G4CoulombScattering.cc

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//
// -------------------------------------------------------------------
//
// GEANT4 Class file
//
//
// File name:     G4CoulombScattering
//
// Author:        Vladimir Ivanchenko 
//
// Creation date: 22.08.2004
//
// Modifications:
// 01.08.06 V.Ivanchenko add choice between G4eCoulombScatteringModel and
//          G4CoulombScatteringModel
//

//
// -------------------------------------------------------------------
//
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#include "G4CoulombScattering.hh"
#include "G4SystemOfUnits.hh"
#include "G4eCoulombScatteringModel.hh"
#include "G4IonCoulombScatteringModel.hh"
#include "G4Proton.hh"
#include "G4EmParameters.hh"

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using namespace std;

G4CoulombScattering::G4CoulombScattering(const G4String& name)
  : G4VEmProcess(name),q2Max(TeV*TeV),isInitialised(false)
{
  //  G4cout << "G4CoulombScattering constructor "<< G4endl;
  SetBuildTableFlag(true);
  SetStartFromNullFlag(false);
  SetIntegral(true);
  SetSecondaryParticle(G4Proton::Proton());
  SetProcessSubType(fCoulombScattering);
}

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G4CoulombScattering::~G4CoulombScattering()
{}

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G4bool G4CoulombScattering::IsApplicable(const G4ParticleDefinition& p)
{
  return (p.GetPDGCharge() != 0.0 && !p.IsShortLived());
}

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void G4CoulombScattering::InitialiseProcess(const G4ParticleDefinition* p)
{
  // second initialisation not allowed for the time being
  // this means that polar angle limit change will not be appled 
  // after first initialisation
  if(isInitialised) { return; }

  G4EmParameters* param = G4EmParameters::Instance();
  G4double a = param->FactorForAngleLimit()*CLHEP::hbarc/CLHEP::fermi;
  q2Max = 0.5*a*a;
  G4double theta = param->MscThetaLimit();

  // restricted or non-restricted cross section table
  G4bool yes = false;
  if(theta == CLHEP::pi) { yes = true; }
  SetStartFromNullFlag(yes);
  /*
  G4cout << "### G4CoulombScattering::InitialiseProcess: "
     << p->GetParticleName()
   << " Emin(MeV)= " << MinKinEnergy()/MeV
   << " Emax(TeV)= " << MaxKinEnergy()/TeV
   << " nbins= " << LambdaBinning()
   << " theta= " << theta
   << G4endl;
  */

  isInitialised = true;
  G4double mass = p->GetPDGMass();
  G4String name = p->GetParticleName();
  //G4cout << name << "  type: " << p->GetParticleType() 
  //<< " mass= " << mass << G4endl;
  yes = true;
  if (mass > GeV || p->GetParticleType() == "nucleus") {
    SetBuildTableFlag(false);
    yes = false;
    if(name != "GenericIon") { SetVerboseLevel(0); }
  } else {
    if(name != "e-" && name != "e+" &&
       name != "mu+" && name != "mu-" && name != "pi+" && 
       name != "kaon+" && name != "proton" ) { SetVerboseLevel(0); }
  }

  if(!EmModel(0)) { 
    if(yes) { SetEmModel(new G4eCoulombScatteringModel()); } 
    else    { SetEmModel(new G4IonCoulombScatteringModel()); }
  }
  G4VEmModel* model = EmModel(0);
  G4double emin = std::max(param->MinKinEnergy(),model->LowEnergyLimit());
  G4double emax = std::min(param->MaxKinEnergy(),model->HighEnergyLimit());
  model->SetPolarAngleLimit(theta);
  model->SetLowEnergyLimit(emin);
  model->SetHighEnergyLimit(emax);
  AddEmModel(1, model);
}

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G4double G4CoulombScattering::MinPrimaryEnergy(const G4ParticleDefinition* part,
                 const G4Material* mat)
{
  // Pure Coulomb scattering
  G4double emin = 0.0;

  // Coulomb scattering combined with multiple or hadronic scattering
  G4double theta = G4EmParameters::Instance()->MscThetaLimit();

  if(0.0 < theta) {
    G4double p2 = q2Max*mat->GetIonisation()->GetInvA23()/(1.0 - cos(theta));
    G4double mass = part->GetPDGMass();
    emin = sqrt(p2 + mass*mass) - mass;
  }

  return emin;
}

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void G4CoulombScattering::StreamProcessInfo(std::ostream& outFile) const
{
  G4double tetmin = G4EmParameters::Instance()->MscThetaLimit()/degree;
  outFile << "      ";
  if(tetmin > 179.) { outFile << "ThetaMin(p)"; }
  else              { outFile << tetmin; }
  outFile << " < Theta(degree) < 180";

  if(q2Max < DBL_MAX) { outFile << "; pLimit(GeV^1)= " << sqrt(q2Max)/GeV; }
  outFile << G4endl;
}

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void G4CoulombScattering::ProcessDescription(std::ostream& out) const
{
  out <<
  "  Coulomb scattering. Simulation of elastic scattering\n" << 
  "    events individually. May be used in combination with multiple\n" << 
  "    scattering, where Coulomb scattering is used for hard (large angle)\n" <<
  "    collisions and multiple scattering for soft collisions.";
  G4VEmProcess::ProcessDescription(out);
}

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