Utilities for simulating nucleon decay. More...

#include <NucleonDecayPrimaryVtxGenerator.h>

Inheritance diagram for genie::NucleonDecayPrimaryVtxGenerator:

Public Member Functions
	NucleonDecayPrimaryVtxGenerator ()

	NucleonDecayPrimaryVtxGenerator (string config)

	~NucleonDecayPrimaryVtxGenerator ()

void	ProcessEventRecord (GHepRecord *event) 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)

void	AddInitialState (GHepRecord *event) const

void	GenerateDecayedNucleonPosition (GHepRecord *event) const

void	GenerateFermiMomentum (GHepRecord *event) const

void	GenerateDecayProducts (GHepRecord *event) const

Private Attributes
int	fCurrInitStatePdg

NucleonDecayMode_t	fCurrDecayMode

int	fCurrDecayedNucleon

bool	fNucleonIsBound

TGenPhaseSpace	fPhaseSpaceGenerator

const NuclearModelI *	fNuclModel

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)

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

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::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

Utilities for simulating nucleon decay.

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

November 03, 2011

Definition at line 30 of file NucleonDecayPrimaryVtxGenerator.h.

Constructor & Destructor Documentation

NucleonDecayPrimaryVtxGenerator::NucleonDecayPrimaryVtxGenerator ( )

Definition at line 34 of file NucleonDecayPrimaryVtxGenerator.cxx.

                                                                  :
 EventRecordVisitorI("genie::NucleonDecayPrimaryVtxGenerator")
 {
 
 }

NucleonDecayPrimaryVtxGenerator::NucleonDecayPrimaryVtxGenerator ( string config )

Definition at line 40 of file NucleonDecayPrimaryVtxGenerator.cxx.

                  :
 EventRecordVisitorI("genie::NucleonDecayPrimaryVtxGenerator",config)
 {
 
 }

NucleonDecayPrimaryVtxGenerator::~NucleonDecayPrimaryVtxGenerator ( )

Definition at line 47 of file NucleonDecayPrimaryVtxGenerator.cxx.

 {
 
 }

Member Function Documentation

void NucleonDecayPrimaryVtxGenerator::AddInitialState ( GHepRecord * event ) const

private

Definition at line 72 of file NucleonDecayPrimaryVtxGenerator.cxx.

 {
 //
 // Add initial state in the event record.
 //
 // If the decayed nucleon is one bound in a nucleus, the event record is
 // initialized as follows:
 //    id: 0, nucleus (kIStInitialState)
 //    |
 //    |---> { id: 1, nucleon         (kIStDecayedState)
 //          { id: 2, remnant nucleus (kIStStableFinalState)
 //
 // If the decayed nucleon is a free one, the event record is initialized as
 // follows:
 //    id: 0, nucleon (kIStInitialState)
 //    |
 //    |---> id: 1, nucleon (kIStDecayedState)
 //
 
   TLorentzVector v4(0,0,0,0);
 
   GHepStatus_t stis = kIStInitialState;
   GHepStatus_t stdc = kIStDecayedState;
   GHepStatus_t stfs = kIStStableFinalState;
 
   int ipdg = fCurrInitStatePdg;
 
   // Decayed nucleon is a bound one.
   if(fNucleonIsBound)
   {
     // add initial nucleus
     double Mi  = PDGLibrary::Instance()->Find(ipdg)->Mass();
     TLorentzVector p4i(0,0,0,Mi);
     event->AddParticle(ipdg,stis,-1,-1,-1,-1, p4i, v4);
 
     // add decayed nucleon
     int dpdg = fCurrDecayedNucleon;
     double mn = PDGLibrary::Instance()->Find(dpdg)->Mass();
     TLorentzVector p4n(0,0,0,mn);
     event->AddParticle(dpdg,stdc, 0,-1,-1,-1, p4n, v4);
 
     // add nuclear remnant
     int A = pdg::IonPdgCodeToA(ipdg);
     int Z = pdg::IonPdgCodeToZ(ipdg);
     A--;
     if(dpdg == kPdgProton) { Z--; }
     int rpdg = pdg::IonPdgCode(A, Z);
     double Mf  = PDGLibrary::Instance()->Find(rpdg)->Mass();
     TLorentzVector p4f(0,0,0,Mf);
     event->AddParticle(rpdg,stfs,0,-1,-1,-1, p4f, v4);
   }
 
