HFCherenkov.cc

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// File:  HFCherenkov.cc
// Description: Generate Cherenkov photons for HF

#include "SimG4CMS/Calo/interface/HFCherenkov.h"

#include "G4Poisson.hh"
#include "G4ParticleDefinition.hh"
#include "G4NavigationHistory.hh"
#include "TMath.h"

#include "Randomize.hh"

#include <CLHEP/Units/SystemOfUnits.h>

//#define EDM_ML_DEBUG

HFCherenkov::HFCherenkov(edm::ParameterSet const& m_HF) {
  ref_index = m_HF.getParameter<double>("RefIndex");
  lambda1 = ((m_HF.getParameter<double>("Lambda1")) / 1.e+7) * CLHEP::cm;
  lambda2 = ((m_HF.getParameter<double>("Lambda2")) / 1.e+7) * CLHEP::cm;
  aperture = m_HF.getParameter<double>("Aperture");
  gain = m_HF.getParameter<double>("Gain");
  checkSurvive = m_HF.getParameter<bool>("CheckSurvive");
  UseNewPMT = m_HF.getParameter<bool>("UseR7600UPMT");
  fibreR = m_HF.getParameter<double>("FibreR") * CLHEP::mm;

  aperturetrapped = aperture / ref_index;
  sinPsimax = 1 / ref_index;

  edm::LogVerbatim("HFShower") << "HFCherenkov:: initialised with ref_index " << ref_index << " lambda1/lambda2 (cm) "
                               << lambda1 / CLHEP::cm << "|" << lambda2 / CLHEP::cm << " aperture(trapped) " << aperture
                               << "|" << aperturetrapped << " sinPsimax " << sinPsimax
                               << " Check photon survival in HF " << checkSurvive << " Gain " << gain << " useNewPMT "
                               << UseNewPMT << " FibreR " << fibreR;

  clearVectors();
}

HFCherenkov::~HFCherenkov() {}

int HFCherenkov::computeNPE(const G4Step* aStep,
                            const G4ParticleDefinition* pDef,
                            double pBeta,
                            double u,
                            double v,
                            double w,
                            double step_length,
                            double zFiber,
                            double dose,
                            int npe_Dose) {
  clearVectors();
  if (!isApplicable(pDef)) {
    return 0;
  }
  if (pBeta < (1 / ref_index) || step_length < 0.0001) {
#ifdef EDM_ML_DEBUG
    edm::LogVerbatim("HFShower") << "HFCherenkov::computeNPE: pBeta " << pBeta << " 1/mu " << (1 / ref_index)
                                 << " step_length " << step_length;
#endif
    return 0;
  }

  double uv = std::sqrt(u * u + v * v);
  int nbOfPhotons = computeNbOfPhotons(pBeta, step_length) * aStep->GetTrack()->GetWeight();
#ifdef EDM_ML_DEBUG
  edm::LogVerbatim("HFShower") << "HFCherenkov::computeNPE: pBeta " << pBeta << " u/v/w " << u << "/" << v << "/" << w
                               << " step_length " << step_length << " zFib " << zFiber << " nbOfPhotons "
                               << nbOfPhotons;
#endif
  if (nbOfPhotons < 0) {
    return 0;
  } else if (nbOfPhotons > 0) {
    G4StepPoint* preStepPoint = aStep->GetPreStepPoint();
    const G4TouchableHandle& theTouchable = preStepPoint->GetTouchableHandle();
    G4ThreeVector localprepos =
        theTouchable->GetHistory()->GetTopTransform().TransformPoint(aStep->GetPreStepPoint()->GetPosition());
    G4ThreeVector localpostpos =
        theTouchable->GetHistory()->GetTopTransform().TransformPoint(aStep->GetPostStepPoint()->GetPosition());

    double length = std::sqrt((localpostpos.x() - localprepos.x()) * (localpostpos.x() - localprepos.x()) +
                              (localpostpos.y() - localprepos.y()) * (localpostpos.y() - localprepos.y()));
    double yemit = std::sqrt(fibreR * fibreR - length * length / 4.);

