Scale variation on RooFFTConvPdf

Dear experts,

I am using a convolution of a Crystal-Ball and a Breit-Wigner using the RooFFTConvPdf to model the signal pdf in the Z’ analysis.

In the past we were using a Voigtian for modelling the signal pdf, in this case the scale variation was modelled by a function that was plugged into the observable parameter of the Voigtian, allowing then the peak to shift to find any potential excess close-by the evaluation point.

However, RooFFTConvPdf constructor seems not to allow a function as an observable as the Voigtian allowed… Is there any work around to this?

Many thanks,


Can you do not do the scaling of the observables on the pdf variables which are given as input to the RooFFTConvPdf ?

Best Regards


Thanks for the reply,

The problem is that when calling RooFFTConvPdf you need to pass an observable, and the two pdf’s and then you override whatever observable choice you made when creating the individual pdf’s.

Am I misunderstanding something?