How to fit two coupled functions to two channels


I’m not sure if anybody is able to help me but maybe there is a simple solution for my problem.

I have to Resonances in two channels coming from the same particle. I would like to fit a coupled breit wigner to it. This means that mean value and width should be the same variable as well as the chi2 that is evaluated for two histograms/graphs simulatiously.

I’m sure that many people have done it and everybody shows results from such fits but I cannot find anywhere an ansatz how to do it technically. Has anybody done this in root already? How do I start? Does somebody know literature? Is it trivial.

I thankful for any hint.


You can look at the tutorial fit/combinedFit.C … Fit.C.html


Exactly what I needed! Thank you very much!