void readClassTree(TString inputFile){

  TCanvas *c1 = new TCanvas("c1","Electron flux",200,10,600,400);
  c1->SetGrid();
  c1->SetTicks();
  c1->Draw();
  TCanvas *c2 = new TCanvas("c2","Energy momentum match",200,10,600,400);
  c2->SetGrid();
  c2->SetTicks();
  c2->Draw();

  // Create some histograms.
  TH1D *eflux = new TH1D("eflux","Electron simulated flux;GeV;counts",100,0.,20.);
  TH2D *qnstrip = new TH2D("qnstrip","qtot/nstrip;GeV;qtot/nstrip",1000,-20.,20.,1000,0.,35.);

  // Open the file
  TFile *file = TFile::Open(inputFile);
  TTree *tree = (TTree*)file->Get("pamcalotree");
  PamCalo *pc = new PamCalo();
  
  tree->SetBranchAddress("PamCalo",&pc);

  for ( Int_t i=0; i<tree->GetEntries(); i++) {

    tree->GetEntry(i);

    if ( pc->energy > -20. && pc->energy < 0. ) eflux->Fill(fabs(pc->energy));
    qnstrip->Fill(pc->energy,pc->qtot/(float)pc->nstrip);

  }
 
  c1->cd();
  eflux->Draw();

  c2->cd();
  c2->SetLogz();
  qnstrip->Draw("colz");

}