    double u_ph = 0, v_ph = 0, w_ph = 0;
    for (int i = 0; i < nbOfPhotons; i++) {
      double rand = G4UniformRand();
      double theta_C = acos(1. / (pBeta * ref_index));
      double phi_C = 2 * M_PI * rand;
      double sinTheta = sin(theta_C);
      double cosTheta = cos(theta_C);
      double cosPhi = cos(phi_C);
      double sinPhi = sin(phi_C);
      //photon momentum
      if (uv < 0.001) {  // aligned with z-axis
        u_ph = sinTheta * cosPhi;
        v_ph = sinTheta * sinPhi;
        w_ph = cosTheta;
      } else {  // general case
        u_ph = uv * cosTheta + sinTheta * cosPhi * w;
        v_ph = sinTheta * sinPhi;
        w_ph = w * cosTheta - sinTheta * cosPhi * uv;
      }
      double r_lambda = G4UniformRand();
      double lambda0 = (lambda1 * lambda2) / (lambda2 - r_lambda * (lambda2 - lambda1));
      double lambda = (lambda0 / CLHEP::cm) * 1.e+7;  // lambda is in nm
      wlini.push_back(lambda);
#ifdef EDM_ML_DEBUG
      edm::LogVerbatim("HFShower") << "HFCherenkov::computeNPE: " << i << " lambda " << lambda << " w_ph " << w_ph;
#endif
      // --------------
      double xemit = length * (G4UniformRand() - 0.5);
      double gam = atan2(yemit, xemit);
      double eps = atan2(v_ph, u_ph);
      double sinBeta = sin(gam - eps);
      double rho = std::sqrt(xemit * xemit + yemit * yemit);
      double sinEta = rho / fibreR * sinBeta;
      double cosEta = std::sqrt(1. - sinEta * sinEta);
      double sinPsi = std::sqrt(1. - w_ph * w_ph);
      double cosKsi = cosEta * sinPsi;

