1 / 55

Latest results on b-spectroscopy from CDF

Latest results on b-spectroscopy from CDF. Elena Vataga (Univ. of New Mexico, USA) On behalf of the CDF Collaboration CERN - October 31, 2006. Why B spectroscopy?. We are not looking for New Physics (but may find subtle discrepancy…)

ull
Download Presentation

Latest results on b-spectroscopy from CDF

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. Latest results on b-spectroscopy from CDF Elena Vataga (Univ. of New Mexico, USA) On behalf of the CDF Collaboration CERN - October 31, 2006

  2. Why B spectroscopy? • We are not looking for New Physics (but may find subtle discrepancy…) • Standard Model is extraordinary. Deserves thorough elucidation. • B-quark discovered in 1977. Wealth of b-mesons is found. Only one b-baryon well established so far. • Effective theories derived from QCD needed for dynamical understanding: HQET • mc,mb,mt> LQCD >> mu, md, ms  Heavy Quark Symmetry • HQET extensively tested for Qq systems; interesting to check predictions for Qqq systems E.Vataga - Latest results on b-spectroscopy from CDF

  3. What’s new? • Observation of orbitally excited Bs** mesons • Observation and mass measurement of Bc J/ψ • Search for b  J/ψ J/ψ • Observation of new beauty baryons b(*) E.Vataga - Latest results on b-spectroscopy from CDF

  4. Tools

  5. Tevatron today results: first fb-1 • Excellent performance of Tevatron in last years • Record Instantaneous luminosity > 2x1032 cm-2 s-1 • Now: delivered ∫Ldt=1.8 fb-1 • Good for b-physicson tape ∫Ldt=1.3 fb-1 E.Vataga - Latest results on b-spectroscopy from CDF

  6. The CDF II detector 96 layer drift chamber 44< r <132 cm, |z|<155 cm |η| ≤ 1.0, 30k channels  coverage || ≤ 1 84% in  silicon layers: 90 cm long, |η| ≤ 2.0 r00 = 1.31.6 cm Trigger: 3 levels 25000 / 300 / 100 Hz L1: COT tracks L2: silicon tracks dead time < 5% Resolution: pT~0.15% pT vertex r- ~ 30 μm ; r-z ~ 80 μm J/ψ mass ~14 MeV/c2 E.Vataga - Latest results on b-spectroscopy from CDF

  7. b b g g b g q b b b b b q g g g q q Flavor Excitation Flavor Creation (gluon fusion) Flavor Creation (annihilation) Gluon Splitting B physics @ Tevatron Compared to e+e- experiments on U(4S) or Z0 • Pro: • pp → bb x-section is >1000 times larger (~10 mb ) • All species of b-hadrons: not just B/B0, also Bs0, Bc, Lb0 • Contro: • QCD background ×103larger than (bb) • multiple interactions, large combinatorics. • Collision rate ~1.7 MHz  tape writing limit ~100 Hz b b g g g q b b b b g g q b g b q q Flavor creation (annihilation) Flavor creation (gluon fusion) Flavor excitation Gluon splitting E.Vataga - Latest results on b-spectroscopy from CDF

  8. B physics @ CDF: triggers are crucial BR~10-5 visible with just trigger confirmation ! Trigger configurations: • Di-muon • Lepton plus displaced track • 2 displaced tracks Bhh ~ 42 TB in BCHARM trigger! Secondary Vertex Trigger (SVT) is unique to CDF! First of its kind to trigger on fully hadronic b/c decays E.Vataga - Latest results on b-spectroscopy from CDF

  9. Bs and Lb mass measurements 220 pb -1 PRL 96, 202001 2006 better precision than the current world overage! E.Vataga - Latest results on b-spectroscopy from CDF

  10. 1fb -1 Lb Lifetime • Measured with fully reconstructed Lbg J/yL0 decay • 542 Lb candidates • World best t(Lb) measurement ! E.Vataga - Latest results on b-spectroscopy from CDF

  11. Lb Lifetime vs theory As precise as previous world average 3.1  different though! World Average (without this result) NLO (C.Tarantino et al., hep-ph/0203089) CDF New Result E.Vataga - Latest results on b-spectroscopy from CDF

