Transcript tth, (h bb) with EventViews → Chris Collins-Tooth, Christian Shaw

tth, (h→bb) with EventViews
Chris Collins-Tooth, Christian Shaw
03-May-2006
28/4/2006
Chris Collins-Tooth
Introduction
• Report from UK Higgs mtg. in London last Friday
• Accessing the tth (h→bb) channel.
• Some output (for 20k Mh=130 GeV) MC Sample:
• Sim,Dig:9.0.4
• Reco:10.0.4
• Soon: CSC...
– These are not even simulated yet.
28/4/2006
Chris Collins-Tooth
Report from UK Higgs mtg
• Lots of interest in ttH H→bb.
– WM,PTD,RG,NK,SD,CT
• If you are interested, join [email protected]
• Made TWiki page for use by ttH H→bb, linked from:
– https://uimon.cern.ch/twiki/bin/view/Atlas/HiggsWorkingGroup
• 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..
28/4/2006
Chris Collins-Tooth
The tth (h→bb) channel
• Event trigger is a high Pt lepton.
28/4/2006
Chris Collins-Tooth
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.
28/4/2006
Chris Collins-Tooth
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..
28/4/2006
Chris Collins-Tooth
Some Output: tth Trigger Lepton
• When only a trigger electron..
• “Trigger electrons” are:
–
–
–
–
Pt>25 GeV
no soft electrons
IsEM applied
Isolation: no more than 15 GeV in cone 0.45
• When there’s only a trigger muon..
• “Trigger muons” are:
– Pt> 20 GeV
– Muon track Chi2NdofCut < 20
– We intend to implement an isolation cut.
28/4/2006
deltaR
(electron only)
deltaR
(muon only)
Chris Collins-Tooth
Electron or Muon?
• When there’s a trigger
electron and some
muons which qualify as
trigger candidates..
– use the electron!!!
• NB: events with >1
trigger electron
candidate are very rare.
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Chris Collins-Tooth
b-jet Energy
• Look at Ebjet/Ebquark
• Adding soft ’s back in to
the jet helps.
• Using Kt alg. also helps..
• Kt R-param=0.45.
– BEWARE there’s a bug!
– Value actually given in
JobOpts=0.2 (=0.45**2).
• Seems like a small effect,
but b-jet combinatorics
sensitive to small energy
shifts!
28/4/2006
Add Muons
Cone
Kt
Chris Collins-Tooth
b-jet Energy
• Look at Ebjet/Ebquark
• Adding soft ’s back in to
the jet helps.
• Using Kt alg. also helps..
• Kt R-param=0.45.
– BEWARE there’s a bug!
– Value actually given in
JobOpts=0.2 (=0.45**2).
• Seems like a small effect,
but b-jet combinatorics
sensitive to small energy
shifts!
28/4/2006
Add Muons
Cone
Kt
Chris Collins-Tooth
Higgs Masses
Add Muons
• Cone 0.7 simply not
applicable to this
channel..too many jets!
• Cone 0.4 not calibrated.
• Input Mh=130 GeV.
• Use Kt with ’s added.
• Mass peaks:
– Cone4, no ’s ~118 GeV
– Kt4, with ’s ~125 GeV
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Cone
Kt
Chris Collins-Tooth
More detail...
• With Kt 0.4, and soft
muons resummed into the
b-jets, we see an
improvement in the reco’d
higgs mass.
• If you want to see exactly
how the tth (h→bb)
analysis is run, you can
see my online log at:
Fit Mean 1.25e+05
Mh
https://uimon.cern.ch/twiki/bin/view/Atlas/HiggsWorkingGroup
28/4/2006
Chris Collins-Tooth
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->ttbb with AcerMC
– Other Backgrounds tbd with Atlfast.
– Significances to follow soon – haven’t had time yet!
28/4/2006
Chris Collins-Tooth
28/4/2006
Chris Collins-Tooth