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Baryonic B Meson Decays

Baryonic B Meson Decays. Min-Zu Wang ( 王名儒 ) National Taiwan University. Charmless decays Charmful decays Summary. List of experimental observations (exclusive baryonic B decays). 1997: first exclusive measurement of B  c pX (X= , ) by CLEO

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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 Charmless decays Charmful decays Summary

  2. List of experimental observations (exclusive baryonic B decays) • 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 For a complete list , seehttp://www.slac.stanford.edu/xorg/hfag Moriond QCD

  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) Moriond QCD

  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 Moriond QCD

  5. p Өp X K+ p at pp rest frame Angular distribution: ppK+ ppK signal PLB 617, 141 (2005) b  s g penguin diagram Proton against K- (p against K+) : Asymmetric! Moriond QCD

  6. 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) Moriond QCD

  7. 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 b  u tree Result for B+ppπ+ Preliminary Moriond QCD

  8. hep-ph/0606141 fitting curve B+→ppK+ B+→ppπ+ PQCD predicted curve Theoretical Predictions • Angular distribution • Perturbative QCD(PQCD): (hep-ph/0606141) • Final-State Interaction (FSI): (hep-ph/0609133) • Intermediate two-body decay • BF 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)) Moriond QCD

  9. Result for Bpph 414fb-1 BppK Bppπ χ2 / d.o.f = 328/ 9 w/o 2 veto bins χ2 / d.o.f = 22/ 9 data point predicted curve(hep-ph/0204185) data point predicted curve(hep-ph/0204185) Preliminary With Charm Veto BF(B+ppK+)= (5.98 ±0.46)×10-6 Aθ= (N+-N-)/(N++N-) = 0.44±0.05 +0.29- 0.27 BF(B+ppπ+)= (1.89 ±0.14)×10-6 Aθ=-0.48±0.12 +0.28- 0.24 data point predicted curve(hep-ph/0606141) χ2 / d.o.f = 115 / 8 Threshold peak Moriond QCD

  10. B+→pΔ0 B+→pΔ++ Upper Limits from Bppπ 414fb-1 B+pΔ0Expected 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 Preliminary 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 Moriond QCD

  11. Phase space pΛγSignal 414fb-1 Study of Preliminary Signal yield: Signal Yield for BpΛγ with MpΛ<2.4GeV/c2: 95.3 Statistical Significance: 14.5σ Full mass range: BF(BpΛγ ): (2.45 ±0.22)x10-6 Theoretical prediction: *Pole Model: Phys.Lett. B533 (2002) BF(B pΛγ ) ~ 1.2 x 10-6 *QCD counting rules: Phys.Lett. B610 (2005) BF(B pΛγ ) ~ 1 x 10-6 +0.44- - 0.38 Moriond QCD

  12. Signal Yield Fit results in bins of cosθp with MpΛ<4.0GeV/c2 (Assuming XpΛ, calculated in X rest frame. θp is defined as the angle between the proton direction and the meson/photon direction.) pΛγAngular distribution Preliminary Moriond QCD

  13. Phase space p Λπ0Signal Signal Yield Signal yield: Signal Yield for BpΛπ0 with MpΛ<2.8GeV/c2: 56.1 Statistical Significance: 10.2σ BF(BpΛπ0 ): (3.00 ±0.33)x10-6 +0.61- 0.53 Study of Preliminary First observation! Moriond QCD

  14. Signal Yield Signal yield: Signal Yield for BpΛπ- with MpΛ<2.8GeV/c2: 129.4 Statistical Significance: 20.0σ BF(BpΛπ- ): (3.23 ±0.29)x10-6 ≠1/2 +0.33- 0.29 Study of Preliminary Phase space p Λπ0Signal Chua&Hou Eur. Phys. J.C29 (2003) 0.20 0.17 0.93 ± 0.21 ? Moriond QCD

  15. Observation of B+c+c-K+ PRL 97, 202003 (2006) 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 Moriond QCD

  16. Observation of B cc PRD74,111105 (2006) B+c0c+ B0c-c+ b →ccs CKM(cc)=VcbVcs* <-> CKM(cp)=VcbVud* Enhancement for smaller Q ? cc  10-3 >> cp  10-5 c π 1% Moriond QCD

  17. Measurement of Λc+ X in tagged B sample N(B+) = 200359± 705 N(B0) = 110735± 424 Moriond QCD

  18. 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 Moriond QCD

  19. Summary • Exclusive baryonic B decays: Well established after few years of B-factory running • BF(2-body) < BF(3-body) • Threshold enhancement in the baryon-antibaryon system  Not a resonance • Searching ground for exotic states and unexpected CP asymmetries Moriond QCD

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