Organization and simultaneous fits: illustration use of ROOT.RooCustomizer and ROOT.RooSimWSTool interface in factory workspace tool in a complex standalone B physics example

**Author:** Clemens Lange, Wouter Verkerke (C++ version)

*This notebook tutorial was automatically generated with ROOTBOOK-izer from the macro found in the ROOT repository on Wednesday, January 19, 2022 at 10:26 AM.*

In [ ]:

```
import ROOT
w = ROOT.RooWorkspace("w")
```

Make signal model for CPV: A bmixing decay function in t (convoluted with a triple Gaussian resolution model) times a Gaussian function the reconstructed mass

In [ ]:

```
w.factory(
"PROD::sig( BMixDecay::sig_t( dt[-20,20], mixState[mixed=1,unmix=-1], tagFlav[B0=1,B0bar=-1], "
"tau[1.54], dm[0.472], w[0.05], dw[0], "
"AddModel::gm({GaussModel(dt,biasC[-10,10],sigmaC[0.1,3],dterr[0.01,0.2]), "
"GaussModel(dt,0,sigmaT[3,10]), "
"GaussModel(dt,0,20)},{fracC[0,1],fracT[0,1]}), "
"DoubleSided ), "
"Gaussian::sig_m( mes[5.20,5.30], mB0[5.20,5.30], sigmB0[0.01,0.05] ))"
)
```

Make background component: A plain decay function in t times an Argus function in the reconstructed mass

In [ ]:

```
w.factory("PROD::bkg( Decay::bkg_t( dt, tau, gm, DoubleSided), " "ArgusBG::bkg_m( mes, 5.291, k[-100,-10]))")
```

Make composite model from the signal and background component

In [ ]:

```
w.factory("SUM::model( Nsig[5000,0,10000]*sig, NBkg[500,0,10000]*bkg )")
```

Introduce a flavour tagging category tagCat as observable with 4 states corresponding to 4 flavour tagging techniques with different performance that require different parameterizations of the fit model

ROOT.RooSimWSTool operation:

```
- Make 4 clones of model (for each tagCat) state, will gain an individual
copy of parameters w, and biasC. The other parameters remain common
- Make a simultaneous pdf of the 4 clones assigning each to the appropriate
state of the tagCat index category
```

ROOT.RooSimWSTool is interfaced as meta-type SIMCLONE in the factory. The $SplitParam() argument maps to the SplitParam() named argument in the ROOT.RooSimWSTool constructor

In [ ]:

```
w.factory("SIMCLONE::model_sim( model, $SplitParam({w,dw,biasC},tagCat[Lep,Kao,NT1,NT2]))")
```

Class ROOT.RooCustomizer makes clones of existing pdfs with certain prescribed modifications (branch of leaf node replacements)

Here we take our model (the original before ROOT.RooSimWSTool modifications) and request that the parameter w (the mistag rate) is replaced with an expression-based function that calculates w in terms of the Dilution parameter D that is defined D = 1-2*w

Make a clone model_D of original 'model' replacing 'w' with 'expr('0.5-D/2',D[0,1])'

In [ ]:

```
w.factory("EDIT::model_D(model, w=expr('0.5-D/2',D[0,1]) )")
```

Print workspace contents

In [ ]:

```
w.Print()
```

Make workspace visible on command line

In [ ]:

```
ROOT.gDirectory.Add(w)
```