (stat) ± 0.14 (syst)

= 0.43 ± 0.13 (stat) ± 0.14 (syst)

BEACH2006


Pentaquark search in ppks

u

u

d

u

u

d

d

s

Pentaquark search in ppKs

  • Θ+(1540) : uudds

  • Θ+ K+nΘ+  K0 p

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

d

d

d

s

dd

u

s

u

u

p

K0

n

K+

Θ+

Θ+

BEACH2006


Pentaquark search in ppks1

Pentaquark 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 x10-7at90% C.L.

BEACH2006


B p b s

bsγMC

+7.1- 6.6

+0.58- 0.53

140fb-1

B+pΛγ (b sγ)

  • PRL 95, 061802, 2005Simultaneous fit on BpΛγ and BpΣ0γSignal Yield for BpΛγ with MpΛ<2.4GeV/c2: 34.1

  • Statistical Significance: 8.6σ

  • BF(BpΛγ )(2.16 ± 0.20)x10-6BF(BpΣ0γ):<4.6 x 10-6

pΛγSignal

Not bremstrahlung

BEACH2006


Photon energy and angular distribution

γ

Photon energy and Angular distribution

θx

p

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

(Assuming XpΛ, calculated in X rest frame.)

Λ

Lab frame

X frame

qq background

bsγMC

Signal Yield

Signal Yield

BEACH2006


Baryonic b meson decays

b s

g

s

s

First observation of bs s s

baryonic decay

Signal Yield in 2D fit: 19.9

Efficiency: 4.0%-6.9%

Statistical Significance: 7.4σ

BF:(2.91 ± 0.38) x 10-6

+6.5- 5.1

+0.90- 0.70

B+ΛΛK+

140fb-1

threshold peaking

  • First Charmless B decay with two Λ!

  • Threshold enhancement again.

  • Compliment to BφK(*)(bsss penguin)

PRL 93,211801, 2004

BEACH2006


Observation of c

Observation of ηc Λ Λ

hep-ex/0606022

new

Ratio for baryon quark-diquark model check

BEACH2006


Observation of b c c k

Observation of B+c+c-K+

Hep-ex/0508015

Unexpected large rate

considering the limited

phase sapce

Threshold effect?

c+ pK-π+ signal

+1.0

-0.9

BF(B+c+c-K+ ) = (6.5 ± 1.1 ± 3.4) × 10-4

BEACH2006


Baryonic b meson decays

Observation of B cc

Hep-ex/0510074

B+c0c+

B0c-c+

CKM(cc)=VcbVcs* <-> CKM(cp)=VcbVud*

Enhancement for smaller Q ?

cc  10-3 >> cp  10-5

c π 1%

BEACH2006


Observation of j p

Observation of J/p

PRD72 051105 (2005)

J/p

J/pp

BEACH2006


Search for inclusive c production in tagged b sample

Search for inclusive Λc+ production in tagged B sample

N(B+) = 200359± 705

N(B0) = 110735± 424

BEACH2006


Determination of bf b c x

Determination of BF(B Λc+ X)

+1.0

-0.6

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 )%

hep-ex/0606026

Useful for the understanding of

the charm counting problem in b decays

+1.8

-1.0

+0.8

-0.4

+0.6

-0.3

BEACH2006


Baryonic b meson decays

BEACH2006


Baryonic b meson decays

BEACH2006


Summary

Summary

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

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

  • Threshold enhancement in the baryon-antibaryon system

  • Searching ground for exotic states

  • Good crosscheck for baryonic charmonium decays

  • More results will be shown this summer

BEACH2006


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