   // Decayed nucleon is a free one
   else
   {
     // Initial state is either a neutron or a proton.
     // Convert the initial state PDG code from the ion convention (10LZZZAAAI)
     // to the usual code for neutrons or protons
     int ipdg_short = -1;
     if(ipdg == kPdgTgtFreeP) ipdg_short = kPdgProton;
     if(ipdg == kPdgTgtFreeN) ipdg_short = kPdgNeutron;
 
     // Decayed nucleon code
     int dpdg = fCurrDecayedNucleon;
 
     if(dpdg != ipdg_short) {
        LOG("NucleonDecay", pWARN)
            << "Couldn't generate given decay ("
            << utils::nucleon_decay::AsString(fCurrDecayMode, fCurrDecayedNucleon) << ")"
            << " for given initial state (PDG = " << ipdg_short << ")";
        genie::exceptions::EVGThreadException exception;
        exception.SetReason("Decay-mode / Initial-state mismatch!");
        exception.SwitchOnFastForward();
        throw exception;
     }
     // add initial nucleon
     double mn  = PDGLibrary::Instance()->Find(ipdg)->Mass();
     TLorentzVector p4i(0,0,0,mn);
     event->AddParticle(dpdg,stis,-1,-1,-1,-1, p4i, v4);
     // add decayed nucleon
     event->AddParticle(dpdg,stdc,0,-1,-1,-1, p4i, v4);
   }
 }

void NucleonDecayPrimaryVtxGenerator::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 392 of file NucleonDecayPrimaryVtxGenerator.cxx.

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

void NucleonDecayPrimaryVtxGenerator::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 398 of file NucleonDecayPrimaryVtxGenerator.cxx.

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

void NucleonDecayPrimaryVtxGenerator::GenerateDecayedNucleonPosition ( GHepRecord * event ) const

private

Definition at line 157 of file NucleonDecayPrimaryVtxGenerator.cxx.

 {
   GHepParticle * initial_nucleus = event->Particle(0);
   int A = initial_nucleus->A();
   if(A <= 2) {
     return;
   }
 
   RandomGen * rnd = RandomGen::Instance();
 
   double R0 = 1.3;
   double dA = (double)A;
   double R = R0 * TMath::Power(dA, 1./3.);
 
   LOG("NucleonDecay", pINFO)
       << "Generating vertex according to a realistic nuclear density profile";
 
   // get inputs to the rejection method
   double ymax = -1;
   double rmax = 3*R;
   double dr   = R/40.;
   for(double r = 0; r < rmax; r+=dr) {
       ymax = TMath::Max(ymax, r*r * utils::nuclear::Density(r,A));
   }
   ymax *= 1.2;
 
   // select a vertex using the rejection method
   TLorentzVector vtx(0,0,0,0);
   unsigned int iter = 0;
   while(1) {
     iter++;
 
     // throw an exception if it hasn't find a solution after many attempts
     if(iter > controls::kRjMaxIterations) {
        LOG("NucleonDecay", pWARN)
            << "Couldn't generate a vertex position after " << iter << " iterations";
        genie::exceptions::EVGThreadException exception;
        exception.SetReason("Couldn't generate vertex");
        exception.SwitchOnFastForward();
        throw exception;
     }
 
     double r = rmax * rnd->RndFsi().Rndm();
     double t = ymax * rnd->RndFsi().Rndm();
     double y = r*r * utils::nuclear::Density(r,A);
     if(y > ymax) {
        LOG("NucleonDecay", pERROR)
           << "y = " << y << " > ymax = " << ymax << " for r = " << r << ", A = " << A;
     }
     bool accept = (t < y);
     if(accept) {
        double phi      = 2*constants::kPi * rnd->RndFsi().Rndm();
        double cosphi   = TMath::Cos(phi);
        double sinphi   = TMath::Sin(phi);
        double costheta = -1 + 2 * rnd->RndFsi().Rndm();
        double sintheta = TMath::Sqrt(1-costheta*costheta);
        vtx.SetX(r*sintheta*cosphi);
        vtx.SetY(r*sintheta*sinphi);
        vtx.SetZ(r*costheta);
        vtx.SetT(0.);
        break;
     }
   } // while 1
 
   GHepParticle * decayed_nucleon = event->Particle(1);
   assert(decayed_nucleon);
   decayed_nucleon->SetPosition(vtx);
 }

void NucleonDecayPrimaryVtxGenerator::GenerateDecayProducts ( GHepRecord * event ) const

private

accept_decay

Definition at line 269 of file NucleonDecayPrimaryVtxGenerator.cxx.

