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Jet Trigger Reconstruction Observations and Efficiency Analysis in ttbar Decay Channels

This presentation by Menelaos Tsiakiris at the NIKHEF TAPM Meeting discusses the analysis of jet trigger reconstruction in ttbar decays, focusing on hadronic channels. The study investigates trigger behaviors for various jet items and evaluates the quality of turn-on curves which are affected by jet energy scale (JES). It presents findings on jet trigger efficiencies, cross-correlation with non-full hadronic cases, and potential mismatching effects observed in low-energy jets. Ultimately, it raises questions about the accuracy of reconstruction and its implications on trigger efficiency and purity.

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Jet Trigger Reconstruction Observations and Efficiency Analysis in ttbar Decay Channels

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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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