Hi, I’m trying to use an extended `RooRealSumPdf`

, but I get a discrepancy from an extended `RooAddPdf`

. The model is `uniform+gaussian`

. The implementations are:

```
modelRSP = RooRealSumPdf("modelRSP","modelRSP",
RooArgList(w.pdf("bkg"), w.pdf("sig")),
RooArgList(w.var("bkgNorm"),w.var("sigNorm")),
True
)
```

And

```
modelRAP = RooAddPdf("modelRAP","modelRAP",
RooArgList(w.pdf("bkg"), w.pdf("sig")),
RooArgList(w.var("bkgNorm"),w.var("sigNorm")),
)
```

When I plot these, I get two different results. In particular, even with the same `sigNorm`

value, the `RooRealSumPdf`

seems to have **less signal** than the `RooAddPdf`

. The plot shows the discrepancy:

I have a stand-alone example of this: errorDemoAddPdfVsSumPdf.py (4.3 KB). Am I missing something here? I’ve tried extending the uniform and gaussian components manually, but I get a similar result. Any help would be very appreciated.