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Hadronic t-t bar selection and Jet Energy Scale calibration

Hadronic t-t bar selection and Jet Energy Scale calibration. Part I : Accessing the trigger information. 09/02 - Menelaos Tsiakiris. Motivation…. Dominant quark production mechanism. qq bar (10%), gg (90%) tt bar. t  Wb (~100%). Main decay modes:

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Hadronic t-t bar selection and Jet Energy Scale calibration

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  1. Hadronic t-tbar selection and Jet Energy Scale calibration Part I : Accessing the trigger information 09/02 - Menelaos Tsiakiris

  2. Motivation… Dominant quark production mechanism • qqbar (10%), gg (90%) ttbar • t  Wb (~100%) • Main decay modes: • di-lepton: ttbar lν lν bb 5% (e+ μ) • lepton + jets: ttbar  lν qq bb 30% (e + μ) • all hadronic : ttbar  qq qq bb 45% Pros: + Largest branching ratio + Kinematics that can be fully reconstructed • quarks (light jets) • b quark jets (displaced vertices) Cons: - very large QCD multijet background challenging for the isolation of the signal - difficulties for triggering

  3. Tools… • Atlas offline – Athena currently on 12.0.4 • UserAnalysis (00-08-43) package  very basic stuff… • Trigger Decision Class (by M.Wielers)  access the trigger information Contains the trigger menu items as defined at reconstruction. Trigger Menu : 12.0.4  official production CSC-03 List of predefined trigger menus in release 12 : https://twiki.cern.ch/twiki/bin/view/Atlas/TriggerMenuVersions • Sample 5012 (QCD) AOD di-jet sample reco. with trigger info • trig1_misal1_csc11_005012.J3_pythia_jetjet.recon.AOD.v12000402 • Sample 5200 (ttbar) AOD semi-leptonic sample reco. with trigger info • trig1_misal1_csc11_005200.T1_McAtNlo_Jimmy.recon.AOD.v12000402

  4. About Trigger Decision … TriggerDecisionMaker Algorithm  runs after the trigger steering  determines which HLT or LVL1items were satisfied  fills the TriggerDecision object TriggerDecision class  User Interface: • Implemented from 11.0.5 - fully functional on 12.0.x • From 12.0.4 also included in AODs Methods… • Obtains the trigger decision for each event … bool isDefined(“L1_2J45”) bool isTriggered(“L1_2J45”) bool isTriggerPassed() void print() void printAccepted() … • Gives the list of signatures running in each trigger level Starting point: Wiki page: https://twiki.cern.ch/twiki/bin/view/Atlas/TriggerDecision Browse code @ CVSView and documentation @ Doxygen

  5. More on Trigger Decision… How-to use: i) Include the Trigger, in the cmt/requirement use TrigSteeringEvent TrigSteeringEvent-* Trigger/TrigEvent ii) Edit AnalysisSkeleton.cxx #include "TrigSteeringEvent/TriggerDecision.h" Default key iii) Retrieve the trigger decision from StoreGate /** Get Trigger Decision */ const TriggerDecision* trigDec = 0; StatusCode sc = m_storeGate->retrieve( trigDec, MyTriggerDecision); if( sc.isFailure() || !trigDec) { mLog << MSG::WARNING << "No Trigger Decision found in TDS" << endreq; return StatusCode::SUCCESS; } !!! This is only for handling the MSG service e.g trigDec->isTriggered(“L1_J35”) Returns true/false MyTriggerDecision+ In case you re-run the trigger hypothesis on an ESD/AOD Need more insight? https://twiki.cern.ch/twiki/bin/view/Atlas/TriggerAnalysisTutorial

  6. Turn – on curve : My analysis: The percentage of jets that pass the energy threshold with respect to their true energy Reco container Per event… Truth container Find highest energetic jet For a trigger request of: E > 50 GeV Trigger Decision findAMatch if (accepted) Fill accepted_histo Fill highest_truth_histo E truth Ideal… Divide

  7. The jet160 item turn-on curves (5012): !!! !!! !!! LVL1: L1_J45 (20GeV) LVL2: L2_ jet160 EF: EF_jet160 “garbage” at low energies !?!?

