PhotonTool.h

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/*
 * PhotonTool.h
 *
 *  Interface for the tool that transforms deposited energies to photons exiting
 *  the fibre ends
 *
 *  Created on 03 Mar 2020
 *      Author: Valerio Formato (based on code by Junjing Wang)
 */

#ifndef HERD_PHOTONTOOL_H_
#define HERD_PHOTONTOOL_H_

#include <random>

#include "algorithms/digitization/FitDigitizationTools/Units.h"

// this in c++17 will become
// namespace Herd::FitDigitizationTools {
namespace Herd {
namespace FitDigitizationTools {

class PhotonTool {

public:
  PhotonTool() : m_generator{}, m_flat_dist{0, 1} {};
  ~PhotonTool() = default;

  double numExpectedPhotons(double effective_energy);
  int numObservedPhotons(double num_expected_photons);
  double averagePropagationTime(double distToSiPM) {
    // because the default unit is cm, convert mm to m 1e-3
    return (distToSiPM * 1e-2) * m_fibrePropagationSpeed;
  };

  double generateScintillationTime() { return -log(m_flat_dist(m_generator)) * m_scintillationDecayTime; }

  void generatePhoton(double &time, double &wavelength, double &posX, double &posZ, double &dXdY, double &dZdY);
  // double &dXdY, double &dZdY, double &newTheta, double &newPhi);

private:
  void generatePosAndDir(double &posX, double &posZ, double &dXdY, double &dZdY);

  bool m_generateWavelength = true;            // "Flag for turning on random wavelength generation"
  const double m_photonsPerMeV = 455.;         //"Average number of photons per MeV"
  const double m_wavelengthShift = 405. * nm;  // "Shift parameter of Wavelength distributions"};
  const double m_wavelengthScale = 77.89 * nm; // "Scale parameter of Wavelength distributions"};
  const double m_wavelengthShape = 0.44;       //  "Shape parameter of Wavelength distributions"};

  // Fibre properties
  const double m_effFibreR = 0.0115;                // "Effective Radius of the fibre"};
  const double m_fibrePropagationSpeed = 6.0;       //(ns/m)   //"Light propagation speed in fibre"};
  const double m_scintillationDecayTime = 2.8 * ns; //"Decay time of scintillation light release"};

  // Random number generators
  std::mt19937 m_generator;
  std::uniform_real_distribution<double> m_flat_dist;
  std::poisson_distribution<unsigned int> m_pois_dist;
  std::normal_distribution<double> m_gauss_dist;
};

} // namespace FitDigitizationTools
} // namespace Herd
#endif