NestAlg.cxx

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#define AVO 6.022e23 //Avogadro's number (#/mol)
#define EMASS 9.109e-31 * CLHEP::kg
#define MillerDriftSpeed true

#define GASGAP 0.25 * CLHEP::cm //S2 generation region
#define BORDER 0 * CLHEP::cm    //liquid-gas border z-coordinate

#define QE_EFF 1    //a base or maximum quantum efficiency
#define phe_per_e 1 //S2 gain for quick studies

// different field regions, for gamma-X studies
#define WIN 0 * CLHEP::mm       //top Cu block (also, quartz window)
#define TOP 0                   //top grid wires
#define ANE 0                   //anode mesh
#define SRF 0                   //liquid-gas interface
#define GAT 0                   //gate grid
#define CTH 0                   //cathode grid
#define BOT 0                   //bottom PMT grid
#define PMT 0                   //bottom Cu block and PMTs
#define MIN_ENE -1 * CLHEP::eV  //lets you turn NEST off BELOW a certain energy
#define MAX_ENE 1. * CLHEP::TeV //lets you turn NEST off ABOVE a certain energy
#define HIENLIM 5 * CLHEP::MeV  //energy at which Doke model used exclusively
#define R_TOL 0.2 * CLHEP::mm   //tolerance (for edge events)
#define R_MAX 1 * CLHEP::km     //for corraling diffusing electrons
#define Density_LXe 2.9         //reference density for density-dep. effects
#define Density_LAr 1.393
#define Density_LNe 1.207
#define Density_LKr 2.413

#include "Geant4/G4Ions.hh"
#include "Geant4/G4OpticalPhoton.hh"
#include "Geant4/G4VProcess.hh"

#include "larsim/LegacyLArG4/G4ThermalElectron.hh"
#include "larsim/LegacyLArG4/NestAlg.h"

#include "CLHEP/Random/RandFlat.h"
#include "CLHEP/Random/RandGauss.h"

G4bool diffusion = true;

G4bool SinglePhase = false, ThomasImelTail = true, OutElectrons = true;

G4double biExc = 0.77; //for alpha particles (bi-excitonic collisions)

//----------------------------------------------------------------------------
// Default constructor will return no photons or electrons unless the set
// methods are called.
NestAlg::NestAlg(CLHEP::HepRandomEngine& engine)
  : fYieldFactor(0)
  , fExcitationRatio(0)
  , fNumScintPhotons(0)
  , fNumIonElectrons(0)
  , fEnergyDep(0.)
  , fEngine(engine)
{
  fElementPropInit[2] = false;
  fElementPropInit[10] = false;
  fElementPropInit[18] = false;
  fElementPropInit[36] = false;
  fElementPropInit[54] = false;
}

//----------------------------------------------------------------------------
NestAlg::NestAlg(double yieldFactor, CLHEP::HepRandomEngine& engine)
  : fYieldFactor(yieldFactor)
  , fExcitationRatio(0.)
  , fNumScintPhotons(0)
  , fNumIonElectrons(0)
  , fEnergyDep(0.)
  , fEngine(engine)
{
  fElementPropInit[2] = false;
  fElementPropInit[10] = false;
  fElementPropInit[18] = false;
  fElementPropInit[36] = false;
  fElementPropInit[54] = false;
}

//----------------------------------------------------------------------------
const G4VParticleChange& NestAlg::CalculateIonizationAndScintillation(G4Track const& aTrack,
                                                                      G4Step const& aStep)
{
  CLHEP::RandGauss GaussGen(fEngine);
  CLHEP::RandFlat UniformGen(fEngine);

  // reset the variables accessed by other objects
  // make the energy deposit the energy in this step,
  // set the number of electrons and photons to 0
  fEnergyDep = aStep.GetTotalEnergyDeposit();
  fNumIonElectrons = 0.;
  fNumScintPhotons = 0.;

  if (!fYieldFactor) //set YF=0 when you want S1Light off in your sim
    return fParticleChange;

  bool fTrackSecondariesFirst = false;
  bool fExcitedNucleus = false;
  bool fVeryHighEnergy = false;
  bool fAlpha = false;
  bool fMultipleScattering = false;
  double fKr83m = 0.;

  if (aTrack.GetParentID() == 0 && aTrack.GetCurrentStepNumber() == 1) {
    fExcitedNucleus = false; //an initialization or reset
    fVeryHighEnergy = false; //initializes or (later) resets this
    fAlpha = false;          //ditto
    fMultipleScattering = false;
  }

  const G4DynamicParticle* aParticle = aTrack.GetDynamicParticle();
  G4ParticleDefinition* pDef = aParticle->GetDefinition();
  G4String particleName = pDef->GetParticleName();
  const G4Material* aMaterial = aStep.GetPreStepPoint()->GetMaterial();
  const G4Material* bMaterial = aStep.GetPostStepPoint()->GetMaterial();

  if ((particleName == "neutron" || particleName == "antineutron") &&
      aStep.GetTotalEnergyDeposit() <= 0)
    return fParticleChange;

  // code for determining whether the present/next material is noble
  // element, or, in other words, for checking if either is a valid NEST
  // scintillating material, and save Z for later L calculation, or
  // return if no valid scintillators are found on this step, which is
  // protection against G4Exception or seg. fault/violation
  G4Element *ElementA = NULL, *ElementB = NULL;
  if (aMaterial) {
    const G4ElementVector* theElementVector1 = aMaterial->GetElementVector();
    ElementA = (*theElementVector1)[0];
  }
  if (bMaterial) {
    const G4ElementVector* theElementVector2 = bMaterial->GetElementVector();
    ElementB = (*theElementVector2)[0];
  }
  G4int z1, z2, j = 1;
  G4bool NobleNow = false, NobleLater = false;
  if (ElementA)
    z1 = (G4int)(ElementA->GetZ());
  else
    z1 = -1;
  if (ElementB)
    z2 = (G4int)(ElementB->GetZ());
  else
    z2 = -1;
  if (z1 == 2 || z1 == 10 || z1 == 18 || z1 == 36 || z1 == 54) {
    NobleNow = true;
    //    j = (G4int)aMaterial->GetMaterialPropertiesTable()->
    //  GetConstProperty("TOTALNUM_INT_SITES"); //get current number
    //if ( j < 0 ) {
    if (aTrack.GetParentID() == 0 && !fElementPropInit[z1]) {
      InitMatPropValues(aMaterial->GetMaterialPropertiesTable(), z1);
      j = 0; //no sites yet
    }        //material properties initialized
  }          //end of atomic number check
  if (z2 == 2 || z2 == 10 || z2 == 18 || z2 == 36 || z2 == 54) {
    NobleLater = true;
    //    j = (G4int)bMaterial->GetMaterialPropertiesTable()->
    //  GetConstProperty("TOTALNUM_INT_SITES");
    //if ( j < 0 ) {
    if (aTrack.GetParentID() == 0 && !fElementPropInit[z2]) {
      InitMatPropValues(bMaterial->GetMaterialPropertiesTable(), z2);
      j = 0; //no sites yet
    }        //material properties initialized
  }          //end of atomic number check

  if (!NobleNow && !NobleLater) return fParticleChange;

  // retrieval of the particle's position, time, attributes at both the
  // beginning and the end of the current step along its track
  G4StepPoint* pPreStepPoint = aStep.GetPreStepPoint();
  G4StepPoint* pPostStepPoint = aStep.GetPostStepPoint();
  G4ThreeVector x1 = pPostStepPoint->GetPosition();
  G4ThreeVector x0 = pPreStepPoint->GetPosition();
  G4double evtStrt = pPreStepPoint->GetGlobalTime();
  G4double t0 = pPreStepPoint->GetLocalTime();
  G4double t1 = pPostStepPoint->GetLocalTime();

  // now check if we're entering a scintillating material (inside) or
  // leaving one (outside), in order to determine (later on in the code,
  // based on the booleans inside & outside) whether to add/subtract
  // energy that can potentially be deposited from the system
  G4bool outside = false, inside = false, InsAndOuts = false;
  G4MaterialPropertiesTable* aMaterialPropertiesTable = aMaterial->GetMaterialPropertiesTable();
  if (NobleNow && !NobleLater) outside = true;
  if (!NobleNow && NobleLater) {
    aMaterial = bMaterial;
    inside = true;
    z1 = z2;
    aMaterialPropertiesTable = bMaterial->GetMaterialPropertiesTable();
  }
  if (NobleNow && NobleLater && aMaterial->GetDensity() != bMaterial->GetDensity())
    InsAndOuts = true;

