Hi

I have a question regarding what really goes on inside the TTree:UnbinnedFit. But first I’ll describe what it is that I want to do.

I have a rather small data sample and I would like to fit to a threedimensional angular distribution with two fit parameters to the data set. The distribution is a user defined function f3 defined as:

Double_t W(Double_t *x, Double_t *fitpar);

where x is the data and fitpar the parameters. The fit is performed using

TTree->UnbinnedFit(“f3”,“thetagp:thetap:phip”,cut10);

Everything works (apart from a rather large error for one of the parameters but improve that by varying the parameters manually instead.)

The questions are: Is the unbinned fit a log likelihood fit to the data?

Is the UnbinnedFit related to RooFit? Is the RooFit documentation relevant in this case?

Best Regards,

Agnes Lundborg