  12. Observation of orbitally excited (L=1) Bs** mesons E.Vataga - Latest results on b-spectroscopy from CDF

  13. Orbitally Excited BsJ Mesons • B*+B+, where  is undetected • Shift of possible Bs2*, Bs1 peaks by M(B*+ - B+) = 45.78 MeV/c2 (see PDG) • Two channels: B+J/ψK, B+D E.Vataga - Latest results on b-spectroscopy from CDF

  14. B+ sample: ~58 000! Use Neural Network to optimize both B+ and Bs** E.Vataga - Latest results on b-spectroscopy from CDF

  15. Orbitally Excited Bs-mesons Bs2* Bs1 Two signals: • B*s2 already seen by OPAL, DELPHI and DØ • Bs1  first observation! E.Vataga - Latest results on b-spectroscopy from CDF

  16. Discovery of Bs1 • N (B*s2) = 94.8  23.4(stat) • N (Bs1) = 36.4  9.0(stat) P-value from Toy MC ~ 210-7 Greater than 5 s ! E.Vataga - Latest results on b-spectroscopy from CDF

  17. Observation of Bc J/yp and mass measurement of Bc E.Vataga - Latest results on b-spectroscopy from CDF

  18. _ b c Bc± J/ψ ± u d p • Bc is not produced at B factories • Observed in semileptonic mode • Full reconstruction allows for precise mass measurement • New analysis • Tune selection on B+ J/y K+ • After approval, “open box”. • Wait for significant excess • Measure properties of the Bc b c c c Bc J/y Bc: change K to a p E.Vataga - Latest results on b-spectroscopy from CDF

  19. _ b c Bc± J/ψ ± Challenges theoretical predictions theories N(Bc) = 45.29.4, S/B = 7.5 • m(Bc) = 6276.5  4.0 (stat) 2.7(syst) MeV/c2 E.Vataga - Latest results on b-spectroscopy from CDF

  20. Search for b  J/ψ J/ψ E.Vataga - Latest results on b-spectroscopy from CDF

  21. _ b b Introduction _ • Spin-singlet bb bound state • s(pp hbX ) ~ mb level at Tevatron energy scale • Large uncertainty on decay branching fraction: • BR(hbJ/J/mmmm) ~10-7  -5 The Bottomonium system _ E.Vataga - Latest results on b-spectroscopy from CDF

  22. Search for bJ/J/ • Exclusive search from CDF RunI and LEP • Inclusive search from CLEO ( (nS)-> hbg ; hb-> hbg) • No significant evidence yet. Run I history (80 pb-1): • 7 events observed/ 1.8 backgr. (2.2 s) • Upper limit 18 pb E.Vataga - Latest results on b-spectroscopy from CDF

  23. Results • Expected 3.6 bkg events; observe 3 events • Set upper limit for production cross section E.Vataga - Latest results on b-spectroscopy from CDF

  24. Observation of new beauty baryons b(*) http://www.fnal.gov/pub/presspass/press_releases/sigma-b-baryon.html E.Vataga - Latest results on b-spectroscopy from CDF

  25. Bottom Baryon States with B=1,C=0,JP = 1/2+, 3/2+ Mass predictions from hep-ph/9406359 E.Vataga - Latest results on b-spectroscopy from CDF

  26. Predictions on b-(*)/b+(*) properties • NRQCD, HQET • Potential models • 1/Nc expansions • Lattice QCD calculations Strong decay with  emission: b b  E.Vataga - Latest results on b-spectroscopy from CDF

  27. Methodology Decay chain: b -()→b0 - b0→ c+- c+→ p K -+ Trigger tracks  soft track from Primary Vertex 1-trk vertex E.Vataga - Latest results on b-spectroscopy from CDF

  28. Strategy Optimize Lb yield Blind Sb signal region Check for possible reflections from other B decays Optimize Sb selection (MC) Evaluate different background contributions Estimate detector resolution for Sb (MC) Understanding of background is crucial! OPEN THE BOX Measure b yields and Masses Set the limit E.Vataga - Latest results on b-spectroscopy from CDF

  29. Discriminating variable • Search for narrow resonances in • Q = m(b)- m(b)- m() • Blinded region 0.03<Q<0.10 GeV/c2 • Work with 2 distributions ( expect m(b- )> m(b+) ) • Same Charge (SC): b-() →b0 - → c+- - ( + c.c ) • Opposite charge (OC): b+() →b0 + → c+- + ( + c.c ) Remove b resolution 5.787<m(b)<5.857 GeV/c2 b-(bdd) and anti-b- b+(buu) and anti-b+ Two  have same/opposite charge E.Vataga - Latest results on b-spectroscopy from CDF

