// 1. Store this macro in a file named "fitMassPeak.cc"
// 2. Start a ROOT session from the macro directory
// 3. Run the macro by typing ".x fitMassPeak.cc"
void fitMassPeak() {
// define variables
RooRealVar mass("mass","Reconstructed Candidate Mass",0.0,8.0,"GeV");
RooRealVar mean("mean","Peak Mass",4.0,2.0,6.0,"GeV");
RooRealVar sigma("sigma","Peak Width",1.0,0.1,2.0,"GeV");
// build model
RooGaussian gauss("gauss","Gaussian Peak Model",mass,mean,sigma);
// read data
RooDataSet *data= RooDataSet::read("data.txt",mass);
// fit model to data
gauss.fitTo(*data);
// plot results
RooPlot *frame= mass.frame();
// create an empty frame
data->plotOn(frame, RooFit::Binning(8));
// plot data histogram using 8 bins
gauss.plotOn(frame);
// superimpose PDF scaled to data
gauss.paramOn(frame);
// superimpose fitted param values
frame->Draw();
}