Heavy Flavor Production at HERA-B in 920 GeV Proton-Nucleus Interactions - PowerPoint PPT Presentation

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Heavy Flavor Production at HERA-B in 920 GeV Proton-Nucleus Interactions

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  1. Charmonium production: J/, ’, c • J/ production cross section • Differential distributions, polarisation • Nuclear dependence • Production ratios ’/ J/, c/ J/ • Hidden and open beauty production: ( ), (ns) • production cross section •  production cross section Heavy Flavor Production at HERA-B in 920 GeV Proton-Nucleus Interactions Hermann Kolanoski Humboldt Universität zu Berlin and DESY Zeuthen for the HERA-B Collaboration Brookhaven, 4.April 2006 Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  2. The HERA-B Experiment 920 GeV protons p + A  X @ spN = 41.6 GeV Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  3. Models of Heavy Flavour Production in Hadronic Interactions Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  4. Factorisation PDF • hadronization • Long distance (~1/(mcv)) process • non-perturbative calculations + input from experiments qq formation short distance (~1/mc) / high momentum process  perturbative calculations Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  5. Perturbative Generation:Color Singlet or Octet? JPC 0-+ 0++ 2++ JPC 1-- 1-- 1++ • Color Singlet Model (CSM): pair is produced as a color singlet with quantum numbers of the final charmonium state.  absolute predictions, but: not supported by experiment • Color Evaporation Model (CEM): pair production is the same for all charmonium states; quantum numbers arranged by “evaporation” of soft gluons.  predicts the same production dynamics of all states; cross section differences only from phase space and wave functions. • Non-Relativistic QCD Model (NRQCD): more rigorous (?) QCD treatment (singlet + octet + non-perturbative ME)  free parameters adjusted to data, predictions tested in different models, energies, final states, … Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  6. J/ e+ p e- Study of Charmonium Suppression • State formation effects: • nuclear absorption • comover absorption • multiple scattering + energy loss • Initial state effects: • shadowing (nuclear PDFs) • parton energy loss • intrinsic charm Measurement of a for 2 wire materials: a ≠ 1 “suppression” Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  7. J/ e+ formation time and length:  (xF) =   c  p e-  = (xF)boost of J/ w.r.t. nucleus xF-Dependence of Nuclear Suppression Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  8. The HERA-B Detector, Trigger and Data Samples Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  9. 184W p-beam 12C 48Ti z [cm] The HERA-B Detector Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  10. 5 MHz Pretriggers: ECAL cluster or muon hit coincidence as trigger seed (custom hardware) 3 MHz First Level Trigger (FLT): Track trigger in hardware using tracking detectors, seeding by pretriggers 20 kHz 100 Hz Second Level Trigger (SLT):FLT tracking confirmed, extrapolation to vertex detector, vertex fit (PC farm) Fourth Level Trigger (4LT):online reconstruction (and filtering) on PC farm 100 Hz The Dilepton Trigger HERA-B detector: data is read out and buffered for 12s(proton bunches cross every 96 ns, 0.5 interactions/BX) Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  11. J/ collection Data samples Data taking has finished in 2003; analysis is close to be finalized Data samples: • 150 M di-lepton trigger events (300 000 J/ψ) • 210 M minimum bias events • 35 M hard photon trigger events 10 more was planned! Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  12. J/ e+ e- + - (2s) c bb (1-3s) Topics of di-lepton trigger analysis 1) pt distribution xF distribution A-dependence polarisation 2) (2s) production ratio 3) c/J/production ratio 4) bb cross section 5)  production 6) (D0  ) Most results are final or close to final Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  13. J/ Production: di-lepton triggered J/→  ~ 177,000 σ= 44 MeV/c2 J/→ e+e- ~ 108,000 J/ σ= 64 MeV/c2 J/ ~ 3000 (2S) /  (2S) ~ 1600 (2S) • absolute cross sections from di-lepton triggered data need reference cross section Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  14. Interlude:J/cross sectionfrom Minimum Bias data Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  15. J/cross sectionfrom Minimum Bias data Important for cross section normalisationof di-lepton triggered data +- e+e- • low statistics • but: efficiency and luminosity well understood •  systematic uncertainties small (usually dominant) Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  16. C Ti Results: W J/y (MinB): A-Dependence and Results α = 0.96  0.01 (fixed to E866) Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  17. J/y (MinB): Comparison with other Results Result from both decay channels: HERA-B ~2X higherthan E771/789 in this energy region (!?) Mesurements are in general not very consistent with each other How to get a reference cross section ??? Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  18. NRQCD Based Evaluation of J/y and y’ Cross Sections • Towards a ‚reference cross section‘: • include all measurements (J/y, y’,c) • combine by ‚QCD-inspired‘ fit F. Maltoni et al. (= HERA-B Collaborators), ‚Analysis of charmonium production at fixed-target experiments in the NRQCD approach‘, hep-ph/0601203 Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  19. Fit results at HERA-B energy s = 41.6 GeV: QCD Based Evaluation of J/y and y’ Cross Sections:Fit Results F. Maltoni et al., ‚Analysis of charmonium production at fixed-target experiments in the NRQCD approach‘, hep-ph/0601203 Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  20. … back to two-lepton triggered data:Charmonium Production Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  21. J/ differential cross sections(preliminary) Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  22. (×10-4) E789 (Au) (×10-3) (×10-2) (×10-1) HERA-B (W) W Au Be C Si Ti [GeV-2] <pT>[GeV/c] (×10) E771 (Si) HERA-B (Ti) HERA-B (C) E672/E706 (Be) A pT[GeV] J/ pT distributions (nucl.dep.) standard fit: preliminary data (di-electron only), compared with p-A results at similar energy (√s = 38.8 GeV) <pT> grows logarithmically with A: Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  23. J/ pT distributions (nucl.dep.) Cronin effect <pT> grows with s: <pT>  0.8 + 0.01·s Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  24. J/y xF distribution Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  25. J/ψ: A-dependence (xF) First measurement at xF < -0.1: constant small suppression preliminary result: R.Vogt, [Nucl.Phys.A700(2002)539.]  = 0.969 ± 0.003stat± 0.021sys Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  26. J/ Polarisation usually only  is given; polarisation depends on reference system (polarisation axis in rest frame of J/) : E771, E672/E706 (Gottfried-Jackson) E866 (Collins-Soper) hadron CM (target system) CDF + (hadron CM) tan  = pT/MJ/  only for pT  0 are the systems different Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  27. ± ± ± ± ± ± HCM GJ CS ± ± ± Preliminary Polarisation Results HCM GJ CS large polarisation at pT=0  max. in CS frame  „natural“ system ? Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  28. y’/J/ production ratio Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  29. y’ production: xF distributions Tungsten Carbon J/→ J/→ , ee A-dependence:(xF) =‘-  CEM for color-1 nuclear absorption NRQCD for color-1 & -8 nuclear absorption fit with const: (E866)=-0.026±0.005 All consistent with no xF dependence. We use average of E866 and NA50: (E866, NA50)=-0.030±0.004 Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  30. y’ production: xF distributions all targets included, corrected for nuclear effects with (E866, NA50) NRQCD CEM Data are consistent with both models (and with no xF dependence) Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  31. y’ production: pT distributions Carbon Tungsten J/→ J/→ • tendency for a wider pT distribution of ′ (increasing with A?) Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  32. y’ production: polarisation Result: compatible with no polarisation difference Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  33. Production ratio y’/ J/y A √s CEM NRQCD Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  34. c /J/ production ratio Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  35. preliminary 2002/2003 data (di-muon sample) background: mixed events after background subtraction entries/(10 MeV/c2) m(μ+μ-γ)-m(μ+μ-) [GeV/c2] c production selection: • measurement: • fraction of J/ψ’s from χc: • kinematical distributions from the 2000 data, with 370 ± 74 χc’s(μ+μ- + e+e-): R(c) = 0.32 ± 0.06 ± 0.04 [Phys. Lett. B 561, 61 (2003)] new data: 40bigger χcstatistics (the largest ever analyzed) Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  36. preliminary (a fraction of the di-muon sample) ET(γ) > 0.4 GeV background: mixed events entries/(1 MeV/c2) c2 c1 after background subtraction m(μ+μ-γ)-m(μ+μ-) [GeV/c2] c1 - c2 separation further step (?): separate different states by varying the selection cuts measure the c2/c1production ratio interesting constraints on the QCD models Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  37. E771 (p-Si) E369/ 610/ 673 (p-Be) π-A ISR (p-p) 2000 expected final precision 2002/3 prelim. E705 (p-Li) CDF (p-p) HERA-B R(c) preliminary evaluation (2002/2003 data): (21 ± 5)% of the produced J/ψ’s come from χc decays based on 1300 χc’s reconstructed in the di-muon channel (less than 10% of the total statistics) Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  38. Beauty production:open& hiddenbeauty Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  39. RD: =5314 m Open and Hidden Beauty Production Detached vertex analysis open pA bb + X J/ + X’ e+ e- , +- Cross sections normalised to prompt J/ using the ‘NRQCD supported’ evaluation: (pN  J/ X) = (502  44) nb/nucleon (with  = 0.96  0.01) hidden pA  (ns) + X e+ e- , +- Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  40. Open beauty production Analysis of 2002/03 data: • e+e- and +- triggered data • C, W, Ti targets (1 for bb) • J/ acceptance: -0.35 < xF < 0.15 (90% of bb cross section) Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  41. B Flavour Confirmation t = 1.39 ± 0.19 ps Long lived candidates around J/ψ mass B lifetime compatible with expected 1.54 ps (PDG) Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  42. -0.35 < xF< 0.1 0 < pT < 6 GeV Open beauty production: R Relative to prompt J/ to minimize uncertainties from efficiencies, luminosity … 2000 data Combined result of 2000 and 2002/3 data: R = 0.032  0.005stat  0.004sys (syst. error mainly from B(bJ/)) PHYSICAL REVIEW D 73, 052005 (2006) 2000 data: Eur. Phys.J. C26 (2003) 345 Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  43. Production Cross section Normalizing to J/from Maltoni et al.: (pN  J/ X) = (502  44) nb/N Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  44. Hidden beauty production(1S) + (2S) + (3S) Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  45. Hidden beauty: (1S) + (2S) + (3S) 30.8±7.4 75±14 DY DY comb comb Fit: A· ((1S) + (2S) + (3S)) + B· Drell-Yan + Combinatorial (1S) : (2S) : (3S) ratio fixed to E605 results shape from MC from like-sign pairs Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  46. Fit “modified Craigie”:  NLO CEM data are compatible with =1 Hidden beauty production: Results Normalized to J/ Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404

  47. Summary • HERA-B collected 300k J/ and 200M min.bias events on various nuclei • Results on charmonium production (partly preliminary): • J/  cross section (and QCD evaluation) • J/ : xF and pT distributions in a new negative xF range • J/ A dependence demonstrate a flat behavior in this region • Fraction of c and (2S) yields relative to J/ • Open and hidden beauty cross sections • Final results on J/ , c and (2S) in 2006 The end of HERA-B is close Hermann Kolanoski HU Berlin - HERA-B Results - BNL060404