Gabriele Cosmo
167 lines
8.0 KiB
C++
167 lines
8.0 KiB
C++
//
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// ********************************************************************
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// * License and Disclaimer *
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// * *
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// * The Geant4 software is copyright of the Copyright Holders of *
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// * the Geant4 Collaboration. It is provided under the terms and *
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// * conditions of the Geant4 Software License, included in the file *
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// * LICENSE and available at http://cern.ch/geant4/license . These *
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// * include a list of copyright holders. *
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// * *
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// * Neither the authors of this software system, nor their employing *
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// * institutes,nor the agencies providing financial support for this *
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// * work make any representation or warranty, express or implied, *
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// * regarding this software system or assume any liability for its *
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// * use. Please see the license in the file LICENSE and URL above *
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// * for the full disclaimer and the limitation of liability. *
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// * *
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// * This code implementation is the result of the scientific and *
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// * technical work of the GEANT4 collaboration. *
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// * By using, copying, modifying or distributing the software (or *
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// * any work based on the software) you agree to acknowledge its *
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// * use in resulting scientific publications, and indicate your *
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// * acceptance of all terms of the Geant4 Software license. *
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// ********************************************************************
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//
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#ifndef PAR03EMSHOWERMODEL_HH
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#define PAR03EMSHOWERMODEL_HH
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#include "G4VFastSimulationModel.hh"
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class Par03EMShowerMessenger;
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class G4FastSimHitMaker;
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/**
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* @brief Example fast simulation model for EM showers.
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*
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* Parametrisation of electrons, positrons, and gammas. It is triggered if those
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* particles enter the detector so that there is sufficient length for the
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* shower development (max depth, controlled by the UI command).
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*
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* Parametrisation is based on the PDG chapter on the electromagnetic cascades
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* (chapter 33.5). Longitudinal profile of the shower is described with Gamma
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* distribution, with beta parameter on average equal to 0.5 (default value,
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* Fig. 33.21), and alpha parameter calcluated from the incident particle energy
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* and material of the detector (critical energy) following Eq.(33.36).
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*
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* Transverse profile is in this model approximated by the Gaussian
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* distribution, with the mean along the shower axis (incident particle momentum
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* direction) and the standard deviation calculated from the detector material
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* (Moliere radius). This assumes that EM shower is in 90% contained within a
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* cylinder of radius equal to Moliere radius, and that area below Gaussian
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* distribution from `mean-1.645 sigma` to `mean+1.645 sigma` is also equal to
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* 90% of total distribution.
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*
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* Parameters of both distributions (alpha, beta for Gamma, sigma for Gaussian)
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* can be overwritten by UI commands.
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*
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* Parametrisation creates N hits of same energy (N can be set by UI command),
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* using rejection sampling to generate position along shower axis from Gamma
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* distribution, and then sampling from uniform and Gaussian distributions to
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* sample phi and radius, respectively. Created hits are deposited in the
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* detector using its readout geometry, using the helper class G4FastSimHitMaker
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* that locates the volume, and calls appropriate sensitive detector class.
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*
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* PDG Chapter 33:
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* https://pdg.lbl.gov/2019/reviews/rpp2018-rev-passage-particles-matter.pdf
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*
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*/
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class Par03EMShowerModel : public G4VFastSimulationModel
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{
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public:
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Par03EMShowerModel(G4String, G4Region*);
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Par03EMShowerModel(G4String);
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~Par03EMShowerModel();
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/// There are no kinematics constraints. True is returned.
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virtual G4bool ModelTrigger(const G4FastTrack&) final;
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/// Model is applicable to electrons, positrons, and photons.
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virtual G4bool IsApplicable(const G4ParticleDefinition&) final;
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/// Take particle out of the full simulation (kill it at the entrance
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/// depositing all the energy). Calculate energy deposited in the detector
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/// according to Gamma distribution (along the particle direction) and
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/// Gaussian distribution in the transverse direction. Mean of the Gaussian is
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/// centred on the shower axis. Create energy deposits on a cylindrical mesh.
