Running on the CMSSW_1_6_12 fast sim soups for Top analysis

The following contains some notes on how to run CMSSW_1_6_12 for the semileptonic (muon) ttbar channel.


  • The completion of the CMSSW_1_6_12 fast sim production was announced here on 2008-06-28.
  • tt is in Chowder soup (see also the Soup definitions).
  • See this link for the chowder files at CERN and here for the DBS entry.
    • note that CERN only has 624866 events (according to DBS; my job ran over 628658 events), other sites have the full 11896860 events.
    • running on this sample, I see 16261 semileptonic (e: 5361, mu: 5495, tau: 5405), 16266 fully hadronic and 4099 fully leptonic events (36626 events in total, 6.3 GB including TQAF generator information and PF jets with two clustering algorithms = 179 kB / event)

Selection of tt events from the soup

Creation of TQAF objects


This object contains top-specific information from the generator level. See TtGenEvent in LXR. It is created by the class TtGenEventReco

Note that this seems to require the new collection genParticles while in CSA07 samples the old genParticleCandidates collection is produced. See also this link.

  • To print the list of generated particles, see here. This seems also to work with e.g.
    InputTag src = decaySubset
    to print the list of decay particles selected for creating the TtGenEvent.

Finding reconstructed muons

Finding reconstructed jets

Particle flow

Particle candidates

Jets (from particle flow candidates ?)

Example plots

Note that TtGenEvent::lepton() only returns leptons, but not anti-leptons. However, it looks like most of the quantities of the returned lepton are set to zero if there is no lepton (as opposed to an antilepton) in the W decay, so probably one can safely add the quantity returned by lepton().xxx and leptonBar().xxx when plotting.

Plot command description
Events->Draw("genEvt.lepton().pdgId()+genEvt.leptonBar().pdgId()","genEvt.isSemiLeptonic()") (generated) particle ids of leptons of W decays (first status 3 lepton in the event)
Events->Draw("genEvt.lepton().pt()+genEvt.leptonBar().pt()","genEvt.isSemiLeptonic()") generated lepton transverse momentum
Events->Draw("genEvt.singleLepton().pdgId()","genEvt.isSemiLeptonic()") plot generated particle ids for semileptonic events


Number of expected events in PTDR analysis

(see also PTDR Vol. II, Section 8.1.3 )

Table 8.4 from PTDR vol II:

  Semi-lept. tt Other tt W+ 4j Wbb + 2j Wbb + 3j S/B
Before selection 365k 1962k 82.5k 109.5k 22.5k 5.9
L1+HLTTrigger 62.2% 5.30% 24.1% 8.35% 8.29% 7.8
Four jets ET > 30 GeV 25.4% 1.01% 4.1% 1.48% 3.37% 9.9
pleptonT > 20 GeV/c 24.8% 0.97% 3.9% 1.41% 3.14% 10.3
b-tag criteria 6.5% 0.24% 0.064% 0.52% 0.79% 25.4
Kinematic fit 6.3% 0.23% 0.059% 0.48% 0.72% 26.7
Selected cross section (pb) 5.21 1.10 0.10 0.08 0.05 26.7
Scaled L = 1/fb 5211 1084 104 82 50 26.7
Scaled L = 100/pb 521.1 108.4 10.4 8.2 5.0 26.7
Scaled L = 10/pb 52.11 10.84 1.04 0.82 0.50 26.7


  • setup python in your CMSSW area (as described here
cvs co PhysicsTools/PythonAnalysis/python
export PYTHONPATH=$CMSSW_BASE/src/PhysicsTools/PythonAnalysis/python:$PYTHONPATH

Configuring from python


-- AndreHolzner - 10 Jul 2008

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Topic revision: r12 - 2008-08-08 - AndreHolzner
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