Generates values for the kinematic variables describing QEL neutrino interaction events. Is a concrete implementation of the EventRecordVisitorI interface. More...

#include <QELEventGenerator.h>

Inheritance diagram for genie::QELEventGenerator:

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Collaboration diagram for genie::QELEventGenerator:

[legend]

Public Member Functions
	QELEventGenerator ()

	QELEventGenerator (string config)

	~QELEventGenerator ()

void	ProcessEventRecord (GHepRecord *event_rec) const

void	Configure (const Registry &config)

void	Configure (string config)

Public Member Functions inherited from genie::EventRecordVisitorI
virtual	~EventRecordVisitorI ()

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. More...

virtual AlgStatus_t	GetStatus (void) const
	Get algorithm status. More...

virtual bool	AllowReconfig (void) const

virtual AlgCmp_t	Compare (const Algorithm *alg) const
	Compare with input algorithm. More...

virtual void	SetId (const AlgId &id)
	Set algorithm ID. More...

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. More...

Private Member Functions
void	LoadConfig (void)

double	ComputeMaxXSec (const Interaction *in) const

void	AddTargetNucleusRemnant (GHepRecord *evrec) const
	add a recoiled nucleus remnant More...

Private Attributes
double	fEb

const NuclearModelI *	fNuclModel
	nuclear model More...

double	fMinAngleEM

QELEvGen_BindingMode_t	fHitNucleonBindingMode

int	fMaxXSecNucleonThrows

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::KineGeneratorWithCache
	KineGeneratorWithCache ()

	KineGeneratorWithCache (string name)

	KineGeneratorWithCache (string name, string config)

	~KineGeneratorWithCache ()

virtual double	ComputeMaxXSec (const Interaction *in, const int nkey) const

virtual double	MaxXSec (GHepRecord *evrec, const int nkey=0) const

virtual double	FindMaxXSec (const Interaction *in, const int nkey=0) const

virtual void	CacheMaxXSec (const Interaction *in, double xsec, const int nkey=0) const

virtual double	Energy (const Interaction *in) const

virtual CacheBranchFx *	AccessCacheBranch (const Interaction *in, const int nkey=0) const

virtual void	AssertXSecLimits (const Interaction *in, double xsec, double xsec_max) const

Protected Member Functions inherited from genie::EventRecordVisitorI
	EventRecordVisitorI ()

	EventRecordVisitorI (string name)

	EventRecordVisitorI (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. More...

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. More...

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. More...

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 More...

int	AddLowRegistry (Registry *rp, bool owns=true)
	add registry with lowest priority, also update ownership More...

int	MergeTopRegistry (const Registry &r)

int	AddTopRegisties (const vector< Registry * > &rs, bool owns=false)
	Add registries with top priority, also udated Ownerships. More...

Protected Attributes inherited from genie::KineGeneratorWithCache
const XSecAlgorithmI *	fXSecModel

double	fSafetyFactor
	ComputeMaxXSec -> ComputeMaxXSec * fSafetyFactor. More...

std::vector< double >	vSafetyFactors
	MaxXSec -> MaxXSec * fSafetyFactors[nkey]. More...

int	fNumOfSafetyFactors
	Number of given safety factors. More...

std::vector< string >	vInterpolatorTypes
	Type of interpolator for each key in a branch. More...

int	fNumOfInterpolatorTypes
	Number of given interpolators types. More...

double	fMaxXSecDiffTolerance
	max{100(xsec-maxxsec)/.5(xsec+maxxsec)} if xsec>maxxsec More...

double	fEMin
	min E for which maxxsec is cached - forcing explicit calc. More...

bool	fGenerateUniformly
	uniform over allowed phase space + event weight? More...

Protected Attributes inherited from genie::Algorithm
bool	fAllowReconfig

bool	fOwnsSubstruc
	true if it owns its substructure (sub-algs,...) More...

AlgId	fID
	algorithm name and configuration set More...

vector< Registry * >	fConfVect

vector< bool >	fOwnerships
	ownership for every registry in fConfVect More...

AlgStatus_t	fStatus
	algorithm execution status More...

