How can I use my own particle data class ?

When using your own classes they should be put in a directory which is linked to via the enviroment variable $CHANSER_CLASSES . Make sure this variable is set before using the skeleton class maker.

Use chanser_skeleton to make template class code, this code will inherit from CLAS12ParticleOutEvent,

  chanser_skeleton CreateClassParticleData.C name=MyParticleOutEvent

(Please choose something more meaningful than MyPArticleOutEvent, this is just for example.)

The class .h and .cpp files should now be in $CHANSER_CLASSES

  ls $CHANSER_CLASSES
  LoadMyClasses.C  MyParticleOutEvent.cpp  MyParticleOutEvent.h

The file LoadMyClasses.C is generated automatically the first time you make a class. And is used to compile and load your class at run time with the line,

  Loader::Compile("$CHANSER_CLASSES/MyParticleOutEvent.cpp");

You can now edit MyParticleOutEvent.h to include data members you want to write to ntuple and to define the function FillData(). For example a very simple particle data would be just to write the particle momentum. For this I add the data member P,

    /////////////////////////////////////////////////
    /// data member for tree branches below here
    /// Experiment developers add your own data members
    /// if you want them in the tree

    Double_t P=0;

And define the FillData function,

    inline void MyParticleOutEvent::FillData(){

      //move the c12p object to this particle for getting detector data
      auto c12p=_part->CLAS12();

      P=c12p->getP(); //Get the momentum from clas12root region_particle
    }

This class will now be compiled and loaded when you run chanser_root. The source code will be saved in the configured root file and automatically loaded for running with chanser_proof.

To use it with a ParticleDataManager,

/////Make particle trees first in case want to add cut flags
ParticleDataManager pdm{"particle",1}; //1 means append FinalState output data to this ntuple, replace with 0 if you do not need this
pdm.SetParticleOut(new MyParticleOutEvent);
FS->RegisterPostKinAction(pdm);