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Open and Hidden Beauty in 920 GeV Proton-Nucleus Collisions

Open and Hidden Beauty in 920 GeV Proton-Nucleus Collisions. Hernan Wahlberg Utrecht University/NIKHEF For HERA-B Collaboration. Outline. HERA-B detector Reference prompt J/ y sample for beauty analysis  ( ) production cross section Open cross section Summary. Hera-B Detector.

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Open and Hidden Beauty in 920 GeV Proton-Nucleus Collisions

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  1. Open and Hidden Beauty in 920 GeV Proton-Nucleus Collisions Hernan Wahlberg Utrecht University/NIKHEF For HERA-B Collaboration Hernan Wahlberg, BEACH04

  2. Outline • HERA-B detector • Reference prompt J/ysample for beauty analysis •  ( ) production cross section • Open cross section • Summary Hernan Wahlberg, BEACH04

  3. Hera-B Detector Hernan Wahlberg, BEACH04

  4. Reference Prompt J/ySample Di-Muon total sample: Approx. 177,000 J/yeventsWidth: 44 MeV/c2 Di-Electron total sample: Approx. 108,000 J/yeventsWidth: 64 MeV/c2 J/ (ee) J/ (mm) (2S) (2S) • Long Tracks (Vertex Detector + Tracking System) • PID: m likelihood , E/p • Dilepton Vertex Probability > 1% • J/Y acceptance: -0.35 < xF < 0.15 Hernan Wahlberg, BEACH04

  5. E772 (A=2) E605 (A=64) :Motivation • Several measurements • available but unclear • situation at √s ~ 40GeV • Theoretical prediction • Hadronization: Possible nuclear suppression ? HERA-B s = 41.6 GeV • HERA-B has good • coverage in the central • region of collisions • ( xF ~ [-0.35,0.15]) Hernan Wahlberg, BEACH04

  6. :Method pA  + X   m+m- ; e+e- • Measurement relative to prompt J/y • Less sensitive to systematic effects • Prompt J/y cross section from E771 and E789 Hernan Wahlberg, BEACH04

  7. :Signal • 25% W + 75 % C (targets) • Mass resolution between 140 and 160 MeV/c2 • Background: • Random combinatorial: estimated by like sign pairs of real data • Drell-Yan: shape estimated from MC • (1S) / (2S) / (3S) relative production fixed to E605 results Hernan Wahlberg, BEACH04

  8. :Preliminary Results • Both channels are compatible • Extrapolation to √S = 38.8 GeV yields: Br• d/dyy=0 = 2.4 ± 0.9 pb/n • compatible with E605 • (more than 1 s) below E772 and E771 Hernan Wahlberg, BEACH04

  9. a-1 Not used in fit : Global Situation • Modified Craigie parameterization to include nuclear suppression (parametera) • Data compatible with no nuclear suppression:  = 0.99  0.05 s (GeV) Hernan Wahlberg, BEACH04

  10. B: Motivation • Theoretical uncertainties: • b quark mass 4.5 - 5 GeV • At NLO, scale (m) dependence • Previous measurements do not agree Hernan Wahlberg, BEACH04

  11. B: Principle of the Measurement pA bb + X b(b) B  J/ + Y J/  m+m- ; e+e- Hernan Wahlberg, BEACH04

  12. B: Principle of the Measurement • B Meson has a long life time ( ~ 9 mm at HERA-B kinematics) • ~ 0.5 mm dilepton vertex resolution • J/y from a B decay will be detached from primary interaction • Only needed: count detached J/y • Measurement relative to prompt J/y • Prompt J/y cross section from E771 and E789 Hernan Wahlberg, BEACH04

  13. P P B: Detached Scheme • B Selection: (30-45% Efficiency) • Lepton impact to the wire • Lepton closest distance of approach to primary • Distance J/y to wire Hernan Wahlberg, BEACH04

  14. B: Real Data vs. MC • Vertex z resolution ~ 500 mm • Good agreement between real data and MC simulation Hernan Wahlberg, BEACH04

  15. B: Signal • Carbon + Tungsten targets • 35% of total sample • Cuts optimized simultaneously • Background: • bb and cc simultaneous semileptonic decays • Combinatorial • Prompt J/y • Unbinned likelihood fit Hernan Wahlberg, BEACH04