AlgMap *	fOwnedSubAlgMp
	local pool for owned sub-algs (taken out of the factory pool) More...

Detailed Description

Generates values for the kinematic variables describing QEL neutrino interaction events. Is a concrete implementation of the EventRecordVisitorI interface.

Author: Andrew Furmanski

Created:: August 04, 2014

License:: Copyright (c) 2003-2024, The GENIE Collaboration For the full text of the license visit http://copyright.genie-mc.org

Definition at line 30 of file QELEventGenerator.h.

Constructor & Destructor Documentation

QELEventGenerator::QELEventGenerator ( )

Definition at line 50 of file QELEventGenerator.cxx.

                                      :
     KineGeneratorWithCache("genie::QELEventGenerator")
 {
 
 }

QELEventGenerator::QELEventGenerator ( string config )

Definition at line 56 of file QELEventGenerator.cxx.

                                                   :
     KineGeneratorWithCache("genie::QELEventGenerator", config)
 {
 
 }

QELEventGenerator::~QELEventGenerator ( )

Definition at line 62 of file QELEventGenerator.cxx.

 {
 
 }

Member Function Documentation

void QELEventGenerator::AddTargetNucleusRemnant ( GHepRecord * evrec ) const

private

add a recoiled nucleus remnant

Definition at line 289 of file QELEventGenerator.cxx.

Referenced by ProcessEventRecord().

 {
     // add the remnant nuclear target at the GHEP record
 
     LOG("QELEvent", pINFO) << "Adding final state nucleus";
 
     double Px = 0;
     double Py = 0;
     double Pz = 0;
     double E  = 0;
 
     GHepParticle * nucleus = evrec->TargetNucleus();
     bool have_nucleus = nucleus != 0;
     if (!have_nucleus) return;
 
     int A = nucleus->A();
     int Z = nucleus->Z();
 
     int fd = nucleus->FirstDaughter();
     int ld = nucleus->LastDaughter();
 
     for(int id = fd; id <= ld; id++) {
 
         // compute A,Z for final state nucleus & get its PDG code and its mass
         GHepParticle * particle = evrec->Particle(id);
         assert(particle);
         int  pdgc = particle->Pdg();
         bool is_p  = pdg::IsProton (pdgc);
         bool is_n  = pdg::IsNeutron(pdgc);
 
         if (is_p) Z--;
         if (is_p || is_n) A--;
 
         Px += particle->Px();
         Py += particle->Py();
         Pz += particle->Pz();
         E  += particle->E();
 
     }//daughters
 
     TParticlePDG * remn = 0;
     int ipdgc = pdg::IonPdgCode(A, Z);
     remn = PDGLibrary::Instance()->Find(ipdgc);
     if(!remn) {
         LOG("HadronicVtx", pFATAL)
             << "No particle with [A = " << A << ", Z = " << Z
             << ", pdgc = " << ipdgc << "] in PDGLibrary!";
         assert(remn);
     }
 
     double Mi = nucleus->Mass();
     Px *= -1;
     Py *= -1;
     Pz *= -1;
     E = Mi-E;
 
     // Add the nucleus to the event record
     LOG("QELEvent", pINFO)
         << "Adding nucleus [A = " << A << ", Z = " << Z
         << ", pdgc = " << ipdgc << "]";
 
     int imom = evrec->TargetNucleusPosition();
     evrec->AddParticle(
             ipdgc,kIStStableFinalState, imom,-1,-1,-1, Px,Py,Pz,E, 0,0,0,0);
 
     LOG("QELEvent", pINFO) << "Done";
     LOG("QELEvent", pINFO) << *evrec;
 }

double QELEventGenerator::ComputeMaxXSec ( const Interaction * in ) const

privatevirtual

Implements genie::KineGeneratorWithCache.

Definition at line 409 of file QELEventGenerator.cxx.

