Baryonic B Meson Decays MinZu Wang National Taiwan

Baryonic B Meson Decays Min-Zu Wang (王名儒) National Taiwan University Introduction Charmless decays Charmed decays Summary 7 -Jun-2002 Hsuan-Cheng Huang

Introduction - Review l 1997: first exclusive measurement of B cp. X (X= , ) by CLEO l 2001: first observation of charmless B+ pp. K+ by Belle l 2002: observation of cp. X (X= , ) by Belle, CLEO, D(*)0 pp by Belle l 2003: first observation of 2 -body decay: B 0 cp (Belle), first evidence of J/ p (Ba. Bar) l 2004: first observation of b→s penguin in baryonic B decays by Belle: B+ p l 2005: doubly charmed baryon modes B c c, B c c. K by Belle 2006/07/03 BEACH 2006

First Observation of Charmless Baryonic B Decays B+ pp. K+ With charmonium veto PRL 88, 181803 (2002) ( ) BF(3 -body) >> 2006/07/03 PRD 65 091103 BF(2 -body) (2002) BEACH 2006

New type of B Decays: Peak at Low Mass Possible explanations ü Baryon form factor? ü Quasi 2 -body Decay? glueball baryonium ü Fragmentation? 2006/07/03 f. J(2220)? Phase-space MC BEACH 2006

Threshold Enhancement PLB 617, 141 -149, 2005 pp. K+ pp. K 0 S Glueball is ruled out 2006/07/03 BEACH 2006 p -

Angular distribution: pp. K+ p pp. K signal X Өp K+ p b s dominant process Fragmentation picture - + Proton against K (p against K ) : flavor dependence! 2006/07/03 BEACH 2006

Information from the pp. K+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 PRD 72 051101 (2005) 2006/07/03 BEACH 2006

Decay diagrams of J/Ψ to baryon pair < λ 1 λ 2|U|JM> = AJ λ 1 λ 2 links DJM λ 1 - λ 2 (θ, φ) Latest BES result : 2006/07/03 BEACH 2006 dominant decay diagram

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+ cos 2 )/(2+2/3 ) χ2 fit Likelihood fit pp signal B= -0. 60 ± 0. 13 (stat) ± 0. 14 (syst) 2006/07/03 = 0. 43 ± 0. 13 (stat) ± 0. 14 (syst) BEACH 2006

Pentaquark search in pp. Ks Θ+(1540) : uudds Θ+ K +n Θ+ us ddd d u K+ n Θ+ K 0 p uu d ds Θ+ ds uu d K 0 p B 0 Θ+ p B 0 pp. K 0, B pp. Ks Search for B signal with a 20 Me. V p. Ks mass window cut at 1540 Me. V 2006/07/03 BEACH 2006

Pentaquark search in pp. Ks Fixed background shape from sideband data Count the events in signal region and compare with background estimation BF product upper limit < 2. 3 x 10 -7 at 90% C. L. 2006/07/03 BEACH 2006

B+ pΛγ (b sγ) 140 fb-1 b sγ MC pΛγSignal PRL 95, 061802, 2005 Simultaneous fit on B pΛγ and B pΣ 0γ Signal Yield for B pΛγ with +7. 1 MpΛ<2. 4 Ge. V/c 2: 34. 1 - 6. 6 Statistical Significance: 8. 6σ BF(B pΛγ )(2. 16 +0. 58 ± 0. 20)x 10 -6 - 0. 53 BF(B pΣ 0γ): <4. 6 x 10 -6 2006/07/03 Not bremstrahlung BEACH 2006

Photon energy and Angular distribution γ θx p Fit results in bins of cosθX with MpΛ<4. 0 Ge. V/c 2 (Assuming X pΛ, calculated in X rest frame. ) Lab frame X frame qq background Signal Yield b sγ MC Signal Yield 2006/07/03 Λ BEACH 2006

b B+ ΛΛK+ g s s s 140 fb-1 threshold peaking First observation of b s s s baryonic decay +6. 5 Signal Yield in 2 D fit: 19. 9 - 5. 1 Efficiency: 4. 0%-6. 9% Statistical Significance: 7. 4σ BF: (2. 91 2006/07/03 +0. 90 - 0. 70 ± 0. 38) x 10 -6 BEACH 2006 1. First Charmless B decay with two Λ! 2. Threshold enhancement again. 3. Compliment to B φK(*) (b sss penguin) PRL 93, 211801, 2004

Observation of ηc ΛΛ hep-ex/0606022 new Ratio for baryon quark-diquark model check 2006/07/03 BEACH 2006

Observation of B+ c+ c-K+ Hep-ex/0508015 Unexpected large rate considering the limited phase sapce Threshold effect? c + BF(B+ c+ c-K+ ) = (6. 5 2006/07/03 +1. 0 -0. 9 ± 1. 1 ± 3. 4) × 10 -4 BEACH 2006 p. K-π+ signal

Observation of B B+ c c Hep-ex/0510074 B 0 c 0 c+ c- c+ CKM( c c)=Vcb. Vcs* <-> CKM( cp)=Vcb. Vud* Enhancement for smaller Q ? c c 10 -3 >> c π 1% 2006/07/03 cp 10 -5 BEACH 2006

Observation of J/ p 2006/07/03 PRD 72 051105 (2005) BEACH 2006 J/ pp

Search for inclusive Λc+ production in tagged B sample N(B+) = 200359± 705 N(B 0) = 110735± 424 2006/07/03 BEACH 2006

Determination of BF(B hep-ex/0606026 Useful for the understanding of the charm counting problem in b decays 2006/07/03 BF(BBF(B 0 BEACH 2006 -> -> Λc+ Λc+ X) X) Λc+ X) +1. 0 =(2. 8± 0. 5± 0. 3 -0. 6 +1. 8 =(5. 0± 1. 0± 0. 5 -1. 0 =(2. 1± 0. 5± 0. 2+0. 8 -0. 4 =(1. 6± 0. 9± 0. 2+0. 6 -0. 3 )% )%

2006/07/03 BEACH 2006

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 baryonantibaryon system Searching ground for exotic states Good crosscheck for baryonic charmonium decays More results will be shown this summer 2006/07/03 BEACH 2006