Fast Simulation

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The CEPC has two set of tools to do fast simulation. The first is based on full simulation and in the Marlin framework, whose physics objects are smeared and sampling with the resolutions and efficiencies obtianed from full simulation. Its usage is almost same as the full simulation and very conventient to be compared with full simulation. The other fast simulation is using DELPHES package with some necessary modifications and carefully validated with full simulation.

Fast simulation within Marlin

Processor of fast simulaiton

<processor name="MyPFAFastSimu" type="PFAFastSimu">
  <!--Enable PFA double counting-->
  <parameter name="EnableChargeSplitting" type="int">1 </parameter>
  <!--Enable Geometry/Energy Dependent Efficiency.-->
  <parameter name="EnableEfficiency" type="int">1 </parameter>
  <!--Enable absobtion of Neutral Cluster to Charged.-->
  <parameter name="EnableNeutralMerge" type="int">1 </parameter>
  <!--Enable Smearing to Final State Particle Momenta.-->
  <parameter name="EnableSmearing" type="int">1 </parameter>
  <!--Enable scan the polar angle-->
  <parameter name="EnableThetaScan" type="int">1 </parameter>
  <!--quark flavor to be selected-->
  <parameter name="Flavor" type="int">0 </parameter>
  <!--Name of the MCParticle input collection-->
  <parameter name="InputCollectionName" type="string" lcioInType="MCParticle">MCParticle </parameter>
  <!--Name of the MCTruthMapping output collection-->
  <parameter name="MCTruthMappingCollectionName" type="string" lcioOutType="LCRelation">RecoMCTruthLink  </parameter>
  <!--If zero an already existing file will not be overwritten.-->
  <parameter name="OverwriteFile" type="int">1 </parameter>
  <!--Name of the ReconstructedParticles output collection-->
  <parameter name="RecoParticleCollectionName" type="string" lcioOutType="ReconstructedParticle"> FastSimPFOs </parameter>
  <!--The name of the ROOT tree-->
  <parameter name="TreeName" type="string">MCPart </parameter>
  <!--The name of the file to which the ROOT tree will be written-->
  <parameter name="TreeOutputFile" type="string">MCTruth.root </parameter>
  <!--verbosity level of this processor ("DEBUG0-4,MESSAGE0-4,WARNING0-4,ERROR0-4,SILENT")-->
  <!--parameter name="Verbosity" type="string">DEBUG </parameter-->


   <processor name="MyStdHepReader"/>
   <processor name="MyPFAFastSimu"/>
   <processor name="MyLGFastJetClustering"/>

existing fast simulation samples

A full sample of 240 GeV and CEPC_v4 setup (3 Tesla B field) can be found at /cefs/data/FastSim/CEPC240/v02, including higgs signal, 2fermion and 4fermion backgrounds. If you want to make a fast simulation analysis, this is a good starting point.

Fast simulation with DELPHES