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Baryonic B Meson Decays

Baryonic B Meson Decays. Min-Zu Wang ( 王名儒 ) National Taiwan University. Introduction Charmless decays Charmful decays Summary. CP violation in Standard Model. In 1973, M. Kobayashi and T. Maskawa realized: CP violation  third generation of quarks

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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 Charmful decays Summary

  2. CP violation in Standard Model • In 1973, M. Kobayashi and T. Maskawa realized: CP violation  third generation of quarks • In SM, CPV can be accommodated via the CKM matrix, which relates quark mass eigenstates to weak eigenstates: • With 3 quark generations, there is 1 phase in the CKM matrix which is physical (can’t be absorbed in redefinition of the fields) • allows possibility of CP violation qi W Vij qj CYCU Seminar

  3. Two B Factories SLAC (史丹福大學) KEK (日本) BaBar Belle CYCU Seminar

  4. 1.7 229M BB Integrated Luminosity CYCU Seminar

  5. B Meson Production • Electron-Positron collider: e+e-(4s)  B0B0 • Only 4s resonance can produce B meson pair • Low B0 production cross-section: ~1 nb • Clean environment, coherent B0B0 production CYCU Seminar

  6. uds charm off Data sideband uds charm off Data sideband Background Suppression SFW Moment (F) Signal MC Likelihood Ratio (LR) uds charm cosθB distribution Data sideband off Optimized by study CYCU Seminar

  7. Signal Extraction ∆E Mbc • PDFs: • Background modeling: a line (curve) to represent the ∆E and the following parametrization first suggested by ARGUS group to represent the Mbc. • Signal modeling: a double Gaussian for ∆E and a Gaussian for Mbc. • 1D-binned fit: maximum Likelihood fit • Branching fraction are calculated by ∆E fit • Mbc fit for cross-check. • 2D-unbinned fit (∆E-Mbc): Extended maximum likelihood fit. ∆E Mbc CYCU Seminar

  8. 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) CYCU Seminar

  9. 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 CYCU Seminar

  10. Observation of B0→ PΛπ-MpΛ Plot PRL90 201802(2003) Search for BPΣ0π- negtive Theoretical Pretiction 78.1fb-1 Data CYCU Seminar

  11. Many rare baryonic decays found PRL92 131801(2004) CYCU Seminar

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

  13. p Өp X K+ p at pp rest frame Angular distribution: ppK+ ppK signal Proton against K- (p against K+) : flavor dependence! CYCU Seminar

  14. 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) CYCU Seminar

  15. Decay diagrams of J/Ψ to baryon pair dominant decay diagram < λ1 λ2|U|JM> = AJλ1 λ2 linksDJMλ1- λ2 (θ,φ) Massless Proton mass + E M Quark mass Kada, Marco and Parisi Quark + scaler diquark Latest BES result : CYCU Seminar

  16. A twist to compare α General form of α:(Phys. Rev. D 51, 3487–3500) ~ - 0.8 CYCU Seminar

  17. 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) CYCU Seminar

  18. 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+ CYCU Seminar

  19. 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. CYCU Seminar

  20. 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 CYCU Seminar

  21. 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 CYCU Seminar

  22. 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 CYCU Seminar

  23. Observation of ηc Λ Λ PRL 97, 162003 (2006) new Ratio for baryon quark-diquark model check CYCU Seminar

  24. Fit result for exp7-43 with Mpp<2.8GeV/c2 • Signal Yield for B+ppπ+ : 180.9 • LR selection: 0.85 • Statistical Significance: 13.5σ • Signal region +19.1-18.3 Mbc>5.27 GeV/c2 |ΔE|<0.05 GeV ppK ppπ 414fb-1 Result for B+ppπ+ CYCU Seminar

  25. hep-ph/0606141 fitting curve B+→ppK+ B+→ppπ+ predicted curve Theoretical Predictions • Angular distribution • Perturbative QCD(PQCD): (hep-ph/0606141) • Final-State Interaction (FSI): (hep-ph/0609133) • Upper limit • 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)) CYCU Seminar

