Tth h bb cuts based analysis status progress
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tth, (h → bb): Cuts-Based analysis status/progress. Chris Collins-Tooth 06-Feb-2007. Samples. Using Common Analysis, v00-01-05 (see TWiki) https://uimon.cern.ch/twiki/bin/view/Atlas/TthhbbAnalysis - ttH_rootples_Example_Analysis Signal tth(h → bb): 5340 (forced l + )

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Tth h bb cuts based analysis status progress

tth, (h→bb): Cuts-Based analysis status/progress

Chris Collins-Tooth

06-Feb-2007


Samples

Samples

  • Using Common Analysis, v00-01-05 (see TWiki)

    • https://uimon.cern.ch/twiki/bin/view/Atlas/TthhbbAnalysis - ttH_rootples_Example_Analysis

  • Signal tth(h→bb):

    • 5340 (forced l + )

    • 5341 (forced l - )

  • Backgrounds used:

    • 5855 AcerMC gg->ttbb (QCD)

    • 5214 AcerMC gg->ttbb (EW)

    • 5212 [email protected]/Herwig ttjj (jj=bb removed).


Cuts used see v00 01 05

Cuts Used (see v00-01-05)

  • Lepton:

    • e: Pt>25 GeV; EtCone<15 GeV;isEM 0x4FF; auth=1||3.

    • .mStaco: Pt>20 GeV; 2/dof<50 < ; EtCone40<50 GeV.

  • Jets: 6j; Pt>20 GeV; ||<5.

  • bJets: 4bj; bjetWeight 5.

  • Neutrino Solution: use colinear appx if no solution.

  • Sample 5212 (ttjj) only: remove if 4 unique bquarks

  • MWlep/had: 80.4  25 GeV.

  • Mt: 175  20 GeV.

  • Background + Combinatorics: Pt(J12+J22)>75 GeV (see later)......


Signal and bg efficiencies

Signal and BG Efficiencies.

  • Latest “full sim” is Compared to Cammin [ATL-PHYS-2003-024]

    • Applied same cuts as Cammin and saved v00-01-05

    • On the whole encouraging.

  • Problem with ttjj

    • many events had >=4 unique b-quarks

    • Had to remove them, as ttjj(jj=bb)  ttbb


Signal and bg efficiencies1

Signal and BG Efficiencies.

higher jet mult.

in [email protected]?

  • Latest “full sim” is Compared to Cammin [ATL-PHYS-2003-024]

    • Applied same cuts as Cammin and saved v00-01-05

    • On the whole encouraging.

  • Problem with ttjj

    • many events had >=4 unique b-quarks

    • Had to remove them, as ttjj(jj=bb)  ttbb


Signal and bg efficiencies2

Signal and BG Efficiencies.

higher jet mult.

in [email protected]?

cut on 2 tops too harsh?

  • Latest “full sim” is Compared to Cammin [ATL-PHYS-2003-024]

    • Applied same cuts as Cammin and saved v00-01-05

    • On the whole encouraging.

  • Problem with ttjj

    • many events had >=4 unique b-quarks

    • Had to remove them, as ttjj(jj=bb)  ttbb


Signal and bg efficiencies3

Signal and BG Efficiencies.

higher jet mult.

in [email protected]?

25%

47%

cut on 2 tops too harsh?

15%

30%

17%

47%

  • Latest “full sim” is Compared to Cammin [ATL-PHYS-2003-024]

    • Applied same cuts as Cammin and saved v00-01-05

    • On the whole encouraging.

  • Problem with ttjj

    • many events had >=4 unique b-quarks

    • Had to remove them, as ttjj(jj=bb)  ttbb


Tth h bb cuts based analysis status progress

Moving on.....

  • Look at signal and BG normalised to 30 fb-1

    • Problem: BG samples not big enough! Use AF?

    • No sensible distributions yet! – Can’t do shape analysis!


Tth h bb cuts based analysis status progress

Optimisations/Cuts..

  • Lots of cut optimisations to consider; also new cuts like Pt(J12+J22)>75 GeV on bJets forming Higgs

    • I will add this cut to the CVS-based analysis


A cut pt j1 2 j2 2 70 gev on bjets forming h

A Cut: Pt(J12+J22)>70 GeV on bJets forming H

  • Red circles: signal (+ black dot = “correct” bjets).

  • Others: backgrounds

#5855 ttbb[QCD]

#5340 poslep

#5341 neglep

Pt J1

Pt J1

Pt J1

Pt J2

Pt J2

Pt J2

#5214 ttbb[EW]

#5212 ttjj


Higgs bjets order by bjetweight

“Higgs bJets”: order by bjetWeight

  • Currently, analysis in CVS produces Higgs from highest Et bJets if >2 remain after t/tbar.

  • Tried using bjetWeight to order the jets if >2 “left over”.

  • No difference really, as most (~99%) of the selected events have only 2 bJets!

    • we have to improve how we reconstruct the tops to beat combinatorics!


Common analysis things i don t like

Common Analysis: things I don’t like...

  • Removal of ttjj where jj=bb

    • Truly awful to devise algorithm to do this in tthhbbClass.cxx (!)

    • Settled on removing events with 4 or more UNIQUE TRUTH b-quarks in ttjj.

    • Typical Herwig b->bMeson->b: check mother, grandmother etc. to see if b is unique

    • We also see eg: b-g-g-g-g-g-bbar where ‘b’ is mother of ‘bbar’, and ‘b’ has no mother.

    • Output ntuple ‘improved-data’ has a new attribute to allow one to remove these events for ttjj: “my_truthUniqueBQuarks” (remove ttjj event if >=4).

    • doplots.C is a root macro in CVS and cuts out these events

  • runtth.sh makes 10 ntuples for samples 5212

    • the list of input files is too large for my shell (zsh)

    • these have to be merged manually into “5212All.root”

      • merge: TChain ch("improved-data");ch.Add("5212*.root");ch.Merge("5212All.root");

  • top-mass window seems too harsh.

  • jet calibration.. is it even done??


Other things to implement

Other things to implement

  • Add soft muons(+n??) back to Jets.

  • Jet energy corrections based on v12.

  • See if there’s any way of improving combinatorics.

  • D=0, instead of colinear solution.

  • Improve Whad light jets (use 3+ jets?- Simon?).

  • S/BG discrimination with Neural Net (Helen).

  • Bill’s fitting code.

  • Others people would like to see / I have forgotten??

  • Volunteers?????

  • Not enough events for a BG shape analysis.


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