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[RF] Bug with RooExtendPdf produces inconsistency in rf204b_extendedLikelihood_rangedFit.C between before 6.26 and after 6.28 #22959
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Description
I am reporting a bug in RooExtendPdf, which can be seen in rf204b_extendedLikelihood_rangedFit.C of the tutorial. In the recent versions, the fit using RooExtendPdf class has wrong best-fit values of 𝑁 =4494 (and 𝛼 is biased as well) while the fit using the composite of signal and background PDFs implemented by RooAddPdf correctly fits the distribution with 𝑁 =9990.
Looking back into the past versions, this issue appears since version 6.28. With version 6.26, RooExtendPdf properly works.
Reproducer
ROOT tutorial: rf204b_extendedLikelihood_rangedFit.C.
ROOT version
Any versions after 6.28
Installation method
Built from source
Operating system
SLES15 and ALMA10
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No response
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[-]Bug with RooExtendPdf produces inconsistency in rf204b_extendedLikelihood_rangedFit.C between before 6.26 and after 6.28[/-][+][RF] Bug with RooExtendPdf produces inconsistency in rf204b_extendedLikelihood_rangedFit.C between before 6.26 and after 6.28[/+][RF] Fix RooExtendPdf yield/shape in ranged extended fits
guitargeek commentedon Aug 3, 2026
Thanks for reporting this long-standing regression! I have opened a PR with a suggested fix:
[RF] Fix RooExtendPdf yield/shape in ranged extended fits
[RF] Fix RooExtendPdf yield/shape in ranged extended fits
[RF] Fix RooExtendPdf yield/shape in ranged extended fits