2006/3/18-2006/3/25 Moriond QCD 1

B -> Baryon decays in Belle

Sheng-Wen LinNational Taiwan University

eric@hep1.phys.ntu.edu.tw

2006/3/19 Moriond QCD 2S.-W. Lin

Introduction

B meson can decay into baryonic final states due to its heavy mass, through b-> cW, b-> uW and b-> s gamma…There are several theoretical models to predict BRs.Topics

1.BR. Measurements for charmless and charmed decays1.BR. Measurements for charmless and charmed decays New baryonic B decays through b-> s gamma and b->c(cs)New baryonic B decays through b-> s gamma and b->c(cs) 2.Low mass enhancements in 3-body charmless baryonic decays2.Low mass enhancements in 3-body charmless baryonic decays Decay angle distribution Decay angle distribution fragmentation picture fragmentation picture 3.Glueball search3.Glueball search 4.Study of J/4.Study of J/ψψ pp and pp and ΛΛΛΛin B in B J/ J/ψψK decayK decay 5.Intermediate states5.Intermediate states Observation only in the charmed baryonic decaysObservation only in the charmed baryonic decays

2006/3/19 Moriond QCD 3S.-W. Lin

Status of charmless baryonic B decays

HFAG

uuddsssuuuud

suu sdd

s

sss

2-body

3-body

3-body

UL updated

2006/3/19 Moriond QCD 4S.-W. Lin

B+pΛγ

PRL 95, 061802, 2005Simultaneous fit to BpΛγ and BpΣ0γSignal Yield for BpΛγ with MpΛ<2.4GeV/c2: 34.1Statistical Significance: 8.6σ

BF(BpΛγ ): 2.16 ± 0.20x10-6

BF(BpΣ0γ):<4.6 x 10-6

140fb-1

pΛγSignal

+7.1- 6.6

+0.58- 0.53

bsγ MCΔE=EB-Ebeam

Mbc=(Ebeam2-PB

2)1/2

2006/3/19 Moriond QCD 5S.-W. Lin

Angular distribution

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

(Assuming XpΛ, calculated in X rest frame.)

qq backgroundSignal Yield

X frame

Λ

γp θx

A=(N+/N-)/(N+-N-)= 0.36+0.23-0.20

Short-distance bsγ

2006/3/19 Moriond QCD 6S.-W. Lin

Threshold Enhancements

in b->s and b-> u modes

PLB 617, 141-149, 2005

ppK+ ppK0S

p-

140fb-1

2006/3/19 Moriond QCD 7S.-W. Lin

Angular distribution: ppK+(b->s mode)

bs dominant processFragmentation picture

us

uudduuus

K+ pp

p

p

K+ӨpX

ppK signal

in pp rest frame

2006/3/19 Moriond QCD 8S.-W. Lin

Angular distribution: pΛπ-(b->u mode)

π-

Λ

p

ӨpX

in pΛ rest frame

Λ

p

π-

ӨpX

in pπ - rest frame

Fragmentation picture

2006/3/19 Moriond QCD 9S.-W. Lin

Glueball Search in B->K p p

The theoretician suggest a possible glueball resonance with mass around 2.3GeV/c2(PLB 544, 139, 2002)Scanning the mass region from 2.2 to 2.4 GeV/c2

No significant signal is found.We set a 90% confidence-level upper limit:BF(B+ glueball K+) x BF( glueball pp) < 4.1x10-7

2006/3/19 Moriond QCD 10S.-W. Lin

J/Ψ helicity angle definition

In general, the angular distribution of In general, the angular distribution of J/ΨJ/Ψ baryon anti- baryon anti-baryon pair can be written as baryon pair can be written as

θαθd

dN 2cos1cos

θ : helicity angle

α : constant

J/Ψ momentum direction

θ

baryon

anti-baryon

2006/3/19 Moriond QCD 11S.-W. Lin

J / Ψ →p p helicity angle distribution

※Efficiency corrected

Likelihood fit

14.013.054.0

357fb-1

2006/3/19 Moriond QCD 12S.-W. Lin

First observation of ηc → ΛΛ

Significance = 8.1σ

Yield = 19.5

BR (ηc->ΛΛ) = 0.87 (stat.) (syst.) ±0.27(PDG)x 10 -3

+0.09-0.14

+0.24 -0.21

+5.1-4.4

12.067.0 19.016.0

C

C pp

2006/3/19 Moriond QCD 13S.-W. Lin

ccs

Br=10% Br=1%

cud

cud

2-body

3-body

4-body

3-body

2-body

Status of charmed baryonic B decays

2006/3/19 Moriond QCD 14S.-W. Lin

B+ c c

+

Br a few 10-3

if Br(c0-+) ~ 1%

( NP B345 (97) 137 )Large Br as 2-body decay

(4.8 ±1.1±1.2)x10-5+1.0-0.9

Br(B+c0c

+

)x Br(c0+-) =

B+/0c0c

+ 0/-, B0/+c0c

0/+, c0/+c

+-/0

bkgnd

8.7 29 evnts

M(c0) M(c

+)

357fb-1

Br(B0c+ p) =(2.19 ±0.32±0.57)x10-5

PRL90(03)121802

+0.56-0.49

2006/3/19 Moriond QCD 15S.-W. Lin

B0 c c

+

( 9.3 ±1.9±2.2 )x10-5+3.7-2.8

Br(B0c-c

+)x Br(c

+-++) =

Br ~ a few 10-3

if Br(c+-++) ~ 1%.

Br(B0c+ p) =(2.19 ±0.32±0.57)x10-5

PRL90(03)121802

+0.56-0.49

9 evnts 3.8

M(c-) M(c

+)

357fb-1

2006/3/19 Moriond QCD 16S.-W. Lin

B-J/ p

17.2±4.1 events11.1

Mbc Mbc

MB=Mrec(B)-MB

MB

Br( B-J/ p ) =

Br( B-J/ p )

Br( B0J/ p p )

< 1.1x10-5

< 8.3x10-7

UL at 90% CL

11.6 ±2.8(stat) (sys) x10-6

+1.8-2.3

2-body invariant masses

253fb-1

2006/3/19 Moriond QCD 17S.-W. Lin

B- c c

+ K-

Br=(6.5 ±0.8±3.4)x10-4+1.0-0.9

48.5 events15.4

c-c

+)

M(c-) M(c

+)

357fb-1

2006/3/19 Moriond QCD 18S.-W. Lin

B0 c c

+ K0

Br=(7.9 ±1.2±4.2)x10-4+2.9-2.3

c-c

+)

hep-ex/0508015

M(c-) M(c

+)

10.5 evts6.6

357fb-1

2006/3/19 Moriond QCD 19S.-W. Lin

Summary

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

Low mass enhancement of di-baryon and decay angle distributioLow mass enhancement of di-baryon and decay angle distribution supports fragmentation picturen supports fragmentation pictureObservation of BObservation of B++ppΛγΛγ(b -> s(b -> sγγ mode) mode)

Charmless baryonic decays :

Charm baryonic decays :BF(2-body) < BF(3-body)BF(2-body) < BF(3-body) < BF(4-body) < BF(4-body)Observation of double charmed decaysObservation of double charmed decays