void truth()
{

  gROOT->Reset();
  gROOT->SetStyle("Plain");
  gStyle->SetOptFit(0);
  gStyle->SetOptStat(0);
  gStyle->SetOptTitle(0110);
  gStyle->SetTitleBorderSize(0);
  gStyle->SetStatBorderSize(1);   


  FILE *fin1;

  const int num130 = 38950;
  const int num300 = 9900;

  float Z1mass130[num130];
  float Z2mass130[num130];
  float Z1mass300[num300];
  float Z2mass300[num300];

  TH1F *hZ1_130mass = new TH1F("hZ1_130mass","",120,0,120);
  TH1F *hZ2_130mass = new TH1F("hZ2_130mass","",120,0,120);

  TH1F *hZ1_300mass = new TH1F("hZ1_300mass","",120,0,120);
  TH1F *hZ2_300mass = new TH1F("hZ2_300mass","",120,0,120);



  fin1 = fopen("Zmass_130GeV.dat","r");
  for(int i=0; i<num130; i++)
    {
      fscanf(fin1,"%f %f\n",&Z1mass130[i],&Z2mass130[i]);
//      printf("%f %f\n",Z1mass130[i],Z2mass130[i]);
      hZ1_130mass->Fill(Z1mass130[i]);
      hZ2_130mass->Fill(Z2mass130[i]);
    }
  fclose(fin1);
  
  fin1 = fopen("Zmass_300GeV.dat","r");
  for(int i=0; i<num300; i++)
    {
      fscanf(fin1,"%f %f\n",&Z1mass300[i],&Z2mass300[i]);
//      printf("%f %f\n",Z1mass300[i],Z2mass300[i]);
      hZ1_300mass->Fill(Z1mass300[i]);
      hZ2_300mass->Fill(Z2mass300[i]);
    }
  fclose(fin1);


  // SCATTER PLOT 

  
  c1 = new TCanvas("c1");
  c1->SetGridx();
  c1->SetGridy();

  TH2F *hZmass = new TH2F("hZmass","",2,0,120,2,0,120);
  hZmass->SetXTitle("M_{Z1} (GeV)");
  hZmass->SetYTitle("M_{Z2} (GeV)");
  TAxis *xaxis = hZmass->GetXaxis();
  xaxis->SetTitleOffset(1.2);
  TAxis *yaxis = hZmass->GetYaxis();
  yaxis->SetTitleOffset(1.2);
  hZmass->Draw();
  
  gr10000 = new TGraph(num130,Z1mass130,Z2mass130);
  gr10000->SetMarkerStyle(20);
  gr10000->SetMarkerSize(0.3);
  gr10000->SetMarkerColor(5);
  gr10000->SetLineColor(1);
  gr10000->SetLineWidth(1);
  gr10000->Draw("P");

  gr20000 = new TGraph(num300,Z1mass300,Z2mass300);
  gr20000->SetMarkerStyle(20);
  gr20000->SetMarkerSize(0.3);
  gr20000->SetMarkerColor(2);
  gr20000->SetLineColor(1);
  gr20000->SetLineWidth(1);
  gr20000->Draw("P");

  c2 = new TCanvas("c2");
  c2->SetGridx();
  c2->SetGridy();
  c2->Divide(1,2);
  
  c2->cd(1);

  hZ1_130mass->SetXTitle("M_{Z1} (GeV) (130GeV Higgs)");
  TAxis *xaxis = hZ1_130mass->GetXaxis();
  xaxis->SetTitleOffset(1.2);
  TAxis *yaxis = hZ1_130mass->GetYaxis();
  yaxis->SetTitleOffset(1.2);
  hZ1_130mass->Draw();

  c2->cd(2);
  hZ2_130mass->SetXTitle("M_{Z2} (GeV) (130GeV Higgs)");
  TAxis *xaxis = hZ2_130mass->GetXaxis();
  xaxis->SetTitleOffset(1.2);
  TAxis *yaxis = hZ2_130mass->GetYaxis();
  yaxis->SetTitleOffset(1.2);
  hZ2_130mass->Draw();
  
  c3 = new TCanvas("c3");
  c3->SetGridx();
  c3->SetGridy();
  c3->Divide(1,2);
  
  c3->cd(1);

  hZ1_300mass->SetXTitle("M_{Z1} (GeV) (300GeV Higgs)");
  TAxis *xaxis = hZ1_300mass->GetXaxis();
  xaxis->SetTitleOffset(1.2);
  TAxis *yaxis = hZ1_300mass->GetYaxis();
  yaxis->SetTitleOffset(1.2);
  hZ1_300mass->Draw();

  c3->cd(2);
  hZ2_300mass->SetXTitle("M_{Z2} (GeV) (300GeV Higgs)");
  TAxis *xaxis = hZ2_300mass->GetXaxis();
  xaxis->SetTitleOffset(1.2);
  TAxis *yaxis = hZ2_300mass->GetYaxis();
  yaxis->SetTitleOffset(1.2);
  hZ2_300mass->Draw();
  
  


}