cint.doc

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`CINT' Analysis Mode

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The file cint.C shows an example of program which can be run via the CINT ROOT interpreter. To run it, just do: "root cint.C". If you are already inside "root", use ".x cint.C".

Interpreted analyses are well suited for small or medium size data samples, for which computer time is not the critical issue, while you want to code just few instructions, maybe interactively. You may also provide simplified C++ instructions to CINT, like:

hrig = new TH1F ("hrig", "Momentum (GeV)", 50, -10., 10.);

instead of

TH1F* hrig = new TH1F ("hrig", "Momentum (GeV)", 50, -10., 10.);

Some additional comments are in order:

• One has to create and/or load the specific AMS Root library containing all the ROOT class definitions, class attributes and utilities. For instance:
  gSystem->Exec("cd ../lib; gmake shared");
  gSystem->Load("../lib/libAMSRoot.so").
  
  

• We can add several Root files with the AMSChain::Add("file") method. The AMSChain class inherits all the methods of the TChain class, but simplifies the life by hiding some AMS internal operations. Example:
  AMSChain* ams = new AMSChain;
  ams->Add("../files/test.root");
  ams->Add("rfio:my_castor_file.root");
  
  

• The analysis is performed on AMSEventR objects:
  
  "AMSEventR* pev = ams.GetEvent()"
  
  
  "AMSEventR* pev = ams.GetEvent(entry_number)"
  
  
  "AMSEventR* pev = ams.GetEvent(run_number, event_number)"
  
  If you prefer not to do pointer coding like "pev->whatever", you can add:
  "AMSEventR &ev = *pev;"
  
  and use "ev.whatever" from that point on.

• In order to access in a simple way all relevant pieces of information many useful definitions, via pointers and vectors, are implemented. For example, the number of hits in ECAL is given by::
  
  cout << "#Ehits: " << ev.nEcalHit() << endl;
  
  or, alternatively:
  cout << "#Ehits: " << pev->nEcalHit() << endl;
  
  The "i" Hit in ECAL belongs to the class EcalHitR, and it may be accessed either as:
  
  EcalHitR hit = ev.EcalHit(i);
  
  or via pointers:
  
  EcalHitR* phit = pev->pEcalHit(i);
  
  A reference to the ith element is obtained as:
  EcalHitR* phit = &ev.EcalHit(i);
  
  The full list of AMS classes and attributes can be found HERE . For instance, in EcalHitR the first member is "Status", which can be accessed either as:
  
  int stat = ev.EcalHit(i).Status;
  
  
  or:
  int stat = pev->pEcalHit(i)->Status;
  
  
  

{
      gROOT->Reset();
      gSystem->Exec("cd ../lib; make shared");
      gSystem->Load("../lib/libAMSRoot.so");

      AMSChain* ams = new AMSChain;
      ams->Add("../files/test.root");
      //ams->Add("http://pcamsf0.cern.ch/f2dah1/MC/AMS02/2004A/protons/el.pl1.10200/738197524.0000001.root");
      //ams->Add("rfio:/castor/cern.ch/ams/MC/AMS02/2004A/protons/el.pl1.10200/738197524.0000001.root");

      TFile* hfile = new TFile ("amstest.root", "RECREATE"); 

      AMSEventList* list = new AMSEventList;

      TH1F* hrig = new TH1F ("hrig", "Momentum (GeV)", 50, -10., 10.);
      
      AMSEventR* pev = NULL;
      while (pev = ams->GetEvent()) {
            for (int i=0; i<pev->nParticle(); i++) {
                  ParticleR* part = pev->pParticle(i);
                  hrig->Fill(part->Momentum);
                  if (pev->nVertex()>0) {
                          list->Add(pev); // Add to list of selected events
                          pev->Fill(); // write it into output ROOT file
                  }
            }
      }

      hrig->Draw();
      hfile->Write();
      list->Write("select.list");

      printf("We have processed %d events\n", (int)ams->GetEntries());
      printf("Histograms saved in '%s'\n", hfile->GetName());
}

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