[6.40] [RF] Fix fractions in expectedEvents for normed RooAddPdf components - #23517
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guitargeek merged 1 commit intoSep 27, 2026
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In RooAddPdf::createExpectedEventsFunc(), the range fractions for the extended likelihood term were computed via 1/(integral of the component pdf over the full default range). This only yields the fraction of the component inside the norm range if the component is normalized over the full default range. That assumption is violated in the new evaluation backend, where pdfs are compiled with arbitrary internal normalization. For example, a RooProdPdf might have each factor normalized over the per-observable union of the fit ranges, which for disjoint multi-dimensional ranges is not the full default range. The extended likelihood term then used wrong expected events and produced wrong fitted yields, e.g. for the product of two Gaussians fitted over eight sideband boxes in two observables, where the Gaussian product got a range fraction of 1.0 instead of ~0.089. Instead, multiply each coefficient with the ratio of two integrals of the same component: numerator over the norm range, denominator over the coefficient reference range (full default range by default, or the range fixed by selectNormalizationRange(), e.g. via the SumCoefRange fit option). Any constant normalization cancels in the ratio, matching the RooAddPdf::expectedEvents() semantics used by the legacy backend. The new C++ unit test covers an extended fit of a Gaussian product plus uniform background in eight 2D sideband ranges, with reference values computed with plain math (erf and logarithms) instead of the legacy backend. Closes root-project#23512. 🤖 Done with the help of AI (cherry picked from commit 7b50e59)
Test Results 22 files 22 suites 3d 9h 17m 47s ⏱️ Results for commit 9f85e80. |
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Backport of #23513, requested by @guitargeek.