G4Eta.cc

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//
// ----------------------------------------------------------------------
//      GEANT 4 class implementation file
//
//      History: first implementation, based on object model of
//      4th April 1996, G.Cosmo
//                              H.Kurashige   7 Jul 96
// **********************************************************************
//  New impelemenataion as an utility class  M.Asai, 26 July 2004
// ----------------------------------------------------------------------
//      Update mass (PDG2006)              Oct. 11 2006 H.Kurashige
//      Update width(PDG2025)              Nov.  4 2025 S.Okada
//
 
#include "G4Eta.hh"
 
#include "G4DecayTable.hh"
#include "G4ParticleTable.hh"
#include "G4PhaseSpaceDecayChannel.hh"
#include "G4String.hh"
#include "G4SystemOfUnits.hh"
#include "G4Types.hh"
#include "G4VDecayChannel.hh"
 
G4Eta* G4Eta::theInstance = nullptr;
 
G4Eta* G4Eta::Definition()
{
  if (theInstance != nullptr) return theInstance;
  const G4String name = "eta";
  // search in particle table]
  G4ParticleTable* pTable = G4ParticleTable::GetParticleTable();
  G4ParticleDefinition* anInstance = pTable->FindParticle(name);
  if (anInstance == nullptr) {
    // create particle
    //
    //    Arguments for constructor are as follows
    //               name             mass          width         charge
    //             2*spin           parity  C-conjugation
    //          2*Isospin       2*Isospin3       G-parity
    //               type    lepton number  baryon number   PDG encoding
    //             stable         lifetime    decay table
    //             shortlived      subType    anti_encoding
 
    // clang-format off
   anInstance = new G4ParticleDefinition(
                 name,    0.547862*GeV,     1.308*keV,         0.0,
                    0,              -1,            +1,
                    0,               0,            +1,
              "meson",               0,             0,         221,
                false,          0.0*ns,          nullptr,
                false,           "eta",           221);
    // clang-format on
 
    // create Decay Table
    auto table = new G4DecayTable();
 
    // create decay channels
    auto mode = new G4VDecayChannel*[4];
    // eta -> gamma + gamma
    mode[0] = new G4PhaseSpaceDecayChannel("eta", 0.3942, 2, "gamma", "gamma");
    // eta -> pi0 + pi0 + pi0
    mode[1] = new G4PhaseSpaceDecayChannel("eta", 0.3256, 3, "pi0", "pi0", "pi0");
    // eta -> pi0 + pi+ + pi-
    mode[2] = new G4PhaseSpaceDecayChannel("eta", 0.226, 3, "pi0", "pi+", "pi-");
    // eta -> gamma + pi+ + pi-
    mode[3] = new G4PhaseSpaceDecayChannel("eta", 0.0468, 3, "gamma", "pi+", "pi-");
 
    for (G4int index = 0; index < 4; index++)
      table->Insert(mode[index]);
    delete[] mode;
 
    anInstance->SetDecayTable(table);
  }
  theInstance = static_cast<G4Eta*>(anInstance);
  return theInstance;
}
 
G4Eta* G4Eta::EtaDefinition()
{
  return Definition();
}
 
G4Eta* G4Eta::Eta()
{
  return Definition();
}