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Searching for the Higgs at ATLAS with the channel t t H 0 (H 0 ->b b )

Searching for the Higgs at ATLAS with the channel t t H 0 (H 0 ->b b ). Lily Asquith UCL HEP XMAS TALKS 18th December 2007. NIKOS. Nikos Konstantinidis: Level 2 Trigger guru ATLANTIS event display overlord ALEPH Higgs Hunter. SIMON. NIKOS. Simon Dean: ATLFast fast simulation software.

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Searching for the Higgs at ATLAS with the channel t t H 0 (H 0 ->b b )

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  1. Searching for the Higgs at ATLAS with the channelttH0(H0->bb) Lily Asquith UCL HEP XMAS TALKS 18th December 2007

  2. NIKOS Nikos Konstantinidis: Level 2 Trigger guru ATLANTIS event display overlord ALEPH Higgs Hunter

  3. SIMON NIKOS Simon Dean: ATLFast fast simulation software. Principal developer of the UCL ttH(H->bb) analysis code

  4. SIMON NIKOS SEBASTIAN Sebastian Boeser: Main developer for HepMCVisual ATLANTIS developer Athena-kit installation man ttH(H->bb) combinatorics

  5. SIMON NIKOS SEBASTIAN CATRIN Catrin Bernius: ttH(H->bb) Trigger ttH(H->bb) background shape- analysis

  6. SIMON NIKOS SEBASTIAN CATRIN LILY Lily Asquith: ttH(H->bb) cut-based analysis Jets: detector effects + b-tagging

  7. SIMON NIKOS SEBASTIAN CATRIN LILY ATLAS detector at CERN’s Large Hadron Collider Should start running Spring 2008 Proton-proton, 14TeV

  8. 14TeV

  9. 14TeV

  10. ‘our’ mass range

  11. ‘our’ mass range H0->bb t->Wb We have 4 b quarks

  12. ‘our’ mass range Require one W to decay leptonically We have a ‘trigger’ lepton

  13. Background swamps signal by ~2000:1 Largest background: tt plus jets and W plus jets: reducible with b-tagging Irreducible background:ttbb

  14. Trigger Trigger reduces vast amount of data to manageable rate. Electron(muon) Pt> 25(20)GeV, ID track, isolation in calorimeter Catrin: lepton trigger efficiency ~ 83%

  15. Pre-selection Need at least 6 jets (>20GeV) in order to reconstruct the event Old ‘pre-selection’ : at least 4 jets b-tagged New pre-selection: at least 4 jets b-taggable (central in eta)

  16. Event Reconstruction

  17. Event Reconstruction Cut on mass 30GeV

  18. Event Reconstruction Cut on mass 30GeV Estimate from fit to reco mass distributions

  19. Hadronic W JETS >3 b-tagged Tops and Higgs >1 untagged Hadronic W BUT b-tagging efficiency here ~ 60% per b-jet:: 13% for all four… 34% of our events lost just through jet segregation.

  20. Hadronic W Use All JETS Not top N b-weighted Hadronic W None with b-weight >n Fewer Jets excluded from W reco= More likely to get the W right BUT more incorrect combinations…

  21. Have a nice holiday!

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