{

   // observable //
   RooRealVar* mass = new RooRealVar("mass", "", 180., 600.);

   // normalization //
   RooRealVar* mu = new RooRealVar("mu", "signal yield", 100., 0., 100000.);
   RooRealVar* correction = new RooRealVar("correction", "Wg signal correction", 1., 0., 100000.); // TODO: replace with efficiency * luminosity
   correction->setConstant(kTRUE);
   RooFormulaVar* N_sig = new RooFormulaVar("N_sig", "@0*@1", RooArgList(*mu, *correction));
   //RooRealVar* N_sig = new RooRealVar("N_sig", "signal yield", 200., 0., 100000.);
   //
   RooRealVar* N_bkg = new RooRealVar("N_bkg", "Wg background yield ", 5000., 0., 100000.);

   // ROOADDPDF //
   // signal //
   RooRealVar* mymean = new RooRealVar("mymean", "", 300., -10., 10.);
   RooRealVar* mysigma = new RooRealVar("mysigma", "", 80., 0., 10.);
   RooGaussian* mygauss = new RooGaussian("mygauss", "", *mass, *mymean, *mysigma);
   RooExtendPdf* extended_mass_signal = new RooExtendPdf("extended_mass_signal_", "", *mygauss, *N_sig);

   // background //
   RooRealVar* mass_exp_c     = new RooRealVar("mass_exp_c", "", -0.6, -10., 10.);
   RooExponential* mass_exp   = new RooExponential("mass_exp", "", *mass, *mass_exp_c);
   RooExtendPdf* extended_mass_background = new RooExtendPdf("extended_mass_background_", "", *mass_exp, *N_bkg);

   // total //
   RooAddPdf* myaddpdf = new RooAddPdf("myaddpdf", "", RooArgSet(*extended_mass_signal, *extended_mass_background)); 

   // generate data //
/*
   RooDataSet* data = myaddpdf->generate(*mass);

   // fit data //
   mymean->setConstant(kTRUE);
   mysigma->setConstant(kTRUE);
   mass_exp_c->setConstant(kTRUE);

   //extended_mass_background->fitTo(*data);
   myaddpdf->fitTo(*data);

   // plot //
   RooPlot* myframe = mass->frame(100);
   data->plotOn(myframe);
   myaddpdf->plotOn(myframe, RooFit::LineColor(kBlue+2));
   myframe->Draw();
*/
   ///////////////////////////////////////////////////
   // DO FULL TOY MC STUDY //
   mymean->setConstant(kTRUE);
   mysigma->setConstant(kTRUE);
   mass_exp_c->setConstant(kTRUE);

   RooMCStudy *mcs = new RooMCStudy(*myaddpdf, RooArgSet(*mass), RooFit::FitModel(*myaddpdf), RooFit::Extended(kTRUE), RooFit::Silence(), RooFit::FitOptions(RooFit::PrintEvalErrors(-1), RooFit::PrintLevel(2), RooFit::Warnings(kFALSE),  RooFit::Save(kTRUE), RooFit::Minos(kTRUE)));

   //mcs->generateAndFit(200);
   mu->setVal(0.);
   mu->setConstant(kTRUE);
   mcs->generate(200, 0, kFALSE, "/sps/atlas/c/cmaiani/ToyStudy_Wg2012/check_bias/prova_%04d.dat");
   mu->setVal(0.);
   mu->setConstant(kFALSE);
   mcs->fit(200, "/sps/atlas/c/cmaiani/ToyStudy_Wg2012/check_bias/prova_%04d.dat");

   // plot relevant distributions //
   RooPlot* frame1 = mcs->plotParam(*mu, RooFit::Bins(25)) ;
   RooPlot* frame2 = mcs->plotError(*mu, RooFit::Bins(25)) ;
   RooPlot* frame3 = mcs->plotPull(*mu, -3., 3., 25, kTRUE);
   TCanvas* c1 = new TCanvas("c1", "", 600, 600); c1->Divide(2,2);
   c1->cd(1);
   frame1->Draw();
   c1->cd(2);
   frame2->Draw();
   c1->cd(3);
   frame3->Draw();
   //
   RooPlot* frame4 = mcs->plotPull(*N_bkg, RooFit::Bins(50), RooFit::FitGauss(kTRUE)) ;
   new TCanvas; frame4->Draw();
   ///////////////////////////////////////////////////
}