Analysis JEventProcessor

Summary

• The DEventProcessor can be minimal in content.
• The code below analyzes the b1pi DReaction, fills reaction-independent histograms, and skims successful events into a new hddm file.
• Code and documentation for the setting up the b1pi DReaction can be found at: DReaction
• Although not shown below, you can also create and fill a ROOT TTree with the DParticleCombo data instead of skimming.

DEventProcessor_b1pi_hists.h

• This is from sim-recon/src/programs/Analysis/plugins/b1pi_hists/

#ifndef _DEventProcessor_b1pi_hists_
#define _DEventProcessor_b1pi_hists_
 
#include "TFile.h"
#include "TROOT.h"
 
#include "JANA/JEventProcessor.h"
 
#include "DANA/DApplication.h"
#include "ANALYSIS/DAnalysisResults.h"
#include "HDDM/DEventWriterREST.h"
 
#include "DFactoryGenerator_b1pi_hists.h"
 
using namespace jana;
 
class DEventProcessor_b1pi_hists : public JEventProcessor
{
  public:
    DEventProcessor_b1pi_hists(){};
    ~DEventProcessor_b1pi_hists(){};
    const char* className(void){return "DEventProcessor_b1pi_hists";}
 
  private:
    jerror_t init(void);            ///< Called once at program start.
    jerror_t brun(JEventLoop *eventLoop, int runnumber);  ///< Called everytime a new run number is detected.
    jerror_t evnt(JEventLoop *eventLoop, int eventnumber);  ///< Called every event.
    jerror_t erun(void);            ///< Called everytime run number changes, provided brun has been called.
    jerror_t fini(void);            ///< Called after last event of last event source has been processed.
 
    // Create reaction-independent actions.
    DHistogramAction_TrackMultiplicity dHistogramAction_TrackMultiplicity;
    DHistogramAction_ThrownParticleKinematics dHistogramAction_ThrownParticleKinematics;
    DHistogramAction_DetectedParticleKinematics dHistogramAction_DetectedParticleKinematics;
    DHistogramAction_GenReconTrackComparison dHistogramAction_GenReconTrackComparison;
};
 
#endif // _DEventProcessor_b1pi_hists_

DEventProcessor_b1pi_hists.cc

• This is from sim-recon/src/programs/Analysis/plugins/b1pi_hists/
• Note the AddFactoryGenerator() line in InitPlugin().

#include "DEventProcessor_b1pi_hists.h"
 
// Routine used to create our DEventProcessor
extern "C"
{
  void InitPlugin(JApplication *app)
  {
    InitJANAPlugin(app);
    app->AddProcessor(new DEventProcessor_b1pi_hists());
    app->AddFactoryGenerator(new DFactoryGenerator_b1pi_hists());
  }
} // "C"
 
//------------------
// init
//------------------
jerror_t DEventProcessor_b1pi_hists::init(void)
{
  return NOERROR;
}
 
//------------------
// brun
//------------------
jerror_t DEventProcessor_b1pi_hists::brun(JEventLoop *locEventLoop, int runnumber)
{
  return NOERROR;
}
 
//------------------
// evnt
//------------------
jerror_t DEventProcessor_b1pi_hists::evnt(JEventLoop *locEventLoop, int eventnumber)
{
  //Fill reaction-independent histograms.
  dHistogramAction_TrackMultiplicity(locEventLoop);
  dHistogramAction_ThrownParticleKinematics(locEventLoop);
  dHistogramAction_DetectedParticleKinematics(locEventLoop);
  dHistogramAction_GenReconTrackComparison(locEventLoop);
 
  //Perform the analysis for this event by requesting the results.
    //For each DReaction, this creates the DParticleCombo objects and performs the DAnalysisActions stored in the DReaction
  vector<const DAnalysisResults*> locAnalysisResultsVector;
  locEventLoop->Get(locAnalysisResultsVector);
 
  //Output TTree //saves the data from the surviving DParticleCombo's of all output-enabled DReaction's to their respective TTree's
  vector<const DEventWriterROOT*> locEventWriterROOTVector;
  locEventLoop->Get(locEventWriterROOTVector);
  locEventWriterROOTVector[0]->Fill_Trees(locEventLoop);
 
  //Mark that the event should be saved if at least one DParticleCombo survived all of the cuts
  bool locSaveEventFlag = false;
  for(size_t loc_i = 0; loc_i < locAnalysisResultsVector.size(); ++loc_i)
  {
    const DAnalysisResults* locAnalysisResults = locAnalysisResultsVector[loc_i];
    if(locAnalysisResults->Get_Reaction()->Get_ReactionName() != "b1pi")
      continue;
    if(locAnalysisResults->Get_NumPassedParticleCombos() == 0)
      continue;
    locSaveEventFlag = true;
    break;
  }
 
  //Save the event to dana_rest_b1pi.hddm
  if(locSaveEventFlag)
  {
    vector<const DEventWriterREST*> locEventWriterRESTVector;
    locEventLoop->Get(locEventWriterRESTVector);
    locEventWriterRESTVector[0]->Write_RESTEvent(locEventLoop, "b1pi");
  }
 
  return NOERROR;
}
 
//------------------
// erun
//------------------
jerror_t DEventProcessor_b1pi_hists::erun(void)
{
  // Any final calculations on histograms (like dividing them)
  // should be done here. This may get called more than once.
  return NOERROR;
}
 
//------------------
// fini
//------------------
jerror_t DEventProcessor_b1pi_hists::fini(void)
{
  return NOERROR;
}