void convertRootCaptureData(string file="/data/chocula/villaa/cascadeSimData/normge_fast.root", string outfile="capture.txt")
{

  //open the file
  TFile *f = new TFile(file.c_str());
  if(!f){
    cerr << "ERROR! (convertRootCaptureData): ROOT file could not be opened." << endl;
    return;
  }
  f->ls();

  //get trees
  TTree *t = f->Get("cascade");
  TTree *te = f->Get("escapeInfo");
  t->AddFriend(te);

  //a way to get resolutions
  //t->SetAlias("rng","sin(2*pi*rndm)*sqrt(-2*log(rndm))");
  
  //get the summed energy and didInteract value 
  t->SetEstimate(4000000);
  t->Draw("Sum$(delE):didInteract","","goff");

  //get the vectors
  Int_t n = t->GetSelectedRows();
  cout << "Got " << n << " events. " << endl;
  Double_t *energy = t->GetV1();
  Double_t *gamma_interact = t->GetV2();

  //print the output
  ofstream out(outfile.c_str());
  for(int i=0;i<10;i++){
    cout << energy[i] << "\t" << gamma_interact[i] << endl;
  }
  out.close();

  return;
}