1 / 30

Baryonic B decays at BELLE

-Outline- Introduction B +  ΛΛ K + B + p Λγ Threshold enhancement Charmed baryonic modes Conclusion. Baryonic B decays at BELLE. Min-Zu Wang National Taiwan University (Belle Collaboration). mwang@phys.ntu.edu.tw. Introduction. Baryonic decays: a unique feature of B meson

ion
Download Presentation

Baryonic B decays at BELLE

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. -Outline- • Introduction • B+ΛΛK+ • B+pΛγ • Threshold enhancement • Charmed baryonic modes • Conclusion Baryonic B decays at BELLE Min-Zu Wang National Taiwan University (Belle Collaboration) mwang@phys.ntu.edu.tw ICHEP04

  2. Introduction • Baryonic decays: a unique feature of B meson • 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 • Recent status report: H.Y. Cheng, hep-ph/0311035 ICHEP04

  3. b s g s s B+ΛΛK+ 140fb-1 threshold peaking First observation of bs s s 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 • First Charmless B decay with two Λ! • Threshold enhancement again. • Compliment to BφK(*)(bsss penguin) +6.5- 5.1 +0.90- 0.70 submitted to PRL ICHEP04

  4. Compare with Bppπ • buud transition with ss popping Search for B+ΛΛπ+ 140fb-1 • Result • Number of Background: 37.5±1.0 • Number of Observed events：41 • Number of Signal UL: < 21.7 No significant signal found for these two modes. 90% confidence-level upper-limit: B (B+ΛΛπ+)<2.8x10-6 Submitted to PRL ICHEP04

  5. B+pΛγ 140fb-1 bsγMC • First observation!Simultaneous 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 ± 0.20x10-6BF(BpΣ0γ):<3.3 x 10-6 pΛγSignal Preliminary Theoretical prediction: *Pole Model: Phys.Lett. B533 (2002) BF(B pΛγ ) ~ 1.2x10-6 BF(B pΣ0γ) ~ 2.9x10-9 *QCD counting rules: (hep-ph/0405283) BF(B pΛγ ) ~ (1.2-2.4)x10-7 BF(B pΣ0γ) ~ (2.8-6.5)x10-7 +7.1- 6.6 +0.58- 0.53 ICHEP04

  6. 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 qq background bsγMC Signal Yield Signal Yield ICHEP04

  7. Improved B+ppK+measurement 140fb-1 threshold peaking Signal Yield in 2D fit: 216.5 Efficiency: 28.3%-35.2% BF: 4.59 ± 0.50 x 10-6 (4.89 x 10-6 PRL92, 131801, 2004) +17.3- 16.6 Preliminary +0.38- 0.34 ICHEP04

  8. p Өp X K+ bs dominant process Fragmentation picture p at pp rest frame s u K+ p u d u u s u u d p Angular distribution: ppK+ ppK signal Proton against K- (p against K+) : flavor dependence! ICHEP04

  9. Glueball Search Possible Hints and Search for Glueball Production in Charmless Rare B Decays Chun-Khiang Chua, Wei-Shu Hou and Shang-Yuu Tsai(PLB544,2002) Preliminary Scanning through the mass region from 2.2 to 2.4 GeV region No significant signal is found. We set a 90% confidence-level upper limit:BF(B+ glueball K+) x BF( glueball  pp) < 4.1x10-7 ICHEP04

  10. Improved B0ppKs measurement 140fb-1 threshold peaking Signal Yield in 2D fit: 28.6 Efficiency: 15.4%-21.0% BF: 1.04 ± 0.12 x 10-6( 0.78 x 10-6 PRL92, 131801, 2004) +6.5- 5.8 Preliminary +0.26- 0.19 ICHEP04

  11. n K+ Θ+ p K0 Θ+ d d u u d u d u u d d u s s u d d u s s Pentaquark search in ppKs • Θ+(1540) : uudds • Θ+ K+n Θ+  K0 p • B0  Θ+ pB0 ppK0, B ppKsSearch for B signal with a 20 MeV pKs mass window cut at 1540MeV ICHEP04

  12. Pentaquark search in ppKs Preliminary 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. ICHEP04

  13. 140fb-1 Improved B0pΛπ- measurement threshold peaking Signal Yield in 2D fit: 48.4 Efficiency: 10.4%-12.6% BF: 3.27 ± 0.46 x 10-6(2.73 x 10-6 PRL90, 201802, 2003) +8.2- 7.4 Preliminary +0.61- 0.43 ICHEP04

  14. p p π- Өp Өp X X Λ at pπ- rest frame π- Λ Angular distribution: pΛπ- at pΛ rest frame Fragmentation picture ICHEP04