 {
   LOG("NucleonDecay", pINFO) << "Generating decay...";
 
   PDGCodeList pdgv = utils::nucleon_decay::DecayProductList(fCurrDecayMode, fCurrDecayedNucleon);
   LOG("NucleonDecay", pINFO) << "Decay product IDs: " << pdgv;
   assert ( pdgv.size() >  1);
 
   LOG("NucleonDecay", pINFO) << "Performing a phase space decay...";
 
   // Get the decay product masses
 
   vector<int>::const_iterator pdg_iter;
   int i = 0;
   double * mass = new double[pdgv.size()];
   double   sum  = 0;
   for(pdg_iter = pdgv.begin(); pdg_iter != pdgv.end(); ++pdg_iter) {
     int pdgc = *pdg_iter;
     double m = PDGLibrary::Instance()->Find(pdgc)->Mass();
     mass[i++] = m;
     sum += m;
   }
 
   LOG("NucleonDecay", pINFO)
     << "Decaying N = " << pdgv.size() << " particles / total mass = " << sum;
 
   int decayed_nucleon_id = 1;
   GHepParticle * decayed_nucleon = event->Particle(decayed_nucleon_id);
   assert(decayed_nucleon);
   TLorentzVector * p4d = decayed_nucleon->GetP4();
   TLorentzVector * v4d = decayed_nucleon->GetX4();
 
   LOG("NucleonDecay", pINFO)
     << "Decaying system p4 = " << utils::print::P4AsString(p4d);
 
   // Set the decay
   bool permitted = fPhaseSpaceGenerator.SetDecay(*p4d, pdgv.size(), mass);
   if(!permitted) {
      LOG("NucleonDecay", pERROR)
        << " *** Phase space decay is not permitted \n"
        << " Total particle mass = " << sum << "\n"
        << " Decaying system p4 = " << utils::print::P4AsString(p4d);
      // clean-up
      delete [] mass;
      delete p4d;
      delete v4d;
      // throw exception
      genie::exceptions::EVGThreadException exception;
      exception.SetReason("Decay not permitted kinematically");
      exception.SwitchOnFastForward();
      throw exception;
   }
 
   // Get the maximum weight
   //double wmax = fPhaseSpaceGenerator.GetWtMax();
   double wmax = -1;
   for(int idec=0; idec<200; idec++) {
      double w = fPhaseSpaceGenerator.Generate();
      wmax = TMath::Max(wmax,w);
   }
   assert(wmax>0);
   wmax *= 2;
 
   LOG("NucleonDecay", pNOTICE)
      << "Max phase space gen. weight @ current hadronic system: " << wmax;
 
   // Generate an unweighted decay
   RandomGen * rnd = RandomGen::Instance();
 
   bool accept_decay=false;
   unsigned int itry=0;
   while(!accept_decay)
   {
      itry++;
 
      if(itry > controls::kMaxUnweightDecayIterations) {
        // report, clean-up and return
        LOG("NucleonDecay", pWARN)
            << "Couldn't generate an unweighted phase space decay after "
            << itry << " attempts";
        // clean up
        delete [] mass;
        delete p4d;
        delete v4d;
        // throw exception
        genie::exceptions::EVGThreadException exception;
        exception.SetReason("Couldn't select decay after N attempts");
        exception.SwitchOnFastForward();
        throw exception;
      }
      double w  = fPhaseSpaceGenerator.Generate();
      if(w > wmax) {
         LOG("NucleonDecay", pWARN)
            << "Decay weight = " << w << " > max decay weight = " << wmax;
      }
      double gw = wmax * rnd->RndHadro().Rndm();
      accept_decay = (gw<=w);
 
      LOG("NucleonDecay", pINFO)
         << "Decay weight = " << w << " / R = " << gw
         << " - accepted: " << accept_decay;
 
