Dear RooFit experts,

I have the following problem I would like to submit to your attention:

I would like to make a 2D-fit to mass and phi angle variables

The likelihood is: nS * (f*P1(m) + (1-f)*P2(m)) * F(phi) + nB*P3(m)

The fit is extended maximum likelihood:

- nS is the yield of the signal
- nB is the yield of the background
- f is the fraction of the probability P1
- 1-f is the fraction of the probability P2
- F is the pdf for the phi angle
- P3 is the pdf for the background

I would like to fit the data in subrange of the mass, let’s call it “massSub” AND I would like to fit the data in subrange of the phi angle let’s call it “phiSub”

My problem is that I don’t know how to tell RooFit how make the fit in these sub-ranges and properly plot the projections. I’m confused about how to use:

Range(…)

SumCoefRange(…)

SplitRange(…)

fixCoefRange(…)

(A) Can you please tell me how would you configure the fitTo(…) method in order to properly execute the fit I just described ?

(B) Can you please tell me how would you plot the mass projection superimposing data and the fit result ?

© Can you please tell me how would you plot the phi angle projection superimposing data and the fit result ?

Thank you very much.

Kind Regards,

- Mauro.