  15. b c u d B- LC+ p p - Belle: new results 140 fb-1 Preliminary 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 ICHEP04

  16. B- LC+ p p - M(Lc+p) structure (Lc+p) mass (LC+p) Low mass structure Phase space function B signals by DE fit for each mass bin M(Lc+p -)>2.6 & M(pp-) >1.6GeV/c2 to remove Sc(2455/2520) & D(1232) Preliminary 6.2s significance SC0(LC+p-) +0.02 -0.03 M = 3.34 ±0.02 GBW = 0.09±0.04 ±0.04 +0.77 - 0.72 BF = ( 3.87±0.43 ±1.01 ) x 10 - 5 ICHEP04

  17. M(Lc+p) <3.6GeV/c2 p B- LC+ p p - Helicity distribution MC helicity c2 /nd Solid line : 0 0.97 Dashed line : 1 1.58 Helicity angle Preliminary Lc+ Q data: dots MC : histograms in B - at rest (Lc+p) direc. ( by DE fit for each mass bin ) ICHEP04

  18. B0 LC+ p p - p - Intermediate 3-body decays Belle 140 fb-1 Sc++(2455) Sc0(2455) 41.0±8.0 35.2±7.8 M(Lc+p +)+c.c. Sc++(2520) Sc0(2520) M(Lc+p -)+c.c. 58±14 19±11 (*1) total BF M(Lc+p ) Preliminary ICHEP04

  19. 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 ICHEP04

  20. Conclusion • First b → sss hyperonic decay found • First b → s γ baryonic decay found • The threshold enhancement in the baryon-antibaryon pair system supports a fragmentation picture • Detailed structures studied in charmed baryonic decays • No hints for pentaquarks and glueballs yet • Keep searching for all kinds of baryonic decay channels, possible pentaquarks, glueballs and especially direct CP violation with increasing statistics ICHEP04

  21. p ∆φ B = 1.5T Λ IP π Fly length ∆r Zdist Λ reconstruction Good Λselection is applied in those analyses. X Z Y ICHEP04

  22. Thretical Prediction • The radiative baryonic B decays (BBB’γ) are of interest because of the rich spin structures. (CP / T violation). They could arise from bsγ transition. • Predicted Branching Fraction: • Pole Model: (hep-ph/0311035) Phys.Lett. B533 (2002) • Br(B PΛγ ) ~ 1.2x10-6 • Br(B PΣ0γ) ~ 2.9x10-9 • QCD counting rules: (hep-ph/0405283) • Br(B PΛγ ) ~ (1.2-2.4)x10-7 • Br(B PΣ0γ) ~ (2.8-6.5)x10-7 • Upper-bound from CLEO: • Br(B PΛγ )+0.3Br(BpΣ0γ)|Eγ>2.0GeV< 3.3x10-6 • 0.4Br(B PΛγ )+ Br(BpΣ0γ)|Eγ>2.0GeV< 6.4x10-6 ICHEP04

  23. Electron 8 GeV Positron3.5 GeV e+ + e- Υ(4S)  B+ + B- e+ + e- Υ(4S)  B0 + B0 The KEKB-factory Tsukuba Interaction Point 3Km Υ(4S) (10.58GeV/c2)  = 0.425 ICHEP04

  24. Aerogel Cherenkov Cnt. n=1.015~1.030 SC solenoid 1.5T ECLCsI(Tl) TOF counter Extreme Forward Calorimeter CentralDriftChamber small cell +He/C2H5 KLMm / KL detection 14/15 lyr. RPC+Fe Silicon VertexDetector Belle Detector 3.5 GeVe+ 8 GeVe- ICHEP04

  25. Particle Selection • We use the PID (ACC+CDC+TOF) system to identify the charged particles. • Proton: • Kaon: • Pion: • Λ: reconstructed from Λpπ- TO From Fake rate ICHEP04

  26. e- e- e+ e+ Υ(4S) B B B Signal Reconstruction In Υ(4S) rest frame: ∆E Mbc 2D scatter plot 1D projection plot ICHEP04

  27. Υ(4S) B decay continuum events Background suppression • The main background for B0pΛπ- and B+ΛΛπ+is continuum qq events. (q=u,d,s,c). • The Topology of continuum events and B decays are different. We choose |cosθThrust| S⊥ R2so R4so R2oo R3oo R4ooas the fisher input and combine it with cosθBto calculate the likelihood ratio. • We define the Super-fox wolfram moment (F) like:We use Fisher’s discriminant to optimize the coefficients. ICHEP04

  28. 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 ICHEP04

  29. 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 ICHEP04

  30. Angular distribution: ppK+ Background yield of ppK+ J/ψK+ (J/ψpp) Consistent with qq background process No fragmentation signature in J/ψK+ ICHEP04

More Related