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Observations on the Jet Trigger reconstruction

This study by Menelaos Tsiakiris from NIKHEF explores trigger behavior for jet items in t tbar decay, using various thresholds to analyze trigger efficiency and reconstruction quality. The study also investigates discrepancies between trigger and truth, evaluating the impact on event selection and reconstruction accuracy.

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Observations on the Jet Trigger reconstruction

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  1. Observations on the Jet Trigger reconstruction Menelaos Tsiakiris UvA - NIKHEF TAPM Meeting, May 3rd, 2007

  2. Motivation: • t tbar decay: Full – Hadronic channel • Investigate trigger behavior for jet items (jet160, 2jet120, 3jet65, 4jet50) • Turn-on curves: Determine the quality of trigger reconstruction • Quality of turn-on curves depends on JES • Extract Jet Trigger Efficiency from pure MC • Cross correlate with No-FullHad case • Determine ttbar selection efficiency • Goal Menelaos Tsiakiris - NIKHEF

  3. Dataset & Tools Tools: Offline 12.0.6, EventViewTrigger Package • Truth: Cone4TruthParticleJets • Trigger - Truth: EV Matching modules (L2, EF) • Investigated items: J160, 2J120, 3J65, 4J50 Item: jet160  L1_J45, L2_jet160, EF_jet160 2jet120  L1_2J45, L2_2jet120, EF_2jet120 3jet65  L1_3J45, L2_3jet65, EF_3jet65 4jet50  L1_4J45, L2_4jet50, EF_4jet50 Dataset used (8500): trig1_misal1_mc12.005204.Ttbar_FullHad_McAtNlo_Jimmy.recon.AOD.v12000601 Menelaos Tsiakiris - NIKHEF

  4. Trigger signatures quality Scheme : • Use only Matched jets (trigger-truth). • Make sure event would’ve passed a specific trigger only by matched trigger jets. (e.g. 2jet120: ≥ 2 matched jets, with: trigger ≥ 120 ) • Get all matched-with-trigger truth • Get matched-with-trigger truth, with trigger equivalent above threshold • Plot the turn-on curve Menelaos Tsiakiris - NIKHEF

  5. Trigger signatures quality Item jet160 LVL2 EF Low energy jets ? • Higher EF threshold? • Lower EF efficiency ? 160 GeV Menelaos Tsiakiris - NIKHEF

  6. Trigger signatures quality Item 2jet120 • Lower threshold, increased effect LVL2 EF 120 GeV Menelaos Tsiakiris - NIKHEF

  7. Trigger signatures quality Items: 3jet65 4jet50 65 GeV • EF: Really large effect !! LVL2 EF Menelaos Tsiakiris - NIKHEF

  8. Trigger – Truth correlation (I) LVL2 • Difference of truth_pt – trigger_pt w.r.t truth. Menelaos Tsiakiris - NIKHEF

  9. Trigger – Truth correlation (II) EF • Low energy jets reconstructed with very high energy ? • Is it indeed a reconstruction effect ? Menelaos Tsiakiris - NIKHEF

  10. Trigger signatures quality A fast check w.r.t. offline Reco… • Same story but with Reco instead of Truth LVL2 EF Effect smaller but still there !! Menelaos Tsiakiris - NIKHEF

  11. Trigger signatures quality A fast check w.r.t. offline Reco… LVL2 EF • … but shouldn’t the EF be a step-function ? Menelaos Tsiakiris - NIKHEF

  12. Trigger – Reco correlation (I) LVL2 Menelaos Tsiakiris - NIKHEF

  13. Trigger – Reco correlation (II) EF • Isn’t the EF using the offline reconstruction? • Indication of mismatching effect ? Menelaos Tsiakiris - NIKHEF

  14. Counting Trigger Decision (I): From 8500 events: Acceptance of ttbarevents: • At least one of the signatures triggered Menelaos Tsiakiris - NIKHEF

  15. Counting Trigger Decision (II): • If event trigger passed because of highest trigger jet(s) • Check of those events passed with at least one (of the highest) jet unmatched • 83.5% of total accepted events are from unmatched jets ? Menelaos Tsiakiris - NIKHEF

  16. Conclusion : • Weird behavior in low energy jets…  Is it matching effect ? Turn-on curves are misleading and therefore quality of reconstruction cannot be estimated. Is there a common way of matching through default tools ?  Is it reconstruction effect ? (hopefully and probably not!) It would seriously affect the Jet trigger efficiency but especially the purity. • Is it something else ? Please let me know if you find it… Menelaos Tsiakiris - NIKHEF

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