genie::LwlynSmithQELCCPXSec Class Reference

Computes neutrino-nucleon(nucleus) QELCC differential cross section Is a concrete implementation of the XSecAlgorithmI interface.
. More...

#include <LwlynSmithQELCCPXSec.h>

Inheritance diagram for genie::LwlynSmithQELCCPXSec:

Collaboration diagram for genie::LwlynSmithQELCCPXSec:

Public Member Functions
	LwlynSmithQELCCPXSec ()
	LwlynSmithQELCCPXSec (string config)
virtual	~LwlynSmithQELCCPXSec ()
double	XSec (const Interaction *i, KinePhaseSpace_t k) const
	Compute the cross section for the input interaction.
double	Integral (const Interaction *i) const
bool	ValidProcess (const Interaction *i) const
	Can this cross section algorithm handle the input process?
void	Configure (const Registry &config)
void	Configure (string param_set)
Public Member Functions inherited from genie::XSecAlgorithmI
virtual	~XSecAlgorithmI ()
virtual bool	ValidKinematics (const Interaction *i) const
	Is the input kinematical point a physically allowed one?
Public Member Functions inherited from genie::Algorithm
virtual	~Algorithm ()
virtual void	FindConfig (void)
virtual const Registry &	GetConfig (void) const
Registry *	GetOwnedConfig (void)
virtual const AlgId &	Id (void) const
	Get algorithm ID.
virtual AlgStatus_t	GetStatus (void) const
	Get algorithm status.
virtual bool	AllowReconfig (void) const
virtual AlgCmp_t	Compare (const Algorithm *alg) const
	Compare with input algorithm.
virtual void	SetId (const AlgId &id)
	Set algorithm ID.
virtual void	SetId (string name, string config)
const Algorithm *	SubAlg (const RgKey &registry_key) const
void	AdoptConfig (void)
void	AdoptSubstructure (void)
virtual void	Print (ostream &stream) const
	Print algorithm info.

Private Member Functions
double	FullDifferentialXSec (const Interaction *i) const
void	LoadConfig (void)

Private Attributes
QELFormFactors	fFormFactors
const QELFormFactorsModelI *	fFormFactorsModel
const XSecIntegratorI *	fXSecIntegrator
double	fCos8c2
	cos^2(cabibbo angle)
double	fXSecCCScale
	external xsec scaling factor for CC
double	fXSecNCScale
	external xsec scaling factor for NC
double	fXSecEMScale
	external xsec scaling factor for EM
const NuclearModelI *	fNuclModel
bool	fLFG
	If the nuclear model is lfg alway average over nucleons.
bool	fDoAvgOverNucleonMomentum
	Average cross section over hit nucleon monentum?
double	fEnergyCutOff
QELEvGen_BindingMode_t	fIntegralNucleonBindingMode
bool	fDoPauliBlocking
	Whether to apply Pauli blocking in FullDifferentialXSec.
const genie::PauliBlocker *	fPauliBlocker
	The PauliBlocker instance to use to apply that correction.

Additional Inherited Members
Static Public Member Functions inherited from genie::Algorithm
static string	BuildParamVectKey (const std::string &comm_name, unsigned int i)
static string	BuildParamVectSizeKey (const std::string &comm_name)
static string	BuildParamMatKey (const std::string &comm_name, unsigned int i, unsigned int j)
static string	BuildParamMatRowSizeKey (const std::string &comm_name)
static string	BuildParamMatColSizeKey (const std::string &comm_name)
Protected Member Functions inherited from genie::XSecAlgorithmI
	XSecAlgorithmI ()
	XSecAlgorithmI (string name)
	XSecAlgorithmI (string name, string config)
Protected Member Functions inherited from genie::Algorithm
	Algorithm ()
	Algorithm (string name)
	Algorithm (string name, string config)
void	Initialize (void)
void	DeleteConfig (void)
void	DeleteSubstructure (void)
Registry *	ExtractLocalConfig (const Registry &in) const
Registry *	ExtractLowerConfig (const Registry &in, const string &alg_key) const
	Split an incoming configuration Registry into a block valid for the sub-algo identified by alg_key.
template<class T>
bool	GetParam (const RgKey &name, T &p, bool is_top_call=true) const
template<class T>
bool	GetParamDef (const RgKey &name, T &p, const T &def) const
template<class T>
int	GetParamVect (const std::string &comm_name, std::vector< T > &v, bool is_top_call=true) const
	Handle to load vectors of parameters.
int	GetParamVectKeys (const std::string &comm_name, std::vector< RgKey > &k, bool is_top_call=true) const
template<class T>
int	GetParamMat (const std::string &comm_name, TMatrixT< T > &mat, bool is_top_call=true) const
	Handle to load matrix of parameters.
template<class T>
int	GetParamMatSym (const std::string &comm_name, TMatrixTSym< T > &mat, bool is_top_call=true) const
int	GetParamMatKeys (const std::string &comm_name, std::vector< RgKey > &k, bool is_top_call=true) const
int	AddTopRegistry (Registry *rp, bool owns=true)
	add registry with top priority, also update ownership
int	AddLowRegistry (Registry *rp, bool owns=true)
	add registry with lowest priority, also update ownership
int	MergeTopRegistry (const Registry &r)
int	AddTopRegisties (const vector< Registry * > &rs, bool owns=false)
	Add registries with top priority, also udated Ownerships.
Protected Attributes inherited from genie::Algorithm
bool	fAllowReconfig
bool	fOwnsSubstruc
	true if it owns its substructure (sub-algs,...)
AlgId	fID
	algorithm name and configuration set
vector< Registry * >	fConfVect
vector< bool >	fOwnerships
	ownership for every registry in fConfVect
AlgStatus_t	fStatus
	algorithm execution status
AlgMap *	fOwnedSubAlgMp
	local pool for owned sub-algs (taken out of the factory pool)