  // retrieve scintillation-related material properties
  G4double Density = aMaterial->GetDensity() / (CLHEP::g / CLHEP::cm3);
  G4double nDensity = Density * AVO;         //molar mass factor applied below
  G4int Phase = aMaterial->GetState();       //solid, liquid, or gas?
  G4double ElectricField(0.), FieldSign(0.); //for field quenching of S1
  G4bool GlobalFields = false;

  if ((WIN == 0) && !TOP && !ANE && !SRF && !GAT && !CTH && !BOT && !PMT) {
    ElectricField = aMaterialPropertiesTable->GetConstProperty("ELECTRICFIELD");
    GlobalFields = true;
  }
  else {
    if (x1[2] < WIN && x1[2] > TOP && Phase == kStateGas)
      ElectricField = aMaterialPropertiesTable->GetConstProperty("ELECTRICFIELDWINDOW");
    else if (x1[2] < TOP && x1[2] > ANE && Phase == kStateGas)
      ElectricField = aMaterialPropertiesTable->GetConstProperty("ELECTRICFIELDTOP");
    else if (x1[2] < ANE && x1[2] > SRF && Phase == kStateGas)
      ElectricField = aMaterialPropertiesTable->GetConstProperty("ELECTRICFIELDANODE");
    else if (x1[2] < SRF && x1[2] > GAT && Phase == kStateLiquid)
      ElectricField = aMaterialPropertiesTable->GetConstProperty("ELECTRICFIELDSURFACE");
    else if (x1[2] < GAT && x1[2] > CTH && Phase == kStateLiquid)
      ElectricField = aMaterialPropertiesTable->GetConstProperty("ELECTRICFIELDGATE");
    else if (x1[2] < CTH && x1[2] > BOT && Phase == kStateLiquid)
      ElectricField = aMaterialPropertiesTable->GetConstProperty("ELECTRICFIELDCATHODE");
    else if (x1[2] < BOT && x1[2] > PMT && Phase == kStateLiquid)
      ElectricField = aMaterialPropertiesTable->GetConstProperty("ELECTRICFIELDBOTTOM");
    else
      ElectricField = aMaterialPropertiesTable->GetConstProperty("ELECTRICFIELD");
  }
  if (ElectricField >= 0)
    FieldSign = 1;
  else
    FieldSign = -1;
  ElectricField = std::abs((1e3 * ElectricField) / (CLHEP::kilovolt / CLHEP::cm));
  G4double Temperature = aMaterial->GetTemperature();
  G4double ScintillationYield, ResolutionScale, R0 = 1.0 * CLHEP::um, DokeBirks[3],
                                                ThomasImel = 0.00, delta = 1 * CLHEP::mm;
  DokeBirks[0] = 0.00;
  DokeBirks[2] = 1.00;
  G4double PhotMean = 7 * CLHEP::eV, PhotWidth = 1.0 * CLHEP::eV; //photon properties
  G4double SingTripRatioR, SingTripRatioX, tau1, tau3, tauR = 0 * CLHEP::ns;
  switch (z1) {                                  //sort prop. by noble element atomic#
  case 2:                                        //helium
    ScintillationYield = 1 / (41.3 * CLHEP::eV); //all W's from noble gas book
    fExcitationRatio = 0.00;                     //nominal (true value unknown)
    ResolutionScale = 0.2;                       //Aprile, Bolotnikov, Bolozdynya, Doke
    PhotMean = 15.9 * CLHEP::eV;
    tau1 = GaussGen.fire(10.0 * CLHEP::ns, 0.0 * CLHEP::ns);
    tau3 = 1.6e3 * CLHEP::ns;
    tauR = GaussGen.fire(13.00 * CLHEP::s, 2.00 * CLHEP::s); //McKinsey et al. 2003
    break;
  case 10: //neon
    ScintillationYield = 1 / (29.2 * CLHEP::eV);
    fExcitationRatio = 0.00; //nominal (true value unknown)
    ResolutionScale = 0.13;  //Aprile et. al book
    PhotMean = 15.5 * CLHEP::eV;
    PhotWidth = 0.26 * CLHEP::eV;
    tau1 = GaussGen.fire(10.0 * CLHEP::ns, 10. * CLHEP::ns);
    tau3 = GaussGen.fire(15.4e3 * CLHEP::ns, 200 * CLHEP::ns); //Nikkel et al. 2008
    break;
  case 18: //argon
    ScintillationYield = 1 / (19.5 * CLHEP::eV);
    fExcitationRatio = 0.21; //Aprile et. al book
    ResolutionScale = 0.107; //Doke 1976
    R0 = 1.568 * CLHEP::um;  //Mozumder 1995
    if (ElectricField) {
      ThomasImel = 0.156977 * pow(ElectricField, -0.1);
      DokeBirks[0] = 0.07 * pow((ElectricField / 1.0e3), -0.85);
      DokeBirks[2] = 0.00;
    }
    else {
      ThomasImel = 0.099;
      DokeBirks[0] = 0.0003;
      DokeBirks[2] = 0.75;
    }
    nDensity /= 39.948; //molar mass in grams per mole
    PhotMean = 9.69 * CLHEP::eV;
    PhotWidth = 0.22 * CLHEP::eV;
    tau1 = GaussGen.fire(6.5 * CLHEP::ns, 0.8 * CLHEP::ns); //err from wgted avg.
    tau3 = GaussGen.fire(1300 * CLHEP::ns, 50 * CLHEP::ns); //ibid.
    tauR = GaussGen.fire(0.8 * CLHEP::ns, 0.2 * CLHEP::ns); //Kubota 1979
    biExc = 0.6;
    break;
  case 36: //krypton
    if (Phase == kStateGas)
      ScintillationYield = 1 / (30.0 * CLHEP::eV);
    else
      ScintillationYield = 1 / (15.0 * CLHEP::eV);
    fExcitationRatio = 0.08; //Aprile et. al book
    ResolutionScale = 0.05;  //Doke 1976
    PhotMean = 8.43 * CLHEP::eV;
    tau1 = GaussGen.fire(2.8 * CLHEP::ns, .04 * CLHEP::ns);
    tau3 = GaussGen.fire(93. * CLHEP::ns, 1.1 * CLHEP::ns);
    tauR = GaussGen.fire(12. * CLHEP::ns, .76 * CLHEP::ns);
    break;
  case 54: //xenon
  default:
    nDensity /= 131.293;
    ScintillationYield = 48.814 + 0.80877 * Density + 2.6721 * pow(Density, 2.);
    ScintillationYield /= CLHEP::keV; //Units: [#quanta(ph/e-) per keV]
    //W = 13.7 eV for all recoils, Dahl thesis (that's @2.84 g/cm^3)
    //the exciton-to-ion ratio (~0.06 for LXe at 3 g/cm^3)
    fExcitationRatio = 0.4 - 0.11131 * Density - 0.0026651 * pow(Density, 2.);
    ResolutionScale = 1.00 * //Fano factor <<1
                      (0.12724 - 0.032152 * Density - 0.0013492 * pow(Density, 2.));
    //~0.1 for GXe w/ formula from Bolotnikov et al. 1995
    if (Phase == kStateLiquid) {
      ResolutionScale *= 1.5; //to get it to be ~0.03 for LXe
      R0 = 16.6 * CLHEP::um;  //for zero electric field
      //length scale above which Doke model used instead of Thomas-Imel
      if (ElectricField) //change it with field (see NEST paper)
        R0 = 69.492 * pow(ElectricField, -0.50422) * CLHEP::um;
      if (ElectricField) { //formulae & values all from NEST paper
        DokeBirks[0] = 19.171 * pow(ElectricField + 25.552, -0.83057) + 0.026772;
        DokeBirks[2] = 0.00; //only volume recombination (above)
      }
      else {                 //zero electric field magnitude
        DokeBirks[0] = 0.18; //volume/columnar recombination factor (A)
        DokeBirks[2] = 0.58; //geminate/Onsager recombination (C)
      }
      //"ThomasImel" is alpha/(a^2*v), the recomb. coeff.
      ThomasImel = 0.05; //aka xi/(4*N_i) from the NEST paper
      //distance used to determine when one is at a new interaction site
      delta = 0.4 * CLHEP::mm; //distance ~30 keV x-ray travels in LXe
      PhotMean = 6.97 * CLHEP::eV;
      PhotWidth = 0.23 * CLHEP::eV;
      // 178+/-14nmFWHM, taken from Jortner JchPh 42 '65.
      //these singlet and triplet times may not be the ones you're
      //used to, but are the world average: Kubota 79, Hitachi 83 (2
      //data sets), Teymourian 11, Morikawa 89, and Akimov '02
      tau1 = GaussGen.fire(3.1 * CLHEP::ns, .7 * CLHEP::ns); //err from wgted avg.
      tau3 = GaussGen.fire(24. * CLHEP::ns, 1. * CLHEP::ns); //ibid.
    }                                                        //end liquid
    else if (Phase == kStateGas) {
      if (!fAlpha)
        fExcitationRatio = 0.07; //Nygren NIM A 603 (2009) p. 340
      else {
        biExc = 1.00;
        ScintillationYield = 1 / (12.98 * CLHEP::eV);
      }                     //Saito 2003
      R0 = 0.0 * CLHEP::um; //all Doke/Birks interactions (except for alphas)
      G4double Townsend = (ElectricField / nDensity) * 1e17;
      DokeBirks[0] = 0.0000; //all geminate (except at zero, low fields)
      DokeBirks[2] = 0.1933 * pow(Density, 2.6199) + 0.29754 -
                     (0.045439 * pow(Density, 2.4689) + 0.066034) * log10(ElectricField);
      if (ElectricField > 6990) DokeBirks[2] = 0.0;
      if (ElectricField < 1000) DokeBirks[2] = 0.2;
      if (ElectricField < 100.) {
        DokeBirks[0] = 0.18;
        DokeBirks[2] = 0.58;
      }
      if (Density < 0.061)
        ThomasImel = 0.041973 * pow(Density, 1.8105);
      else if (Density >= 0.061 && Density <= 0.167)
        ThomasImel = 5.9583e-5 + 0.0048523 * Density - 0.023109 * pow(Density, 2.);
      else
        ThomasImel = 6.2552e-6 * pow(Density, -1.9963);
      if (ElectricField) ThomasImel = 1.2733e-5 * pow(Townsend / Density, -0.68426);
      // field\density dependence from Kobayashi 2004 and Saito 2003
      PhotMean = 7.1 * CLHEP::eV;
      PhotWidth = 0.2 * CLHEP::eV;
      tau1 = GaussGen.fire(5.18 * CLHEP::ns, 1.55 * CLHEP::ns);
      tau3 = GaussGen.fire(100.1 * CLHEP::ns, 7.9 * CLHEP::ns);
    } //end gas information (preliminary guesses)
    else {
      tau1 = 3.5 * CLHEP::ns;
      tau3 = 20. * CLHEP::ns;
      tauR = 40. * CLHEP::ns;
    } //solid Xe
  }

