COHXSecAR.cxx

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//____________________________________________________________________________
/*
 Copyright (c) 2003-2025, The GENIE Collaboration
 For the full text of the license visit http://copyright.genie-mc.org
 
 Costas Andreopoulos <c.andreopoulos \at cern.ch>
 University of Liverpool
*/
//____________________________________________________________________________
 
#include <TMath.h>
#include <Math/IFunction.h>
#include <Math/Integrator.h>
#include <Math/IntegratorMultiDim.h>
#include "Math/AdaptiveIntegratorMultiDim.h"
 
#include "Framework/Conventions/GBuild.h"
#include "Framework/Conventions/Constants.h"
#include "Framework/Conventions/Controls.h"
#include "Framework/Conventions/Units.h"
#include "Physics/Coherent/XSection/COHXSecAR.h"
#include "Physics/XSectionIntegration/GSLXSecFunc.h"
#include "Framework/Messenger/Messenger.h"
#include "Framework/ParticleData/PDGUtils.h"
#include "Framework/Numerical/MathUtils.h"
#include "Framework/Utils/Range1.h"
#include "Framework/Numerical/GSLUtils.h"
 
using namespace genie;
using namespace genie::constants;
using namespace genie::controls;
using namespace genie::utils;
 
//____________________________________________________________________________
COHXSecAR::COHXSecAR() :
XSecIntegratorI("genie::COHXSecAR")
{
 
}
//____________________________________________________________________________
COHXSecAR::COHXSecAR(string config) :
XSecIntegratorI("genie::COHXSecAR", config)
{
 
}
//____________________________________________________________________________
COHXSecAR::~COHXSecAR()
{
 
}
//____________________________________________________________________________
double COHXSecAR::Integrate(
      const XSecAlgorithmI * model, const Interaction * in) const
{
  const InitialState & init_state = in -> InitState();
 
  if(! model->ValidProcess(in) ) return 0.;
 
  const KPhaseSpace & kps = in->PhaseSpace();
  if(!kps.IsAboveThreshold()) {
     LOG("COHXSecAR", pDEBUG)  << "*** Below energy threshold";
     return 0;
  }
 
  Range1D_t y_lim = kps.Limits(kKVy);
 
  // Check this
  double Enu      = init_state.ProbeE(kRfLab);
  double Elep_min = (1.-y_lim.max) * Enu;
  double Elep_max = (1.-y_lim.min) * Enu;
 
  LOG("COHXSecAR", pINFO)
       << "Lepton energy integration range = [" << Elep_min << ", " << Elep_max << "]";
 
  Interaction * interaction = new Interaction(*in);
  interaction->SetBit(kISkipProcessChk);
  //interaction->SetBit(kISkipKinematicChk);
 
  double xsec = 0;
  if (fSplitIntegral) {
    utils::gsl::dXSec_dElep_AR * func =
      new utils::gsl::dXSec_dElep_AR(model, interaction, fGSLIntgType, fGSLRelTol, fGSLMaxEval);
 
    //~ ROOT::Math::IntegrationOneDim::Type ig_type = ROOT::Math::IntegrationOneDim::kNONADAPTIVE;
    ROOT::Math::IntegrationOneDim::Type ig_type = ROOT::Math::IntegrationOneDim::kADAPTIVE;
 
    double abstol = 1; // Pretty sure this parameter is unused by ROOT.
    int size = 1000;  // Max number of subintervals, won't reach nearly this.
    int rule = 2; // See https://www.gnu.org/software/gsl/manual/gsl-ref_17.html#SEC283
                  // Rule 2 is 21 points min
    ROOT::Math::Integrator ig(*func,ig_type,abstol,fGSLRelTol,size,rule);
 
    xsec = ig.Integral(Elep_min, Elep_max) * (1E-38 * units::cm2);
    delete func;
  }
  else {
    double zero    = kASmallNum;
    double pi      = kPi-kASmallNum ;
    double twopi   = 2*kPi-kASmallNum ;
 
    //~ ROOT::Math::IBaseFunctionMultiDim * func =
          //~ new utils::gsl::wrap::d5Xsec_dEldOmegaldOmegapi(model, interaction);
    //~ double kine_min[5] = { Elep_min, zero , zero    , zero, zero };
    //~ double kine_max[5] = { Elep_max, pi   , twopi   , pi  , twopi};
 
    ROOT::Math::IBaseFunctionMultiDim * func =
          new utils::gsl::d4Xsec_dEldThetaldOmegapi(model, interaction);
    double kine_min[4] = { Elep_min, zero , zero    , zero    };
    double kine_max[4] = { Elep_max, pi   , pi      , twopi   };
 
    ROOT::Math::IntegrationMultiDim::Type ig_type =
      utils::gsl::IntegrationNDimTypeFromString(fGSLIntgType);
 
    double abstol = 1; //We mostly care about relative tolerance.
    ROOT::Math::IntegratorMultiDim ig(*func, ig_type, abstol, fGSLRelTol, fGSLMaxEval);
 
    xsec = ig.Integral(kine_min, kine_max) * (1E-38 * units::cm2);
    delete func;
  }
 
  delete interaction;
 
  return xsec;
}
//____________________________________________________________________________
void COHXSecAR::Configure(const Registry & config)
{
  Algorithm::Configure(config);
  this->LoadConfig();
}
//____________________________________________________________________________
void COHXSecAR::Configure(string config)
{
  Algorithm::Configure(config);
  this->LoadConfig();
}
//____________________________________________________________________________
void COHXSecAR::LoadConfig(void)
{
  // Get GSL integration type & relative tolerance
  GetParamDef( "gsl-integration-type", fGSLIntgType, string("vegas") ) ;
 
  int max_eval;
  GetParamDef( "gsl-max-eval", max_eval, 4000 ) ;
  fGSLMaxEval    = (unsigned int) max_eval ;
 
  GetParamDef( "gsl-relative-tolerance", fGSLRelTol,  0.01) ;
  GetParamDef( "split-integral", fSplitIntegral, true ) ;
 
}
//_____________________________________________________________________________