Detailed Description

Computes neutrino-nucleon(nucleus) QELCC differential cross section Is a concrete implementation of the XSecAlgorithmI interface.
.

References:\n C.H.Llewellyn Smith, Physics Reports (Sect. C of Physics Letters) 3,

No. 5 (1972) 261-379

Author

Costas Andreopoulos <c.andreopoulos \at cern.ch> University of Liverpool

Created:\n May 05, 2004

License:\n Copyright (c) 2003-2025, The GENIE Collaboration

For the full text of the license visit http://copyright.genie-mc.org

Definition at line 37 of file LwlynSmithQELCCPXSec.h.

Constructor & Destructor Documentation

LwlynSmithQELCCPXSec() [1/2]

LwlynSmithQELCCPXSec::LwlynSmithQELCCPXSec

(

)

Definition at line 41 of file LwlynSmithQELCCPXSec.cxx.

                                           :
XSecAlgorithmI("genie::LwlynSmithQELCCPXSec")
{
 
}

References genie::XSecAlgorithmI::XSecAlgorithmI().

LwlynSmithQELCCPXSec() [2/2]

LwlynSmithQELCCPXSec::LwlynSmithQELCCPXSec

(

string

config

)

Definition at line 47 of file LwlynSmithQELCCPXSec.cxx.

                                                        :
XSecAlgorithmI("genie::LwlynSmithQELCCPXSec", config)
{
 
}

References genie::XSecAlgorithmI::XSecAlgorithmI().

~LwlynSmithQELCCPXSec()

LwlynSmithQELCCPXSec::~LwlynSmithQELCCPXSec ( )

virtual

Definition at line 53 of file LwlynSmithQELCCPXSec.cxx.

{
 
}

Member Function Documentation

Configure() [1/2]

void LwlynSmithQELCCPXSec::Configure ( const Registry & config )

virtual

Configure the algorithm with an external registry The registry is merged with the top level registry if it is owned, Otherwise a copy of it is added with the highest priority

Reimplemented from genie::Algorithm.

Definition at line 413 of file LwlynSmithQELCCPXSec.cxx.

{
  Algorithm::Configure(config);
  this->LoadConfig();
}

References genie::Algorithm::Configure(), and LoadConfig().

Configure() [2/2]

void LwlynSmithQELCCPXSec::Configure ( string config )

virtual

Configure the algorithm from the AlgoConfigPool based on param_set string given in input An algorithm contains a vector of registries coming from different xml configuration files, which are loaded according a very precise prioriy This methods will load a number registries in order of priority: 1) "Tunable" parameter set from CommonParametes. This is loaded with the highest prioriry and it is designed to be used for tuning procedure Usage not expected from the user. 2) For every string defined in "CommonParame" the corresponding parameter set will be loaded from CommonParameter.xml 3) parameter set specified by the config string and defined in the xml file of the algorithm 4) if config is not "Default" also the Default parameter set from the same xml file will be loaded Effectively this avoids the repetion of a parameter when it is not changed in the requested configuration

Reimplemented from genie::Algorithm.

Definition at line 419 of file LwlynSmithQELCCPXSec.cxx.

{
  Algorithm::Configure(config);
  this->LoadConfig();
}

References genie::Algorithm::Configure(), and LoadConfig().

FullDifferentialXSec()

double LwlynSmithQELCCPXSec::FullDifferentialXSec ( const Interaction * i ) const

private

Definition at line 169 of file LwlynSmithQELCCPXSec.cxx.

