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Open and hidden beauty production in 920 GeV proton –nucleus collisions at HERA-B

Open and hidden beauty production in 920 GeV proton –nucleus collisions at HERA-B. M.Mevius DESY. Outline. the HERA-B experiment open b production upsilon production conclusions. The HERA-B Detector. Data Sample. Data taking is finished in 2003; analysis is in progress.

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Open and hidden beauty production in 920 GeV proton –nucleus collisions at HERA-B

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  1. Open and hidden beauty production in 920 GeV proton –nucleus collisions at HERA-B M.Mevius DESY M.Mevius

  2. Outline the HERA-B experiment open b production upsilon production conclusions M.Mevius

  3. The HERA-B Detector M.Mevius

  4. Data Sample • Data taking is finished in 2003; analysis is in progress • dilepton trigger: • pretriggers • high ETECAL clusters, MUON hits • FLT: hardware trigger • track finding behind magnet • SLT: software trigger • track finding behind magnet and in VDS • vertex reconstruction • online event reconstruction 150 M dilepton trigger events 300 000 J/ (>1000 per hour) 10 000 c 3 500 (2S) additional: 210 M minimum bias events M.Mevius

  5. muon channel muon channel electron channel electron channel ~ 108,000J/ → ee σ= 64 MeV/c2 ~ 108,000J/ ee σ= 64 MeV/c2 J/ J/ ~ 177,000J/σ= 44 MeV/c2 / /   (2S) (2S) ~ 1600 ~ 3000(2S) Dilepton spectra • Long Tracks (Vertex Detector + Tracking System) • PID: likelihood , E/p • Dilepton Vertex Probability > 1% • J/ acceptance: -0.35 < xF < 0.15 ~ 1600 M.Mevius

  6. open b production • Theoretical uncertainties: • b quark mass 4.5 - 5 GeV • At NLO, scale (m) dependence • Previous measurements do not agree between each other M.Mevius

  7. Measurement relative to direct J/ production to minimize trigger/reconstruction uncertainties R= relative efficiency1 open b production pn bb + X b(b) B  J/ + X J/  m+m- ; e+e- B selection eff. from MC M.Mevius

  8. open b production B Meson has a long life time ( ~ 9 mm at HERA-B kinematics) ~ 0.5 mm dilepton vertex resolution J/ from a B decay will be detached from primary interaction • B Selection: (30-45% Efficiency) • Lepton impact to the wire • Distance J/ to wire M.Mevius

  9. open b production • Vertex z resolution ~ 500 μm • Good agreement between data and MC simulation • good separation between direct and detached J/ • Background: • bb and cc simultaneous semileptonic decays • Combinatorial • Prompt J/ Cuts optimized simultaneously M.Mevius

  10. open b production • C,W,Ti targets • Unbinned likelihood fit preliminary 20% sys. error under investigation main contribution: Br(bbJ/X) = 2.320.20% M.Mevius

  11. E771/E789 preliminary J/ cross section E771/E789 : scaled to HERA-B cms energy (J/)=357 ± 2 ± 36 nb/nucleon using E771/E789 result: HERA-B measurement on min. bias data ongoing M.Mevius

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

  13. upsilon production pA  + X   μ +μ- ; e+e- • Measurement relative to prompt J/ • Less sensitive to systematic effects • Prompt J/y cross section from E771 and E789 M.Mevius

  14. 25% W + 75 % C (targets) Mass resolution between 140 and 160 MeV/c2 Background: upsilon production Random combinatorial: estimated from like sign pairs in data Drell-Yan: shape estimated from MC • (1S) / (2S) / (3S) relative production fixed to E605 results 8 M.Mevius

  15. upsilon production • 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 M.Mevius

  16. Modified Craigie parameterization to include nuclear suppression (parameter ) Data compatible with no nuclear suppression:  = 0.99  0.05 Not used in fit upsilon production a-1 M.Mevius

  17. Conclusions • HERA-B has finished data taking • preliminary results: • (bb) : • using: (J/)=357±2±36 nb/nucleon •  production: M.Mevius

  18. model dependence Default model: MRST PDF, Peterson FF e=0.006 Studied variations: Sys cont. to s(bb ) • ±1.5% • ±1% • ±2% • ±3% • ±1% • ±2% • 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% Total: ±5% M.Mevius

  19. J/ from b decays kinematics 92% of J/y are produced in our xF range M.Mevius

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