genie::Pythia6Decayer2023 Class Reference

Interface to PYTHIA particle decayer.
The Pythia6Decayer2023 is a concrete implementation of the Decayer interface. More...

#include <Pythia6Decayer2023.h>

Inheritance diagram for genie::Pythia6Decayer2023:

Collaboration diagram for genie::Pythia6Decayer2023:

Public Member Functions
	Pythia6Decayer2023 ()
	Pythia6Decayer2023 (string config)
virtual	~Pythia6Decayer2023 ()
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
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.
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.
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.
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)
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 Attributes inherited from genie::Decayer
bool	fGenerateWeighted
	generate weighted or unweighted decays?
bool	fRunBefHadroTransp
	is invoked before or after FSI?
PDGCodeList	fParticlesToDecay
	list of particles to be decayed
PDGCodeList	fParticlesNotToDecay
	list of particles for which decay is inhibited
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

Interface to PYTHIA particle decayer.
The Pythia6Decayer2023 is a concrete implementation of the Decayer interface.

Author

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

Created:\n June 20, 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 33 of file Pythia6Decayer2023.h.

Constructor & Destructor Documentation

Pythia6Decayer2023() [1/2]

Pythia6Decayer2023::Pythia6Decayer2023

(

)

Definition at line 52 of file Pythia6Decayer2023.cxx.

                                       :
Decayer("genie::Pythia6Decayer2023")
{
  this->Initialize();
}

References genie::Decayer::Decayer(), and Initialize().

Pythia6Decayer2023() [2/2]

Pythia6Decayer2023::Pythia6Decayer2023

(

string

config

)

Definition at line 58 of file Pythia6Decayer2023.cxx.

                                                    :
Decayer("genie::Pythia6Decayer2023", config)
{
  this->Initialize();
}

References genie::Decayer::Decayer(), and Initialize().

~Pythia6Decayer2023()

Pythia6Decayer2023::~Pythia6Decayer2023 ( )

virtual

Definition at line 64 of file Pythia6Decayer2023.cxx.

{
 
}

Member Function Documentation

Decay()

bool Pythia6Decayer2023::Decay ( int ip, GHepRecord * event ) const

private

Definition at line 102 of file Pythia6Decayer2023.cxx.

{
  fWeight = 1.; // reset previous decay weight
 
#ifdef __GENIE_PYTHIA6_ENABLED__
  // 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;
#else
  LOG("Pythia6Decay", pFATAL)
    << "calling GENIE/PYTHIA6 decay without enabling PYTHIA6";
  gAbortingInErr = true;
  std::exit(1);
 
return false;
#endif
}

References genie::GHepParticle::Energy(), genie::units::fm, genie::Decayer::fRunBefHadroTransp, fWeight, genie::gAbortingInErr, genie::PDGLibrary::Instance(), genie::pdg::IsHadron(), genie::kIStDecayedState, genie::kIStHadronInTheNucleus, genie::kIStNucleonTarget, genie::kIStStableFinalState, LOG, genie::units::m, genie::GHepParticle::Mass(), genie::units::mm, genie::GHepParticle::P4(), genie::GHepParticle::Pdg(), pFATAL, pINFO, pNOTICE, pWARN, genie::GHepParticle::Px(), genie::GHepParticle::Py(), genie::GHepParticle::Pz(), genie::units::s, genie::GHepParticle::SetStatus(), SLOG, genie::GHepParticle::Status(), SumOfBranchingRatios(), and genie::GHepParticle::X4().

Referenced by ProcessEventRecord().

FindPythiaDecayChannel()

int Pythia6Decayer2023::FindPythiaDecayChannel ( int kc, TDecayChannel * ch ) const

private

Definition at line 366 of file Pythia6Decayer2023.cxx.

{
  if(!dc) return -1;
 
#ifdef __GENIE_PYTHIA6_ENABLED__
  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();
#else
  LOG("Pythia6Decay", pFATAL)
    << "calling GENIE/PYTHIA6 decay without enabling PYTHIA6";
  gAbortingInErr = true;
  std::exit(1);
#endif
 
 
  return -1;
}

References genie::gAbortingInErr, LOG, MatchDecayChannels(), pFATAL, pINFO, pNOTICE, and pWARN.

Referenced by InhibitDecay(), and UnInhibitDecay().

InhibitDecay()

void Pythia6Decayer2023::InhibitDecay ( int pdgc, TDecayChannel * ch = 0 ) const

privatevirtual

Implements genie::Decayer.

Definition at line 260 of file Pythia6Decayer2023.cxx.