{
  // First we need access to all of the particles in the interaction
  // The particles were stored in the lab frame
  const Kinematics&   kinematics = interaction -> Kine();
  const InitialState& init_state = interaction -> InitState();
 
  const Target& tgt = init_state.Tgt();
 
  const TLorentzVector leptonMom = kinematics.FSLeptonP4();
  const TLorentzVector outNucleonMom = kinematics.HadSystP4();
 
  // Apply Pauli blocking if enabled
  if ( fDoPauliBlocking && tgt.IsNucleus() && !interaction->TestBit(kIAssumeFreeNucleon) ) {
    int final_nucleon_pdg = interaction->RecoilNucleonPdg();
    double kF = fPauliBlocker->GetFermiMomentum(tgt, final_nucleon_pdg,
      tgt.HitNucPosition());
    double pNf = outNucleonMom.P();
    if ( pNf < kF ) return 0.;
  }
 
  // Note that GetProbeP4 defaults to returning the probe 4-momentum in the
  // struck nucleon rest frame, so we have to explicitly ask for the lab frame
  // here
  TLorentzVector * tempNeutrino = init_state.GetProbeP4(kRfLab);
  TLorentzVector neutrinoMom = *tempNeutrino;
  delete tempNeutrino;
  TLorentzVector * inNucleonMom = init_state.TgtPtr()->HitNucP4Ptr();
 
  // *** CALCULATION OF "q" and "qTilde" ***
  // According to the de Forest prescription for handling the off-shell
  // initial struck nucleon, the cross section calculation should proceed
  // as if for a free nucleon, except that an effective value of the 4-momentum
  // transfer qTilde should be used in which the difference between the on-
  // and off-shell energies of the hit nucleon has been subtracted from the
  // energy transfer q0.
 
  // HitNucMass() looks up the PDGLibrary (on-shell) value for the initial
  // struck nucleon
  double mNi = init_state.Tgt().HitNucMass();
 
  // Hadronic matrix element for CC neutrino interactions should really use
  // the "nucleon mass," i.e., the mean of the proton and neutrino masses.
  // This expression would also work for NC and EM scattering (since the
  // initial and final on-shell nucleon masses would be the same)
  double mNucleon = ( mNi + interaction->RecoilNucleon()->Mass() ) / 2.;
 
  // Ordinary 4-momentum transfer
  TLorentzVector qP4 = neutrinoMom - leptonMom;
 
  // Initial struck nucleon 4-momentum in which it is forced to be on-shell
  double inNucleonOnShellEnergy = std::sqrt( std::pow(mNi, 2)
    + std::pow(inNucleonMom->P(), 2) );
  TLorentzVector inNucleonMomOnShell( inNucleonMom->Vect(), inNucleonOnShellEnergy );
 
  // Effective 4-momentum transfer (according to the deForest prescription) for
  // use in computing the hadronic tensor
  TLorentzVector qTildeP4 = outNucleonMom - inNucleonMomOnShell;
 
  double Q2 = -1. * qP4.Mag2();
  double Q2tilde = -1. * qTildeP4.Mag2();
 
  // If the binding energy correction causes an unphysical value
  // of q0Tilde or Q2tilde, just return 0.
  if ( qTildeP4.E() <= 0. && init_state.Tgt().IsNucleus() &&
    !interaction->TestBit(kIAssumeFreeNucleon) ) return 0.;
  if ( Q2tilde <= 0. ) return 0.;
 
  // Store Q2tilde in the kinematic variable representing Q2.
  // This will ensure that the form factors are calculated correctly
  // using the de Forest prescription (Q2tilde instead of Q2).
  interaction->KinePtr()->SetQ2(Q2tilde);
 
  // Calculate the QEL form factors
  fFormFactors.Calculate(interaction);
 
  double F1V   = fFormFactors.F1V();
  double xiF2V = fFormFactors.xiF2V();
  double FA    = fFormFactors.FA();
  double Fp    = fFormFactors.Fp();
 
  // Restore Q2 in the interaction's kinematic variables
  // now that the form factors have been computed
  interaction->KinePtr()->SetQ2( Q2 );
 
  // Overall factor in the differential cross section
  double Gfactor = kGF2*fCos8c2 / ( 8. * kPi * kPi * inNucleonOnShellEnergy
    * neutrinoMom.E() * outNucleonMom.E() * leptonMom.E() );
 
  // Now, we can calculate the cross section
  double tau = Q2tilde / (4 * std::pow(mNucleon, 2));
  double h1 = FA*FA*(1 + tau) + tau*(F1V + xiF2V)*(F1V + xiF2V);
  double h2 = FA*FA + F1V*F1V + tau*xiF2V*xiF2V;
  double h3 = 2.0 * FA * (F1V + xiF2V);
  double h4 = 0.25 * xiF2V*xiF2V *(1-tau) + 0.5*F1V*xiF2V + FA*Fp - tau*Fp*Fp;
 
  bool is_neutrino = pdg::IsNeutrino(init_state.ProbePdg());
  int sign = (is_neutrino) ? -1 : 1;
  double l1 = 2*neutrinoMom.Dot(leptonMom)*std::pow(mNucleon, 2);
  double l2 = 2*(neutrinoMom.Dot(inNucleonMomOnShell)) * (inNucleonMomOnShell.Dot(leptonMom)) - neutrinoMom.Dot(leptonMom)*std::pow(mNucleon, 2);
  double l3 = (neutrinoMom.Dot(inNucleonMomOnShell) * qTildeP4.Dot(leptonMom)) - (neutrinoMom.Dot(qTildeP4) * leptonMom.Dot(inNucleonMomOnShell));
  l3 *= sign;
  double l4 = neutrinoMom.Dot(leptonMom) * qTildeP4.Dot(qTildeP4) - 2*neutrinoMom.Dot(qTildeP4)*leptonMom.Dot(qTildeP4);
  double l5 = neutrinoMom.Dot(inNucleonMomOnShell) * leptonMom.Dot(qTildeP4) + leptonMom.Dot(inNucleonMomOnShell)*neutrinoMom.Dot(qTildeP4) - neutrinoMom.Dot(leptonMom)*inNucleonMomOnShell.Dot(qTildeP4);
 
  double LH = 2 *(l1*h1 + l2*h2 + l3*h3 + l4*h4 + l5*h2);
 
  double xsec = Gfactor * LH;
 
  // Apply the factor that arises from elimination of the energy-conserving
  // delta function
  xsec *= genie::utils::EnergyDeltaFunctionSolutionQEL( *interaction );
 
  const ProcessInfo& proc_info = interaction->ProcInfo();
 
  // Apply given scaling factor
  double xsec_scale = 1 ;
  if( proc_info.IsWeakCC() ) xsec_scale = fXSecCCScale;
  else if( proc_info.IsWeakNC() ) xsec_scale = fXSecNCScale;
 
  xsec *= xsec_scale ;
 
  // Number of scattering centers in the target
  const Target & target = init_state.Tgt();
  int nucpdgc = target.HitNucPdg();
  int NNucl = (pdg::IsProton(nucpdgc)) ? target.Z() : target.N();
 
#ifdef __GENIE_LOW_LEVEL_MESG_ENABLED__
  LOG("LwlynSmith", pDEBUG)
    << "Nuclear suppression factor R(Q2) = " << R << ", NNucl = " << NNucl;
#endif
 
  xsec *= NNucl; // nuclear xsec
 
  return xsec;
 
}

References genie::utils::EnergyDeltaFunctionSolutionQEL(), fCos8c2, fDoPauliBlocking, fFormFactors, fPauliBlocker, fXSecCCScale, fXSecNCScale, genie::InitialState::GetProbeP4(), genie::Target::HitNucMass(), genie::Target::HitNucP4Ptr(), genie::Target::HitNucPdg(), genie::Target::HitNucPosition(), genie::pdg::IsNeutrino(), genie::Target::IsNucleus(), genie::pdg::IsProton(), genie::ProcessInfo::IsWeakCC(), genie::ProcessInfo::IsWeakNC(), genie::constants::kGF2, genie::kIAssumeFreeNucleon, genie::Interaction::KinePtr(), genie::constants::kPi, genie::kRfLab, LOG, genie::Target::N(), pDEBUG, genie::InitialState::ProbePdg(), genie::Interaction::ProcInfo(), genie::Interaction::RecoilNucleon(), genie::Interaction::RecoilNucleonPdg(), genie::Kinematics::SetQ2(), genie::InitialState::Tgt(), genie::InitialState::TgtPtr(), and genie::Target::Z().

Referenced by XSec().

Integral()

double LwlynSmithQELCCPXSec::Integral ( const Interaction * i ) const

virtual

Integrate the model over the kinematic phase space available to the input interaction (kinematical cuts can be included)

Implements genie::XSecAlgorithmI.

Definition at line 308 of file LwlynSmithQELCCPXSec.cxx.

{
  // If we're using the new spline generation method (which integrates
  // over the kPSQELEvGen phase space used by QELEventGenerator) then
  // let the cross section integrator do all of the work. It's smart
  // enough to handle free nucleon vs. nuclear targets, different
  // nuclear models (including the local Fermi gas model), etc.
  // TODO: think about doing this in a better way
  if ( fXSecIntegrator->Id().Name() == "genie::NewQELXSec" ) {
    return fXSecIntegrator->Integrate(this, in);
  }
 
  // Otherwise, use the old integration method (kept for use with
  // the historical default G18_00x series of tunes)
  bool nuclear_target = in->InitState().Tgt().IsNucleus();
  if(!nuclear_target || !fDoAvgOverNucleonMomentum) {
    return fXSecIntegrator->Integrate(this,in);
  }
 
  double E = in->InitState().ProbeE(kRfHitNucRest);
  if(fLFG || E < fEnergyCutOff) {
    // clone the input interaction so as to tweak the
    // hit nucleon 4-momentum in the averaging loop
    Interaction in_curr(*in);
 
    // hit target
    Target * tgt = in_curr.InitState().TgtPtr();
 
    // get nuclear masses (init & final state nucleus)
    int nucleon_pdgc = tgt->HitNucPdg();
    bool is_p = pdg::IsProton(nucleon_pdgc);
    int Zi = tgt->Z();
    int Ai = tgt->A();
    int Zf = (is_p) ? Zi-1 : Zi;
    int Af = Ai-1;
    PDGLibrary * pdglib = PDGLibrary::Instance();
    TParticlePDG * nucl_i = pdglib->Find( pdg::IonPdgCode(Ai, Zi) );
    TParticlePDG * nucl_f = pdglib->Find( pdg::IonPdgCode(Af, Zf) );
    if(!nucl_f) {
      LOG("LwlynSmith", pFATAL)
        << "Unknwown nuclear target! No target with code: "
        << pdg::IonPdgCode(Af, Zf) << " in PDGLibrary!";
      exit(1);
    }
    double Mi  = nucl_i -> Mass(); // initial nucleus mass
    double Mf  = nucl_f -> Mass(); // remnant nucleus mass
 
    // throw nucleons with fermi momenta and binding energies
    // generated according to the current nuclear model for the
    // input target and average the cross section
    double xsec_sum = 0.;
    const int nnuc = 2000;
    // VertexGenerator for generating a position before generating
    // each nucleon
    VertexGenerator * vg = new VertexGenerator();
    vg->Configure("Default");
    for(int inuc=0;inuc<nnuc;inuc++){
      // Generate a position in the nucleus
      TVector3 nucpos = vg->GenerateVertex(&in_curr,tgt->A());
      tgt->SetHitNucPosition(nucpos.Mag());
 
      // Generate a nucleon
      fNuclModel->GenerateNucleon(*tgt, nucpos.Mag());
      TVector3 p3N = fNuclModel->Momentum3();
      double   EN  = Mi - TMath::Sqrt(p3N.Mag2() + Mf*Mf);
      TLorentzVector* p4N = tgt->HitNucP4Ptr();
      p4N->SetPx (p3N.Px());
      p4N->SetPy (p3N.Py());
      p4N->SetPz (p3N.Pz());
      p4N->SetE  (EN);
 
      double xsec = fXSecIntegrator->Integrate(this,&in_curr);
      xsec_sum += xsec;
    }
    double xsec_avg = xsec_sum / nnuc;
    delete vg;
    return xsec_avg;
  }else{
    return fXSecIntegrator->Integrate(this,in);
  }
}

References genie::Target::A(), genie::VertexGenerator::Configure(), fDoAvgOverNucleonMomentum, fEnergyCutOff, genie::PDGLibrary::Find(), fLFG, fNuclModel, fXSecIntegrator, genie::VertexGenerator::GenerateVertex(), genie::Target::HitNucP4Ptr(), genie::Target::HitNucPdg(), genie::Interaction::InitState(), genie::PDGLibrary::Instance(), genie::pdg::IonPdgCode(), genie::Target::IsNucleus(), genie::pdg::IsProton(), genie::kRfHitNucRest, LOG, pFATAL, genie::InitialState::ProbeE(), genie::Target::SetHitNucPosition(), genie::InitialState::Tgt(), genie::InitialState::TgtPtr(), and genie::Target::Z().

LoadConfig()

void LwlynSmithQELCCPXSec::LoadConfig ( void )

private

Definition at line 425 of file LwlynSmithQELCCPXSec.cxx.

{
  // Cross section scaling factor
  GetParam( "QEL-CC-XSecScale", fXSecCCScale ) ;
  GetParam( "QEL-NC-XSecScale", fXSecNCScale ) ;
 
  double thc ;
  GetParam( "CabibboAngle", thc ) ;
  fCos8c2 = TMath::Power(TMath::Cos(thc), 2);
 
   // load QEL form factors model
  fFormFactorsModel = dynamic_cast<const QELFormFactorsModelI *> (
                                             this->SubAlg("FormFactorsAlg"));
  assert(fFormFactorsModel);
  fFormFactors.SetModel(fFormFactorsModel); // <-- attach algorithm
 
   // load XSec Integrator
  fXSecIntegrator =
      dynamic_cast<const XSecIntegratorI *> (this->SubAlg("XSec-Integrator"));
  assert(fXSecIntegrator);
 
  // Get nuclear model for use in Integral()
  RgKey nuclkey = "IntegralNuclearModel";
  fNuclModel = dynamic_cast<const NuclearModelI *> (this->SubAlg(nuclkey));
  assert(fNuclModel);
 
  fLFG = fNuclModel->ModelType(Target()) == kNucmLocalFermiGas;
 
  bool average_over_nuc_mom ;
  GetParamDef( "IntegralAverageOverNucleonMomentum", average_over_nuc_mom, false ) ;
  // Always average over initial nucleons if the nuclear model is LFG
  fDoAvgOverNucleonMomentum = fLFG || average_over_nuc_mom ;
 
  fEnergyCutOff = 0.;
 
  // Get averaging cutoff energy
  GetParamDef("IntegralNuclearInfluenceCutoffEnergy", fEnergyCutOff, 2.0 ) ;
 
  // Method to use to calculate the binding energy of the initial hit nucleon when
  // generating splines
  std::string temp_binding_mode;
  GetParamDef( "IntegralNucleonBindingMode", temp_binding_mode, std::string("UseNuclearModel") );
  fIntegralNucleonBindingMode = genie::utils::StringToQELBindingMode( temp_binding_mode );
 
  // Get PauliBlocker for possible use in FullDifferentialXSec()
  GetParamDef( "IntegralNucleonBindingMode", temp_binding_mode, std::string("UseNuclearModel") );
  fPauliBlocker = dynamic_cast<const PauliBlocker*>( this->SubAlg("PauliBlockerAlg") );
  assert( fPauliBlocker );
 
  // Decide whether or not it should be used in FullDifferentialXSec
  GetParamDef( "DoPauliBlocking", fDoPauliBlocking, true );
}

References fCos8c2, fDoAvgOverNucleonMomentum, fDoPauliBlocking, fEnergyCutOff, fFormFactors, fFormFactorsModel, fIntegralNucleonBindingMode, fLFG, fNuclModel, fPauliBlocker, fXSecCCScale, fXSecIntegrator, fXSecNCScale, genie::Algorithm::GetParam(), genie::Algorithm::GetParamDef(), genie::kNucmLocalFermiGas, genie::utils::StringToQELBindingMode(), and genie::Algorithm::SubAlg().

Referenced by Configure(), and Configure().

ValidProcess()

bool LwlynSmithQELCCPXSec::ValidProcess ( const Interaction * i ) const

virtual

Can this cross section algorithm handle the input process?

Implements genie::XSecAlgorithmI.

Definition at line 390 of file LwlynSmithQELCCPXSec.cxx.

{
  if(interaction->TestBit(kISkipProcessChk)) return true;
 
  const InitialState & init_state = interaction->InitState();
  const ProcessInfo &  proc_info  = interaction->ProcInfo();
 
  if(!proc_info.IsQuasiElastic()) return false;
 
  int  nuc = init_state.Tgt().HitNucPdg();
  int  nu  = init_state.ProbePdg();
 
  bool isP   = pdg::IsProton(nuc);
  bool isN   = pdg::IsNeutron(nuc);
  bool isnu  = pdg::IsNeutrino(nu);
  bool isnub = pdg::IsAntiNeutrino(nu);
 
  bool prcok = proc_info.IsWeakCC() && ((isP&&isnub) || (isN&&isnu));
  if(!prcok) return false;
 
  return true;
}

References genie::Target::HitNucPdg(), genie::Interaction::InitState(), genie::pdg::IsAntiNeutrino(), genie::pdg::IsNeutrino(), genie::pdg::IsNeutron(), genie::pdg::IsProton(), genie::ProcessInfo::IsQuasiElastic(), genie::ProcessInfo::IsWeakCC(), genie::kISkipProcessChk, genie::InitialState::ProbePdg(), genie::Interaction::ProcInfo(), and genie::InitialState::Tgt().

Referenced by XSec().

XSec()

double LwlynSmithQELCCPXSec::XSec ( const Interaction * i, KinePhaseSpace_t k ) const

virtual

Compute the cross section for the input interaction.

Implements genie::XSecAlgorithmI.

Definition at line 58 of file LwlynSmithQELCCPXSec.cxx.

{
  if(! this -> ValidProcess    (interaction) ) {LOG("LwlynSmith",pWARN) << "not a valid process"; return 0.;}
  if(! this -> ValidKinematics (interaction) ) {LOG("LwlynSmith",pWARN) << "not valid kinematics"; return 0.;}
 
  // If computing the full differential cross section, then all four momentum
  // four-vectors (probe, hit nucleon, final lepton, and final nucleon) should
  // have been set already, with the hit nucleon off-shell as appropriate.
  if (kps == kPSQELEvGen) {
    return this->FullDifferentialXSec(interaction);
  }
 
  // Get kinematics & init-state parameters
  const Kinematics &   kinematics = interaction -> Kine();
  const InitialState & init_state = interaction -> InitState();
  const Target & target = init_state.Tgt();
 
  double E  = init_state.ProbeE(kRfHitNucRest);
  double E2 = TMath::Power(E,2);
  double ml = interaction->FSPrimLepton()->Mass();
  double M  = target.HitNucMass();
  double q2 = kinematics.q2();
 
  // One of the xsec terms changes sign for antineutrinos
  bool is_neutrino = pdg::IsNeutrino(init_state.ProbePdg());
  int sign = (is_neutrino) ? -1 : 1;
 
  // Calculate the QEL form factors
  fFormFactors.Calculate(interaction);
 
  double F1V   = fFormFactors.F1V();
  double xiF2V = fFormFactors.xiF2V();
  double FA    = fFormFactors.FA();
  double Fp    = fFormFactors.Fp();
 
#ifdef __GENIE_LOW_LEVEL_MESG_ENABLED__
  LOG("LwlynSmith", pDEBUG) << "\n" << fFormFactors;
#endif
 
  // Calculate auxiliary parameters
  double ml2     = TMath::Power(ml,    2);
  double M2      = TMath::Power(M,     2);
  double M4      = TMath::Power(M2,    2);
  double FA2     = TMath::Power(FA,    2);
  double Fp2     = TMath::Power(Fp,    2);
  double F1V2    = TMath::Power(F1V,   2);
  double xiF2V2  = TMath::Power(xiF2V, 2);
  double Gfactor = M2*kGF2*fCos8c2 / (8*kPi*E2);
  double s_u     = 4*E*M + q2 - ml2;
  double q2_M2   = q2/M2;
 
  // Compute free nucleon differential cross section
  double A = (0.25*(ml2-q2)/M2) * (
              (4-q2_M2)*FA2 - (4+q2_M2)*F1V2 - q2_M2*xiF2V2*(1+0.25*q2_M2)
              -4*q2_M2*F1V*xiF2V - (ml2/M2)*(
               (F1V2+xiF2V2+2*F1V*xiF2V)+(FA2+4*Fp2+4*FA*Fp)+(q2_M2-4)*Fp2));
  double B = -1 * q2_M2 * FA*(F1V+xiF2V);
  double C = 0.25*(FA2 + F1V2 - 0.25*q2_M2*xiF2V2);
 
  double xsec = Gfactor * (A + sign*B*s_u/M2 + C*s_u*s_u/M4);
 
  // Apply given scaling factor
  double xsec_scale = 1 ;
  const ProcessInfo& proc_info = interaction->ProcInfo();
  
  if( proc_info.IsWeakCC() ) xsec_scale = fXSecCCScale;
  else if( proc_info.IsWeakNC() ) xsec_scale = fXSecNCScale;
  xsec *= xsec_scale ;
 
#ifdef __GENIE_LOW_LEVEL_MESG_ENABLED__
  LOG("LwlynSmith", pDEBUG)
     << "dXSec[QEL]/dQ2 [FreeN](E = "<< E << ", Q2 = "<< -q2 << ") = "<< xsec;
  LOG("LwlynSmith", pDEBUG)
                 << "A(Q2) = " << A << ", B(Q2) = " << B << ", C(Q2) = " << C;
#endif
 
  //----- The algorithm computes dxsec/dQ2
  //      Check whether variable tranformation is needed
  if(kps!=kPSQ2fE) {
    double J = utils::kinematics::Jacobian(interaction,kPSQ2fE,kps);
 
#ifdef __GENIE_LOW_LEVEL_MESG_ENABLED__
    LOG("LwlynSmith", pDEBUG)
     << "Jacobian for transformation to: "
                  << KinePhaseSpace::AsString(kps) << ", J = " << J;
#endif
    xsec *= J;
  }
 
  //----- if requested return the free nucleon xsec even for input nuclear tgt
  if( interaction->TestBit(kIAssumeFreeNucleon) ) return xsec;
 
  //----- compute nuclear suppression factor
  //      (R(Q2) is adapted from NeuGEN - see comments therein)
  double R = nuclear::NuclQELXSecSuppression("Default", 0.5, interaction);
 
  //----- number of scattering centers in the target
  int nucpdgc = target.HitNucPdg();
  int NNucl = (pdg::IsProton(nucpdgc)) ? target.Z() : target.N();
 
#ifdef __GENIE_LOW_LEVEL_MESG_ENABLED__
  LOG("LwlynSmith", pDEBUG)
       << "Nuclear suppression factor R(Q2) = " << R << ", NNucl = " << NNucl;
#endif
 
  xsec *= (R*NNucl); // nuclear xsec
 
  return xsec;
}

References genie::KinePhaseSpace::AsString(), fCos8c2, fFormFactors, genie::Interaction::FSPrimLepton(), FullDifferentialXSec(), fXSecCCScale, fXSecNCScale, genie::Target::HitNucMass(), genie::Target::HitNucPdg(), genie::pdg::IsNeutrino(), genie::pdg::IsProton(), genie::ProcessInfo::IsWeakCC(), genie::ProcessInfo::IsWeakNC(), genie::utils::kinematics::Jacobian(), genie::constants::kGF2, genie::kIAssumeFreeNucleon, genie::constants::kPi, genie::kPSQ2fE, genie::kPSQELEvGen, genie::kRfHitNucRest, LOG, genie::Target::N(), genie::utils::nuclear::NuclQELXSecSuppression(), pDEBUG, genie::InitialState::ProbeE(), genie::InitialState::ProbePdg(), genie::Interaction::ProcInfo(), pWARN, genie::InitialState::Tgt(), genie::XSecAlgorithmI::ValidKinematics(), ValidProcess(), and genie::Target::Z().

Member Data Documentation

fCos8c2

double genie::LwlynSmithQELCCPXSec::fCos8c2

private

cos^2(cabibbo angle)

Definition at line 62 of file LwlynSmithQELCCPXSec.h.

Referenced by FullDifferentialXSec(), LoadConfig(), and XSec().

fDoAvgOverNucleonMomentum

bool genie::LwlynSmithQELCCPXSec::fDoAvgOverNucleonMomentum

private

Average cross section over hit nucleon monentum?

Definition at line 71 of file LwlynSmithQELCCPXSec.h.

Referenced by Integral(), and LoadConfig().

fDoPauliBlocking

bool genie::LwlynSmithQELCCPXSec::fDoPauliBlocking

private

Whether to apply Pauli blocking in FullDifferentialXSec.

Definition at line 80 of file LwlynSmithQELCCPXSec.h.

Referenced by FullDifferentialXSec(), and LoadConfig().

fEnergyCutOff

double genie::LwlynSmithQELCCPXSec::fEnergyCutOff

private

Average only for energies below this cutoff defining the region where nuclear modeling details do matter

Definition at line 72 of file LwlynSmithQELCCPXSec.h.

Referenced by Integral(), and LoadConfig().

fFormFactors

QELFormFactors genie::LwlynSmithQELCCPXSec::fFormFactors

mutableprivate

Definition at line 59 of file LwlynSmithQELCCPXSec.h.

Referenced by FullDifferentialXSec(), LoadConfig(), and XSec().

fFormFactorsModel

const QELFormFactorsModelI* genie::LwlynSmithQELCCPXSec::fFormFactorsModel

private

Definition at line 60 of file LwlynSmithQELCCPXSec.h.

Referenced by LoadConfig().

fIntegralNucleonBindingMode

QELEvGen_BindingMode_t genie::LwlynSmithQELCCPXSec::fIntegralNucleonBindingMode

private

Enum specifying the method to use when calculating the binding energy of the initial hit nucleon during spline generation

Definition at line 77 of file LwlynSmithQELCCPXSec.h.

Referenced by LoadConfig().

fLFG

bool genie::LwlynSmithQELCCPXSec::fLFG

private

If the nuclear model is lfg alway average over nucleons.

Definition at line 70 of file LwlynSmithQELCCPXSec.h.

Referenced by Integral(), and LoadConfig().

fNuclModel

const NuclearModelI* genie::LwlynSmithQELCCPXSec::fNuclModel

private

Definition at line 69 of file LwlynSmithQELCCPXSec.h.

Referenced by Integral(), and LoadConfig().

fPauliBlocker

const genie::PauliBlocker* genie::LwlynSmithQELCCPXSec::fPauliBlocker

private

The PauliBlocker instance to use to apply that correction.

Definition at line 82 of file LwlynSmithQELCCPXSec.h.

Referenced by FullDifferentialXSec(), and LoadConfig().

fXSecCCScale

double genie::LwlynSmithQELCCPXSec::fXSecCCScale

private

external xsec scaling factor for CC

Definition at line 64 of file LwlynSmithQELCCPXSec.h.

Referenced by FullDifferentialXSec(), LoadConfig(), and XSec().

fXSecEMScale

double genie::LwlynSmithQELCCPXSec::fXSecEMScale

private

external xsec scaling factor for EM

Definition at line 66 of file LwlynSmithQELCCPXSec.h.

fXSecIntegrator

const XSecIntegratorI* genie::LwlynSmithQELCCPXSec::fXSecIntegrator

private

Definition at line 61 of file LwlynSmithQELCCPXSec.h.

Referenced by Integral(), and LoadConfig().

fXSecNCScale

double genie::LwlynSmithQELCCPXSec::fXSecNCScale

private

external xsec scaling factor for NC

Definition at line 65 of file LwlynSmithQELCCPXSec.h.

Referenced by FullDifferentialXSec(), LoadConfig(), and XSec().

---

The documentation for this class was generated from the following files:

• LwlynSmithQELCCPXSec.h
• LwlynSmithQELCCPXSec.cxx