Dear all,

Hopefully this is my last question regarding this project… thanks to all for their help and advice.

I have successfully generated a set of RooRealVars using the RooSimPdfBuilder class:

```
Plot label is "simPdf"
--- RooAbsPdf ---
Cached value = 0
1) 0x46e4aa0 RooRealVar:: a_a_param_a1 = 0.5 L(0 - 1) "a_a_param (a1)"
2) 0x46e6f20 RooRealVar:: a_a_param_a2 = 0.5 L(0 - 1) "a_a_param (a2)"
3) 0x46e3d80 RooRealVar:: a_d_param_a1 = 0.5 L(0 - 1) "a_d_param (a1)"
4) 0x46fb020 RooRealVar:: a_d_param_a2 = 0.5 L(0 - 1) "a_d_param (a2)"
5) 0x7fff9465a020 RooRealVar:: gamma = 0.5 L(0 - 1) "gamma"
6) 0x46ef570 RooRealVar:: h_a_param_h1 = 0.5 L(0 - 1) "h_a_param (h1)"
7) 0x4704bc0 RooRealVar:: h_a_param_h2 = 0.5 L(0 - 1) "h_a_param (h2)"
8) 0x46fc120 RooRealVar:: h_d_param_h1 = 0.5 L(0 - 1) "h_d_param (h1)"
9) 0x47176d0 RooRealVar:: h_d_param_h2 = 0.5 L(0 - 1) "h_d_param (h2)"
```

I now need to apply a condition to these parameters such that:

(sum over a_a_param_a(i)) = n i.e. a1 + a2 + a3 + … + an = n

This reduces the free parameters of my subsequent fit by 1 and will help everything converge happily.

I’d usually do this using a RooForumuIaVar, but I can’t see a way to do this using the RooRealVars that have been automatically generated by the RooSimPdfBuilder class.

Can anyone see a work around?

Best,

S