Baryonic B Meson Decays

Baryonic B Meson DecaysBaryonic B Meson Decays

Charmless decaysCharmful decays Summary

Min-Zu Wang (王名儒 )National Taiwan University

2007/3/18 Moriond QCD

List of experimental observations (exclusive baryonic B decays)

List of experimental observations (exclusive baryonic B decays)

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

For a complete list , see http://www.slac.stanford.edu/xorg/hfag


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)

( )


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


Angular distribution: ppK+

p

p

K+ӨpX

Proton against K- (p against K

+) : Asymmetric!

ppK signal

at pp rest frame

b s g penguin diagramPLB 617, 141 (2005)


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

•The lower bands shown in the plots are J/ψ and ηc.

•Asymmetry near threshold of ppbar indicates flavor dependence

•Anti-proton moves slower in parallel with proton PRD72 051101 (2005)


Result for B+ppπ+Result for B+ppπ+

• Fit result with Mpp<2.85GeV/c2

• Signal Yield for B+ppπ+ : 180.9• Statistical Significance: 13.5σ• Signal region

+19.1-18.3

Mbc>5.27 GeV/c2 |ΔE|<0.05 GeV

ppK

ppπ

Preliminary

b u tree


Theoretical PredictionsTheoretical Predictions

Angular distributionPerturbative QCD(PQCD):

(hep-ph/0606141)Final-State Interaction (FSI):

(hep-ph/0609133)

Intermediate two-body decayBF of B+→pΔ++ was predicted to be

2.9×10-7 (QCD sum rules, Nucl. Phys. B 345, 137 (1990) )

3.2×10-4 (pole model, Phys. Rev. D 43, 1599 (1991); Phys. Lett. B 237, 513

(1990))

1.4×10-6 (pole model, Phys. Rev. D 66, 014020 (2002))

PQCD predicted curve

hep-ph/0606141

B+→ppK+

B+→ppπ+

fitting curve


414fb-1Result for Bpph

BF(B+ppK+)= (5.98 ±0.46)×10-6

Aθ= (N+-N-)/(N++N-)

= 0.44±0.05

+0.29- 0.27

data point predicted curve (hep-ph/0204185)

BF(B+ppπ+)= (1.89 ±0.14)×10-6

Aθ=-0.48±0.12

+0.28- 0.24

BppK Bppπ



χ2 / d.o.f = 22/ 9χ2 / d.o.f = 328/ 9 w/o 2 veto bins

χ2 / d.o.f = 115 / 8

With Charm Veto

Threshold peak

Preliminary


Upper Limits from Bppπ 414fb-1

B+→pΔ++

B+→pΔ0

B+pΔ0 Expected background: 81.4Background uncertainty: 2.0%Observed event: 86 Systematic error: 7.3% Yield upper-limit: 28.3Averaged efficiency: 4.0±0.1%

BF(B+pΔ0)< 1.42×10-6

B+pΔ++ Expected background: 73.0Background uncertainty: 2.1%Observed event: 59Systematic error: 7.3%Yield upper-limit: 9.1Averaged efficiency: 11.7±0.2%

BF(B+pΔ++)< 1.4×10-7

Preliminary


Study of Study of pB

Theoretical prediction:Theoretical prediction:

*Pole Model*Pole Model: Phys.Lett. B533 (2002)BF(B pΛγ ) ~ 1.2 x 10-6

*QCD counting rules*QCD counting rules: Phys.Lett. B610 (2005)

BF(B pΛγ ) ~ 1 x 10-6

Signal yield:Signal yield:

Signal Yield for BpΛγ with MpΛ<2.4GeV/c2: 95.3Statistical Significance: 14.5σFull mass range:BF(BpΛγ ): (2.45 ±0.22)x10-6+0.44-

- 0.38

414fb-1

Phase space pΛγSignal

Preliminary


pΛγAngular distributionpΛγAngular distribution

Signal YieldFit results in bins of cosθp with MpΛ<4.0GeV/c2

(Assuming XpΛ, calculated in X rest frame. θp is defined as the angle between the proton direction and the meson/photon direction.)

Preliminary


Study of Study of 0 pB

Phase spacep Λπ0 Signal


Signal Yield for BpΛπ0 with MpΛ<2.8GeV/c2: 56.1Statistical Significance: 10.2σBF(BpΛπ0 ): (3.00 ±0.33)x10-6+0.61

- 0.53

Signal Yield

First observation!

Preliminary


Study of Study of pB

Phase spacep Λπ0 Signal


Signal Yield for BpΛπ- with MpΛ<2.8GeV/c2: 129.4Statistical Significance: 20.0σ

BF(BpΛπ- ): (3.23 ±0.29)x10-6

≠1/2

+0.33- 0.29

90.0)(

)( 0

pBBF

pBBF

Signal Yield

0.200.17

Chua&HouEur. Phys. J.C29(2003)

0.93 ± 0.21

Preliminary

?


Observation of B+c+c

-K+ Observation of B+c+c

-K+

Unexpected large rate considering the limited phase sapce

Threshold effect?

PRL 97, 202003 (2006)

c+ pK-π+ signal

BF(B+c+c

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


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

cc 10-3 >> cp 10-5

Observation of B cc

Enhancement for smaller Q ?

PRD74,111105 (2006)

B+ c0c

+ B0 c-c

+

c π 1%

b →ccs


Measurement of Λc+ X

in tagged B sample

Measurement of Λc+ X

in tagged B sample

N(B+) = 200359± 705

N(B0) = 110735± 424


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


SummarySummary

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

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

Threshold enhancement in the baryon-Threshold enhancement in the baryon-antibaryon system antibaryon system Not a resonance Not a resonance

Searching ground for exotic states and Searching ground for exotic states and unexpected CP asymmetriesunexpected CP asymmetries

Documents

Baryonic B Meson Decays