How to write this pdf format in RooFit?

Hi, all:

I would like to write the following pdf format as signal shape:

BW convolved with a Gaussian function, here for the Gaussian function, the resolution is mass dependent (the format is known), not constant.

How to write in RooFit? Thanks in advance!

RooVoigtian is what you are looking for.


But in RooVoigtian, the resolution of Gaussian should be RooAbsReal. For my case, the resolution is the function of the mass. How?

Hi ChengPing,

You gave the answer yourself: RooVoigtian takes a RooAbsReal as resolution argument, not a RooRealVar, so one can simply enter
a formula here that depends on the mass, e.g.

// Observable
RooRealVar m(“m”,“m”,-10,10) ;

// Resolution as function of mass
RooRealVar a(“a”,“a”,0.1,-1,1) ;
RooFormulaVar sigma(“sigma”,“m*a+1”,RooArgSet(m,a)) ;

// Pdf
RooRealVar m0(“m0”,“m0”,0) ;
RooRealVar gamma(“gamma”,“gamma”,1) ;
RooVoigtian v(“v”,“v”,m,m0,gamma,sigma) ;