I have a question regarding AddNormFactor in HistFactory. In my model I have 3 different backgrounds.
I have added a normalisation factor for background1 in the standard way and it is free to vary within a certain range. Now I would like to constrain the normalisation of background 2 to be 1/3 of the normalisation of background1. In Roofit I would do it as RooFormula, but I can not find a way to do this in the HistFatory formalism.
How can I do this?