From \$ROOTSYS/tutorials/roofit/rf513_wsfactory_tools.C

```/////////////////////////////////////////////////////////////////////////
//
// 'ORGANIZATION AND SIMULTANEOUS FITS' RooFit tutorial macro #513
//
//  Illustration use of RooCustomizer and RooSimWSTool interface
//  in factory workspace tool in a complex standalone B physics example
//
// 04/2009 - Wouter Verkerke
//
/////////////////////////////////////////////////////////////////////////

#ifndef __CINT__
#include "RooGlobalFunc.h"
#endif
#include "RooRealVar.h"
#include "RooDataSet.h"
#include "RooGaussian.h"
#include "RooConstVar.h"
#include "RooChebychev.h"
#include "RooAddPdf.h"
#include "RooWorkspace.h"
#include "RooPlot.h"
#include "TCanvas.h"
#include "TAxis.h"
using namespace RooFit ;

void rf513_wsfactory_tools()
{
RooWorkspace* w = new RooWorkspace("w") ;

// B u i l d   a   c o m p l e x   e x a m p l e   p . d . f .
// -----------------------------------------------------------

// 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
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
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
w->factory("SUM::model( Nsig[5000,0,10000]*sig, NBkg[500,0,10000]*bkg )") ;

// E x a m p l e   o f   R o o S i m W S T o o l   i n t e r f a c e
// ------------------------------------------------------------------

// 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
//
// RooSimWSTool operation:
//     - Make 4 clones of model (for each tagCat) state, that will gain an individual
//       copy of parameters w,dw and biasC. The other parameters remain common
//     - Make a simultaneous p.d.f. of the 4 clones assigning each to the appropriate
//       state of the tagCat index category

// RooSimWSTool is interfaced as meta-type SIMCLONE in the factory. The \$SplitParam()
// argument maps to the SplitParam() named argument in the RooSimWSTool constructor
w->factory("SIMCLONE::model_sim( model, \$SplitParam({w,dw,biasC},tagCat[Lep,Kao,NT1,NT2]))") ;

// E x a m p l e   o f   R o o C u s t o m i z e r   i n t e r f a c e
// -------------------------------------------------------------------
//
// Class RooCustomizer makes clones of existing p.d.f.s with certain prescribed
// modifications (branch of leaf node replacements)
//
// Here we take our model (the original before 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 as D = 1-2*w

// Make a clone model_D of original 'model' replacing 'w' with 'expr('0.5-D/2',D[0,1])'
w->factory("EDIT::model_D(model, w=expr('0.5-D/2',D[0,1]) )") ;

// Print workspace contents
w->Print() ;

// Make workspace visible on command line
gDirectory->Add(w) ;
}

```
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