tth, (h?bb) with EventViews

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tth, (h?bb) with EventViews

• Chris Collins-Tooth, Christian Shaw
• 03-May-2006

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Introduction

• Report from UK Higgs mtg. in London last Friday
• Accessing the tth (h?bb) channel.
• Some output (for 20k Mh130 GeV) MC Sample
• Sim,Dig9.0.4
• Reco10.0.4
• Soon CSC...
• These are not even simulated yet.

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Report from UK Higgs mtg

• Lots of interest in ttH H?bb.
• WM,PTD,RG,NK,SD,CT
• If you are interested, join atlas-uk-higgs_at_cern.ch
  
• Made TWiki page for use by ttH H?bb, linked from
• https//uimon.cern.ch/twiki/bin/view/Atlas/HiggsWo
  rkingGroup
• I Decided to make code available on this page for
  11.0.3 EventView-based ttH (H?bb) analysis.
• Focus for next meeting will be work for CSC.
• We will undoubtedly need to re-make AOD, since no
  truth info.
• I aim to concentrate on jet algorithms and muon
  purity..

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The tth (h?bb) channel

• Event trigger is a high Pt lepton.

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The tth (h?bb) channel

• Event trigger is a high Pt lepton.
• Aim throw away most of the event leaving the
  correct two b-jets, allowing Mh
  reconstruction.

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The tth (h?bb) channel

• Event trigger is a high Pt lepton.
• Aim throw away most of the event leaving the
  correct two b-jets, allowing Mh
  reconstruction.
• Many combinatorical possibilities!
• Must keep them in the list of possible Event
  Views until we can judge which is the most
  accurate combination (from comparison to truth,
  t-mass reco.)

• EventView software tools suited to this..

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Some Output tth Trigger Lepton

• When only a trigger electron..
• Trigger electrons are
• Ptgt25 GeV
• no soft electrons
• IsEM applied
• Isolation no more than 15 GeV in cone 0.45
• When theres only a trigger muon..
• Trigger muons are
• Ptgt 20 GeV
• Muon track Chi2NdofCut lt 20
• We intend to implement an isolation cut.

deltaR (electron only)
deltaR (muon only)
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Electron or Muon?

• When theres a trigger electron and some muons
  which qualify as trigger candidates..
• use the electron!!!
• NB events with gt1 trigger electron candidate are
  very rare.

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b-jet Energy

• Look at Ebjet/Ebquark
• Adding soft ?s back in to the jet helps.
• Using Kt alg. also helps..
• Kt R-param0.45.
• BEWARE theres a bug!
• Value actually given in JobOpts0.2 (0.452).
• Seems like a small effect, but b-jet
  combinatorics sensitive to small energy shifts!

Add Muons
Cone
Kt
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b-jet Energy

• Look at Ebjet/Ebquark
• Adding soft ?s back in to the jet helps.
• Using Kt alg. also helps..
• Kt R-param0.45.
• BEWARE theres a bug!
• Value actually given in JobOpts0.2 (0.452).
• Seems like a small effect, but b-jet
  combinatorics sensitive to small energy shifts!

Add Muons
Cone
better mean, more symmetric
Kt
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Higgs Masses
Add Muons

• Cone 0.7 simply not applicable to this
  channel..too many jets!
• Cone 0.4 not calibrated.
• Input Mh130 GeV.
• Use Kt with ?s added.
• Mass peaks
• Cone4, no ?s 118 GeV
• Kt4, with ?s 125 GeV

Cone
Kt
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More detail...

• With Kt 0.4, and soft muons resummed into the
  b-jets, we see an improvement in the recod higgs
  mass.
• If you want to see exactly how the tth (h?bb)
  analysis is run, you can see my online log at

https//uimon.cern.ch/twiki/bin/view/Atlas/HiggsWo
rkingGroup
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Finally

• Looking at TruthJet energies...
• Ebjet/Ebquark has many effects folded in.
• Where there is a good match, Interesting to look
  at Ebjet/Etruthjet and Etruthjet/Ebquark.
• Backgrounds
• We simulated gg-gtttbb with AcerMC
• Other Backgrounds tbd with Atlfast.
• Significances to follow soon havent had time
  yet!

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