  8. Offline reconstruction algorithm Reco container Trigger Reco Container Trigger reconstruction algorithm Find highest energetic jet Truth container Trigger Decision Fast solution… Truth container findAMatch if (accepted) Find highest energetic jet Trigger Decision Fill highest_truth_histo Fill accepted_histo if (accepted) Fill highest_truth_histo Divide Fill accepted_histo Divide

  9. The jet160 item turn-on curves (5012): The “garbage” are gone… ! But for this sample the jet160 item is not good …. Very few events  next slide

  10. The jet160 item (5012): Truth distribution Only very few events above 180 GeV

  11. The 2jet120 item (5012): based LVL1: L1_2J45 LVL2: L2_ jet120L2_jet120 EF: EF_jet120EF_jet120 Still few statistics Note the naming convention for L2 and EF!

  12. New sample 5200. Semi-leptonic ttbar… … just looked at it a few days ago Truth distribution … very few events after 220 GeV !

  13. The jet160 item on a 5200 sample , 4000 events: 90 – 100% AnalysisSkeleton INFO The L1 J45 : 3987  ~100% AnalysisSkeleton INFO The L2 jet160 : 2281  57% AnalysisSkeleton INFO The EF jet160 : 421  11% Bit sloppy here… ~ 80% -100% Starts building up after 160 GeV

  14. The 2jet120 item (5200) 4000 events: ~ 80% - 90% AnalysisSkeleton INFO The L1 2J45 : 3859  96% AnalysisSkeleton INFO The L2 2jet120 : 1930  48% AnalysisSkeleton INFO The EF 2jet120 : 278  7% ~ 50% - 60% Starts to build up only after 120 GeV

  15. The 3jet65 item (5200) 4000 events: ~ 90% ! ~ 80% - 90% LVL1: L1_3J45 LVL2: L2_ jet65L2_jet65L2_jet65 EF: EF_jet65EF_jet65EF_jet65 AnalysisSkeleton INFO The L1 3J45 : 3434  85% AnalysisSkeleton INFO The L2 3jet65 : 2508 63% AnalysisSkeleton INFO The EF 3jet65 : 522  13% ~ hardly 40 - 50% Again…

  16. The 4jet50 item (5200) 4000 events: ~ 70 % !!! ~ 60% - 70% LVL1: L1_4J45 LVL2: L2_ jet50L2_jet50L2_jet50L2_jet50 EF: EF_jet50EF_jet50EF_jet50EF_jet50 No more than 40% AnalysisSkeleton INFO The L1 2J45 : 2392  60% AnalysisSkeleton INFO The L2 2jet120 : 1771  44% AnalysisSkeleton INFO The EF 2jet120 : 406  10 % again Total accepted events: 3987 passed LVL1 : 99% 3137 passed LVL2 : 78% 857 passed EF : 21%

  17. About Jet Energy Scale… • The efficiency of the jet triggers depends heavily on the quality of the Jet Energy Scale calibrations in the online system. • As an introduction to this study I looked on the JES based on offline reconstruction For the di-jet 5012 sample

  18. JES : 5012 di-jet sample Fitting each bin of the x-axis with a gaussian and plotting the Constant(height) , Mean and Sigma Offset of 2 GeV The distribution is getting wider for high energies (less events ?)

  19. About Jet Energy Scale… For the ttbar 5200 sample

  20. JES : 5200 ttbar sample Not the same as 5012 !

  21. My to-do list … • Run the onlinereconstruction algorithm. (Samples ??) • Do the turn-on curves based on the trigger reco. algorithm and improve diagrams (e.g. errors) • Examine JES for the online case • Look into EventView Trigger package https://twiki.cern.ch/twiki/bin/view/Atlas/EventViewTrigger

  22. THANK YOU!

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