Interface to PYTHIA particle decayer.
The PythiaDecayer is a concrete implementation of the Decayer interface. More...

#include <PythiaDecayer.h>

Inheritance diagram for genie::PythiaDecayer:

Public Member Functions
	PythiaDecayer ()

	PythiaDecayer (string config)

virtual	~PythiaDecayer ()

void	ProcessEventRecord (GHepRecord *event) const

Private Member Functions
void	Initialize (void) const

bool	IsHandled (int pdgc) const

void	InhibitDecay (int pdgc, TDecayChannel *ch=0) const

void	UnInhibitDecay (int pdgc, TDecayChannel *ch=0) const

bool	Decay (int ip, GHepRecord *event) const

double	SumOfBranchingRatios (int kc) const

int	FindPythiaDecayChannel (int kc, TDecayChannel *ch) const

bool	MatchDecayChannels (int ic, TDecayChannel *ch) const

Private Attributes
TPythia6 *	fPythia
	PYTHIA6 wrapper class. More...

double	fWeight

Additional Inherited Members
Protected Member Functions inherited from genie::Decayer
	Decayer ()

	Decayer (string name)

	Decayer (string name, string config)

virtual void	LoadConfig (void)

virtual bool	ToBeDecayed (int pdgc, GHepStatus_t ist) const

virtual bool	IsUnstable (int pdgc) const

virtual	~Decayer ()

void	Configure (const Registry &config)

void	Configure (string config)

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

	EventRecordVisitorI (string name)

	EventRecordVisitorI (string name, string config)

virtual	~EventRecordVisitorI ()

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

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...

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...

Static Protected 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)

Protected Attributes inherited from genie::Decayer
bool	fGenerateWeighted
	generate weighted or unweighted decays? More...

bool	fRunBefHadroTransp
	is invoked before or after FSI? More...

PDGCodeList	fParticlesToDecay
	list of particles to be decayed More...

PDGCodeList	fParticlesNotToDecay
	list of particles for which decay is inhibited 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

Interface to PYTHIA particle decayer.
The PythiaDecayer is a concrete implementation of the Decayer interface.

Author: Costas Andreopoulos <constantinos.andreopoulos cern.ch> University of Liverpool & STFC Rutherford Appleton Laboratory

June 20, 2004

Definition at line 30 of file PythiaDecayer.h.

Constructor & Destructor Documentation

PythiaDecayer::PythiaDecayer ( )

Definition at line 45 of file PythiaDecayer.cxx.

                              :
 Decayer("genie::PythiaDecayer")
 {
   this->Initialize();
 }

PythiaDecayer::PythiaDecayer ( string config )

Definition at line 51 of file PythiaDecayer.cxx.

                                           :
 Decayer("genie::PythiaDecayer", config)
 {
   this->Initialize();
 }

PythiaDecayer::~PythiaDecayer ( )

virtual

Definition at line 57 of file PythiaDecayer.cxx.

 {
 
 }

Member Function Documentation

bool PythiaDecayer::Decay	(	int	ip,
		GHepRecord *	event
	)		const

private

Definition at line 95 of file PythiaDecayer.cxx.

 {
   fWeight = 1.; // reset previous decay weight
 
   // Get particle to be decayed
   GHepParticle * decay_particle = event->Particle(decay_particle_id);
   if(!decay_particle) return 0;
 
   // Get the particle 4-momentum, 4-position and PDG code
   TLorentzVector decay_particle_p4 = *(decay_particle->P4());
   int decay_particle_pdg_code = decay_particle->Pdg();
 
   // Convert to PYTHIA6 particle code and check whether decay is inhibited
   int kc   = fPythia->Pycomp(decay_particle_pdg_code);
   int mdcy = fPythia->GetMDCY(kc, 1);
   if(mdcy == 0) {
     LOG("Pythia6Decay", pNOTICE)
        << (PDGLibrary::Instance())->Find(decay_particle_pdg_code)->GetName()
        << " decays are inhibited!";
     return false;
   }
 
