Likelihood fit fails to fit the tail

[yofeng]

Hi RooFit experts,

I’m trying to build one 3rd order dijet function to fit the smooth background. With chi2 fit the fitting result looks good compared with data.

However, if I do a likelihood fit, the fit fails and the agreement in the tail region looks bad.

I attached my script and the histogram here. Could anyone take a look and see if something is wrong?

Thanks a lot.

Best,
Yongbin

testfit.py (1.6 KB)

test.root (6.5 KB)

[moneta]

Hi,

I think this could be related to an open issue of binned likelihood fit in RooFit, see https://sft.its.cern.ch/jira/browse/ROOT-3874

The same fit works correctly in ROOT when using the binned likelihood fit there. Attached is your script extended to use ROOT

Lorenzo

[moneta]

testfit.py (3.0 KB)