#ifdef EDM_ML_DEBUG
      if (cosKsi < aperturetrapped && w_ph > 0.) {
        edm::LogVerbatim("HFShower") << "HFCherenkov::Trapped photon : " << u_ph << " " << v_ph << " " << w_ph << " "
                                     << xemit << " " << gam << " " << eps << " " << sinBeta << " " << rho << " "
                                     << sinEta << " " << cosEta << " "
                                     << " " << sinPsi << " " << cosKsi;
      } else {
        edm::LogVerbatim("HFShower") << "HFCherenkov::Rejected photon : " << u_ph << " " << v_ph << " " << w_ph << " "
                                     << xemit << " " << gam << " " << eps << " " << sinBeta << " " << rho << " "
                                     << sinEta << " " << cosEta << " "
                                     << " " << sinPsi << " " << cosKsi;
      }
#endif
      if (cosKsi < aperturetrapped  // photon is trapped inside fiber
          && w_ph > 0.              // and moves to PMT
          && sinPsi < sinPsimax) {  // and is not reflected at fiber end
        wltrap.push_back(lambda);
        double prob_HF = 1.0;
        if (checkSurvive) {
          double a0_inv = 0.1234;                          //meter^-1
          double a_inv = a0_inv + 0.14 * pow(dose, 0.30);  // ?
          double z_meters = zFiber;
          prob_HF = exp(-z_meters * a_inv);
        }
        rand = G4UniformRand();
#ifdef EDM_ML_DEBUG
        edm::LogVerbatim("HFShower") << "HFCherenkov::computeNPE: probHF " << prob_HF << " Random " << rand
                                     << " Survive? " << (rand < prob_HF);
#endif
        if (rand < prob_HF) {  // survived in HF
          wlatten.push_back(lambda);
          double effHEM = computeHEMEff(lambda);
          // compute number of bounces in air guide
          rand = G4UniformRand();
          double phi = 0.5 * M_PI * rand;
          double rad_bundle = 19.;  // bundle radius
          double rad_lg = 25.;      //  light guide radius
          rand = G4UniformRand();
          double rad = rad_bundle * std::sqrt(rand);
          double rho = rad * sin(phi);
          double tlength = 2. * std::sqrt(rad_lg * rad_lg - rho * rho);
          double length_lg = 430;
          double sin_air = sinPsi * 1.46;
          double tang = sin_air / std::sqrt(1. - sin_air * sin_air);
          int nbounce = length_lg / tlength * tang + 0.5;
          double eff = pow(effHEM, nbounce);
          rand = G4UniformRand();
#ifdef EDM_ML_DEBUG
          edm::LogVerbatim("HFShower") << "HFCherenkov::computeNPE: w_ph " << w_ph << " effHEM " << effHEM << " eff "
                                       << eff << " Random " << rand << " Survive? " << (rand < eff);
#endif
          if (rand < eff) {  // survived HEM
            wlhem.push_back(lambda);
            double qEffic = computeQEff(lambda);
            rand = G4UniformRand();
#ifdef EDM_ML_DEBUG
            edm::LogVerbatim("HFShower") << "HFCherenkov::computeNPE: qEffic " << qEffic << " Random " << rand
                                         << " Survive? " << (rand < qEffic);
#endif
            if (rand < qEffic) {  // made photoelectron
              npe_Dose += 1;
              momZ.push_back(w_ph);
              wl.push_back(lambda);
              wlqeff.push_back(lambda);
            }          // made pe
          }            // passed HEM
        }              // passed fiber
      }                // end of  if(w_ph < w_aperture), trapped inside fiber
    }                  // end of ++NbOfPhotons
  }                    // end of if(NbOfPhotons)}
  int npe = npe_Dose;  // Nb of photoelectrons
#ifdef EDM_ML_DEBUG
  edm::LogVerbatim("HFShower") << "HFCherenkov::computeNPE: npe " << npe;
#endif
  return npe;
}

int HFCherenkov::computeNPEinPMT(
    const G4ParticleDefinition* pDef, double pBeta, double u, double v, double w, double step_length) {
  clearVectors();
  int npe_ = 0;
  if (!isApplicable(pDef)) {
    return 0;
  }
  if (pBeta < (1 / ref_index) || step_length < 0.0001) {
#ifdef EDM_ML_DEBUG
    edm::LogVerbatim("HFShower") << "HFCherenkov::computeNPEinPMT: pBeta " << pBeta << " 1/mu " << (1 / ref_index)
                                 << " step_length " << step_length;
#endif
    return 0;
  }