   // Get sub of BRs and compute weight if decay channels were inhibited
   double sumbr = this->SumOfBranchingRatios(kc);
   if(sumbr <= 0) {
     LOG("Pythia6Decay", pWARN)
        << "The sum of enabled "
        << (PDGLibrary::Instance())->Find(decay_particle_pdg_code)->GetName()
        << " decay channel branching ratios is non-positive!";
     return false;
   }
   fWeight = 1./sumbr; // update weight to account for inhibited channels
 
   // Run PYTHIA6 decay
   int    ip    = 0;
   double E     = decay_particle_p4.Energy();
   double theta = decay_particle_p4.Theta();
   double phi   = decay_particle_p4.Phi();
   fPythia->SetMSTJ(22,1);
   py1ent_(&ip, &decay_particle_pdg_code, &E, &theta, &phi);
 
   // Get decay products
   fPythia->GetPrimaries();
   TClonesArray * impl = (TClonesArray *) fPythia->ImportParticles("All");
   if(!impl) {
     LOG("Pythia6Decay", pWARN)
       << "TPythia6::ImportParticles() returns a null list!";
     return false;
   }
 
   // Copy the PYTHIA6 container to the GENIE event record
 
   // Check whether the interaction is off a nuclear target or free nucleon
   // Depending on whether this module is run before or after the hadron
   // transport module it would affect the daughters status code
   GHepParticle * target_nucleus = event->TargetNucleus();
   bool in_nucleus = (target_nucleus!=0);
 
   // the values of space coordinates from pythia are in mm.
   // our conventions want it in fm
   constexpr double space_scale = units::mm / units::fm ; 
 
   //  the values of time coordinate from pythia is in mm/c.
   // our conventions want it in ys 
   constexpr double time_scale = 1e21 * units::m / units::s ; 
 
   TMCParticle * p = 0;
   TIter particle_iter(impl);
   while( (p = (TMCParticle *) particle_iter.Next()) ) {
     // Convert from TMCParticle to GHepParticle
     GHepParticle mcp = GHepParticle(
         p->GetKF(),                // pdg
         GHepStatus_t(p->GetKS()),  // status
         p->GetParent(),            // first parent
         0,                         // second parent
         p->GetFirstChild(),        // first daughter
         p->GetLastChild(),         // second daughter
         p->GetPx(),                // px
         p->GetPy(),                // py
         p->GetPz(),                // pz
         p->GetEnergy(),            // e
         p->GetVx() * space_scale , // x
         p->GetVy() * space_scale , // y
         p->GetVz() * space_scale , // z
         p->GetTime() * time_scale  // t
     );
 
     if(mcp.Status()==kIStNucleonTarget) continue; // mother particle, already in GHEP
 
     int daughter_pdg_code = mcp.Pdg();
     SLOG("Pythia6Decay", pINFO)
        << "Adding daughter particle wit PDG code = "
        << daughter_pdg_code << ", m = " << mcp.Mass()
        << " GeV, E = " << mcp.Energy() << " GeV)";
 
     bool is_hadron = pdg::IsHadron(daughter_pdg_code);
     bool hadron_in_nuc = (in_nucleus && is_hadron && fRunBefHadroTransp);
 
     GHepStatus_t daughter_status_code = (hadron_in_nuc) ?
          kIStHadronInTheNucleus : kIStStableFinalState;
 
     TLorentzVector daughter_p4(
        mcp.Px(),mcp.Py(),mcp.Pz(),mcp.Energy());
 
     event->AddParticle(
        daughter_pdg_code, daughter_status_code,
        decay_particle_id,-1,-1,-1,
        daughter_p4, * mcp.X4() );
   }
 
   // Update the event weight for each weighted particle decay
   double weight = event->Weight() * fWeight;
   event->SetWeight(weight);
 
   // Mark input particle as a 'decayed state' & add its daughter links
   decay_particle->SetStatus(kIStDecayedState);
 
   return true;
 }

int PythiaDecayer::FindPythiaDecayChannel	(	int	kc,
		TDecayChannel *	ch
	)		const

private

Definition at line 321 of file PythiaDecayer.cxx.

