Cheatsheet: CMSSW Analysis a la Framework

CMSSW

Accessing physics objects

Electrons (PAT/MiniAOD)

Wiki pages	WorkBookPATDataFormats#PatElectron, WorkBookElectronAnalysis
Add to buildfile	<use name="DataFormats/PatCandidates"/>	Related error: undefined reference to `pat::Electron::electronID(std::string const&) const
Header file(s)	#include <DataFormats/PatCandidates/interface/Electron.h>
Label	slimmedElectrons
Collection type	pat::ElectronCollection (vector<pat::Electron>)
Object reference	link
Notes	To see available electron IDs in data, type a wrong ID name in the electronID method and framework will list them along with the error message.

Show legacy information  Hide legacy information 

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 GenParticle

Electrons

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

Photons

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

Jets

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 midPointCone5GenJets
Collection type	CaloJetCollection GenJetCollection
Physics object	reco::Jet

Muons

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.

MET

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
Other	Handle<CaloMETCollection> met; iEvent.getByLabel("met", met); const CaloMET calomet = met->front(); cout << "met px=" << calomet.px() << ", py=" << calomet.py() << endl;

Vertices

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

Tracks

Physics Object

reco::Track

CaloTowers

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.

"Handling" the data

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

In the class definition, define as private the token

edm::EDGetTokenT< pat::ElectronCollection > tok_electrons_;

std::string labelElec_("slimmedElectrons");
tok_electrons_ = consumes< pat::ElectronCollection >(edm::InputTag(labelElec_));

Handle<pat::ElectronCollection> elec;
iEvent.getByToken( tok_electrons_, elec );

Show legacy information  Hide legacy information 

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

# by module and product label
Handle<MuonCollection>trackPtr;
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

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: " << particle.pt() 
            << " eta: " << particle.eta() 
            << " phi: " << particle.phi() << endl;
      someHisto ->Fill( particle.pt() ); 
   };

   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

   include "HLTrigger/HLTfilters/data/hltHighLevel.cfi"                                                                                                                           
   replace hltHighLevel.HLTPaths = {"CandHLT1SumET"}

Sending a string to your analysis module from cfg file

   module somename = YourAnalysisClass {    
      ...
      untracked string fname = "somefile.root"
      ...
   }

class YourAnalysisClass : public edm::EDAnalyzer{
   ...
   private:
      ...
      std::string fname_;
      ...

YourAnalysisClass::YourAnalysisClass(const edm::ParameterSet& cfg):
   fname_ ( cfg.getUntrackedParameter<string>( "fname" ) ) ,
   <further parameters received here> {
... constructor code here... }

YourAnalysisClass::YourAnalysisClass(const edm::ParameterSet& cfg){
   fname =  cfg.getUntrackedParameter<string>( "fname" );
   ... More constructor code/further parameter receiving code 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

service =  RandomNumberGeneratorService {
   # This is to initialize the random engine of the source
    untracked uint32 sourceSeed = 123456789
}

Arsenal

• Candidate selectors allow you to preselect physics objects on the fly, right within the cfg file.
• Gen decay tree analysis modules, ParticleListDrawer_Utility
• Candidate combiner reconstructs decayed particles (e.g. mu+mu- -> Z).
• Various matching modules
• Isolation stuff.
• Modules for filtering events.
• Common math functions

Locating/Accessing Datasets

1. To access root files from CMSSW, use the following format:

   source = PoolSource{ 
      untracked vstring fileNames = {'rfio:/castor/cern.ch/path/to/someData.root', '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 srm.cern.ch , 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/cern.ch/cms/<location>. You can pick e.g. individual files this way. ( "rfio:/castor/cern.ch/cms/store/RelVal/.../somedata.root" 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";

• 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 (cern.ch): /afs/cern.ch/cms/sw/slc4_ia32_gcc345/cms/cmssw/CMSSW_X_Y_Z,
• 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

untracked vstring outputCommands = 
  {
    "keep *",
    "drop *_*_*_HLT",
    "keep FEDRawDataCollection_*_*_*"
  }

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_*_*"}

Notes

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

Useful Links Dump

• Which CMSSW version to go?
• Trigger Tables, HLT, L1, Menu
• Module cfg file parameters
• CMSSW reference manual
• CMSSW CVS (source) code browser
• CMSSW CVS search facility (LXR)
• Installing CMSSW with apt-get
• Cthulhu is always there to help you with your whatever problems!

r53 - 2016-05-26 - 15:27:57 - HalilGamsizkan