   } //!accept_decay
 
   // Insert final state products into a TClonesArray of GHepParticle's
   TLorentzVector v4(*v4d);
   int idp = 0;
   for(pdg_iter = pdgv.begin(); pdg_iter != pdgv.end(); ++pdg_iter) {
      int pdgc = *pdg_iter;
      TLorentzVector * p4fin = fPhaseSpaceGenerator.GetDecay(idp);
      GHepStatus_t ist =
         utils::nucleon_decay::DecayProductStatus(fNucleonIsBound, pdgc);
      event->AddParticle(pdgc, ist, decayed_nucleon_id,-1,-1,-1, *p4fin, v4);
      idp++;
   }
 
   // Clean-up
   delete [] mass;
   delete p4d;
   delete v4d;
 }

void NucleonDecayPrimaryVtxGenerator::GenerateFermiMomentum ( GHepRecord * event ) const

private

Definition at line 227 of file NucleonDecayPrimaryVtxGenerator.cxx.

 {
   GHepParticle * initial_nucleus = event->Particle(0);
   int A = initial_nucleus->A();
   if(A <= 2) {
     return;
   }
 
   GHepParticle * decayed_nucleon = event->Particle(1);
   GHepParticle * remnant_nucleus = event->Particle(2);
   assert(decayed_nucleon);
   assert(remnant_nucleus);
 
   // generate a Fermi momentum & removal energy
   Target tgt(initial_nucleus->Pdg());
   tgt.SetHitNucPdg(decayed_nucleon->Pdg());
   fNuclModel->GenerateNucleon(tgt);
   TVector3 p3 = fNuclModel->Momentum3();
   double w    = fNuclModel->RemovalEnergy();
 
   LOG("FermiMover", pINFO)
      << "Generated nucleon momentum: ("
      << p3.Px() << ", " << p3.Py() << ", " << p3.Pz() << "), "
      << "|p| = " << p3.Mag();
   LOG("NucleonDecay", pINFO)
      << "Generated nucleon removal energy: w = " << w;
 
   double pF2 = p3.Mag2(); // (fermi momentum)^2
 
   double Mi  = PDGLibrary::Instance()->Find(initial_nucleus->Pdg())-> Mass(); // initial nucleus mass
   double Mf  = PDGLibrary::Instance()->Find(remnant_nucleus->Pdg())-> Mass(); // remnant nucleus mass
 
   double EN = Mi - TMath::Sqrt(pF2 + Mf*Mf);
 
   TLorentzVector p4nucleon(   p3.Px(),    p3.Py(),    p3.Pz(), EN);
   TLorentzVector p4remnant(-1*p3.Px(), -1*p3.Py(), -1*p3.Pz(), Mi-EN);
 
   decayed_nucleon->SetMomentum(p4nucleon);
   remnant_nucleus->SetMomentum(p4remnant);
 }

void NucleonDecayPrimaryVtxGenerator::LoadConfig ( void )

private

Definition at line 404 of file NucleonDecayPrimaryVtxGenerator.cxx.

 {
 //  AlgConfigPool * confp = AlgConfigPool::Instance();
 //  const Registry * gc = confp->GlobalParameterList();
 
   fNuclModel = 0;
 
   RgKey nuclkey = "NuclearModel";
   fNuclModel = dynamic_cast<const NuclearModelI *> (this->SubAlg(nuclkey));
   assert(fNuclModel);
 }

void NucleonDecayPrimaryVtxGenerator::ProcessEventRecord ( GHepRecord * event ) const

virtual

Implements genie::EventRecordVisitorI.

Definition at line 52 of file NucleonDecayPrimaryVtxGenerator.cxx.

 {
   Interaction * interaction = event->Summary();
   fCurrInitStatePdg = interaction->InitState().Tgt().Pdg();
   fCurrDecayMode = (NucleonDecayMode_t) interaction->ExclTag().DecayMode();
   fCurrDecayedNucleon = interaction->InitState().Tgt().HitNucPdg();
 
   LOG("NucleonDecay", pNOTICE)
     << "Simulating decay " << utils::nucleon_decay::AsString(fCurrDecayMode, fCurrDecayedNucleon)
     << " for an initial state with code: " << fCurrInitStatePdg;
 
   fNucleonIsBound = (pdg::IonPdgCodeToA(fCurrInitStatePdg) > 1);
 
   this->AddInitialState(event);
   this->GenerateDecayedNucleonPosition(event);
   this->GenerateFermiMomentum(event);
   this->GenerateDecayProducts(event);
 }