CollinsSpillerFragm.cxx

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//____________________________________________________________________________
/*
 Copyright (c) 2003-2020, The GENIE Collaboration
 For the full text of the license visit http://copyright.genie-mc.org

 Costas Andreopoulos <constantinos.andreopoulos \at cern.ch>
 University of Liverpool & STFC Rutherford Appleton Laboratory
*/
//____________________________________________________________________________

#include "Physics/Hadronization/CollinsSpillerFragm.h"
#include "Physics/Hadronization/FragmentationFunctions.h"

using namespace genie;

//___________________________________________________________________________
CollinsSpillerFragm::CollinsSpillerFragm() :
FragmentationFunctionI("genie::CollinsSpillerFragm")
{

}
//___________________________________________________________________________
CollinsSpillerFragm::CollinsSpillerFragm(string config) :
FragmentationFunctionI("genie::CollinsSpillerFragm", config)
{

}
//___________________________________________________________________________
CollinsSpillerFragm::~CollinsSpillerFragm()
{
  delete fFunc;
}
//___________________________________________________________________________
double CollinsSpillerFragm::Value(double z) const
{
// Evaluate the fragmentation function

  if(z<0 || z>1) return 0;
  return fFunc->Eval(z);
}
//___________________________________________________________________________
double CollinsSpillerFragm::GenerateZ(void) const
{
// Return a random number using the fragmentation function as PDF

  return fFunc->GetRandom();
}
//___________________________________________________________________________
void CollinsSpillerFragm::Configure(const Registry & config)
{
  Algorithm::Configure(config);
  this->BuildFunction();
}
//___________________________________________________________________________
void CollinsSpillerFragm::Configure(string config)
{
  Algorithm::Configure(config);
  this->BuildFunction();
}
//___________________________________________________________________________
void CollinsSpillerFragm::BuildFunction(void)
{
  fFunc = new TF1("fFunc",genie::utils::frgmfunc::collins_spiller_func,0,1,2);

  fFunc->SetParNames("Norm","Epsilon");

  double N = -1. ;
  GetParam( "CSFrag-Norm", N, false ) ;

  double e = 0. ;
  GetParam( "CSFrag-Epsilon", e, false ) ;

  // if the normalization parameter was left negative, explicitly normalize
  // the fragmentation function
  if(N<0) {
    N=1;
    fFunc->SetParameters(N,e);
    double I = fFunc->Integral(0,1);
    assert(I>0);
    N = 1./I;
  }
  fFunc->SetParameters(N,e);
}
//___________________________________________________________________________