 {
   if(!dc) return -1;
 
   int first_channel = fPythia->GetMDCY(kc,2);
   int last_channel  = fPythia->GetMDCY(kc,2) + fPythia->GetMDCY(kc,3) - 1;
 
   bool found_match = false;
 
   // loop over pythia decay channels
   for(int ichannel = first_channel;
           ichannel < last_channel; ichannel++) {
 
      // does the  current pythia channel matches the input TDecayChannel?
      LOG("Pythia6Decay", pINFO)
          << "\nComparing PYTHIA's channel = " << ichannel
          << " with TDecayChannel = " << dc->Number();
 
      found_match = this->MatchDecayChannels(ichannel,dc);
      if(found_match) {
          LOG("Pythia6Decay", pNOTICE)
             << " ** TDecayChannel id = " << dc->Number()
             << " corresponds to PYTHIA6 channel id = " << ichannel;
          return ichannel;
      }//match?
   }//loop pythia decay ch.
 
   LOG("Pythia6Decay", pWARN)
      << " ** No PYTHIA6 decay channel match found for "
      << "TDecayChannel id = " << dc->Number();
 
   return -1;
 }

void PythiaDecayer::InhibitDecay	(	int	pdgc,
		TDecayChannel *	ch = `0`
	)		const

privatevirtual

Implements genie::Decayer.

Definition at line 237 of file PythiaDecayer.cxx.

 {
   if(! this->IsHandled(pdg_code)) return;
 
   int kc = fPythia->Pycomp(pdg_code);
 
   if(!dc) {
     LOG("Pythia6Decay", pINFO)
        << "Switching OFF ALL decay channels for particle = " << pdg_code;
     fPythia->SetMDCY(kc, 1,0);
     return;
   }
 
   LOG("Pythia6Decay", pINFO)
      << "Switching OFF decay channel = " << dc->Number()
      << " for particle = " << pdg_code;
 
   int ichannel = this->FindPythiaDecayChannel(kc, dc);
   if(ichannel != -1) {
     fPythia->SetMDME(ichannel,1,0); // switch-off
   }
 }

void PythiaDecayer::Initialize ( void ) const

private

Definition at line 215 of file PythiaDecayer.cxx.

 {
   fPythia = TPythia6::Instance();
   fWeight = 1.;
 
   // sync GENIE/PYTHIA6 seeds
   RandomGen::Instance();
 }

bool PythiaDecayer::IsHandled ( int pdgc ) const

privatevirtual

Implements genie::Decayer.

Definition at line 224 of file PythiaDecayer.cxx.

 {
 // does not handle requests to decay baryon resonances
 
  bool is_handled = (!utils::res::IsBaryonResonance(pdg_code));
 
  LOG("Pythia6Decay", pDEBUG)
     << "Can decay particle with PDG code = " << pdg_code
     << "? " << ((is_handled)? "Yes" : "No");
 
   return is_handled;
 }

bool PythiaDecayer::MatchDecayChannels	(	int	ic,
		TDecayChannel *	ch
	)		const

private

Definition at line 355 of file PythiaDecayer.cxx.

 {
   // num. of daughters in the input TDecayChannel & the input PYTHIA ichannel
   int nd = dc->NDaughters();
 
   int py_nd = 0;
   for (int i = 1; i <= 5; i++) {
      if(fPythia->GetKFDP(ichannel,i) != 0) py_nd++;
   }
 
   LOG("Pythia6Decay", pDEBUG)
     << "NDaughters: PYTHIA = " << py_nd << ", ROOT's TDecayChannel = " << nd;
 
   if(nd != py_nd) return false;
 
   //
   // if the two channels have the same num. of daughters, then compare them
   //
 
   // store decay daughters for the input TDecayChannel
   vector<int> dc_daughter(nd);
   int k=0;
   for( ; k < nd; k++) {
      dc_daughter[k] = dc->DaughterPdgCode(k);
   }
   // store decay daughters for the input PYTHIA's ichannel
   vector<int> py_daughter(nd);
   k=0;
   for(int i = 1; i <= 5; i++) {
      if(fPythia->GetKFDP(ichannel,i) == 0) continue;
      py_daughter[k] = fPythia->GetKFDP(ichannel,i);
      k++;
   }
 
   // sort both daughter lists
   sort( dc_daughter.begin(), dc_daughter.end() );
   sort( py_daughter.begin(), py_daughter.end() );
 
   // compare
   for(int i = 0; i < nd; i++) {
     if(dc_daughter[i] != py_daughter[i]) return false;
   }
   return true;
 }

void PythiaDecayer::ProcessEventRecord ( GHepRecord * event ) const

virtual

Implements genie::EventRecordVisitorI.

