1 / 19

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.

ivory-conner
Download Presentation

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

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. 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

More Related