  // log present and running tally of energy deposition in this section
  G4double anExcitationEnergy =
    ((const G4Ions*)(pDef))->GetExcitationEnergy(); //grab nuclear energy level
  G4double TotalEnergyDeposit =                     //total energy deposited so far
    aMaterialPropertiesTable->GetConstProperty("ENERGY_DEPOSIT_TOT");
  G4bool convert = false, annihil = false;
  //set up special cases for pair production and positron annihilation
  if (pPreStepPoint->GetKineticEnergy() >= (2 * CLHEP::electron_mass_c2) &&
      !pPostStepPoint->GetKineticEnergy() && !aStep.GetTotalEnergyDeposit() &&
      aParticle->GetPDGcode() == 22) {
    convert = true;
    TotalEnergyDeposit = CLHEP::electron_mass_c2;
  }
  if (pPreStepPoint->GetKineticEnergy() && !pPostStepPoint->GetKineticEnergy() &&
      aParticle->GetPDGcode() == -11) {
    annihil = true;
    TotalEnergyDeposit += aStep.GetTotalEnergyDeposit();
  }
  G4bool either = false;
  if (inside || outside || convert || annihil || InsAndOuts) either = true;
  //conditions for returning when energy deposits too low
  if (anExcitationEnergy < 100 * CLHEP::eV && aStep.GetTotalEnergyDeposit() < 1 * CLHEP::eV &&
      !either && !fExcitedNucleus)
    return fParticleChange;
  //add current deposit to total energy budget
  if (!annihil) TotalEnergyDeposit += aStep.GetTotalEnergyDeposit();
  if (!convert)
    aMaterialPropertiesTable->AddConstProperty("ENERGY_DEPOSIT_TOT", TotalEnergyDeposit);
  //save current deposit for determining number of quanta produced now
  TotalEnergyDeposit = aStep.GetTotalEnergyDeposit();

  // check what the current "goal" E is for dumping scintillation,
  // often the initial kinetic energy of the parent particle, and deal
  // with all other energy-related matters in this block of code
  G4double InitialKinetEnergy = aMaterialPropertiesTable->GetConstProperty("ENERGY_DEPOSIT_GOL");
  //if zero, add up initial potential and kinetic energies now
  if (InitialKinetEnergy == 0) {
    G4double tE = pPreStepPoint->GetKineticEnergy() + anExcitationEnergy;
    if ((fabs(tE - 1.8 * CLHEP::keV) < CLHEP::eV || fabs(tE - 9.4 * CLHEP::keV) < CLHEP::eV) &&
        Phase == kStateLiquid && z1 == 54)
      tE = 9.4 * CLHEP::keV;
    if (fKr83m && ElectricField != 0) DokeBirks[2] = 0.10;
    aMaterialPropertiesTable->AddConstProperty("ENERGY_DEPOSIT_GOL", tE);
    //excited nucleus is special case where accuracy reduced for total
    //energy deposition because of G4 inaccuracies and scintillation is
    //forced-dumped when that nucleus is fully de-excited
    if (anExcitationEnergy) fExcitedNucleus = true;
  }
  //if a particle is leaving, remove its kinetic energy from the goal
  //energy, as this will never get deposited (if depositable)
  if (outside) {
    aMaterialPropertiesTable->AddConstProperty(
      "ENERGY_DEPOSIT_GOL", InitialKinetEnergy - pPostStepPoint->GetKineticEnergy());
    if (aMaterialPropertiesTable->GetConstProperty("ENERGY_DEPOSIT_GOL") < 0)
      aMaterialPropertiesTable->AddConstProperty("ENERGY_DEPOSIT_GOL", 0);
  }
  //if a particle is coming back into your scintillator, then add its
  //energy to the goal energy
  if (inside) {
    aMaterialPropertiesTable->AddConstProperty(
      "ENERGY_DEPOSIT_GOL", InitialKinetEnergy + pPreStepPoint->GetKineticEnergy());
    if (TotalEnergyDeposit > 0 && InitialKinetEnergy == 0) {
      aMaterialPropertiesTable->AddConstProperty("ENERGY_DEPOSIT_GOL", 0);
      TotalEnergyDeposit = .000000;
    }
  }
  if (InsAndOuts) {
    //G4double dribble = pPostStepPoint->GetKineticEnergy() -
    //pPreStepPoint->GetKineticEnergy();
    aMaterialPropertiesTable->AddConstProperty("ENERGY_DEPOSIT_GOL",
                                               (-0.1 * CLHEP::keV) + InitialKinetEnergy -
                                                 pPostStepPoint->GetKineticEnergy());
    InitialKinetEnergy =
      bMaterial->GetMaterialPropertiesTable()->GetConstProperty("ENERGY_DEPOSIT_GOL");
    bMaterial->GetMaterialPropertiesTable()->AddConstProperty(
      "ENERGY_DEPOSIT_GOL",
      (-0.1 * CLHEP::keV) + InitialKinetEnergy + pPreStepPoint->GetKineticEnergy());
    if (aMaterialPropertiesTable->GetConstProperty("ENERGY_DEPOSIT_GOL") < 0)
      aMaterialPropertiesTable->AddConstProperty("ENERGY_DEPOSIT_GOL", 0);
    if (bMaterial->GetMaterialPropertiesTable()->GetConstProperty("ENERGY_DEPOSIT_GOL") < 0)
      bMaterial->GetMaterialPropertiesTable()->AddConstProperty("ENERGY_DEPOSIT_GOL", 0);
  }
  InitialKinetEnergy =
    aMaterialPropertiesTable->GetConstProperty("ENERGY_DEPOSIT_GOL"); //grab current goal E
  if (annihil) //if an annihilation occurred, add energy of two gammas
    InitialKinetEnergy += 2 * CLHEP::electron_mass_c2;
  //if pair production occurs, then subtract energy to cancel with the
  //energy that will be added in the line above when the e+ dies
  if (convert) InitialKinetEnergy -= 2 * CLHEP::electron_mass_c2;
  //update the relevant material property (goal energy)
  aMaterialPropertiesTable->AddConstProperty("ENERGY_DEPOSIT_GOL", InitialKinetEnergy);
  if (anExcitationEnergy < 1e-100 && aStep.GetTotalEnergyDeposit() == 0 &&
      aMaterialPropertiesTable->GetConstProperty("ENERGY_DEPOSIT_GOL") == 0 &&
      aMaterialPropertiesTable->GetConstProperty("ENERGY_DEPOSIT_TOT") == 0)
    return fParticleChange;

  G4String procName;
  if (aTrack.GetCreatorProcess())
    procName = aTrack.GetCreatorProcess()->GetProcessName();
  else
    procName = "NULL";
  if (procName == "eBrem" && outside && !OutElectrons) fMultipleScattering = true;

