B -> Baryon decays in Belle

B -> Baryon decays in Belle Sheng-Wen Lin National Taiwan University eric@hep1.phys.ntu.edu.tw Moriond QCD

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 decays New baryonic B decays through b-> s gamma and b->c(cs) 2.Low mass enhancements in 3-body charmless baryonic decays Decay angle distribution  fragmentation picture 3.Glueball search 4.Study of J/ψ  pp and ΛΛin B  J/ψK decay 5.Intermediate states Observation only in the charmed baryonic decays Moriond QCD

sss Status of charmless baryonic B decays HFAG sg 3-body suu sdd uud 3-body suu dss 2-body uud UL updated Moriond QCD

bsγMC +7.1- 6.6 +0.58- 0.53 B+pΛγ 140fb-1 Mbc=(Ebeam2-PB2)1/2 • PRL 95, 061802, 2005Simultaneous fit to 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 ± 0.20x10-6BF(BpΣ0γ):<4.6 x 10-6 ΔE=EB-Ebeam pΛγSignal Moriond QCD

Angular distribution Fit results in bins of cosθX with MpΛ<4.0GeV/c2 (Assuming XpΛ, calculated in X rest frame.) X frame γ qq background θx p Signal Yield Λ +0.23 -0.20 A=(N+/N-)/(N+-N-)= 0.36 Short-distance bsγ Moriond QCD

Threshold Enhancements in b->s and b-> u modes 140fb-1 • PLB 617, 141-149, 2005 p- ppK+ ppK0S Moriond QCD

Angular distribution: ppK+(b->s mode) p Өp X K+ bs dominant process Fragmentation picture p in pp rest frame s u K+ p u d u u s u u d p ppK signal Moriond QCD

p p π- Өp Өp X X Λ in pπ- rest frame π- Λ Angular distribution: pΛπ-(b->u mode) in pΛ rest frame Fragmentation picture Moriond QCD

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 Moriond QCD

J/Ψ helicity angle definition In general, the angular distribution of J/Ψ baryon anti-baryon pair can be written as θ : helicity angle α : constant baryon θ anti-baryon J/Ψ momentum direction Moriond QCD

J / Ψ →p p helicity angle distribution 357fb-1 Likelihood fit ※Efficiency corrected Moriond QCD

First observation of ηc → ΛΛ Significance = 8.1σ Yield = 19.5 +5.1 -4.4 +0.09 -0.14 +0.24 -0.21 BR (ηc->ΛΛ) = 0.87 (stat.) (syst.) ±0.27(PDG)x 10 -3 Moriond QCD

cud cud ccs Status of charmed baryonic B decays Br=1% Br=10% 2-body 3-body 4-body 3-body 2-body Moriond QCD

Br(B+Xc0Lc+)x Br(Xc0X+p-) = +1.0 -0.9 (4.8 ±1.1±1.2)x10-5 bkgnd +0.56 -0.49 Br(B0Lc+ p) =(2.19 ±0.32±0.57)x10-5 PRL90(03)121802 B+/0Xc0Lc+ p0/-, B0/+Xc0Sc0/+, Sc0/+Lc+p -/0 357fb-1 B+ Xc0Lc+ 29 evnts 8.7 s Br  a few 10-3 if Br(Xc0X-p+) ~ 1% ( NP B345 (97) 137 ) Large Br as 2-body decay M(Lc+) M(Xc0) Moriond QCD

B0 Xc-Lc+ +0.56 -0.49 Br(B0Lc+ p) =(2.19 ±0.32±0.57)x10-5 PRL90(03)121802 357fb-1 Br(B0Xc-Lc+)x Br(Xc+X-p+p+) = 9 evnts 3.8s +3.7 -2.8 ( 9.3 ±1.9±2.2 )x10-5 Br ~ a few 10-3 if Br(Xc+X-p+p+) ~ 1%. M(Lc+) M(Xc-) Moriond QCD

B-J/yL p Br( B-J/yL p ) = Br( B-J/yS0 p ) Br( B0J/y p p ) 253fb-1 DMB=Mrec(B)-MB 17.2±4.1 events 11.1s 11.6 ±2.8(stat) (sys) x10-6 +1.8 -2.3 DMB Mbc Mbc 2-body invariant masses < 1.1x10-5 < 8.3x10-7 UL at 90% CL Moriond QCD

M(Lc-Lc+) +1.0 -0.9 Br=(6.5 ±0.8±3.4)x10-4 357fb-1 B- Lc-Lc+ K- 48.5 events 15.4s M(Lc-) M(Lc+) Moriond QCD

B0 Lc-Lc+ K0 +2.9 -2.3 Br=(7.9 ±1.2±4.2)x10-4 M(Lc-Lc+) 357fb-1 10.5 evts 6.6s hep-ex/0508015 M(Lc-) M(Lc+) Moriond QCD

Summary Charmless baryonic decays : • BF(2-body) < BF(3-body) • Low mass enhancement of di-baryon and decay angle distribution supports fragmentation picture • Observation of B+pΛγ(b -> sγ mode) Charm baryonic decays : BF(2-body) < BF(3-body) < BF(4-body) Observation of double charmed decays Moriond QCD

B -> Baryon decays in Belle