  16. B: Sample Cross Check Hernan Wahlberg, BEACH04

  17. B: Preliminary Result • Only statistical errors • Good compatibility of two channels • 1.3 s lower than HERA–B (2000) Hernan Wahlberg, BEACH04

  18. B: Ongoing studies • Simultaneous semileptonic decays • Search of exclusive decays • Lifetime measurement Hernan Wahlberg, BEACH04

  19. Conclusions • Events observed in hidden and open beauty in the 2002-2003 data sample • Preliminary  cross section measurement: 3.4 ± 0.8 pb/n • in agreement with E605 • Global fit to  data consistent with no nuclear suppression • Preliminary bb cross section measurement (35% of the total statistics) • The complete HERA-B sample will be significantly larger than previous fixed target experiments Hernan Wahlberg, BEACH04

  20. Back-up slides Hernan Wahlberg, BEACH04

  21. Essential bibliography P.NASON, QCD at High Energy, Proc. Of the XX Int. Symp. on Lepton and Photon Interactions at High Energies, hep-ph/0111024 P.NASON et al., Adv. Ser. Direct. High Energy Phys. 15(1998), 609 H1 Coll. T.Sloan et al., Proc. QCD 2001 Conf., Moriond, March 2001. ZEUS Coll. J.Breitweg et al., Eur.Phys.J.C18(2001) L3 Coll. M.Acciarri et al., Phys.Lett.B503(2001) 10 OPAL Coll. OPAL Phys.Note PN455, August 29,2001 N. Kidonakis et al., Phys.Rev. D64 (2001) 114001-1 R. Bonciani et al., Nucl.Phys.B529 (1998) 424 T.Alexopoulos et al., Phys.Rev.Lett.82 (1999) 41 D.M.Jansen et al., Phys.Rev.Lett.74 (1995)3118 Hernan Wahlberg, BEACH04

  22. Detector characteristics (I) • Large acceptance: 15-220 mrad in x (bending plane), 15-160 mrad in y (vertical plane)  Target – up to 8 wires inserted into the halo of 920 GeV proton beam (C, Ti) • VDS – Vertex Detector System. Dilepton vertex resolutions: sz  600 mm, sx,y 70 mm • Dipole Magnet- field integral 2.13 Tm • OTR – Outer Tracker. Honeycomb drift cells; wire pitch 5/10 mm; spatial hit resolution 350 mm; Backward hemisfere in CM (negative xF) World largerst honeycomb tracker: 1000 modules, 115000 channels • ITR – Inner Tracker: MicroStrip Gas Chambers, pitch 100 mm, resolution 100 mm; Forward hemisfere in CM (positive xF) World largerst (gas) micro pattern tracker Hernan Wahlberg, BEACH04

  23. Detector characteristics (II) • RICH – Ring Imaging Cherenkov Hodoscope C4F10 radiator gas, 2 planes of PMT 4s separation: e/p p [3.4, 15] GeV/c, p/K p  [12,54] GeV/c • ECAL – Electromagnetic CALorimeter – Sandwich sampling calorimeter (“Shashlik”); Pb and W as converter; 3 regions • MUON detector – 4 tracking stations; Gas pixel chambers, Proportional tube chambers, some with segmented cathodes • DAQ system – High bandwidth, high trigger and logging rates • TRIGGER. - Pretriggers on ECAL & MUON seeds - FLT hardware based on ITR/OTR - SLT software trigger; Tracking+Vertexing; linux farm with 240 nodes  Event reconstruction; on-line, linux farm with 200 nodes Hernan Wahlberg, BEACH04

  24. Changing PDFs from MRST to CTEQ b quark mass from 4.5 to 5.0 GeV/c2 QCD renormalization scale m from 0.5 mo to 2 mo Fragmentation functions Peterson form with e from 0.002 to 0.008 Kartvelishvili form with ab from 12.4 to 15.0 <kT2> from 0.125 to 2.0 GeV2 Fraction of b-baryons produced in the b-hadronization process from 0 to 12% ±1.5% ±1% ±2% ±3% ±1% ±2% b production model systematics Default model: MRST PDF, Peterson FF e=0.006 Studied variations: Sys cont. to s(bb ) Total: ±5% Hernan Wahlberg, BEACH04

  25. J/y from b decays kinematics 92% of J/y are produced in our xF range Hernan Wahlberg, BEACH04

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