Cheatsheet: CMSSW Analysis a la Framework

An unofficial information dump page for CMSSW.


Accessing physics objects

Generator Particles

Wiki page WorkBookGenParticleCandidate
Add to buildfile <use name=SimDataFormats/HepMCProduct>
Header file(s) #include "DataFormats/Candidate/interface/Candidate.h" and
#include "DataFormats/JetReco/interface/GenJet.h" if you need GEN jets
Label genParticleCandidates
Collection type CandidateCollection
Physics Object Candidate


Wiki page WorkBookElectronReco
Add to buildfile <use name=DataFormats/EgammaReco>
Header file(s) #include "DataFormats/EgammaCandidates/interface/PixelMatchGsfElectron.h"
Label pixelMatchGsfElectrons
Collection type PixelMatchGsfElectronCollection
Physics Object PixelMatchGsfElectron


Wiki page WorkBookPhotonReco
Add to buildfile <use name=DataFormats/EgammaReco>
Header file(s) #include "DataFormats/EgammaCandidates/interface/Photon.h"
Label correctedPhotons or photons
Collection type PhotonCollection
Physics object reco::Photon


Wiki page WorkBookJetAnalysis
Add to buildfile <use name=DataFormats/JetReco>
Header file(s) #include "DataFormats/JetReco/interface/CaloJet.h"
#include "DataFormats/JetReco/interface/GenJet.h"
Label Many, e.g. iterativeCone5CaloJets
Collection type CaloJetCollection
Physics object reco::Jet


Wiki page WorkBookMuonAnalysis
Add to buildfile <use name=DataFormats/MuonReco>
<use name=RecoMuon/TrackingTools>
Header file(s) #include "DataFormats/MuonReco/interface/Muon.h"
Label muons
Collection type MuonCollection
Physics Object reco::Muon
Example code available
See this hypernews thread for the muons with fast simulation.


Wiki page ???
Add to buildfile <use name=DataFormats/METReco>
Header file(s) #include "DataFormats/METReco/interface/CaloMETCollection.h"
Label met
Collection type CaloMETCollection
Physics Object reco::CaloMET
Example code Below, or in SusyAnalyzer
Handle<CaloMETCollection> met;
iEvent.getByLabel("met", met);
const CaloMET calomet = met->front();
cout << "met px=" << calomet.px() << ", py=" << << endl; 


Wiki page WorkBookOfflinePrimaryVertexFinding
Add to buildfile ???
Header file(s) #include <DataFormats/VertexReco/interface/Vertex.h>
#include <DataFormats/VertexReco/interface/VertexFwd.h>
Label offlinePrimaryVerticesFromCTFTracks and offlinePrimaryVerticesFromRSTracks
Collection type VertexCollection
Physics object reco::Vertex
Example code


Physics Object reco::Track


These are combined objects from ECAL cells and HCAL towers, they represent the whole calorimetry and are used for e.g. jet reconstruction.
Wiki page
Header file(s) #include "DataFormats/CaloTowers/interface/CaloTowerCollection.h"
Label towerMaker
Collection type CaloTowerCollection
Physics object CaloTower
Example code
Info 1

  • More labels, collections and documentation available here.
  • Namespace documentations: reco, edm.

What is a reco::Particle::LorentzVector ?

  • This is reco::Particle
  • On this page we find that LorentzVector is actually a typedef. Let's click on it.
  • We find what it actually is: typedef math::XYZTLorentzVector reco::Particle::LorentzVector . So it's a math::XYZTLorentzVector . Let's click on it.
  • Now we find typedef XYZTLorentzVectorD math::XYZTLorentzVector, so it's actually math::XYZTLorentzVectorD. We click on it.
  • We find that typedef ROOT::Math::LorentzVector<ROOT::Math::PxPyPzE4D > math::XYZTLorentzVectorD. OK, but no hyperlinks anymore. Let's try google:
  • We google search for ROOT::Math::LorentzVector<ROOT::Math::PxPyPzE4D > and eventually find it's reference page.

"Handling" the data

One accesses the data in the root file thru "handles". Handles types are templated with the collection/data type in the root file. EdmDumpEvent prints the collection types in the first column of it's output.

