Instructions for CMSSW22X

Set your runtime environment (shown for release %WBRELEASENEW%):

Run standard photon reconstruction

The following example shows how to reconstruct standard Photons starting from RecHits, which are assumed to already exist in the input sample.

Check out the package RecoEgamma/Examples with tag V00-01-09 from the CVS repository and compile it:

cvs co -r  V00-01-09 RecoEgamma/Examples
cd RecoEgamma/Examples
scramv1 b

Go into the test directory of RecoEgamma/Examples and examine the file egamma120DigisToPhotons.cfg.

The maxEvents parameter is used to define the number of events to be processed, in this case 1000. The next part specifies the input files, in this case a release validation sample of particle gun back-to-back photons with transverse energy 35 GeV, generated with CMSSW_1_6_0. Any sample containing RecHits generated with CMSSW_1_6_X can be used here. Such samples can be found using DBS2.

    source = PoolSource {
        untracked vstring fileNames = {

The following specifies the output filename, in this case photons.root, and the event content to be stored, in this case, the RECO content:

    include "Configuration/EventContent/data/EventContent.cff"    
    module RECO = PoolOutputModule {
        untracked string fileName = 'photons.root'
        using RECOSIMEventContent

The next 2 lines are standard includes for running reconstruction. Using FakeConditions means that no conditions data (alignment and calibration coefficients) are read from the conditions database.

    include "Configuration/StandardSequences/data/FakeConditions.cff"
    include "Configuration/StandardSequences/data/Reconstruction.cff"

Next, the path is defined, which specifies the sequences of modules which will be run. In this case, the sequences run are:

  • ckftracks, defined in Reconstruction.cff: Reconstructs CKF tracks globally (NOT required for photon reco, but needed for primary vertex reco used in the example analysis).
  • ecalClusteringSequence, defined in ecalClusteringSequence.cff: Standalone ECAL reconstruction strting from EcalRecHits: BasicClusters, SuperClusters and PreshowerClusters.
  • vertexreco, defined in Reconstruction.cff: Primary vertex reconstruction (NOT required for photon reco, but needed for the example analysis)
  • photonSequence, defined in photonSequence.cff: Reconstructs photons from SuperClusters and applies energy corrections.

    path p = { ckftracks, ecalClusteringSequence, electronPixelSeeds, vertexreco, photonSequence }

Run the reconstruction

To run the reconstruction, go the RecoEgamma/Examples/test directory and type:
cmsRun recHitsToPhotons.cfg

The resulting output root file will include an Event tree containing Photons, BasicClusters, SuperClusters as well as the event Monte Carlo truth (edmHepMCProduct). You can check the content of the root tree by simply browsing the file with a root browser.

* Snapshot of a Root Browser for the root file produced after running the PhotonProducer:


Collections ending with __Rec were already in the events that were read in. The collections reconstructed in the example end with __Rec1, the name of the process in the first line of recHitsToPixelMatchGsfElectrons.cfg

The Photon objects after energy corrections are in the collection:

The SuperClusters associated to the photons are in the collections:

Responsible: Nancy Marinelli
Last reviewed by: NancyMarinelli - 26 Jun 2009

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