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/// Parameters of the mesh (size, number of cells) and of the distributions
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/// (alpha, beta for Gamma, sigma for Gaussian) can be set with UI commands.
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virtual void DoIt(const G4FastTrack&, G4FastStep&) final;
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/// Print current settings.
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void Print() const;
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/// Set standard deviation of a Gaussian distribution that describes the
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/// transverse shower profile.
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inline void SetSigma(const G4double aSigma) { fSigma = aSigma; };
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/// Get standard deviation of a Gaussian distribution that describes the
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/// transverse shower profile.
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inline G4double GetSigma() const { return fSigma; };
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/// Set alpha parameter of a Gamma distribution that describes the
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/// longitudinal shower profile.
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inline void SetAlpha(const G4double aAlpha) { fAlpha = aAlpha; };
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/// Get alpha parameter of a Gamma distribution that describes the
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/// longitudinal shower profile.
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inline G4double GetAlpha() const { return fAlpha; };
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/// Set beta parameter of a Gamma distribution that describes the longitudinal
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/// shower profile.
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inline void SetBeta(const G4double aBeta) { fBeta = aBeta; };
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/// Get beta parameter of a Gamma distribution that describes the longitudinal
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/// shower profile.
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inline G4double GetBeta() const { return fBeta; };
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/// Set number of (same energy) hits created in the parametrisation.
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inline void SetNbOfHits(const G4int aNumber) { fNbOfHits = aNumber; };
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/// Get number of (same energy) hits created in the parametrisation.s
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inline G4int GetNbOfHits() const { return fNbOfHits; };
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/// Set maximum depth of shower created in fast simulation. It is expressed in
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/// units of radiaton length.
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inline void SetLongMaxDepth(const G4double aDepth)
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{
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fLongMaxDepth = aDepth;
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};
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/// Get maximum depth of shower created in fast simulation. It is expressed in
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/// units of radiaton length.
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inline G4double GetLongMaxDepth() const { return fLongMaxDepth; };
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private:
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/// Gamma distribution
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inline G4double Gamma(G4double x, G4double alpha, G4double beta)
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{
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return (std::pow(beta, alpha) / std::tgamma(alpha) * std::pow(x, alpha - 1) *
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std::exp(-beta * x));
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}
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/// Gaussian distribution
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inline G4double Gaussian(G4double x, G4double sigma = 1, G4double x0 = 0)
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{
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G4double tmp = (x - x0) / sigma;
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return (1.0 / (std::sqrt(2 * CLHEP::pi) * sigma)) * std::exp(-tmp * tmp / 2);
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}
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private:
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/// Messenger for configuration
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Par03EMShowerMessenger* fMessenger;
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/// Helper class for creation of hits within the sensitive detector
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std::unique_ptr<G4FastSimHitMaker> fHitMaker;
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/// Standard deviation of the Gaussian distribution
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/// Can be changed with UI command `/Par03/fastSim/transverseProfile/sigma
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/// <sigma>`
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/// If sigma is smaller than 0, it will be estimated from the detector
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/// material (Moliere radius).
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G4double fSigma = -1;
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/// Alpha parameter of the Gamma distribution
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/// Can be changed with UI command `/Par03/fastSim/longitudunalProfile/alpha
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/// <alpha>`
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/// If alpha is smaller than 0, it will be estimated from particle energy and
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/// the detector material.
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G4double fAlpha = -1;
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/// Beta parameter of the Gamma distribution
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/// Can be changed with UI command `/Par03/fastSim/longitudinalProfile/beta
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/// <beta>`
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G4double fBeta = 0.5;
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/// Number of (same energy) hits created by the parametrisation. Can be
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/// changed with UI command `/Par03/fastSim/numberOfHits <number>`
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G4int fNbOfHits = 100;
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/// Maximum depth of a shower created in fast simulation.
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/// It is expressed in units of radiation length. Can be changed with UI
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/// command `/Par03/fastSim/longitudinalProfile/maxDepth <depth>`
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G4double fLongMaxDepth = 30;
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};
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#endif /* PAR03EMSHOWERMODEL_HH */ |