Definition at line 62 of file PythiaDecayer.cxx.

 {
   LOG("ResonanceDecay", pINFO)
     << "Running PYTHIA6 particle decayer "
     << ((fRunBefHadroTransp) ? "*before*" : "*after*") << " FSI";
 
   // Loop over particles, find unstable ones and decay them
   TObjArrayIter piter(event);
   GHepParticle * p = 0;
   int ipos = -1;
 
   while( (p = (GHepParticle *) piter.Next()) ) {
     ipos++;
 
     LOG("Pythia6Decay", pDEBUG) << "Checking: " << p->Name();
 
     int pdg_code = p->Pdg();
     GHepStatus_t status_code = p->Status();
 
     if(!this->IsHandled  (pdg_code)) continue;
     if(!this->ToBeDecayed(pdg_code, status_code)) continue;
 
     LOG("Pythia6Decay", pNOTICE)
           << "Decaying unstable particle: " << p->Name();
 
     bool decayed = this->Decay(ipos, event);
     assert(decayed); // handle this more graciously and throw an exception
   }
 
   LOG("Pythia6Decay", pNOTICE)
      << "Done finding & decaying unstable particles";
 }

double PythiaDecayer::SumOfBranchingRatios ( int kc ) const

private

Definition at line 292 of file PythiaDecayer.cxx.

 {
 // Sum of branching ratios for enabled channels
 //
   double sumbr=0.;
 
   int first_channel = fPythia->GetMDCY(kc,2);
   int last_channel  = fPythia->GetMDCY(kc,2) + fPythia->GetMDCY(kc,3) - 1;
 
   bool has_inhibited_channels=false;
 
   // loop over pythia decay channels
   for(int ichannel = first_channel;
           ichannel < last_channel; ichannel++) {
 
      bool enabled = (fPythia->GetMDME(ichannel,1) == 1);
      if (!enabled) {
        has_inhibited_channels = true;
      } else {
        sumbr += fPythia->GetBRAT(ichannel);
      }
   }
 
   if(!has_inhibited_channels) return 1.;
   LOG("Pythia6Decay", pINFO) << "Sum{BR} = " << sumbr;
 
   return sumbr;
 }

void PythiaDecayer::UnInhibitDecay	(	int	pdgc,
		TDecayChannel *	ch = `0`
	)		const

privatevirtual

dc

Implements genie::Decayer.

Definition at line 260 of file PythiaDecayer.cxx.

 {
   if(! this->IsHandled(pdg_code)) return;
 
   int kc = fPythia->Pycomp(pdg_code);
 
   if(!dc) {
     LOG("Pythia6Decay", pINFO)
       << "Switching ON all PYTHIA decay channels for particle = " << pdg_code;
 
     fPythia->SetMDCY(kc, 1,1);
 
     int first_channel = fPythia->GetMDCY(kc,2);
     int last_channel  = fPythia->GetMDCY(kc,2) + fPythia->GetMDCY(kc,3) - 1;
 
     for(int ichannel = first_channel;
             ichannel < last_channel; ichannel++) {
          fPythia->SetMDME(ichannel,1,1); // switch-on
     }
     return;
   }//!dc
 
   LOG("Pythia6Decay", pINFO)
      << "Switching OFF decay channel = " << dc->Number()
      << " for particle = " << pdg_code;
 
   int ichannel = this->FindPythiaDecayChannel(kc, dc);
   if(ichannel != -1) {
     fPythia->SetMDME(ichannel,1,1); // switch-on
   }
 }

Member Data Documentation

TPythia6* genie::PythiaDecayer::fPythia

mutableprivate

PYTHIA6 wrapper class.

Definition at line 51 of file PythiaDecayer.h.

double genie::PythiaDecayer::fWeight

mutableprivate

Definition at line 52 of file PythiaDecayer.h.

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

Generator/src/Physics/Decay/PythiaDecayer.h
Generator/src/Physics/Decay/PythiaDecayer.cxx

Public Member Functions

Private Member Functions

Private Attributes

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation