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Update: inclusive b-jet cross sections (w/ Andreas Warburton & Greg Williams)

Rob Snihur – McGill University QCD mtg., May 10, 2007. Update: inclusive b-jet cross sections (w/ Andreas Warburton & Greg Williams). Analysis strategy Data samples Jet selection Jet p T correction Jet p T distributions p T cuts and merging triggers Di-(b)jet cross sections

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Update: inclusive b-jet cross sections (w/ Andreas Warburton & Greg Williams)

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  1. Rob Snihur – McGill University QCD mtg., May 10, 2007 Update: inclusive b-jet cross sections(w/ Andreas Warburton & Greg Williams) Analysis strategy Data samples Jet selection Jet pT correction Jet pT distributions pT cuts and merging triggers Di-(b)jet cross sections MC reweighting Monte Carlo Data over MC Unfolding To do list Summary

  2. Analysis strategy • Use inclusive jet triggers • Complements SVT analyses • Extend existing analyses in a general way • Perform jet cross section analyses in parallel • b-taggers: SecVtx, JetProbin association with • JetClu, MidPoint, kT • Cone = 0.4, 0.7, 1.0 • >= 1, 2, 3 jets • Can also measure generic-jet cross sections • Use clones for Stntuple analysis modules • Motivation: debugging & easy cross-checks against blessed results

  3. Data samples • 4 Inclusive jet triggers: jet20, 50, 70, 100 • 3 data running periods: d, h, i • 12 Stntuple samples: • Gexo[0-3]d, gexo[0-3]h, gjt[1-4]bi • Total integrated lumi = 1.00-1.02/fb • Breakdown for d,h,i: (348, 525-542, 127 pb-1) • Jet50 jobs for d & h failed: so only 127 pb-1 • Goodrun list v14: QCD with Si • MC: pythia dijet Gen6 with pT-hat > • 18, 40, 60, 90 (120, 150 not yet included) GeV • Stntuple bt0s[q-t]b

  4. Jet selection • Generic jets with Midpoint 0.7 • b-tagged jets with SecVtx • Using Midpoint 0.7 • Using JetClu 0.4 • QCD Good Run List v14 w/ Si • |z-vertex| < 60 cm • METSig < 3.5, 5, 6, 7 • |y| < 1.2 • Uncorrected pT > 45, 70, 95, 130 GeV

  5. An interim correction (same for all types of jets) Apply a 4th order polynomial (from Monica’s note) Jet pT correction pT of matched hadron jets(Gev/c) pT: uncorrected / corrected Corrected jet pT (Gev/c) Corrected jet pT (Gev/c)

  6. Jet pT distributions MidPoint 0.7 SecVtx +MP7 • No y or pT cuts applied • MidPoint 0.7, SecVtx MP7, SecVtx JC4 • Prescales accounted for by weighting each event by trigger table lookup • 0i data only (for this slide) SecVtx +JC4

  7. pT cuts and merging triggers SecVtx +MP7 MidPoint 0.7 • Select jets with • |y| < 1.2 • Uncorrected pT > 45, 70, 95, 130 GeV • Use these conservative pT cuts for now, same for all algorithms • May be able to lower oT cuts, on an algorithm-by-algorithm basis • Plot of Nevents/∫L = “cross section” • Rebinned: 0,38,43,48,54,60,67,74,82,90,98,111,119,128,138,150,160,173,187,202,218,236,272,326,400,500,800 • Each bin contains data from exactly one trigger N/∫L(nb/Gev/c) N/∫L(nb/Gev/c) Corrected jet pT (Gev/c) Corrected jet pT (Gev/c) SecVtx +JC4 N/∫L(nb/Gev/c) Corrected jet pT (Gev/c)

  8. Di-(b)jet cross sections SecVtx +MP7 MidPoint 0.7 • |y2| < 1.2 • pT(2) > 20 GeV/c • N/∫L vs. leading jet pT N/∫L(nb/Gev/c) N/∫L(nb/Gev/c) Corrected jet pT (Gev/c) Corrected jet pT (Gev/c) SecVtx +JC4 N/∫L(nb/Gev/c) Corrected jet pT (Gev/c)

  9. MC reweighting • Follow R. Field (QCD mtg. feb21_2002) • Example: run 211315pT -hat unweighted & weighted • The (q,r,s,t)=(18,40,70,90) GeV samples had 1815,1815,436,436 events. • Weighted cross sections appear x1000 too high • Suspect units problem 1 run N/∫L(nb/ 5 Gev/c) Number of events pT-hat (Gev/c) pT-hat(Gev/c) Full MC sample N/∫L(nb/5 Gev/c) pT-hat (Gev/c)

  10. Monte Carlo SecVtx +MP7 MidPoint 0.7 • SecVtx: • Bump at ~190 GeV • Deficit at 350 GeV N/∫L(nb/Gev/c) N/∫L(nb/Gev/c) Corrected jet pT (Gev/c) Corrected jet pT (Gev/c) SecVtx +JC4 N/∫L(nb/Gev/c) Corrected jet pT (Gev/c)

  11. Data over MC SecVtx +MP7 • “Cross section” ratio: data / MC • Both at CAL level • These ratios will be used to derive MC pT spectrum reweighting Data/MC Data/MC MidPoint 0.7 Corrected jet pT (Gev/c) Corrected jet pT (Gev/c) SecVtx +JC4 Data/MC Corrected jet pT (Gev/c)

  12. Unfolding • Use MC to measure cross section at hadron-jet level and calorimeter-jet level • Ratio is the unfolding correction • Apply it bin-by-bin • Similarly, measure parton-jet cross section to derive hadronization correction (had/par), which will be applied to the theory Hadron/calorimeter Hadron/parton MidPoint 0.7 MidPoint 0.7 Corrected jet pT (Gev/c) Corrected jet pT (Gev/c)

  13. To do list • Reweighting • To match the data pT spectrum • Derive jet corrections • GRL v16 • Check trigger efficiencies • Compare to blessed analyses • Theory (Andreas) • B fraction (Greg’s talk) • Tagging efficiency (Greg’s talk)

  14. Summary • Measuring N-jet and N-b-jet cross sections for 1+/fb • Will incorporate new data • Variety of jet & tagging algorithms in parallel • See Greg’s talk for b-fraction & tag-efficiency

  15. Backups

  16. Trigger Efficiencies • JetClu 0.7 • 99% @ 58 & 112 GeV • We use 70 & 130 GeV

  17. Data vs. MC (backup) • Ratio: MC / (0i data) • LO MC sigma may be too low • Need to reweight MC spectrum

  18. Unfolding (backup) • Use MC to measure cross section at hadron-jet level and colorimeter-jet level • Ratio is the unfolding correction • Apply it bin-by-bin • Still choppy!

  19. MC reweighting (backup)

  20. Sigma(b-jet) ratios MC/0d 0i MC/0i MC

  21. B-jet cross section • SecVtx tags w/ JetClu 0.4 • 0i data • More choppy at low pT

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