  // next 2 codeblocks deal with position-related things
  if (fAlpha) delta = 1000. * CLHEP::km;
  G4int i, k, counter = 0;
  G4double pos[3];
  if (outside) { //leaving
    if (aParticle->GetPDGcode() == 11 && !OutElectrons) fMultipleScattering = true;
    x1 = x0; //prevents generation of quanta outside active volume
  }          //no scint. for e-'s that leave

  char xCoord[80];
  char yCoord[80];
  char zCoord[80];
  G4bool exists = false;    //for querying whether set-up of new site needed
  for (i = 0; i < j; i++) { //loop over all saved interaction sites
    counter = i;            //save site# for later use in storing properties
    sprintf(xCoord, "POS_X_%d", i);
    sprintf(yCoord, "POS_Y_%d", i);
    sprintf(zCoord, "POS_Z_%d", i);
    pos[0] = aMaterialPropertiesTable->GetConstProperty(xCoord);
    pos[1] = aMaterialPropertiesTable->GetConstProperty(yCoord);
    pos[2] = aMaterialPropertiesTable->GetConstProperty(zCoord);
    if (sqrt(pow(x1[0] - pos[0], 2.) + pow(x1[1] - pos[1], 2.) + pow(x1[2] - pos[2], 2.)) < delta) {
      exists = true;
      break; //we find interaction is close to an old one
    }
  }
  if (!exists && TotalEnergyDeposit) { //current interaction too far away
    counter = j;
    sprintf(xCoord, "POS_X_%i", j);
    sprintf(yCoord, "POS_Y_%i", j);
    sprintf(zCoord, "POS_Z_%i", j);
    //save 3-space coordinates of the new interaction site
    aMaterialPropertiesTable->AddConstProperty(xCoord, x1[0]);
    aMaterialPropertiesTable->AddConstProperty(yCoord, x1[1]);
    aMaterialPropertiesTable->AddConstProperty(zCoord, x1[2]);
    j++;                       //increment number of sites
    aMaterialPropertiesTable-> //save
      AddConstProperty("TOTALNUM_INT_SITES", j);
  }

  // this is where nuclear recoil "L" factor is handled: total yield is
  // reduced for nuclear recoil as per Lindhard theory

  //we assume you have a mono-elemental scintillator only
  //now, grab A's and Z's of current particle and of material (avg)
  G4double a1 = ElementA->GetA();
  z2 = pDef->GetAtomicNumber();
  G4double a2 = (G4double)(pDef->GetAtomicMass());
  if (particleName == "alpha" || (z2 == 2 && a2 == 4))
    fAlpha = true; //used later to get S1 pulse shape correct for alpha
  if (fAlpha || abs(aParticle->GetPDGcode()) == 2112) a2 = a1; //get average A for element at hand
  G4double epsilon = 11.5 * (TotalEnergyDeposit / CLHEP::keV) * pow(z1, (-7. / 3.));
  G4double gamma = 3. * pow(epsilon, 0.15) + 0.7 * pow(epsilon, 0.6) + epsilon;
  G4double kappa = 0.133 * pow(z1, (2. / 3.)) * pow(a2, (-1. / 2.)) * (2. / 3.);
  //check if we are dealing with nuclear recoil (Z same as material)
  if ((z1 == z2 && pDef->GetParticleType() == "nucleus") || particleName == "neutron" ||
      particleName == "antineutron") {
    fYieldFactor = (kappa * gamma) / (1 + kappa * gamma); //Lindhard factor
    if (z1 == 18 && Phase == kStateLiquid)
      fYieldFactor = 0.23 * (1 + exp(-5 * epsilon)); //liquid argon L_eff
    //just a few safety checks, like for recombProb below
    if (fYieldFactor > 1) fYieldFactor = 1;
    if (fYieldFactor < 0) fYieldFactor = 0;
    if (ElectricField == 0 && Phase == kStateLiquid) {
      if (z1 == 54) ThomasImel = 0.19;
      if (z1 == 18) ThomasImel = 0.25;
    } //special TIB parameters for nuclear recoil only, in LXe and LAr
    fExcitationRatio = 0.69337 + 0.3065 * exp(-0.008806 * pow(ElectricField, 0.76313));
  }
  else
    fYieldFactor = 1.000; //default

  // determine ultimate #quanta from current E-deposition (ph+e-)
  G4double MeanNumberOfQuanta = //total mean number of exc/ions
    ScintillationYield * TotalEnergyDeposit;
  //the total number of either quanta produced is equal to product of the
  //work function, the energy deposited, and yield reduction, for NR
  G4double sigma = sqrt(ResolutionScale * MeanNumberOfQuanta); //Fano
  G4int NumQuanta =                                            //stochastic variation in NumQuanta
    G4int(floor(GaussGen.fire(MeanNumberOfQuanta, sigma) + 0.5));
  G4double LeffVar = GaussGen.fire(fYieldFactor, 0.25 * fYieldFactor);
  if (LeffVar > 1) { LeffVar = 1.00000; }
  if (LeffVar < 0) { LeffVar = 0; }
  if (fYieldFactor < 1) NumQuanta = BinomFluct(NumQuanta, LeffVar);
  //if E below work function, can't make any quanta, and if NumQuanta
  //less than zero because Gaussian fluctuated low, update to zero
  if (TotalEnergyDeposit < 1 / ScintillationYield || NumQuanta < 0) NumQuanta = 0;

  // next section binomially assigns quanta to excitons and ions
  G4int NumExcitons = BinomFluct(NumQuanta, fExcitationRatio / (1 + fExcitationRatio));
  G4int NumIons = NumQuanta - NumExcitons;

  // this section calculates recombination following the modified Birks'
  // Law of Doke, deposition by deposition, and may be overridden later
  // in code if a low enough energy necessitates switching to the
  // Thomas-Imel box model for recombination instead (determined by site)
  G4double dE, dx = 0, LET = 0, recombProb;
  dE = TotalEnergyDeposit / CLHEP::MeV;
  if (particleName != "e-" && particleName != "e+" && z1 != z2 && particleName != "mu-" &&
      particleName != "mu+") {
    //in other words, if it's a gamma,ion,proton,alpha,pion,et al. do not
    //use the step length provided by Geant4 because it's not relevant,
    //instead calculate an estimated LET and range of the electrons that
    //would have been produced if Geant4 could track them
    LET = CalculateElectronLET(1000 * dE, z1);
    if (LET) dx = dE / (Density * LET); //find the range based on the LET
    if (abs(aParticle->GetPDGcode()) == 2112) dx = 0;
  }
  else { //normal case of an e-/+ energy deposition recorded by Geant
    dx = aStep.GetStepLength() / CLHEP::cm;
    if (dx) LET = (dE / dx) * (1 / Density); //lin. energy xfer (prop. to dE/dx)
    if (LET > 0 && dE > 0 && dx > 0) {
      G4double ratio = CalculateElectronLET(dE * 1e3, z1) / LET;
      if (j == 1 && ratio < 0.7 && !ThomasImelTail && particleName == "e-") {
        dx /= ratio;
        LET *= ratio;
      }
    }
  }
  DokeBirks[1] = DokeBirks[0] / (1 - DokeBirks[2]); //B=A/(1-C) (see paper)
  //Doke/Birks' Law as spelled out in the NEST paper
  recombProb = (DokeBirks[0] * LET) / (1 + DokeBirks[1] * LET) + DokeBirks[2];
  if (Phase == kStateLiquid) {
    if (z1 == 54) recombProb *= (Density / Density_LXe);
    if (z1 == 18) recombProb *= (Density / Density_LAr);
  }
  //check against unphysicality resulting from rounding errors
  if (recombProb < 0) recombProb = 0;
  if (recombProb > 1) recombProb = 1;
  //use binomial distribution to assign photons, electrons, where photons
  //are excitons plus recombined ionization electrons, while final
  //collected electrons are the "escape" (non-recombined) electrons
  G4int NumPhotons = NumExcitons + BinomFluct(NumIons, recombProb);
  G4int NumElectrons = NumQuanta - NumPhotons;

  fEnergyDep = TotalEnergyDeposit;
  fNumIonElectrons = NumElectrons;
  fNumScintPhotons = NumPhotons;

  // next section increments the numbers of excitons, ions, photons, and
  // electrons for the appropriate interaction site; it only appears to
  // be redundant by saving seemingly no longer needed exciton and ion
  // counts, these having been already used to calculate the number of ph
  // and e- above, whereas it does need this later for Thomas-Imel model
  char numExc[80];
  char numIon[80];
  char numPho[80];
  char numEle[80];
  sprintf(numExc, "N_EXC_%i", counter);
  sprintf(numIon, "N_ION_%i", counter);
  aMaterialPropertiesTable->AddConstProperty(numExc, NumExcitons);
  aMaterialPropertiesTable->AddConstProperty(numIon, NumIons);
  sprintf(numPho, "N_PHO_%i", counter);
  sprintf(numEle, "N_ELE_%i", counter);
  aMaterialPropertiesTable->AddConstProperty(numPho, NumPhotons);
  aMaterialPropertiesTable->AddConstProperty(numEle, NumElectrons);

