ROOFit: pdf convolution and RooClassFactory

Roofit and RooStats
1

Hi all,
I need to make the convolution of 2 pdfs in RooFit.
At the moment, I use something like this (and it works)

{
RooRealVar x(“x”,“x”,-10,10);
RooRealVar mean1(“mean1”,“mean of landau”,2);
RooRealVar sigma1(“sigma1”,“sigma of landau”,1);
RooLandau landau(“landau”,“landau”,x,mean1,sigma1);
RooRealVar mean2(“mean2”,“mean of gaussian”,0);
RooRealVar sigma2(“sigma2”,“sigma of gaussian”,2);
RooGaussian gauss(“gauss”,“gaussian PDF”,x,mean2,sigma2);
// Plot PDF
RooNumConvPdf model(“model”,“model”,x,landau,gauss);
RooPlot* xframe = x.frame();
model.plotOn(xframe);
xframe->Draw();
}

What if I want to implement this using RooClassFactory to define a new pdf? How should I write my evaluate()?
In principle, I’d like to be able to write something like

RooModel model(“model”, “model”, x, mean1, sigma1, mean2, sigma2)

Is it possible?

Cheers,
Giuseppe

2

Hi Giuseppe,

this is certainly possible. This procedure requires you implementing the convolution code.
If you are trying to achieve a faster evaluation, I would suggest to have a look to the much more efficient RooFFTConvPdf before diving in your own implementation of the convolution.

Cheers,
Danilo