References genie::Interaction::AsString(), genie::utils::BindHitNucleon(), genie::utils::ComputeFullQELPXSec(), genie::utils::CosTheta0Max(), e, fMinAngleEM, fNuclModel, genie::KineGeneratorWithCache::fSafetyFactor, genie::KineGeneratorWithCache::fXSecModel, genie::Target::HitNucPosition(), genie::Interaction::InitState(), genie::kISkipKinematicChk, genie::kISkipProcessChk, genie::kOnShell, LOG, pDEBUG, pINFO, genie::NuclearModelI::Prob(), genie::NuclearModelI::SetMomentum3(), genie::NuclearModelI::SetRemovalEnergy(), SLOG, and genie::InitialState::Tgt().

 {
     // Computes the maximum differential cross section in the requested phase
     // space. This method overloads KineGeneratorWithCache::ComputeMaxXSec
     // method and the value is cached at a circular cache branch for retrieval
     // during subsequent event generation.
     // The computed max differential cross section does not need to be the exact
     // maximum. The number used in the rejection method will be scaled up by a
     // safety factor. But it needs to be fast.
     LOG("QELEvent", pINFO) << "Computing maximum cross section to throw against";
 
     double xsec_max = -1;
     double dummy_Eb = 0.;
 
     // Clone the input interaction so that we can modify it a bit
     Interaction * interaction = new Interaction( *in );
     interaction->SetBit( kISkipProcessChk );
     interaction->SetBit( kISkipKinematicChk );
 
     // We'll select the max momentum and zero binding energy.
     // That should give us the nucleon with the highest xsec
     const Target& tgt = interaction->InitState().Tgt();
     // Pick a really slow nucleon to start, but not one at rest,
     // since Prob() for the Fermi gas family of models is zero
     // for a vanishing nucleon momentum
     double max_momentum = 0.010;
     double search_step = 0.1;
     const double STEP_STOP = 1e-6;
     while ( search_step > STEP_STOP ) {
       double pNi_next = max_momentum + search_step;
 
       // Set the nucleon we're using to be upstream at max energy and unbound
       fNuclModel->SetMomentum3( TVector3(0., 0., -pNi_next) );
       fNuclModel->SetRemovalEnergy( 0. );
 
       // Set the nucleon total energy to be on-shell with a quick call to
       // BindHitNucleon()
       genie::utils::BindHitNucleon(*interaction, *fNuclModel, dummy_Eb, kOnShell);
 
       // TODO: document this, won't work for spectral functions
       double dummy_w = -1.;
       double prob = fNuclModel->Prob(pNi_next, dummy_w, tgt,
         tgt.HitNucPosition());
 
       double costh0_max = genie::utils::CosTheta0Max( *interaction );
 
       if ( prob > 0. && costh0_max > -1. ) max_momentum = pNi_next;
       else search_step /= 2.;
     }
 
     {
         // Set the nucleon we're using to be upstream at max energy and unbound
         fNuclModel->SetMomentum3( TVector3(0., 0., -max_momentum) );
         fNuclModel->SetRemovalEnergy( 0. );
 
         // Set the nucleon total energy to be on-shell with a quick call to
         // BindHitNucleon()
         genie::utils::BindHitNucleon(*interaction, *fNuclModel, dummy_Eb, kOnShell);
 
         // Just a scoping block for now
         // OK, we're going to scan the COM frame angles to get the point of max xsec
         // We'll bin in solid angle, and find the maximum point
         // Then we'll bin/scan again inside that point
         // Rinse and repeat until the xsec stabilises to within some fraction of our safety factor
         const double acceptable_fraction_of_safety_factor = 0.2;
         const int max_n_layers = 100;
         const int N_theta = 10;
         const int N_phi = 10;
         double phi_at_xsec_max = -1;
         double costh_at_xsec_max = 0;
         double this_nuc_xsec_max = -1;
 