  // increment and save the total track length, and save interaction
  // times for later, when generating the scintillation quanta
  char trackL[80];
  char time00[80];
  char time01[80];
  char energy[80];
  sprintf(trackL, "TRACK_%i", counter);
  sprintf(energy, "ENRGY_%i", counter);
  sprintf(time00, "TIME0_%i", counter);
  sprintf(time01, "TIME1_%i", counter);
  delta = aMaterialPropertiesTable->GetConstProperty(trackL);
  G4double energ = aMaterialPropertiesTable->GetConstProperty(energy);
  delta += dx * CLHEP::cm;
  energ += dE * CLHEP::MeV;
  aMaterialPropertiesTable->AddConstProperty(trackL, delta);
  aMaterialPropertiesTable->AddConstProperty(energy, energ);
  if (TotalEnergyDeposit > 0) {
    G4double deltaTime = aMaterialPropertiesTable->GetConstProperty(time00);
    //for charged particles, which continuously lose energy, use initial
    //interaction time as the minimum time, otherwise use only the final
    if (aParticle->GetCharge() != 0) {
      if (t0 < deltaTime) aMaterialPropertiesTable->AddConstProperty(time00, t0);
    }
    else {
      if (t1 < deltaTime) aMaterialPropertiesTable->AddConstProperty(time00, t1);
    }
    deltaTime = aMaterialPropertiesTable->GetConstProperty(time01);
    //find the maximum possible scintillation "birth" time
    if (t1 > deltaTime) aMaterialPropertiesTable->AddConstProperty(time01, t1);
  }

  // begin the process of setting up creation of scint./ionization
  TotalEnergyDeposit =
    aMaterialPropertiesTable->GetConstProperty("ENERGY_DEPOSIT_TOT"); //get the total E deposited
  InitialKinetEnergy =
    aMaterialPropertiesTable->GetConstProperty("ENERGY_DEPOSIT_GOL"); //E that should have been
  if (InitialKinetEnergy > HIENLIM && abs(aParticle->GetPDGcode()) != 2112) fVeryHighEnergy = true;
  G4double safety; //margin of error for TotalE.. - InitialKinetEnergy
  if (fVeryHighEnergy && !fExcitedNucleus)
    safety = 0.2 * CLHEP::keV;
  else
    safety = 2. * CLHEP::eV;

  //force a scintillation dump for NR and for full nuclear de-excitation
  if (!anExcitationEnergy && pDef->GetParticleType() == "nucleus" &&
      aTrack.GetTrackStatus() != fAlive && !fAlpha)
    InitialKinetEnergy = TotalEnergyDeposit;
  if (particleName == "neutron" || particleName == "antineutron")
    InitialKinetEnergy = TotalEnergyDeposit;

  //force a dump of all saved scintillation under the following
  //conditions: energy goal reached, and current particle dead, or an
  //error has occurred and total has exceeded goal (shouldn't happen)
  if (std::abs(TotalEnergyDeposit - InitialKinetEnergy) < safety ||
      TotalEnergyDeposit >= InitialKinetEnergy) {
    dx = 0;
    dE = 0;
    //calculate the total number of quanta from all sites and all
    //interactions so that the number of secondaries gets set correctly
    NumPhotons = 0;
    NumElectrons = 0;
    for (i = 0; i < j; i++) {
      sprintf(numPho, "N_PHO_%d", i);
      sprintf(numEle, "N_ELE_%d", i);
      sprintf(trackL, "TRACK_%d", i);
      sprintf(energy, "ENRGY_%d", i);
      //add up track lengths of all sites, for a total LET calc (later)
      dx += aMaterialPropertiesTable->GetConstProperty(trackL);
      dE += aMaterialPropertiesTable->GetConstProperty(energy);
    }

    G4int buffer = 100;
    if (fVeryHighEnergy) buffer = 1;
    fParticleChange.SetNumberOfSecondaries(buffer * (NumPhotons + NumElectrons));

    if (fTrackSecondariesFirst) {
      if (aTrack.GetTrackStatus() == fAlive) fParticleChange.ProposeTrackStatus(fSuspend);
    }

    // begin the loop over all sites which generates all the quanta
    for (i = 0; i < j; i++) {
      // get the position X,Y,Z, exciton and ion numbers, total track
      // length of the site, and interaction times
      sprintf(xCoord, "POS_X_%d", i);
      sprintf(yCoord, "POS_Y_%d", i);
      sprintf(zCoord, "POS_Z_%d", i);
      sprintf(numExc, "N_EXC_%d", i);
      sprintf(numIon, "N_ION_%d", i);
      sprintf(numPho, "N_PHO_%d", i);
      sprintf(numEle, "N_ELE_%d", i);
      NumExcitons = (G4int)aMaterialPropertiesTable->GetConstProperty(numExc);
      NumIons = (G4int)aMaterialPropertiesTable->GetConstProperty(numIon);
      sprintf(trackL, "TRACK_%d", i);
      sprintf(energy, "ENRGY_%d", i);
      sprintf(time00, "TIME0_%d", i);
      sprintf(time01, "TIME1_%d", i);
      delta = aMaterialPropertiesTable->GetConstProperty(trackL);
      energ = aMaterialPropertiesTable->GetConstProperty(energy);
      t0 = aMaterialPropertiesTable->GetConstProperty(time00);
      t1 = aMaterialPropertiesTable->GetConstProperty(time01);

      //if site is small enough, override the Doke/Birks' model with
      //Thomas-Imel, but not if we're dealing with super-high energy
      //particles, and if it's NR force Thomas-Imel (though NR should be
      //already short enough in track even up to O(100) keV)
      if ((delta < R0 && !fVeryHighEnergy) || z2 == z1 || fAlpha) {
        if (z1 == 54 && ElectricField && //see NEST paper for ER formula
            Phase == kStateLiquid) {
          if (abs(z1 - z2) && //electron recoil
              abs(aParticle->GetPDGcode()) != 2112) {
            ThomasImel = 0.056776 * pow(ElectricField, -0.11844);
            if (fAlpha) //technically ER, but special
              ThomasImel = 0.057675 * pow(ElectricField, -0.49362);
          }      //end electron recoil (ER)
          else { //nuclear recoil
            // spline of NR data of C.E. Dahl PhD Thesis Princeton '09
            // functions found using zunzun.com
            ThomasImel = -0.15169 * pow((ElectricField + 215.25), 0.01811) + 0.20952;
          } //end NR information
          // Never let LY exceed 0-field yield!
          if (ThomasImel > 0.19) ThomasImel = 0.19;
          if (ThomasImel < 0.00) ThomasImel = 0.00;
        } //end non-zero E-field segment
        if (Phase == kStateLiquid) {
          if (z1 == 54) ThomasImel *= pow((Density / 2.84), 0.3);
          if (z1 == 18) ThomasImel *= pow((Density / Density_LAr), 0.3);
        }
        //calculate the Thomas-Imel recombination probability, which
        //depends on energy via NumIons, but not on dE/dx, and protect
        //against seg fault by ensuring a positive number of ions
        if (NumIons > 0) {
          G4double xi;
          xi = (G4double(NumIons) / 4.) * ThomasImel;
          if (InitialKinetEnergy == 9.4 * CLHEP::keV) {
            G4double NumIonsEff =
              1.066e7 * pow(t0 / CLHEP::ns, -1.303) * (0.17163 + 162.32 / (ElectricField + 191.39));
            if (NumIonsEff > 1e6) NumIonsEff = 1e6;
            xi = (G4double(NumIonsEff) / 4.) * ThomasImel;
          }
          if (fKr83m && ElectricField == 0) xi = (G4double(1.3 * NumIons) / 4.) * ThomasImel;
          recombProb = 1 - log(1 + xi) / xi;
          if (recombProb < 0) recombProb = 0;
          if (recombProb > 1) recombProb = 1;
        }
        //just like Doke: simple binomial distribution
        NumPhotons = NumExcitons + BinomFluct(NumIons, recombProb);
        NumElectrons = (NumExcitons + NumIons) - NumPhotons;
        //override Doke NumPhotons and NumElectrons
        aMaterialPropertiesTable->AddConstProperty(numPho, NumPhotons);
        aMaterialPropertiesTable->AddConstProperty(numEle, NumElectrons);
      }

      // grab NumPhotons/NumElectrons, which come from Birks if
      // the Thomas-Imel block of code above was not executed
      NumPhotons = (G4int)aMaterialPropertiesTable->GetConstProperty(numPho);
      NumElectrons = (G4int)aMaterialPropertiesTable->GetConstProperty(numEle);
      // extra Fano factor caused by recomb. fluct.
      G4double FanoFactor = 0; //ionization channel
      if (Phase == kStateLiquid && fYieldFactor == 1) {
        FanoFactor = 2575.9 * pow((ElectricField + 15.154), -0.64064) - 1.4707;
        if (fKr83m) TotalEnergyDeposit = 4 * CLHEP::keV;
        if ((dE / CLHEP::keV) <= 100 && ElectricField >= 0) {
          G4double keVee = (TotalEnergyDeposit / (100. * CLHEP::keV));
          if (keVee <= 0.06)
            FanoFactor *= -0.00075 + 0.4625 * keVee + 34.375 * pow(keVee, 2.);
          else
            FanoFactor *= 0.069554 + 1.7322 * keVee - .80215 * pow(keVee, 2.);
        }
      }
      if (Phase == kStateGas && Density > 0.5)
        FanoFactor = 0.42857 - 4.7857 * Density + 7.8571 * pow(Density, 2.);
      if (FanoFactor <= 0 || fVeryHighEnergy) FanoFactor = 0;
      NumQuanta = NumPhotons + NumElectrons;
      if (z1 == 54 && FanoFactor)
        NumElectrons =
          G4int(floor(GaussGen.fire(NumElectrons, sqrt(FanoFactor * NumElectrons)) + 0.5));
      NumPhotons = NumQuanta - NumElectrons;
      if (NumElectrons <= 0) NumElectrons = 0;
      if (NumPhotons <= 0)
        NumPhotons = 0;
      else {        //other effects
        if (fAlpha) //bi-excitonic quenching due to high dE/dx
          NumPhotons = BinomFluct(NumPhotons, biExc);
        NumPhotons = BinomFluct(NumPhotons, QE_EFF);
      }
      NumElectrons = G4int(floor(NumElectrons * phe_per_e + 0.5));

      // new stuff to make Kr-83m work properly
      if (fKr83m || InitialKinetEnergy == 9.4 * CLHEP::keV) fKr83m += dE / CLHEP::keV;
      if (fKr83m > 41) fKr83m = 0;
      if (SinglePhase)    //for a 1-phase det. don't propagate e-'s
        NumElectrons = 0; //saves simulation time

      // reset material properties numExc, numIon, numPho, numEle, as
      // their values have been used or stored elsewhere already
      aMaterialPropertiesTable->AddConstProperty(numExc, 0);
      aMaterialPropertiesTable->AddConstProperty(numIon, 0);
      aMaterialPropertiesTable->AddConstProperty(numPho, 0);
      aMaterialPropertiesTable->AddConstProperty(numEle, 0);

      // start particle creation loop
      if (InitialKinetEnergy < MAX_ENE && InitialKinetEnergy > MIN_ENE && !fMultipleScattering)
        NumQuanta = NumPhotons + NumElectrons;
      else
        NumQuanta = 0;
      for (k = 0; k < NumQuanta; k++) {
        G4double sampledEnergy;
        std::unique_ptr<G4DynamicParticle> aQuantum;

        // Generate random direction
        G4double cost = 1. - 2. * UniformGen.fire();
        G4double sint = std::sqrt((1. - cost) * (1. + cost));
        G4double phi = CLHEP::twopi * UniformGen.fire();
        G4double sinp = std::sin(phi);
        G4double cosp = std::cos(phi);
        G4double px = sint * cosp;
        G4double py = sint * sinp;
        G4double pz = cost;

        // Create momentum direction vector
        G4ParticleMomentum photonMomentum(px, py, pz);

        // case of photon-specific stuff
        if (k < NumPhotons) {
          // Determine polarization of new photon
          G4double sx = cost * cosp;
          G4double sy = cost * sinp;
          G4double sz = -sint;
          G4ThreeVector photonPolarization(sx, sy, sz);
          G4ThreeVector perp = photonMomentum.cross(photonPolarization);
          phi = CLHEP::twopi * UniformGen.fire();
          sinp = std::sin(phi);
          cosp = std::cos(phi);
          photonPolarization = cosp * photonPolarization + sinp * perp;
          photonPolarization = photonPolarization.unit();

          // Generate a new photon or electron:
          sampledEnergy = GaussGen.fire(PhotMean, PhotWidth);
          aQuantum =
            std::make_unique<G4DynamicParticle>(G4OpticalPhoton::OpticalPhoton(), photonMomentum);
          aQuantum->SetPolarization(
            photonPolarization.x(), photonPolarization.y(), photonPolarization.z());
        }

        else { // this else statement is for ionization electrons
          if (ElectricField) {
            // point all electrons straight up, for drifting
            G4ParticleMomentum electronMomentum(0, 0, -FieldSign);
            aQuantum = std::make_unique<G4DynamicParticle>(G4ThermalElectron::ThermalElectron(),
                                                           electronMomentum);
            if (Phase == kStateGas) {
              sampledEnergy = GetGasElectronDriftSpeed(ElectricField, nDensity);
            }
            else
              sampledEnergy =
                GetLiquidElectronDriftSpeed(Temperature, ElectricField, MillerDriftSpeed, z1);
          }
          else {
            // use "photonMomentum" for the electrons in the case of zero
            // electric field, which is just randomized vector we made
            aQuantum = std::make_unique<G4DynamicParticle>(G4ThermalElectron::ThermalElectron(),
                                                           photonMomentum);
            sampledEnergy = 1.38e-23 * (CLHEP::joule / CLHEP::kelvin) * Temperature;
          }
        }

        //assign energy to make particle real
        aQuantum->SetKineticEnergy(sampledEnergy);

        // Generate new G4Track object:
        // emission time distribution

        // first an initial birth time is provided that is typically
        // <<1 ns after the initial interaction in the simulation, then
        // singlet, triplet lifetimes, and recombination time, are
        // handled here, to create a realistic S1 pulse shape/timing
        G4double aSecondaryTime = t0 + UniformGen.fire() * (t1 - t0) + evtStrt;
        if (tau1 < 0) { tau1 = 0; }
        if (tau3 < 0) { tau3 = 0; }
        if (tauR < 0) { tauR = 0; }
        if (aQuantum->GetDefinition()->GetParticleName() == "opticalphoton") {
          if (abs(z2 - z1) && !fAlpha && //electron recoil
              abs(aParticle->GetPDGcode()) != 2112) {
            LET = (energ / CLHEP::MeV) / (delta / CLHEP::cm) * (1 / Density); //avg LET over all
            //in future, this will be done interaction by interaction
            // Next, find the recombination time, which is LET-dependent
            // via ionization density (Kubota et al. Phys. Rev. B 20
            // (1979) 3486). We find the LET-dependence by fitting to the
            // E-dependence (Akimov et al. Phys. Lett. B 524 (2002) 245).
            if (Phase == kStateLiquid && z1 == 54)
              tauR =
                3.5 * ((1 + 0.41 * LET) / (0.18 * LET)) * CLHEP::ns * exp(-0.00900 * ElectricField);
            //field dependence based on fitting Fig. 9 of Dawson et al.
            //NIM A 545 (2005) 690
            //singlet-triplet ratios adapted from Kubota 1979, converted
            //into correct units to work here, and separately done for
            //excitation and recombination processes for electron recoils
            //and assumed same for all LET (may vary)
            SingTripRatioX = GaussGen.fire(0.17, 0.05);
            SingTripRatioR = GaussGen.fire(0.8, 0.2);
            if (z1 == 18) {
              SingTripRatioR =
                0.2701 + 0.003379 * LET - 4.7338e-5 * pow(LET, 2.) + 8.1449e-6 * pow(LET, 3.);
              SingTripRatioX = SingTripRatioR;
              if (LET < 3) {
                SingTripRatioX = GaussGen.fire(0.36, 0.06);
                SingTripRatioR = GaussGen.fire(0.5, 0.2);
              }
            }
          }
          else if (fAlpha) { //alpha particles
            SingTripRatioR = GaussGen.fire(2.3, 0.51);
            //currently based on Dawson 05 and Tey. 11 (arXiv:1103.3689)
            //real ratio is likely a gentle function of LET
            if (z1 == 18)
              SingTripRatioR = (-0.065492 + 1.9996 * exp(-dE / CLHEP::MeV)) /
                                 (1 + 0.082154 / pow(dE / CLHEP::MeV, 2.)) +
                               2.1811;
            SingTripRatioX = SingTripRatioR;
          }
          else { //nuclear recoil
            //based loosely on Hitachi et al. Phys. Rev. B 27 (1983) 5279
            //with an eye to reproducing Akimov 2002 Fig. 9
            SingTripRatioR = GaussGen.fire(7.8, 1.5);
            if (z1 == 18) SingTripRatioR = 0.22218 * pow(energ / CLHEP::keV, 0.48211);
            SingTripRatioX = SingTripRatioR;
          }
          // now, use binomial distributions to determine singlet and
          // triplet states (and do separately for initially excited guys
          // and recombining)
          if (k > NumExcitons) {
            //the recombination time is non-exponential, but approximates
            //to exp at long timescales (see Kubota '79)
            aSecondaryTime += tauR * (1. / UniformGen.fire() - 1);
            if (UniformGen.fire() < SingTripRatioR / (1 + SingTripRatioR))
              aSecondaryTime -= tau1 * log(UniformGen.fire());
            else
              aSecondaryTime -= tau3 * log(UniformGen.fire());
          }
          else {
            if (UniformGen.fire() < SingTripRatioX / (1 + SingTripRatioX))
              aSecondaryTime -= tau1 * log(UniformGen.fire());
            else
              aSecondaryTime -= tau3 * log(UniformGen.fire());
          }
        }
        else { //electron trapping at the liquid/gas interface
          G4double gainField = 12;
          G4double tauTrap = 884.83 - 62.069 * gainField;
          if (Phase == kStateLiquid) aSecondaryTime -= tauTrap * CLHEP::ns * log(UniformGen.fire());
        }

        // emission position distribution --
        // Generate the position of a new photon or electron, with NO
        // stochastic variation because that could lead to particles
        // being mistakenly generated outside of your active region by
        // Geant4, but real-life finite detector position resolution
        // wipes out any effects from here anyway...
        std::string sx(xCoord);
        std::string sy(yCoord);
        std::string sz(zCoord);
        x0[0] = aMaterialPropertiesTable->GetConstProperty(xCoord);
        x0[1] = aMaterialPropertiesTable->GetConstProperty(yCoord);
        x0[2] = aMaterialPropertiesTable->GetConstProperty(zCoord);
        G4double radius = sqrt(pow(x0[0], 2.) + pow(x0[1], 2.));
        //re-scale radius to ensure no generation of quanta outside
        //the active volume of your simulation due to Geant4 rounding
        if (radius >= R_TOL) {
          if (x0[0] == 0) { x0[0] = 1 * CLHEP::nm; }
          if (x0[1] == 0) { x0[1] = 1 * CLHEP::nm; }
          radius -= R_TOL;
          phi = atan(x0[1] / x0[0]);
          x0[0] = fabs(radius * cos(phi)) * ((fabs(x0[0])) / (x0[0]));
          x0[1] = fabs(radius * sin(phi)) * ((fabs(x0[1])) / (x0[1]));
        }
        //position of the new secondary particle is ready for use
        G4ThreeVector aSecondaryPosition = x0;
        if (k >= NumPhotons && diffusion && ElectricField > 0) {
          G4double D_T = 64 * pow(1e-3 * ElectricField, -.17);
          //fit to Aprile and Doke 2009, arXiv:0910.4956 (Fig. 12)
          G4double D_L = 13.859 * pow(1e-3 * ElectricField, -0.58559);
          //fit to Aprile and Doke and Sorensen 2011, arXiv:1102.2865
          if (Phase == kStateLiquid && z1 == 18) {
            D_T = 93.342 * pow(ElectricField / nDensity, 0.041322);
            D_L = 0.15 * D_T;
          }
          if (Phase == kStateGas && z1 == 54) {
            D_L = 4.265 + 19097 / ElectricField - 1.7397e6 / pow(ElectricField, 2.) +
                  1.2477e8 / pow(ElectricField, 3.);
            D_T *= 0.01;
          }
          D_T *= CLHEP::cm2 / CLHEP::s;
          D_L *= CLHEP::cm2 / CLHEP::s;
          if (ElectricField < 100 && Phase == kStateLiquid) D_L = 8 * CLHEP::cm2 / CLHEP::s;
          G4double vDrift = sqrt((2 * sampledEnergy) / (EMASS));
          if (BORDER == 0) x0[2] = 0;
          G4double sigmaDT = sqrt(2 * D_T * fabs(BORDER - x0[2]) / vDrift);
          G4double sigmaDL = sqrt(2 * D_L * fabs(BORDER - x0[2]) / vDrift);
          G4double dr = std::abs(GaussGen.fire(0., sigmaDT));
          phi = CLHEP::twopi * UniformGen.fire();
          aSecondaryPosition[0] += cos(phi) * dr;
          aSecondaryPosition[1] += sin(phi) * dr;
          aSecondaryPosition[2] += GaussGen.fire(0., sigmaDL);
          radius =
            std::sqrt(std::pow(aSecondaryPosition[0], 2.) + std::pow(aSecondaryPosition[1], 2.));
          if (aSecondaryPosition[2] >= BORDER && Phase == kStateLiquid) {
            if (BORDER != 0) aSecondaryPosition[2] = BORDER - R_TOL;
          }
          if (aSecondaryPosition[2] <= PMT && !GlobalFields) aSecondaryPosition[2] = PMT + R_TOL;
        } //end of electron diffusion code

        // GEANT4 business: stuff you need to make a new track
        if (aSecondaryTime < 0) aSecondaryTime = 0; //no neg. time
                                                    /*
          auto aSecondaryTrack =
          std::make_unique<G4Track>(aQuantum,aSecondaryTime,aSecondaryPosition);
          if ( k < NumPhotons || radius < R_MAX )
          {

        */
      }

      //reset bunch of things when done with an interaction site
      aMaterialPropertiesTable->AddConstProperty(xCoord, 999 * CLHEP::km);
      aMaterialPropertiesTable->AddConstProperty(yCoord, 999 * CLHEP::km);
      aMaterialPropertiesTable->AddConstProperty(zCoord, 999 * CLHEP::km);
      aMaterialPropertiesTable->AddConstProperty(trackL, 0 * CLHEP::um);
      aMaterialPropertiesTable->AddConstProperty(energy, 0 * CLHEP::eV);
      aMaterialPropertiesTable->AddConstProperty(time00, DBL_MAX);
      aMaterialPropertiesTable->AddConstProperty(time01, -1 * CLHEP::ns);

    } //end of interaction site loop

    //more things to reset...
    aMaterialPropertiesTable->AddConstProperty("TOTALNUM_INT_SITES", 0);
    aMaterialPropertiesTable->AddConstProperty("ENERGY_DEPOSIT_TOT", 0 * CLHEP::keV);
    aMaterialPropertiesTable->AddConstProperty("ENERGY_DEPOSIT_GOL", 0 * CLHEP::MeV);
    fExcitedNucleus = false;
    fAlpha = false;
  }

  //don't do anything when you're not ready to scintillate
  else {
    fParticleChange.SetNumberOfSecondaries(0);
    return fParticleChange;
  }

  return fParticleChange;
}

//----------------------------------------------------------------------------
G4double NestAlg::GetGasElectronDriftSpeed(G4double /*efieldinput*/, G4double /*density*/)
{
  std::cout << "WARNING: NestAlg::GetGasElectronDriftSpeed(G4double, G4double) "
            << "is not defined, returning bogus value of -999." << std::endl;

  return -999.;
}

//----------------------------------------------------------------------------
G4double NestAlg::GetLiquidElectronDriftSpeed(G4double tempinput,
                                              G4double efieldinput,
                                              G4bool Miller,
                                              G4int Z)
{
  if (efieldinput < 0) efieldinput *= (-1);
  //Liquid equation one (165K) coefficients
  G4double onea = 144623.235704015, oneb = 850.812714257629, onec = 1192.87056676815,
           oned = -395969.575204061, onef = -355.484170008875, oneg = -227.266219627672,
           oneh = 223831.601257495, onei = 6.1778950907965, onej = 18.7831533426398,
           onek = -76132.6018884368;
  //Liquid equation two (200K) coefficients
  G4double twoa = 17486639.7118995, twob = -113.174284723134, twoc = 28.005913193763,
           twod = 167994210.094027, twof = -6766.42962575088, twog = 901.474643115395,
           twoh = -185240292.471665, twoi = -633.297790813084, twoj = 87.1756135457949;
  //Liquid equation three (230K) coefficients
  G4double thra = 10626463726.9833, thrb = 224025158.134792, thrc = 123254826.300172,
           thrd = -4563.5678061122, thrf = -1715.269592063, thrg = -694181.921834368,
           thrh = -50.9753281079838, thri = 58.3785811395493, thrj = 201512.080026704;
  G4double y1 = 0, y2 = 0, f1 = 0, f2 = 0, f3 = 0, edrift = 0, t1 = 0, t2 = 0, slope = 0,
           intercept = 0;