  double uv = std::sqrt(u * u + v * v);
  int nbOfPhotons = computeNbOfPhotons(pBeta, step_length);
#ifdef EDM_ML_DEBUG
  edm::LogVerbatim("HFShower") << "HFCherenkov::computeNPEinPMT: pBeta " << pBeta << " u/v/w " << u << "/" << v << "/"
                               << w << " step_length " << step_length << " nbOfPhotons " << nbOfPhotons;
#endif
  if (nbOfPhotons < 0) {
    return 0;
  } else if (nbOfPhotons > 0) {
    double w_ph = 0;
    for (int i = 0; i < nbOfPhotons; i++) {
      double rand = G4UniformRand();
      double theta_C = acos(1. / (pBeta * ref_index));
      double phi_C = 2 * M_PI * rand;
      double sinTheta = sin(theta_C);
      double cosTheta = cos(theta_C);
      double cosPhi = cos(phi_C);
      //photon momentum
      if (uv < 0.001) {  // aligned with z-axis
        w_ph = cosTheta;
      } else {  // general case
        w_ph = w * cosTheta - sinTheta * cosPhi * uv;
      }
      double r_lambda = G4UniformRand();
      double lambda0 = (lambda1 * lambda2) / (lambda2 - r_lambda * (lambda2 - lambda1));
      double lambda = (lambda0 / CLHEP::cm) * 1.e+7;  // lambda is in nm
      wlini.push_back(lambda);
#ifdef EDM_ML_DEBUG
      edm::LogVerbatim("HFShower") << "HFCherenkov::computeNPEinPMT: " << i << " lambda " << lambda << " w_ph " << w_ph
                                   << " aperture " << aperture;
#endif
      if (w_ph > aperture) {  // phton trapped inside PMT glass
        wltrap.push_back(lambda);
        rand = G4UniformRand();
#ifdef EDM_ML_DEBUG
        edm::LogVerbatim("HFShower") << "HFCherenkov::computeNPEinPMT: Random " << rand << " Survive? " << (rand < 1.);
#endif
        if (rand < 1.0) {  // survived all the times and sent to photo-cathode
          wlatten.push_back(lambda);
          double qEffic = computeQEff(lambda);  //Quantum efficiency of the PMT
          rand = G4UniformRand();
#ifdef EDM_ML_DEBUG
          edm::LogVerbatim("HFShower") << "HFCherenkov::computeNPEinPMT: qEffic " << qEffic << " Random " << rand
                                       << " Survive? " << (rand < qEffic);
#endif
          if (rand < qEffic) {  // made photoelectron
            npe_ += 1;
            momZ.push_back(w_ph);
            wl.push_back(lambda);
            wlqeff.push_back(lambda);
          }  // made pe
        }    // accepted all Cherenkov photons
      }      // end of  if(w_ph < w_aperture), trapped inside glass
    }        // end of ++NbOfPhotons
  }          // end of if(NbOfPhotons)}
#ifdef EDM_ML_DEBUG
  edm::LogVerbatim("HFShower") << "HFCherenkov::computeNPEinPMT: npe " << npe_;
#endif
  return npe_;
}

std::vector<double> HFCherenkov::getWLIni() {
  std::vector<double> v = wlini;
  return v;
}

std::vector<double> HFCherenkov::getWLTrap() {
  std::vector<double> v = wltrap;
  return v;
}

std::vector<double> HFCherenkov::getWLAtten() {
  std::vector<double> v = wlatten;
  return v;
}

std::vector<double> HFCherenkov::getWLHEM() {
  std::vector<double> v = wlhem;
  return v;
}

std::vector<double> HFCherenkov::getWLQEff() {
  std::vector<double> v = wlqeff;
  return v;
}

std::vector<double> HFCherenkov::getWL() {
  std::vector<double> v = wl;
  return v;
}

std::vector<double> HFCherenkov::getMom() {
  std::vector<double> v = momZ;
  return v;
}

int HFCherenkov::computeNbOfPhotons(double beta, G4double stepL) {
  double pBeta = beta;
  double alpha = 0.0073;
  double step_length = stepL;
  double theta_C = acos(1. / (pBeta * ref_index));
  double lambdaDiff = (1. / lambda1 - 1. / lambda2);
  double cherenPhPerLength = 2 * M_PI * alpha * lambdaDiff * CLHEP::cm;
  double d_NOfPhotons = cherenPhPerLength * sin(theta_C) * sin(theta_C) * (step_length / CLHEP::cm);
  int nbOfPhotons = int(d_NOfPhotons);
#ifdef EDM_ML_DEBUG
  edm::LogVerbatim("HFShower") << "HFCherenkov::computeNbOfPhotons: StepLength " << step_length << " theta_C "
                               << theta_C << " lambdaDiff " << lambdaDiff << " cherenPhPerLength " << cherenPhPerLength
                               << " Photons " << d_NOfPhotons << " " << nbOfPhotons;
#endif
  return nbOfPhotons;
}

double HFCherenkov::computeQEff(double wavelength) {
  double qeff(0.);
  if (UseNewPMT) {
    if (wavelength <= 350) {
      qeff = 2.45867 * (TMath::Landau(wavelength, 353.820, 59.1324));
    } else if (wavelength > 350 && wavelength < 500) {
      qeff = 0.441989 * exp(-pow((wavelength - 358.371), 2) / (2 * pow((138.277), 2)));
    } else if (wavelength >= 500 && wavelength < 550) {
      qeff = 0.271862 * exp(-pow((wavelength - 491.505), 2) / (2 * pow((47.0418), 2)));
    } else if (wavelength >= 550) {
      qeff = 0.137297 * exp(-pow((wavelength - 520.260), 2) / (2 * pow((75.5023), 2)));
    }
#ifdef EDM_ML_DEBUG
    edm::LogVerbatim("HFShower") << "HFCherenkov:: for new PMT : wavelength === " << wavelength << "\tqeff  ===\t"
                                 << qeff;
#endif
  } else {
    double y = (wavelength - 275.) / 180.;
    double func = 1. / (1. + 250. * pow((y / 5.), 4));
    double qE_R7525 = 0.77 * y * exp(-y) * func;
    qeff = qE_R7525;
#ifdef EDM_ML_DEBUG
    edm::LogVerbatim("HFShower") << "HFCherenkov::computeQEff: wavelength " << wavelength << " y/func " << y << "/"
                                 << func << " qeff " << qeff;
    edm::LogVerbatim("HFShower") << "HFCherenkov:: for old PMT : wavelength === " << wavelength << "; qeff = " << qeff;
#endif
  }
  return qeff;
}

double HFCherenkov::computeHEMEff(double wavelength) {
  double hEMEff = 0;
  if (wavelength < 400.) {
    hEMEff = 0.;
  } else if (wavelength >= 400. && wavelength < 410.) {
    //hEMEff = .99 * (wavelength - 400.) / 10.;
    hEMEff = (-1322.453 / wavelength) + 4.2056;
  } else if (wavelength >= 410.) {
    hEMEff = 0.99;
    if (wavelength > 415. && wavelength < 445.) {
      //abs(wavelength - 430.) < 15.
      //hEMEff = 0.95;
      hEMEff = 0.97;
    } else if (wavelength > 550. && wavelength < 600.) {
      // abs(wavelength - 575.) < 25.)
      //hEMEff = 0.96;
      hEMEff = 0.98;
    } else if (wavelength > 565. && wavelength <= 635.) {  // added later
      // abs(wavelength - 600.) < 35.)
      hEMEff = (701.7268 / wavelength) - 0.186;
    }
  }
#ifdef EDM_ML_DEBUG
  edm::LogVerbatim("HFShower") << "HFCherenkov::computeHEMEff: wavelength " << wavelength << " hEMEff " << hEMEff;
#endif
  return hEMEff;
}

double HFCherenkov::smearNPE(int npe) {
  double pe = 0.;
  if (npe > 0) {
    for (int i = 0; i < npe; ++i) {
      double val = G4Poisson(gain);
      pe += (val / gain) + 0.001 * G4UniformRand();
    }
  }
#ifdef EDM_ML_DEBUG
  edm::LogVerbatim("HFShower") << "HFCherenkov::smearNPE: npe " << npe << " pe " << pe;
#endif
  return pe;
}

void HFCherenkov::clearVectors() {
  wl.clear();
  wlini.clear();
  wltrap.clear();
  wlatten.clear();
  wlhem.clear();
  wlqeff.clear();
  momZ.clear();
}

bool HFCherenkov::isApplicable(const G4ParticleDefinition* aParticleType) {
  bool tmp = (aParticleType->GetPDGCharge() != 0);
#ifdef EDM_ML_DEBUG
  edm::LogVerbatim("HFShower") << "HFCherenkov::isApplicable: aParticleType " << aParticleType->GetParticleName()
                               << " PDGCharge " << aParticleType->GetPDGCharge() << " Result " << tmp;
#endif
  return tmp;
}