         double costh_range_min = -1.;
         double costh_range_max = genie::utils::CosTheta0Max( *interaction );
         double phi_range_min = 0.;
         double phi_range_max = 2*TMath::Pi();
         for (int ilayer = 0 ; ilayer < max_n_layers ; ilayer++) {
           double last_layer_xsec_max = this_nuc_xsec_max;
           double costh_increment = (costh_range_max-costh_range_min) / N_theta;
           double phi_increment   = (phi_range_max-phi_range_min) / N_phi;
           // Now scan through centre-of-mass angles coarsely
           for (int itheta = 0; itheta < N_theta; itheta++){
               double costh = costh_range_min + itheta * costh_increment;
               for (int iphi = 0; iphi < N_phi; iphi++) { // Scan around phi
                   double phi = phi_range_min + iphi * phi_increment;
                   // We're after an upper limit on the cross section, so just
                   // put the nucleon on-shell and call it good. The last
                   // argument is false because we've already called
                   // BindHitNucleon() above
                   double xs = genie::utils::ComputeFullQELPXSec(interaction,
                     fNuclModel, fXSecModel, costh, phi, dummy_Eb, kOnShell, fMinAngleEM, false);
 
                   if (xs > this_nuc_xsec_max){
                       phi_at_xsec_max = phi;
                       costh_at_xsec_max = costh;
                       this_nuc_xsec_max = xs;
                   }
                   //
               } // Done with phi scan
           }// Done with centre-of-mass angles coarsely
 
           // Calculate the range for the next layer
           costh_range_min = costh_at_xsec_max - costh_increment;
           costh_range_max = costh_at_xsec_max + costh_increment;
           phi_range_min = phi_at_xsec_max - phi_increment;
           phi_range_max = phi_at_xsec_max + phi_increment;
 
           double improvement_factor = this_nuc_xsec_max/last_layer_xsec_max;
           if (ilayer && (improvement_factor-1) < acceptable_fraction_of_safety_factor * (fSafetyFactor-1)) {
             break;
           }
         }
         if (this_nuc_xsec_max > xsec_max) {
             xsec_max = this_nuc_xsec_max;
             LOG("QELEvent", pINFO) << "best estimate for xsec_max = " << xsec_max;
         }
 
         delete interaction;
     }
     // Apply safety factor, since value retrieved from the cache might
     // correspond to a slightly different energy
     xsec_max *= fSafetyFactor;
 
 #ifdef __GENIE_LOW_LEVEL_MESG_ENABLED__
     SLOG("QELEvent", pDEBUG) << interaction->AsString();
     SLOG("QELEvent", pDEBUG) << "Max xsec in phase space = " << max_xsec;
     SLOG("QELEvent", pDEBUG) << "Computed using alg = " << *fXSecModel;
 #endif
 
     LOG("QELEvent", pINFO) << "Computed maximum cross section to throw against - value is " << xsec_max;
     return xsec_max;
 }

void QELEventGenerator::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 358 of file QELEventGenerator.cxx.

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

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

void QELEventGenerator::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 364 of file QELEventGenerator.cxx.

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

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

void QELEventGenerator::LoadConfig ( void )

private

Definition at line 370 of file QELEventGenerator.cxx.

References genie::KineGeneratorWithCache::fEMin, genie::KineGeneratorWithCache::fGenerateUniformly, fHitNucleonBindingMode, genie::KineGeneratorWithCache::fMaxXSecDiffTolerance, fMaxXSecNucleonThrows, fMinAngleEM, fNuclModel, genie::KineGeneratorWithCache::fSafetyFactor, genie::Algorithm::GetParamDef(), genie::utils::StringToQELBindingMode(), and genie::Algorithm::SubAlg().

Referenced by Configure().

 {
     // Load sub-algorithms and config data to reduce the number of registry
     // lookups
         fNuclModel = 0;
 
     RgKey nuclkey = "NuclearModel";
 
     fNuclModel = dynamic_cast<const NuclearModelI *> (this->SubAlg(nuclkey));
     assert(fNuclModel);
 
     // Safety factor for the maximum differential cross section
     GetParamDef( "MaxXSec-SafetyFactor", fSafetyFactor, 1.6  ) ;
 
     // Minimum energy for which max xsec would be cached, forcing explicit
     // calculation for lower eneries
     GetParamDef( "Cache-MinEnergy", fEMin, 1.00 ) ;
 