  26. B+→pΔ0 B+→ppπ+. signal region. sideband region B+→pΔ++ Current Work: B+→ppπ+ 414fb-1 We apply Mpπ<1.4 GeV/c2 for B+→pΔ0 and B+→pΔ++ study. B+→pΔ0expected background:81.2background uncertainty:2.0%observed event:?upper-limit:? averaged efficiency:4.0±0.1%BF(B+→pΔ0)< ? B+→pΔ++expected background:72.3background uncertainty:2.1%observed event:?upper-limit:? averaged efficiency:11.6±0.2%BF(B+→pΔ++)< ? Preliminary CYCU Seminar

  27. The studies of intermediate two-body decays: We apply 2.262<MΛπ<2.310 GeV/c2 for B0Λcp. BF(B0Λc p): ? BF(B0Λc p): (2.19 ±0.32 ±0.57) x10-5(PRL 90 121802) We apply Mpπ<1.40 GeV/c2 for B0ΛΔ0. BF(B0ΛΔ0 ) < ? We apply 1.30<MΛπ<1.45 GeV/c2 for B-Σ*0 p. BF(B0Σ*+ p) < ? +0.56- 0.49 Current Work: CYCU Seminar

  28. 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 ): Study of First observation! CYCU Seminar

  29. θ p Λ π- ω p θpb B π- Study of helicity selection rules in weak decay • Decay parameter α: • Transition rate R is proportional to (1+αcosθ). • θ is defined as the angle between the initial hyperon polarization and the momentum of the final baryon. • αΛ=0.642±0.013 (PDG, Journal of Phys. G33, 1 (2006)) • The effective angular asymmetry parameter α :(J. Phys. G: Nucl. Part. Phys. 29(2003) B15-B22) • For the cascade decay BΛXπ-pX : • θpb is defined as the supplementary angle between the emitted proton momentum and the B momentum in the Λ rest frame. CYCU Seminar

  30. Measurement of α inΛdecays • Paper J.Phys. G29, 15 (2003) reported that the dΓ/d cosθ is proportion to (1+αcosθ) when the s quark comes from bLsL penguin-type transition. • Systematic error CYCU Seminar

  31. b c u d B0 D(*)0 p p Belle: PRL 89, 151802 (2002) 29.4 fb-1 B0 D0pp B0 D0* pp D0  K- p+ 33.6evnts 8.9s total 19.3 evnts 5.6s D0  K- p+ p-p+ 24.2evnts 5.6s 34.2evnts D0  K- p+ p0 5.1s D*0 D0p0 CYCU Seminar

  32. b c u d b c d u u u d d B0Lc+p First observation of baryonic 2-body decay Belle : PRL 90, 121802 (2003) 78 fb-1 +5.0 - 4.4 Lc+ B0 19.6 5.8 s p +0.56 - 0.49 Br = ( 2.19 ±0.32±0.57 ) x 10- 5 Stat. Sys. error of Br (Lc+) CYCU Seminar

  33. b c u d B- LC+ p p - Belle140 fb-1 PRL 97, 242001 (2006) BF x 10-5 264±20 signals +0.74 - 0.66 +0.56 - 0.49 + 6.6 - 5.9 SC(2455)0 32.6 + 5.7 - 5.0 SC(2520)0 12.8 Observation of new 2-body decay sideband ~ 25% of total BF CYCU Seminar

  34. M(Lc+p) structure in 3, 4 body decays B-  (Lc+p) p- Preliminary consistent with 4-body MC phase space, fine structures ? B0  (Lc+p) p+ p- MC 4-body phase space B Signals by DE fit SC++/0 (2455/2520) excluded CYCU Seminar

  35. 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 CYCU Seminar

  36. 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% CYCU Seminar

  37. Observation of J/p PRD72 051105 (2005) J/p J/pp CYCU Seminar

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

  39. 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 CYCU Seminar

  40. 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 • Searching ground for exotic states • Good crosscheck for baryonic charmonium decays • Lots of local contributions, both experimental and theoretical CYCU Seminar

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