Intro & executive summary

This is a collection of tcMet performance & validation plots updating some of the info in our draft note. Samples used are summer & Fall 08 samples:

• • /ZJets-madgraph/Fall08_IDEAL_V9_reco-v2/GEN-SIM-RECO
  • /WW_2l/Summer08_IDEAL_V9_v2/GEN-SIM-RECO

For now, we looked at the performance in:

• DY events looking for fake MET rejection
• WW events for real MET performance

In Summary, we see:

• ~x3 rejection of fake MET for a cut at 30GeV (similar to 1.6.x performance)
• ~20% improvement of MET resolution in events with real MET (again similar to 1.6.x)
• ~20% improvement in the determination of the direction of the MET as well.

Results for events with fake MET (DY):

• we observe significant reduction of the tail of the MET distribution for di-lepton final states, consistent with that seen previously in release 16X
• metMuonCorr is met corrected for muons

• table for cut MET > 30 GeV

MET	muons	electrons
metMuonCorr	5640	4921
tcMET	1852	1721
factor	3.1	2.9

• table for cut MET > 50 GeV

MET	muons	electrons
metMuonCorr	748	644
tcMET	204	192
factor	3.7	3.4

Results for events with real MET (WW):

• WW decaying to two leptons has real MET via neutrinos produced along wtih the leptons thus tcMET should have little effect on the MET distribution for this process as observed above

• table for cut MET > 30 GeV

MET	muons	electrons
metMuonCorr	3643	4289
tcMET	3722	4349
factor	1.02	1.01

• table for cut MET > 50 GeV

MET	muons	electrons
metMuonCorr	1983	2216
tcMET	2025	2271
factor	1.02	1.02

• although our goal is to reduce the tails of fake MET distributions, it is also interesting to look at what effect tcMET has on MET resolution
• below are plots comparing the difference between corrected MET and generator MET for muon corrected MET and tcMET

• in both cases, the mean is shifted closer to 0 and the RMS improves
  • the resolution improves by at least 20% in both final states

• below are the same plots as a fraction of the generator MET

Comparison of MET direction

• below are plots of delta phi between corrected MET and generator MET for events with real MET

• in both final states, direction resolution improves by ~20%

Comparison with patMET

• Since patMET is about to be used extensively, we compare to what one get from it, out of the box.
  • patMET (met_pat_metCor) is corrected for both muons and Jets

• table for cut MET > 30 GeV

MET	muons	electrons
met_pat_metCor	4967	6371
metMuonCorr	5640	4921
tcMET	1852	1721
pat factor	2.7	3.7
muon factor	3.1	2.9

• table for cut MET > 50 GeV

MET	muons	electrons
met_pat_metCor	593	714
metMuonCorr	748	644
tcMET	204	192
pat factor	2.9	3.7
muon factor	3.7	3.4

• patMET performs better than muon corrected MET in the muon final state, but worse in the electron final state
  • this result is in agreement with what we saw for muon+!JES corrections to MET in 16X
• tcMET significantly reduces the tail of the MET distribution relative to both types of MET

Definitions and notations

• caloMET corrected for muons will serve as the baseline for all comparisons

• for comparison of MET in dilepton events, we require the following:
  • dimuon final state
    • two global muons
    • pt > 20 GeV
    • no additional leptons with pt > 20 GeV
  • dielectron final state
    • two electrons
    • pt > 20 GeV
    • no additional leptons with pt > 20 GeV
• for comparison of MET in dijet events, we require the following:

...

• we use the standard CMS muon correction scheme. Details: met muon corrections are done using JetMETCorrections/Type1MET/python/metMuonCorrections_cff.py which corrects for global muons that also pass
  • nhits > 5
  • pt > 10 (from global fit), abs(eta) < 2.5
  • qoverp_error < 0.5

• metMuonCorr is MET corrected for muons using the standard CMS method
• met_pat_metCor is PAT MET, where MET has been corrected for muons and the jet energy scale (JES)

Validation, N-1 plots

• tracking has changed considerably between 16X and 22X and thus the quality cuts on tracks must be revisited

• quality cuts in 16X were
  • nhits > 6
  • chi2/ndof < 5
  • abs(d0) < 0.05

• changes between 16X and 22X
  • tracking improved at lower pt
  • changed the way hits are defined
    • can now have more than one hit per layer
  • displaced beamSpot requires correction

• below are new N-1 plots using ZJets sample

• Number of valid hits, N-1 plot
  

• tracking group recommends cut of nhits > 10

• Normalized chi-squared, N-1 plot
  

• Corrected impact parameter, N-1 plot
  

• the new track quality cuts are:
  • nhits > 10
  • chi2/ndof < 4
  • abs(d0corr) < 0.1

Instructions and Example Use ( How to run it...)

• The following tags are available for using tcMET in 22X releases. After setting up a 22X release area, one should check out
  • cvs co -r V02-05-00-20 RecoMET/METAlgorithms
  • cvs co -r V02-08-02-16 RecoMET/METProducers
  • cvs co -r V00-04-02-16 RecoMET/Configuration
  • cvs co -r V00-06-02-09 DataFormats/METReco

• After building, to see how to incorporate tcMet correction to your analysis sequence, see example in test file. This example will produce a tcMET collection.

• The implementation of tcMET makes use of the metMuonCorrections module that is part of 22X releases. As a result, the user must include the cff file in their cfg (as is done in the above example) and place the module in their path before tcMet as shown below.

# load muon corrections for !MET module
process.load("JetMETCorrections.Type1MET.MetMuonCorrections_cff")

# load track-corrected MET module
process.load("RecoMET.METProducers.TCMET_cfi")

# run sequence of muon+track MET corrections
process.p = cms.Path(process.MetMuonCorrections*process.tcMet)

* the configuration files for the modules are

• • JetMETCorrections/Type1MET/python/corMetMuons_cfi.py
  • JetMETCorrections/Type1MET/python/MetMuonCorrectiosn_cff.py
  • RecoMET/METProducers/python/TCMET_cfi.py

It is recommended to use the configurations provided.

• After running a test job, you should see a tcMet collection in your TBrowser

• The tcMet collection can be accessed in the usual way:

Handle< View<MET> > tcmet_h;
    
iEvent.getByLabel("tcMet", tcmet_h);
  
*evt_tcmet        = (tcmet_h->front()).et();
*evt_tcmetPhi     = (tcmet_h->front()).phi();
*evt_tcsumet      = (tcmet_h->front()).sumEt();

-- FrankGolf - 19 Feb 2009