     // Maximum allowed fractional cross section deviation from maxim cross
     // section used in rejection method
     GetParamDef( "MaxXSec-DiffTolerance", fMaxXSecDiffTolerance, 999999. ) ;
     assert(fMaxXSecDiffTolerance>=0);
 
     // Generate kinematics uniformly over allowed phase space and compute
     // an event weight?
     GetParamDef( "UniformOverPhaseSpace", fGenerateUniformly, false ) ;
 
     GetParamDef( "SF-MinAngleEMscattering", fMinAngleEM, 0. ) ;
 
     // Decide how to handle the binding energy of the initial state struck
     // nucleon
     std::string binding_mode;
     GetParamDef( "HitNucleonBindingMode", binding_mode, std::string("UseNuclearModel") );
 
     fHitNucleonBindingMode = genie::utils::StringToQELBindingMode( binding_mode );
 
     GetParamDef( "MaxXSecNucleonThrows", fMaxXSecNucleonThrows, 800 );
 }

void QELEventGenerator::ProcessEventRecord ( GHepRecord * event_rec ) const

virtual

Implements genie::EventRecordVisitorI.

Definition at line 67 of file QELEventGenerator.cxx.

References genie::units::A, genie::GHepParticle::A(), genie::GHepRecord::AddParticle(), AddTargetNucleusRemnant(), genie::KineGeneratorWithCache::AssertXSecLimits(), genie::utils::BindHitNucleon(), genie::XclsTag::CharmHadronPdg(), genie::Kinematics::ClearRunningValues(), genie::utils::ComputeFullQELPXSec(), genie::utils::CosTheta0Max(), genie::EventGeneratorI::CrossSectionAlg(), genie::GHepRecord::EventFlags(), genie::Interaction::ExclTag(), fEb, genie::KineGeneratorWithCache::fGenerateUniformly, fHitNucleonBindingMode, genie::PDGLibrary::Find(), fMinAngleEM, fNuclModel, genie::Kinematics::FSLeptonP4(), genie::Interaction::FSPrimLeptonPdg(), genie::KineGeneratorWithCache::fXSecModel, genie::gAbortingInErr, genie::NuclearModelI::GenerateNucleon(), gQ2, genie::Kinematics::HadSystP4(), genie::GHepRecord::HitNucleon(), genie::GHepRecord::HitNucleonPosition(), genie::Target::HitNucP4(), genie::Interaction::InitState(), genie::Interaction::InitStatePtr(), genie::RunningThreadInfo::Instance(), genie::RandomGen::Instance(), genie::PDGLibrary::Instance(), genie::pdg::IonPdgCode(), genie::XclsTag::IsCharmEvent(), genie::Target::IsNucleus(), genie::pdg::IsProton(), genie::XclsTag::IsStrangeEvent(), genie::kIAssumeFreeNucleon, genie::Interaction::KinePtr(), genie::kISkipKinematicChk, genie::kISkipProcessChk, genie::kIStHadronInTheNucleus, genie::kIStStableFinalState, genie::kKineGenErr, genie::constants::kPi, genie::kPSQELEvGen, genie::kRfHitNucRest, genie::controls::kRjMaxIterations, LOG, genie::KineGeneratorWithCache::MaxXSec(), pDEBUG, genie::GHepParticle::Pdg(), pFATAL, pINFO, pNOTICE, genie::GHepRecord::Probe(), genie::InitialState::ProbeE(), genie::GHepRecord::ProbePosition(), pWARN, genie::Kinematics::Q2(), genie::Interaction::RecoilNucleonPdg(), genie::RandomGen::RndKine(), genie::RunningThreadInfo::RunningThread(), genie::GHepRecord::SetDiffXSec(), genie::Target::SetHitNucPosition(), genie::GHepParticle::SetMomentum(), genie::NuclearModelI::SetMomentum3(), genie::utils::SetPrimaryLeptonPolarization(), genie::Kinematics::SetQ2(), genie::exceptions::EVGThreadException::SetReason(), genie::NuclearModelI::SetRemovalEnergy(), genie::GHepParticle::SetRemovalEnergy(), genie::Kinematics::SetW(), genie::Kinematics::Setx(), genie::Kinematics::Sety(), genie::XclsTag::StrangeHadronPdg(), genie::GHepRecord::Summary(), genie::exceptions::EVGThreadException::SwitchOnFastForward(), genie::GHepRecord::TargetNucleus(), genie::InitialState::Tgt(), genie::InitialState::TgtPtr(), genie::utils::kinematics::WQ2toXY(), genie::GHepParticle::X4(), and genie::GHepParticle::Z().