Taken from Benedikt's presentation:

# by module and default product label
Handle<TrackVector> trackPtr;
iEvent.getByLabel("tracker", trackPtr );

# by module and product label
string muonModule_ = "paramMuons"
string muonProduct_ = "ParamGlobalMuons"
iEvent.getByLabel(muonModule_, muonProduct_, muons);

# by type (what happens if not unique?)
vector<Handle<SimHitVector> > allPtr;
iEvent.getByType( allPtr );

# by Selector
ParameterSelector<int> coneSel("coneSize",5);
Handle<JetVector> jetPtr;
iEvent.get( coneSel, jetPtr );

Looping over particles

Handle types are edm::Handle<CollectionType> and collection types are usually std::vector<ObjectType>.

if your product contains objects of type ObjectType, contained in collection of type CollectionType , and handled by the variable theHandle:

   for (size_t j = 0; j < theHandle->size(); ++ j ) {
      const ObjectType & particle = (*theHandle)[ j ];
      cout << "->   electron" << j << " pT: " << 
            << " eta: " << particle.eta() 
            << " phi: " << particle.phi() << endl;
      someHisto ->Fill( ); 
Yet another loop using an iterator
   size_t idx = 0;
   for( CollectionType::const_iterator cand = theHandle->begin(); 
         cand != theHandle->end(); ++ cand, ++ idx ) {
         // do something, cand is a pointer to your object
         cout << "Electron #" << idx << ": pt=" << cand->pt() << endl;      

Code snippets/recipes

Filtering events according to hlt path

This goes to the cfg file:
   include "HLTrigger/HLTfilters/data/hltHighLevel.cfi"                                                                                                                           
   replace hltHighLevel.HLTPaths = {"CandHLT1SumET"}

Sending a string to your analysis module from cfg file

Let's send a filename to our analysis class. Your cfg file should look like zis:
   module somename = YourAnalysisClass {    
      untracked string fname = "somefile.root"
and the header of your analysis class:
class YourAnalysisClass : public edm::EDAnalyzer{
      std::string fname_;
finally the analysis class constructor:
YourAnalysisClass::YourAnalysisClass(const edm::ParameterSet& cfg):
   fname_ ( cfg.getUntrackedParameter<string>( "fname" ) ) ,
   <further parameters received here> {
... constructor code here... }
Alternative way to receive parameters from within constructor:
YourAnalysisClass::YourAnalysisClass(const edm::ParameterSet& cfg){
   fname =  cfg.getUntrackedParameter<string>( "fname" );
   ... More constructor code/further parameter receiving code here.. }
More information about other types is here. Info about cfg files is here.

Is a parameter provided in the cfg file?

MyAnalyzer::MyAnalyzer(const edm::ParameterSet &conf) {
    if (conf.exists("some_parameter")) do_something

Does a certain product exist in your root file?

  Handle<L1GlobalTriggerReadoutRecord> L1GTRR;
  try {iEvent.getByLabel(l1GTReadoutRecTag_,L1GTRR);} catch (...) {;}
  if ( L1GTRR.isValid() ) { // exists
edm::Handle<edm::TriggerResults> trh;
try {iEvent.getByLabel(triggerInputTag_,trh);} 
catch( cms::Exception& ex ) { LogWarning("HWWTreeDumper") << "Trigger results: " << triggerInputTag_ << " not found"; }
if (!trh.isValid())
   throw cms::Exception("ProductNotValid") << "TriggerResults product not valid";

Setting the event generator random number seed

Implementation in the cfg file is:
service =  RandomNumberGeneratorService {
   # This is to initialize the random engine of the source
    untracked uint32 sourceSeed = 123456789


There are numerous useful tools available for analyses. Using these tools will usually result in shorter code, and more reliable results; and the most important, If some of your results are just not OK, you can blame the developers on it smile

Locating/Accessing Datasets

  1. To access root files from CMSSW, use the following format:
    source = PoolSource{ 
       untracked vstring fileNames = {'rfio:/castor/', 'another file', ... }  
    Here the rfio: prefix means that the file is on CASTOR. For a local file, use the file: prefix.
  2. Now let's locate where the data is. Browse to the DBS Dataset Discovery Page and search for the dataset of your interest.
  3. Once you find your dataset, check it's location. If located at , then you can access it directly from lxplus since it's on CASTOR. Click "plain". You'll see a long list of root files in the form:
    /store/mc/year/month/day/<~dataset name>/<some number>/longnamedfile.root
    This path translates to CASTOR location /castor/<location>. You can pick e.g. individual files this way. ( "rfio:/castor/" or "/store/RelVal/.../somedata.root" ).
  4. If you want to access the whoel dataset, click "cff" instead of "plain" on dataset's page. This will show you a cff file containing paths and names of all root files belonging to that dataset. Directly include this cff file in your cfg file.
  5. Hint: While working on a single root file which is on CASTOR, copying it to /tmp/$USER and then accessing from there may speed up things.

Framework messages to file

    # Keep the logging output to a nice level #
    include "FWCore/MessageService/data/MessageLogger.cfi"
    replace MessageLogger.destinations = {"detailedInfo.txt"}

Other possibly useful stuff

  • Event selection using trigger-HLT bits: here.
  • Skipping missing input root files (goes into the PoolSource part):
    untracked bool skipBadFiles = true #  skip missing or inaccessible files. Defaults to false
    Note that this won't prevent crashes with bad root files.
  • Skipping the first n events in a root file:
       source = PoolSource {
          untracked vstring fileNames = { <empty or list of files> }
          untracked uint32 skipEvents  = 21
    Skips the first 21 events. Note that the FirstEvent / FirstRun options may not work the same way.
  • Throwing exceptions
    throw cms::Exception("ErrorName") << "Message";
FIXME: Add header
  • Skeleton code generators are very useful.
  • Getting the cross-section of the generated event:
     Handle<double> genCrossSect;
     evt.getByLabel( "genEventRunInfo:PreCalculatedCrossSection", genCrossSect);
  • Useful tool: addpkg , checks out packages from CVS.
  • List of candidate clone producers.
  • List of clone producers immediately available as modules.
  • CMSSW location on AFS ( /afs/,
  • Other interesting locations on AFS (header files):
    • $CMSSW_ROOT/src/DataFormats/Candidate/interface
    • $CMSSW_ROOT/src/DataFormats/Math/interface
  • Saving a Subsample of the AOD plus the User Data
  • See which physics objects a root file contains: EdmDumpEventContent <root file>
  • scramv1 p is the shorthand for scramv1 project . Other shorthands: r for runtime , s for setup
  • I don't know what exactly scramv1 b --fast does but I think unless you do not change your buildfiles and add/remove new source files it's safe to use this option which speeds up the compile.

Dropping Products

Put into PoolSource module block
untracked vstring outputCommands = 
    "keep *",
    "drop *_*_*_HLT",
    "keep FEDRawDataCollection_*_*_*"
More info available here.

Keeping Products

untracked vstring outputCommands = {    
     "drop *",
    # HepMC event. Famos uses it
     "keep edmHepMCProduct_source_*_*",
     "keep edmGenInfoProduct_source_*_*",

    # or
    "keep *_source_*_*",

   # Old gen event format
    "keep *_genParticleCandidates_*_*",

    # New gen event format
    "keep *_genParticles_*_*",          # to be removed when no external MC ref's left

   # Keep trigger results
    "keep edmTriggerResults_TriggerResults_*_*",

    # if you chose to save all particles into a  collection in PAT layer0, to make it persistent
    "keep *_*_allJets_*", 

   # Gen jets
    "keep *_midPointCone5GenJetsNoNuBSM_*_*",

   # Calo towers
   "keep *_towerMaker_*_*",

    # CSA07 Stuff
    "keep *_genEventWeight_*_*",
    "keep *_genEventScale_*_*",
    "keep *_genEventProcID_*_*",
    "keep *_csa07EventWeightProducer_*_*"}

Possibly Useful Files/Paths:

  • CSA07 Soups:
    • gumbo: /castor/
    • chowder all events: /CSA07AllEvents/CMSSW_1_6_7-CSA07-Tier0-A3-Chowder/RECO


  • Keep your buildfiles as clean as possible. Smaller buildfiles, faster compiles.

Useful Links Dump

r51 - 2016-04-23 - 13:21:22 - HalilGamsizkan

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Topic revision: r51 - 2016-04-23 - HalilGamsizkan
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