  30. Expected background E.Vataga - Latest results on b-spectroscopy from CDF

  31. Largest in the World! b sample Reflections Combinatorial background Signal region:[5.565, 5.670] E.Vataga - Latest results on b-spectroscopy from CDF

  32. Cut are optimized with signal region blinded. Signal is taken from PYTHIA Background is taken from the sidebands. Optimization is done maximizing FOM (S)/B No cut on pT () b optimization cross-check on D*D0, included in systematic E.Vataga - Latest results on b-spectroscopy from CDF

  33. Background Composition replaced E.Vataga - Latest results on b-spectroscopy from CDF

  34. Corrections to MC samples • PYTHIA bb • Do not expect perfect description for b-baryons – experimental data are limited • Needs reweighting • PT(b) • PT(soft ) • Included in systematic E.Vataga - Latest results on b-spectroscopy from CDF

  35. Fitting background Combinatorial B mesons b HA+UE alternative fit shapes in systematics E.Vataga - Latest results on b-spectroscopy from CDF

  36. E.Vataga - Latest results on b-spectroscopy from CDF

  37. Detector resolution and signal width • Estimated detector resolution from MC generating signal with 0 natural width ~ 2 MeV/c2 • Cross-check on D* D0 (MC) • (b) is predicted by HQET: • Dominated by natural width Width grows with Q hep-ph/9406359 E.Vataga - Latest results on b-spectroscopy from CDF

  38. Sum of Background Fits • Smooth background shape in signal window • Fixed fit parameters before opening the box E.Vataga - Latest results on b-spectroscopy from CDF

  39. Unblinded Q distribution Significant excess in both distributions! • Naïve S/(S+B) ~ 9 s E.Vataga - Latest results on b-spectroscopy from CDF

  40. Simultaneous unbinned NLL fit for both b-(*)/b+(*) distributions Background frozen 4 peaks: Breit-Wigner  Gaussians (b) = function (Q) 7 Floating parameters: Num of events in 4 peaks: N (b) Q(b-) and Q (b+) Common parameter Q(b*)-Q(b) Fitting the signal E.Vataga - Latest results on b-spectroscopy from CDF

  41. Fit: values and errors E.Vataga - Latest results on b-spectroscopy from CDF

  42. Signal significance • Naïve: 9s • P-value calculation: > 5s (not enough Toy MC) • Evaluate Likelihood Ratio for different hypothesis: 4 peaks are 2.6 1019 more likely then no peak at all • Background fluctuation is statistically excluded • Hypothesis with 4 peaks in the most favorable E.Vataga - Latest results on b-spectroscopy from CDF

  43. Summary • We observe four b resonant states 240 events in total • The significance of the signal > 5 • The signal is consistent with the lowest lying b() states • We measure Q values: E.Vataga - Latest results on b-spectroscopy from CDF

  44. Plans • Increase statistics by • b0→ c+-from different triggers (~1000) • b0→ J/ψL0 (~ 500) • b0→ c+ 3 • Measure m = M(b*) – M(b) for “+” and “–” separately • Measure widths E.Vataga - Latest results on b-spectroscopy from CDF

  45. Conclusions • CDF makes fundamental contributions in b-spectroscopy • Performing the world most precise measurements of b Bc Bs B+ B0masses • Discovering new particles: • b() →b • Bs1 →B*K • Bc J/ψ  • Setting new limits: • b  J/ψ J/ψ • And all these with only THE FIRST fb-1 ! E.Vataga - Latest results on b-spectroscopy from CDF

  46. E.Vataga - Latest results on b-spectroscopy from CDF

  47. BACKUP E.Vataga - Latest results on b-spectroscopy from CDF

  48. b() masses • Using m(b) = 5619.7±1.2(stat) ±1.2(syst) E.Vataga - Latest results on b-spectroscopy from CDF

  49. Systematic Errors

  50. Sb Motivation • Lb only established B baryon • Enough statistics at Tevatron to probe other heavy baryons • Next accessible baryons: Sb: b{qq}, q = u,d; = 3/2+(Sb*) JP = SQ + sqq = 1/2+ (Sb) • HQET extensively tested for Qq systems; interesting to check predictions for Qqq systems • Baryon spectroscopy also tests Lattice QCD and potential quark models E.Vataga - Latest results on b-spectroscopy from CDF

More Related