Update: b-jet cross section(s) (w/ Andreas & Greg)

# Update: b-jet cross section(s) (w/ Andreas & Greg)

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## Update: b-jet cross section(s) (w/ Andreas & Greg)

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1. Rob Snihur – McGill University CDF Canada mtg., Sept. 04, 2007 Update: b-jet cross section(s)(w/ Andreas & Greg) Matching Tests Jet pT corrections

2. Matching Tests • Use matching for • Tagging efficiency (requires a ~pure sample of MC b-jets) • B-fraction (tagged jets matched to MC b-jets) • Absolute pt-jet corrections (cal jets to hadron jets) • Matching details matter! • Metric: use delta-r • Pt ordering • All jets or selected jets • Kinematic cuts • Tag = +-1? • Parton ID = uds, c, b, g • Direction of matching

3. Cartoons • h CalHad 11 22 3 CalHad 11 22 3 x y x y 3 1 2 2 1 z

4. Delta R Plots: cal vs had • Top: me (old) • Bottom: Greg (new)

5. Deriving jet pT corrections • On a jet-by-jet basis, correct the measured pT(cal)  pT(hadron) • Absolute • Relative • Offset (due to UE, MI, etc.) • Must also be consistent with unfolding corrections • Corrects the shape of pT spectrum due to resolution effects • Follow kT, demonstrate 2 methods • Bin in pT of calorimeter jets • Bin in pT(mean) = (pT(cal) + pT(had)) / 2

6. Absolute jet pT correction • Match cal jets to hadron jets • Plot • pT(had) - pT(cal) • pT(had) / pT(cal) • Versus pT(cal) & pT(mean) • Extract mean y-values and x-values • Plot & fit it

7. pT(had)/pT(cal) in bins of pT(cal)

8. pT(had) in bins of pT(mean)

9. pT(cal) in bins of pT(mean)

10. pT(had)-pT(cal) in bins of pT(mean)

11. pT(had)/pT(cal) in bins of pT(mean)

12. Immediate next steps • From the previous plots, extact mean values. For the following plots • pT(had)-pT(cal) vs pt(cal) in bins of pT(cal) • pT(had)/pT(cal) vs pt(mean) in bins of pT(mean) • Fit these with a polynomial

13. Plans and next steps • Analyze new MC • Unfolding correction • Reweighting • To match the data pT spectrum • Theory

14. Taggable Efficiency? • Only “taggable” jets get a tag value • Taggable def’n: Not only pt and eta/y cuts • See y vs. pt plots of JetClu and SecVtx • Number of tracks?