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g + b, g + c production

g + b, g + c production. Tara Shears, University of Liverpool. Motivation. Good testbed for quantitative QCD tests  +c events could be used to probe charm quark content of proton bb, cc events: imperfect NLO description

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g + b, g + c production

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  1. g + b, g + c production Tara Shears, University of Liverpool

  2. Motivation • Good testbed for quantitative QCD tests •  +c events could be used to probe charm quark content of proton • bb, cc events: imperfect NLO description •  + heavy flavour sensitive to new physics (eg. chargino neutralino production)

  3. LO NLO Production Dominates for gc Diagrams equal for gb Coupling  charge2 s(cg) ~ 4.s(bg) b quark ~ 60% c quark content of p (PRD 012003)

  4. Method: Apply standard run 2 g selection Estimate fakes from CPR info Use tagging algorithm for b/c id Run 1 used lepton pt We use sec. vtx tag (SECVTX – will update with better) Divide data into Et bins, tag, take b,c frac. from MC => s Datasets: CPH108 (25 Iso trigger) Good online run, clc, smx, cal, trigger, svx Good offline cal,cot L = 66.05 3.76 pb-1 MC: Pythia g + jet (LO) Will use madgraph for NLO Method / data

  5. Photon + jet sel. eff. Require at least 1 jet > 15 GeV, >=2 tracks, for tagging

  6. Tagging eff. & composition From Pythia MC..

  7. Data s(gq) = N(gq)/(eff(gjet).eff(tag).eff(trg).L) = no.tags * q fraction Not known yet

  8. Systematic errors • Photon + jet selection: ±1.7% from g id (test on Z, loose cuts) • Jet e scale: not yet done • Fake rate est.: use standard procedure • B/c fractions: take arbitrary ±10% • SECVTX systematics: not yet done (small for top) • Trigger systematics: not yet done • Luminosity: use quoted ±5.8%

  9. Results 1. gb Nb. E(trg) = 1 here!

  10. Results 2. gc Nb. E(trg) = 1 here!

  11. Indications of excess at high Et? Points: data (stat. Error and sysstat shown by notches) Histogram: Pythia g+jet (LO)

  12. Indications of excess at high Et? Points: data (stat. Error and sysstat shown by notches) Histogram: Pythia g+jet (LO)

  13. Work plan Immediately: • Trigger efficiency (+sys.) • SECVTX tagging sys., jet selection sys. • Other photon backgrounds (eg. e->g) (small) • Add more data Next: • Tighten photon cuts to reduce fake, use CES • Derive b/c fraction from data • Use improved b/c tag • Compare to NLO (Madgraph?) Longer term: • Extend to lower photon Et

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