WARNING:Minization -- RooFitGlue: Minimized function has

Roofit and RooStats
1

Dear expert,

Fitting with Roofit I am getting warnings such as:

[#0] WARNING:Minization -- RooFitGlue: Minimized function has error status.
Returning maximum FCN so far (4.51693e+06) to force MIGRAD to back out of this region. Error log follows
Parameter values: Gamma=-7.61463, cof1=-2.68304, f1=0.0649471, f2=0.996126, fsig=0.0256133, m0=101.224, scale=-4.71293, sigma=21.404
RooAddPdf::sum[ fsig * sig + fTop * bgtop + [%] * bg ]
    p.d.f value is less than zero (-0.001269), forcing value to zero @ !refCoefNorm=(), !pdfs=(sig = 0.0078143/1,bgtop = 3.95806/1810.81,bg = -0.00151963/1), !coefficients=(fsig = 0.0256133 ± 0.00881652,fTop = 0.00306596)

If my total pdf is positive should not be a problem but why I have a lot of these messages?
How can I get rid of these warnings or, at least understand that they don’t hide something vital for my fit?
How can I be sure that my fit result is ok? (besides checking fit status and covariance matrix)

cheers,
delo

2

Hi,

If you are getting these message in a region far away from the minimum, should not be a problem. If instead you are getting them for parameter values close to the minimum it can be problematic.
If you can remove, by setting better ranges on the parameter values, it would be better. Otherwise I would try to perform a scan of the likelihood in some of the parameters around its minimum, to check that everything is fine.

Best Regards

Lorenzo

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