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output_config.md

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Output Configuration

The DelphesEDM4HepConverter takes an OutputSetting parameter to configure which delphes branches go into which edm4hep output collections. In the current implementation of the conversions this is filled from an additional configuration file that defines the necessary parameters:

edm4hep_output_config.tcl. This tcl file has to be passed to the conversion executable as parameter from the command line. No changes to the delphes card that is used are necessary.1 An exemplary call could look something like this (replacing the delphes_card.tcl and the input_file.stdhep with actual input files):

DelphesSTDHEP_EDM4HEP delphes_card.tcl \
                      edm4hep_output_config.tcl \
                      edm4hep_output.root \
                      input_file.stdhep

A module EDM4HepOutput is introduced solely for the purpose of being able to easily reuse the tcl parser from delphes and to introduce a logical containment for the parameters. The names of the delphes branches are taken from the TreeWriter module defintion and used in the EDM4HepOutput.

Collection conversions

The configuration mainly steers which Delphes collections are still available in the edm4hep output. A description of which Delphes output classes correspond to which edm4hep classes can be found below. The collections specified in the EDM4HepOutput module are the BranchNames taken from the TreeWriter definition. Each of the following configuration parameters takes a list of collection names that will then also be available in the output.

ReconstructedParticleCollections

All Track and Tower input collections that will be stored in one global edm4hep::ReconstructedParticleCollection. These will be associated to the generated particles stored as edm4hep::MCParticles. The converter works under the assumption that this is a non-overlapping list of particles. It is the users responsibility to make sure that this is the case. (See known issues).

ParticleFlowCandidate collections from Delphes can also be stored as separate ReconstructedParticleCollections in the output, but they currently have no associations to the generated particles. Note that they are not added to the global ReconstructedParticleCollection described above, as that would lead to double counting.

GenParticleCollection

All Delphes GenParticle collections that will be considered and stored as edm4hep::MCParticle. Each Delphes collection will be put into its own edm4hep output collection under the same name, but all generated particles will be considered for the associations to the ReconstructedParticles in the global collection (See above). Usually it is enough to use the Particle branch here since that contains all generated particles from Delphes.

JetCollections

All Delphes Jet collections that will be converted and stored. Each delphes collection gets its own edm4hep output collection under the same name. The jet constituents are taken from the global ReconstructedParticle collection (See above).

MuonCollections

All Delphes Muon collections that will be converted and stored. Each delphes collection gets its own edm4hep output collection under the same name. Only particles from the global ReconstructedParticle collection are considered.

ElectronCollections

All Delphes Electron collections that will be converted and stored. Each delphes collection gets its own edm4hep output collection under the same name. Only particles from the global ReconstructedParticle collection are considered.

PhotonCollections

All Delphes Photon collections that will be converted and stored. Each delphes collection gets its own edm4hep output collection under the same name. Only particles from the global ReconstructedParticle collection are considered.

MissingETCollections

All Delphes MissingET collections that will be converted and stored. Each delphes collection gets its own edm4hep output collection under the same name. The filled collection contains only one element per event.

ScalarHTCollections

All Delphes ScalarHT collections that will be converted and stored. Each delphes collection gets its own edm4hep output collection under the same name. The filled collection contains only one element per event.

The parameters RecoParticleCollectionName and RecoMCParticleLinkCollectionName control the names of the global reconstructed particle collection and the collection with the RecoMCParticleLinks that can be used to find the MCParticles associated to ReconstructedParticles (and vice versa).

Class conversions

The following table lists which Delphes classes correspond to which edm4hep classes. For the conversion the Delphes classes are taken from the TreeWriter (the BranchClass for each Branch defined in there)

Delphes edm4hep
GenParticle MCParticle
Track ReconstructedParticle with associated Track
Tower ReconstructedParticle with associated Cluster
Jet ReconstructedParticle
Muon ReconstructedParticle (subset collection)
Electron ReconstructedParticle (subset collection)
Photon ReconstructedParticle (subset collection)
MissingET ReconstructedParticle
ScalarHT ParticleID
ParticleFlowCandidate ReconstructedParticle
n/a RecoMCParticleLink

All Delphes classes that are not listed here are currently not converted.

EventHeader Collection

The EventHeader collection is used to store information from the Delphes Event classes. It always contains one element pre event with member variables eventNumber and weight. This is currently only implemented for the DelphesPythia8Reader.

Isolation variable

The isolation variable as calculated by the Delphes isolation module, will be added as a UserDataCollection for each collection of Electron, Muon and Photon during the conversion, called <collection_name>_IsolationVar.

Known issues

  • Not all available information is used in the conversion. An incomplete list of things that are currently not available in edm4hep:

    • Jet substructure variables (including subjets)

  • No conversion of EventHeader information for readers other than DelphesPythia8Reader

Footnotes

  1. As long as all collections requested for the conversion to edm4hep are defined as output branches in the TreeWriter section of the Delphes card. If not, they need to be added there. ↩