 {
     LOG("QELEvent", pDEBUG) << "Generating QE event kinematics...";
 
     // Get the random number generators
     RandomGen * rnd = RandomGen::Instance();
 
     // Access cross section algorithm for running thread
     RunningThreadInfo * rtinfo = RunningThreadInfo::Instance();
     const EventGeneratorI * evg = rtinfo->RunningThread();
     fXSecModel = evg->CrossSectionAlg();
 
     // Get the interaction and check we are working with a nuclear target
     Interaction * interaction = evrec->Summary();
     // Skip if not a nuclear target
     if(interaction->InitState().Tgt().IsNucleus()) {
         // Skip if no hit nucleon is set
         if(! evrec->HitNucleon()) {
             LOG("QELEvent", pFATAL) << "No hit nucleon was set";
             gAbortingInErr = true;
             exit(1);
         }
     } // is nuclear target
 
     // set the 'trust' bits
     interaction->SetBit(kISkipProcessChk);
     interaction->SetBit(kISkipKinematicChk);
 
     // Access the hit nucleon and target nucleus entries at the GHEP record
     GHepParticle * nucleon = evrec->HitNucleon();
     GHepParticle * nucleus = evrec->TargetNucleus();
     bool have_nucleus = (nucleus != 0);
 
     // Store the hit nucleon radius before computing the maximum differential
     // cross section (important when using the local Fermi gas model)
     Target* tgt = interaction->InitState().TgtPtr();
     double hitNucPos = nucleon->X4()->Vect().Mag();
     tgt->SetHitNucPosition( hitNucPos );
 
     //-- For the subsequent kinematic selection with the rejection method:
     //   Calculate the max differential cross section or retrieve it from the
     //   cache. Throw an exception and quit the evg thread if a non-positive
     //   value is found.
     //   If the kinematics are generated uniformly over the allowed phase
     //   space the max xsec is irrelevant
     double xsec_max = (fGenerateUniformly) ? -1 : this->MaxXSec(evrec);
 
     // For a composite nuclear target, check to make sure that the
     // final nucleus has a recognized PDG code
     if ( have_nucleus ) {
       // compute A,Z for final state nucleus & get its PDG code
       int nucleon_pdgc = nucleon->Pdg();
       bool is_p  = pdg::IsProton(nucleon_pdgc);
       int Z = (is_p) ? nucleus->Z()-1 : nucleus->Z();
       int A = nucleus->A() - 1;
       TParticlePDG * fnucleus = 0;
       int ipdgc = pdg::IonPdgCode(A, Z);
       fnucleus = PDGLibrary::Instance()->Find(ipdgc);
       if (!fnucleus) {
         LOG("QELEvent", pFATAL)
             << "No particle with [A = " << A << ", Z = " << Z
             << ", pdgc = " << ipdgc << "] in PDGLibrary!";
         exit(1);
       }
     }
 
     // In the accept/reject loop, each iteration samples a new value of
     //   - the hit nucleon 3-momentum,
     //   - its binding energy (only actually used if fHitNucleonBindingMode == kUseNuclearModel)
     //   - the final lepton scattering angles in the neutrino-and-hit-nucleon COM frame
     //     (measured with respect to the velocity of the COM frame as seen in the lab frame)
     unsigned int iter = 0;
     bool accept = false;
     while (1) {
 
         iter++;
         LOG("QELEvent", pINFO) << "Attempt #: " << iter;
         if(iter > kRjMaxIterations) {
             LOG("QELEvent", pWARN)
                 << "Couldn't select a valid (pNi, Eb, cos_theta_0, phi_0) tuple after "
                 << iter << " iterations";
             evrec->EventFlags()->SetBitNumber(kKineGenErr, true);
             genie::exceptions::EVGThreadException exception;
             exception.SetReason("Couldn't select kinematics");
             exception.SwitchOnFastForward();
             throw exception;
         }
 
