Simulatenous fit of various regions with different kinematic observables and binning

Dear experts,

Apologies if this is a trivial question or was asked before, I could not find an answer on the web or on this forum.

We are using Roofit without HistFactory. We would like to perform a simultaneous fit of many regions, therefore we use a RooSimultaneous and fit it to a “combined” RooDataHist.

  • If the pdfs in each region are binned in the same way (observable, binning), there are no problems and data are built using the following constructor:
RooDataHist::RooDataHist 	( 	const char *  	name,
		const char *  	title,
		const RooArgList &  	vars,
		RooCategory &  	indexCat,
		std::map< std::string, RooDataHist *>  	dhistMap,
		Double_t  	wgt = 1.0 
	)
  • issues arise when we want some regions to be binned differently or w.r.t other observables. We do not know how to create the corresponding RooDataHist. Indeed, it is clearly written in the documentation regarding the RooDataHist constructor we used previously:

The ranges and number of bins are taken from the input histogram and must be the same in all histograms

What are we missing? How can the ranges and number of bins can be different in each regions?

Thanks a lot for your help!

Best wishes
Matthias

Dear all,

this is a kind reminder about this issue. Does anyone have any idea?

For now we use the following “hack”: we added some “1-bin” region by binning them the same way than the others but having only 1 bin filled with all the events and the other bins set to 0. It seems to work but it would be nice to get a confirmation from experts.

Thanks a lot for your help!

Cheers
Matthias

Dear all,

new reminder. Is there any Roofit expert around? Do you need more information?

Best wishes
Matthias

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