  //Equations defined
  f1 = onea / (1 + exp(-(efieldinput - oneb) / onec)) +
       oned / (1 + exp(-(efieldinput - onef) / oneg)) +
       oneh / (1 + exp(-(efieldinput - onei) / onej)) + onek;
  f2 = twoa / (1 + exp(-(efieldinput - twob) / twoc)) +
       twod / (1 + exp(-(efieldinput - twof) / twog)) +
       twoh / (1 + exp(-(efieldinput - twoi) / twoj));
  f3 = thra * exp(-thrb * efieldinput) + thrc * exp(-(pow(efieldinput - thrd, 2)) / (thrf * thrf)) +
       thrg * exp(-(pow(efieldinput - thrh, 2) / (thri * thri))) + thrj;

  if (efieldinput < 20 && efieldinput >= 0) {
    f1 = 2951 * efieldinput;
    f2 = 5312 * efieldinput;
    f3 = 7101 * efieldinput;
  }
  //Cases for tempinput decides which 2 equations to use lin. interpolation
  if (tempinput < 200.0 && tempinput > 165.0) {
    y1 = f1;
    y2 = f2;
    t1 = 165.0;
    t2 = 200.0;
  }
  if (tempinput < 230.0 && tempinput > 200.0) {
    y1 = f2;
    y2 = f3;
    t1 = 200.0;
    t2 = 230.0;
  }
  if ((tempinput > 230.0 || tempinput < 165.0) && !Miller) {
    G4cout << "\nWARNING: TEMPERATURE OUT OF RANGE (165-230 K)\n";
    return 0;
  }
  if (tempinput == 165.0)
    edrift = f1;
  else if (tempinput == 200.0)
    edrift = f2;
  else if (tempinput == 230.0)
    edrift = f3;
  else { //Linear interpolation
    //frac=(tempinput-t1)/(t2-t1);
    slope = (y1 - y2) / (t1 - t2);
    intercept = y1 - slope * t1;
    edrift = slope * tempinput + intercept;
  }

  if (Miller) {
    if (efieldinput <= 40.)
      edrift = -0.13274 + 0.041082 * efieldinput - 0.0006886 * pow(efieldinput, 2.) +
               5.5503e-6 * pow(efieldinput, 3.);
    else
      edrift = 0.060774 * efieldinput / pow(1 + 0.11336 * pow(efieldinput, 0.5218), 2.);
    if (efieldinput >= 1e5) edrift = 2.7;
    if (efieldinput >= 100)
      edrift -= 0.017 * (tempinput - 163);
    else
      edrift += 0.017 * (tempinput - 163);
    edrift *= 1e5; //put into units of cm/sec. from mm/usec.
  }
  if (Z == 18)
    edrift = 1e5 * (.097384 * pow(log10(efieldinput), 3.0622) - .018614 * sqrt(efieldinput));
  if (edrift < 0) edrift = 0.;
  edrift = 0.5 * EMASS * pow(edrift * CLHEP::cm / CLHEP::s, 2.);
  return edrift;
}

//----------------------------------------------------------------------------
G4double NestAlg::CalculateElectronLET(G4double E, G4int Z)
{
  G4double LET;
  switch (Z) {
  case 54:
    //use a spline fit to online ESTAR data
    if (E >= 1)
      LET = 58.482 - 61.183 * log10(E) + 19.749 * pow(log10(E), 2) + 2.3101 * pow(log10(E), 3) -
            3.3469 * pow(log10(E), 4) + 0.96788 * pow(log10(E), 5) - 0.12619 * pow(log10(E), 6) +
            0.0065108 * pow(log10(E), 7);
    //at energies <1 keV, use a different spline, determined manually by
    //generating sub-keV electrons in Geant4 and looking at their ranges, since
    //ESTAR does not go this low
    else if (E > 0 && E < 1)
      LET = 6.9463 + 815.98 * E - 4828 * pow(E, 2) + 17079 * pow(E, 3) - 36394 * pow(E, 4) +
            44553 * pow(E, 5) - 28659 * pow(E, 6) + 7483.8 * pow(E, 7);
    else
      LET = 0;
    break;
  case 18:
  default:
    if (E >= 1)
      LET = 116.70 - 162.97 * log10(E) + 99.361 * pow(log10(E), 2) - 33.405 * pow(log10(E), 3) +
            6.5069 * pow(log10(E), 4) - 0.69334 * pow(log10(E), 5) + .031563 * pow(log10(E), 6);
    else if (E > 0 && E < 1)
      LET = 100;
    else
      LET = 0;
  }
  return LET;
}

//----------------------------------------------------------------------------
G4int NestAlg::BinomFluct(G4int N0, G4double prob)
{
  CLHEP::RandGauss GaussGen(fEngine);
  CLHEP::RandFlat UniformGen(fEngine);

  G4double mean = N0 * prob;
  G4double sigma = sqrt(N0 * prob * (1 - prob));
  G4int N1 = 0;
  if (prob == 0.00) return N1;
  if (prob == 1.00) return N0;

  if (N0 < 10) {
    for (G4int i = 0; i < N0; i++) {
      if (UniformGen.fire() < prob) N1++;
    }
  }
  else {
    N1 = G4int(floor(GaussGen.fire(mean, sigma) + 0.5));
  }
  if (N1 > N0) N1 = N0;
  if (N1 < 0) N1 = 0;
  return N1;
}

//----------------------------------------------------------------------------
void NestAlg::InitMatPropValues(G4MaterialPropertiesTable* nobleElementMat, int z)
{
  char xCoord[80];
  char yCoord[80];
  char zCoord[80];
  char numExc[80];
  char numIon[80];
  char numPho[80];
  char numEle[80];
  char trackL[80];
  char time00[80];
  char time01[80];
  char energy[80];

  // for loop to initialize the interaction site mat'l properties
  for (G4int i = 0; i < 10000; i++) {
    sprintf(xCoord, "POS_X_%d", i);
    sprintf(yCoord, "POS_Y_%d", i);
    sprintf(zCoord, "POS_Z_%d", i);
    nobleElementMat->AddConstProperty(xCoord, 999 * CLHEP::km);
    nobleElementMat->AddConstProperty(yCoord, 999 * CLHEP::km);
    nobleElementMat->AddConstProperty(zCoord, 999 * CLHEP::km);
    sprintf(numExc, "N_EXC_%d", i);
    sprintf(numIon, "N_ION_%d", i);
    sprintf(numPho, "N_PHO_%d", i);
    sprintf(numEle, "N_ELE_%d", i);
    nobleElementMat->AddConstProperty(numExc, 0);
    nobleElementMat->AddConstProperty(numIon, 0);
    nobleElementMat->AddConstProperty(numPho, 0);
    nobleElementMat->AddConstProperty(numEle, 0);
    sprintf(trackL, "TRACK_%d", i);
    sprintf(energy, "ENRGY_%d", i);
    sprintf(time00, "TIME0_%d", i);
    sprintf(time01, "TIME1_%d", i);
    nobleElementMat->AddConstProperty(trackL, 0 * CLHEP::um);
    nobleElementMat->AddConstProperty(energy, 0 * CLHEP::eV);
    nobleElementMat->AddConstProperty(time00, DBL_MAX);
    nobleElementMat->AddConstProperty(time01, -1 * CLHEP::ns);
  }

  // we initialize the total number of interaction sites, a variable for
  // updating the amount of energy deposited thus far in the medium, and a
  // variable for storing the amount of energy expected to be deposited
  nobleElementMat->AddConstProperty("TOTALNUM_INT_SITES", 0);
  nobleElementMat->AddConstProperty("ENERGY_DEPOSIT_TOT", 0 * CLHEP::keV);
  nobleElementMat->AddConstProperty("ENERGY_DEPOSIT_GOL", 0 * CLHEP::MeV);

  fElementPropInit[z] = true;

  return;
}

//----------------------------------------------------------------------------
G4double UnivScreenFunc(G4double E, G4double Z, G4double A)
{
  G4double a_0 = 5.29e-11 * CLHEP::m;
  G4double a = 0.626 * a_0 * pow(Z, (-1. / 3.));
  G4double epsilon_0 = 8.854e-12 * (CLHEP::farad / CLHEP::m);
  G4double epsilon =
    (a * E * 2. * CLHEP::twopi * epsilon_0) / (2 * pow(CLHEP::eplus, 2.) * pow(Z, 2.));
  G4double zeta_0 = pow(Z, (1. / 6.));
  G4double m_N = A * 1.66e-27 * CLHEP::kg;
  G4double hbar = 6.582e-16 * CLHEP::eV * CLHEP::s;
  if (Z == 54) {
    epsilon *= 1.068; //zeta_0 = 1.63;
  }                   //special case for LXe from Bezrukov et al. 2011
  G4double s_n = log(1 + 1.1383 * epsilon) /
                 (2. * (epsilon + 0.01321 * pow(epsilon, 0.21226) + 0.19593 * sqrt(epsilon)));
  G4double s_e =
    (a_0 * zeta_0 / a) * hbar *
    sqrt(8 * epsilon * 2. * CLHEP::twopi * epsilon_0 / (a * m_N * pow(CLHEP::eplus, 2.)));
  return 1.38e5 * 0.5 * (1 + tanh(50 * epsilon - 0.25)) * epsilon * (s_e / s_n);
}