{
  if(! this->IsHandled(pdg_code)) return;
 
#ifdef __GENIE_PYTHIA6_ENABLED__
  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
  }
#else
  LOG("Pythia6Decay", pFATAL)
    << "calling GENIE/PYTHIA6 decay without enabling PYTHIA6";
  gAbortingInErr = true;
  std::exit(1);
#endif
 
}

References FindPythiaDecayChannel(), genie::gAbortingInErr, IsHandled(), LOG, pFATAL, and pINFO.

Initialize()

void Pythia6Decayer2023::Initialize ( void ) const

private

Definition at line 231 of file Pythia6Decayer2023.cxx.

{
#ifdef __GENIE_PYTHIA6_ENABLED__
  fPythia = TPythia6::Instance();
  fWeight = 1.;
 
  // sync GENIE/PYTHIA6 seeds
  RandomGen::Instance();
#else
  LOG("Pythia6Decay", pFATAL)
    << "calling GENIE/PYTHIA6 decay without enabling PYTHIA6";
  gAbortingInErr = true;
  std::exit(1);
#endif
}

References fWeight, genie::gAbortingInErr, genie::RandomGen::Instance(), LOG, and pFATAL.

Referenced by Pythia6Decayer2023(), and Pythia6Decayer2023().

IsHandled()

bool Pythia6Decayer2023::IsHandled ( int pdgc ) const

privatevirtual

Implements genie::Decayer.

Definition at line 247 of file Pythia6Decayer2023.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;
}

References genie::utils::res::IsBaryonResonance(), LOG, and pDEBUG.

Referenced by InhibitDecay(), ProcessEventRecord(), and UnInhibitDecay().

MatchDecayChannels()

bool Pythia6Decayer2023::MatchDecayChannels ( int ic, TDecayChannel * ch ) const

private

Definition at line 408 of file Pythia6Decayer2023.cxx.

{
  // num. of daughters in the input TDecayChannel & the input PYTHIA ichannel
  int nd = dc->NDaughters();
 
#ifdef __GENIE_PYTHIA6_ENABLED__
  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;
  }
#else
  LOG("Pythia6Decay", pFATAL)
    << "calling GENIE/PYTHIA6 decay without enabling PYTHIA6";
  gAbortingInErr = true;
  std::exit(1);
#endif
 
  return true;
}

References genie::gAbortingInErr, LOG, pDEBUG, and pFATAL.

Referenced by FindPythiaDecayChannel().

ProcessEventRecord()

void Pythia6Decayer2023::ProcessEventRecord ( GHepRecord * event ) const

virtual

Implements genie::EventRecordVisitorI.

Definition at line 69 of file Pythia6Decayer2023.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";
}

References Decay(), genie::Decayer::fRunBefHadroTransp, IsHandled(), LOG, genie::GHepParticle::Name(), pDEBUG, genie::GHepParticle::Pdg(), pINFO, pNOTICE, genie::GHepParticle::Status(), and genie::Decayer::ToBeDecayed().

SumOfBranchingRatios()

double Pythia6Decayer2023::SumOfBranchingRatios ( int kc ) const

private

Definition at line 330 of file Pythia6Decayer2023.cxx.

{
// Sum of branching ratios for enabled channels
//
  double sumbr=0.;
 
#ifdef __GENIE_PYTHIA6_ENABLED__
  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;
#else
  LOG("Pythia6Decay", pFATAL)
    << "calling GENIE/PYTHIA6 decay without enabling PYTHIA6";
  gAbortingInErr = true;
  std::exit(1);
#endif
 
  return sumbr;
}

References genie::gAbortingInErr, LOG, pFATAL, and pINFO.

Referenced by Decay().

UnInhibitDecay()

void Pythia6Decayer2023::UnInhibitDecay ( int pdgc, TDecayChannel * ch = 0 ) const

privatevirtual

Implements genie::Decayer.

Definition at line 291 of file Pythia6Decayer2023.cxx.

{
  if(! this->IsHandled(pdg_code)) return;
 
#ifdef __GENIE_PYTHIA6_ENABLED__
  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
  }
#else
  LOG("Pythia6Decay", pFATAL)
    << "calling GENIE/PYTHIA6 decay without enabling PYTHIA6";
  gAbortingInErr = true;
  std::exit(1);
#endif
}

References FindPythiaDecayChannel(), genie::gAbortingInErr, IsHandled(), LOG, pFATAL, and pINFO.

Member Data Documentation

fWeight

double genie::Pythia6Decayer2023::fWeight

mutableprivate

Definition at line 57 of file Pythia6Decayer2023.h.

Referenced by Decay(), and Initialize().

---

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

• Pythia6Decayer2023.h
• Pythia6Decayer2023.cxx