         // If the target is a composite nucleus, then sample an initial nucleon
         // 3-momentum and removal energy from the nuclear model.
         if ( tgt->IsNucleus() ) {
           fNuclModel->GenerateNucleon(*tgt, hitNucPos);
         }
         else {
           // Otherwise, just set the nucleon to be at rest in the lab frame and
           // unbound. Use the nuclear model to make these assignments. The call
           // to BindHitNucleon() will apply them correctly below.
           fNuclModel->SetMomentum3( TVector3(0., 0., 0.) );
           fNuclModel->SetRemovalEnergy( 0. );
         }
 
         // Put the hit nucleon off-shell (if needed) so that we can get the correct
         // value of cos_theta0_max
         genie::utils::BindHitNucleon(*interaction, *fNuclModel,
           fEb, fHitNucleonBindingMode);
 
         double cos_theta0_max = std::min(1., CosTheta0Max(*interaction));
 
         // If the allowed range of cos(theta_0) is vanishing, skip doing the
         // full differential cross section calculation (it will be zero)
         if ( cos_theta0_max <= -1. ) continue;
 
         // Pick a direction
         // NOTE: In the kPSQELEvGen phase space used by this generator,
         // these angles are specified with respect to the velocity of the
         // probe + hit nucleon COM frame as measured in the lab frame. That is,
         // costheta = 1 means that the outgoing lepton's COM frame 3-momentum
         // points parallel to the velocity of the COM frame.
         double costheta = rnd->RndKine().Uniform(-1., cos_theta0_max); // cosine theta
         double phi = rnd->RndKine().Uniform( 2.*kPi ); // phi: [0, 2pi]
 
         // Set the "bind_nucleon" flag to false in this call to ComputeFullQELPXSec
         // since we've already done that above
         LOG("QELEvent", pDEBUG) << "cth0 = " << costheta << ", phi0 = " << phi;
         double xsec = genie::utils::ComputeFullQELPXSec(interaction, fNuclModel,
           fXSecModel, costheta, phi, fEb, fHitNucleonBindingMode, fMinAngleEM, false);
 
         // select/reject event
         this->AssertXSecLimits(interaction, xsec, xsec_max);
 
         double t = xsec_max * rnd->RndKine().Rndm();
 
 #ifdef __GENIE_LOW_LEVEL_MESG_ENABLED__
         LOG("QELEvent", pDEBUG)
             << "xsec= " << xsec << ", Rnd= " << t;
 #endif
         accept = (t < xsec);
 
         // If the generated kinematics are accepted, finish-up module's job
         if(accept) {
             double gQ2 = interaction->KinePtr()->Q2(false);
             LOG("QELEvent", pINFO) << "*Selected* Q^2 = " << gQ2 << " GeV^2";
 
             // reset bits
             interaction->ResetBit(kISkipProcessChk);
             interaction->ResetBit(kISkipKinematicChk);
             interaction->ResetBit(kIAssumeFreeNucleon);
 
             // get neutrino energy at struck nucleon rest frame and the
             // struck nucleon mass (can be off the mass shell)
             const InitialState & init_state = interaction->InitState();
             double E  = init_state.ProbeE(kRfHitNucRest);
             double M = init_state.Tgt().HitNucP4().M();
             LOG("QELKinematics", pNOTICE) << "E = " << E << ", M = "<< M;
 
             // The hadronic inv. mass is equal to the recoil nucleon on-shell mass.
             // For QEL/Charm events it is set to be equal to the on-shell mass of
             // the generated charm baryon (Lamda_c+, Sigma_c+ or Sigma_c++)
             // Similarly for strange baryons
             //
             const XclsTag & xcls = interaction->ExclTag();
             int rpdgc = 0;
             if (xcls.IsCharmEvent()) {
                 rpdgc = xcls.CharmHadronPdg();
             } else if (xcls.IsStrangeEvent()) {
                 rpdgc = xcls.StrangeHadronPdg();
             } else {
                 rpdgc = interaction->RecoilNucleonPdg();
             }
             assert(rpdgc);
             double gW = PDGLibrary::Instance()->Find(rpdgc)->Mass();
             LOG("QELEvent", pNOTICE) << "Selected: W = "<< gW;
 
             // (W,Q2) -> (x,y)
             double gx=0, gy=0;
             kinematics::WQ2toXY(E,M,gW,gQ2,gx,gy);
 
             // lock selected kinematics & clear running values
             interaction->KinePtr()->SetQ2(gQ2, true);
             interaction->KinePtr()->SetW (gW,  true);
             interaction->KinePtr()->Setx (gx,  true);
             interaction->KinePtr()->Sety (gy,  true);
             interaction->KinePtr()->ClearRunningValues();
 
             // set the cross section for the selected kinematics
             evrec->SetDiffXSec(xsec, kPSQELEvGen);
 
             TLorentzVector lepton(interaction->KinePtr()->FSLeptonP4());
             TLorentzVector outNucleon(interaction->KinePtr()->HadSystP4());
             TLorentzVector x4l(*(evrec->Probe())->X4());
 
             // Add the final-state lepton to the event record
             evrec->AddParticle(interaction->FSPrimLeptonPdg(), kIStStableFinalState,
               evrec->ProbePosition(), -1, -1, -1, interaction->KinePtr()->FSLeptonP4(), x4l);
 
             // Set its polarization
             utils::SetPrimaryLeptonPolarization( evrec );
 
             // Add the final-state nucleon to the event record
             GHepStatus_t ist = (tgt->IsNucleus()) ? kIStHadronInTheNucleus : kIStStableFinalState;
             evrec->AddParticle(interaction->RecoilNucleonPdg(), ist, evrec->HitNucleonPosition(),
               -1, -1, -1, interaction->KinePtr()->HadSystP4(), x4l);
 
             // Store struck nucleon momentum and binding energy
             TLorentzVector p4ptr = interaction->InitStatePtr()->TgtPtr()->HitNucP4();
             LOG("QELEvent",pNOTICE) << "pn: " << p4ptr.X() << ", "
               << p4ptr.Y() << ", " << p4ptr.Z() << ", " << p4ptr.E();
             nucleon->SetMomentum(p4ptr);
             nucleon->SetRemovalEnergy(fEb);
 
             // add a recoiled nucleus remnant
             this->AddTargetNucleusRemnant(evrec);
 
             break; // done
         } else { // accept throw
             LOG("QELEvent", pDEBUG) << "Reject current throw...";
         }
 
     } // iterations - while(1) loop
     LOG("QELEvent", pINFO) << "Done generating QE event kinematics!";
 }

Member Data Documentation

double genie::QELEventGenerator::fEb

mutableprivate

Definition at line 47 of file QELEventGenerator.h.

Referenced by ProcessEventRecord().

QELEvGen_BindingMode_t genie::QELEventGenerator::fHitNucleonBindingMode

private

Enum that indicates which approach should be used to handle the binding energy of the struck nucleon

Definition at line 60 of file QELEventGenerator.h.

Referenced by LoadConfig(), and ProcessEventRecord().

int genie::QELEventGenerator::fMaxXSecNucleonThrows

private

The number of nucleons to sample from the nuclear model when choosing a maximum momentum to use in ComputeMaxXSec()

Definition at line 64 of file QELEventGenerator.h.

Referenced by LoadConfig().

double genie::QELEventGenerator::fMinAngleEM

mutableprivate

Definition at line 56 of file QELEventGenerator.h.

Referenced by ComputeMaxXSec(), LoadConfig(), and ProcessEventRecord().

const NuclearModelI* genie::QELEventGenerator::fNuclModel

private

nuclear model

Definition at line 54 of file QELEventGenerator.h.

Referenced by ComputeMaxXSec(), LoadConfig(), and ProcessEventRecord().

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

Public Member Functions

Private Member Functions

Private Attributes

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation