How to write this pdf format in RooFit?

Roofit and RooStats
1

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!

2

RooVoigtian is what you are looking for.

Cheers.

3

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

4

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) ;

Wouter