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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. 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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  1. Baryonic B Meson Decays Min-Zu Wang (王名儒) National Taiwan University Introduction Charmless decays Charmed decays Summary

  2. 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

  3. 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

  4. 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

  5. Threshold Enhancement • PLB 617, 141-149, 2005 p- ppK+ ppK0S Glueball is ruled out BEACH2006

  6. 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

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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

  12. 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

  13. 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

  14. 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

  15. Observation of ηc Λ Λ hep-ex/0606022 new Ratio for baryon quark-diquark model check BEACH2006

  16. 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

  17. 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

  18. Observation of J/p PRD72 051105 (2005) J/p J/pp BEACH2006

  19. Search for inclusive Λc+ production in tagged B sample N(B+) = 200359± 705 N(B0) = 110735± 424 BEACH2006

  20. 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

  21. BEACH2006

  22. BEACH2006

  23. 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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