Define Profile Likelihood Ratio

[Kane_Jay]

Hi，
I want to calculate the profile likelihood ratio with RooFit and RooStats , I have the signal model (with 2 parameters ), bkg model and data set; i use the HistFactory produce the modelconfig; but the Likelihood function is Possion(PoI,nusiance par)*Gauss(nuisance par) ;I dont know how to add Gauss fuction into likelihood function, So is there any way to achieve it with RooFit or RooStats？
best regards

kane

[eguiraud]

Hi @Kane_Jay ,
sorry for the late reply! We need @moneta or @jonas here, let’s ping them.

Cheers,
Enrico

[moneta]

Hi,
I am not sure I understand well your question. If you use the HistFactory, it will build for you the model pdf. Given the model pdf and the data you can provide them as input to the RooStats ProfileLikelihoodCalculator which will compute the profile likelihood ratio.
(see tutorial ROOT: tutorials/roostats/StandardProfileLikelihoodDemo.C File Reference )
Otherwise you can also obtain directly in RooFit the likelihood using RooAbsPdf::createNLL and RooNLLVar::createProfile (see tutorial ROOT: tutorials/roofit/rf605_profilell.C File Reference).

Cheers

Lorenzo