void test_2dIntegration() {
  
  using namespace RooFit;
  
  RooRealVar x("x", "x", 0, 200);
  x.setRange("signal", 30, 200);
  
  RooRealVar y("y", "y", 0, 200);
  y.setRange("signal", 30, 200);
  
  TFile * inFile = new TFile("test_file.root","READ");
  TH2F * myHisto = (TH2F*) inFile -> Get("hn_QCDIsoShapeHisto");
  RooDataHist rooQCDIsoShapeHisto("rooQCDIsoShapeHisto", "QCDIso", RooArgList(x,y), myHisto); // per arrivare alle funzioni di fit
  RooHistPdf QCDIsoPdf("QCDIsoPdf", "QCDIso", RooArgList(x,y), rooQCDIsoShapeHisto, 0) ; // le funzioni di fit
  
  RooPlot* rooPlot = x.frame();
  rooQCDIsoShapeHisto.plotOn(rooPlot, DataError(RooAbsData::SumW2));
  QCDIsoPdf.plotOn(rooPlot, LineColor(kBlue));
  TCanvas* c1 = new TCanvas();
  rooPlot->Draw();
  
  RooAbsReal* QCDTrueIntegral = QCDIsoPdf.createIntegral(RooArgSet(x,y), NormSet(RooArgSet(x,y)), Range("signal"));   
  std::cout << "======>>>>>> MC NQCD in signal region = " << QCDTrueIntegral->getVal() << std::endl;
  
  
}