G4MuonRadiativeDecayChannelWithSpin.hh

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// G4MuonRadiativeDecayChannelWithSpin
//
// Class description:
//
// This class describes radiative muon decay kinematics, but
// gives incorrect energy spectrum for neutrinos.
// Samples Radiative Muon Decay.
// References:
// - TRIUMF/TWIST Technote TN-55:
//   "Radiative muon decay" by P. Depommier and A. Vacheret
// - Yoshitaka Kuno and Yasuhiro Okada
//   "Muon Decays and Physics Beyond the Standard Model"
//   Rev. Mod. Phys. 73, 151 (2001)
 
// Author: P.Gumplinger - Triumf, 25 July 2007   
// Revision: D. Mingming - Center for HEP, Tsinghua Univ., 10 August 2011 
// --------------------------------------------------------------------
#ifndef G4MuonRadiativeDecayChannelWithSpin_hh
#define G4MuonRadiativeDecayChannelWithSpin_hh 1
 
#include <CLHEP/Units/PhysicalConstants.h>
 
#include "globals.hh"
#include "Randomize.hh"
#include "G4ThreeVector.hh"
#include "G4VDecayChannel.hh"
 
class G4MuonRadiativeDecayChannelWithSpin : public G4VDecayChannel
{
  public:
 
    G4MuonRadiativeDecayChannelWithSpin(const G4String& theParentName,
                                              G4double  theBR);
    virtual ~G4MuonRadiativeDecayChannelWithSpin();
 
    virtual G4DecayProducts* DecayIt(G4double);
 
  protected:
 
    G4MuonRadiativeDecayChannelWithSpin(const G4MuonRadiativeDecayChannelWithSpin&);
    G4MuonRadiativeDecayChannelWithSpin& operator=(const G4MuonRadiativeDecayChannelWithSpin&);
      // Copy constructor and assignment operator
  
  private:
 
    G4MuonRadiativeDecayChannelWithSpin();
 
    G4double fron(G4double Pmu, G4double x, G4double y,
                  G4double cthetaE, G4double cthetaG, G4double cthetaEG);
 
    void rn3dim(G4double& x, G4double& y, G4double& z, G4double xlong);
      // Generates random vectors, uniformly distributed over the surface 
      // of a sphere of given radius
 
    G4double atan4(G4double x, G4double y);
};
 
// ------------------------
// Inline methods
// ------------------------
 
inline void G4MuonRadiativeDecayChannelWithSpin::rn3dim(G4double& x,
                                                        G4double& y,
                                                        G4double& z,
                                                        G4double xlong)
{
  G4double a = 0.; G4double b = 0.; G4double c = 0.; G4double r = 0.;
 
  do
  {
    a = G4UniformRand() - 0.5;
    b = G4UniformRand() - 0.5;
    c = G4UniformRand() - 0.5;
    r = a*a + b*b + c*c;
  } while (r > 0.25); // Loop checking, 09.08.2015, K.Kurashige
 
  G4double rinv = xlong/(std::sqrt(r)); 
  x = a * rinv;
  y = b * rinv;
  z = c * rinv;
 
  return;
}
 
inline G4double G4MuonRadiativeDecayChannelWithSpin::atan4(G4double x,
                                                           G4double y)
{
  G4double phi = 0.;
 
  if        (x==0. && y>0.){
    phi = 0.5*CLHEP::pi;
  } else if (x==0. && y<0.){
    phi = 1.5*CLHEP::pi;
  } else if (y==0. && x>0.){
    phi = 0.;
  } else if (y==0. && x<0.){
    phi = CLHEP::pi;
  } else if (x>0.         ){
    phi = std::atan(y/x);
  } else if (x<0.         ){
    phi = std::atan(y/x) + CLHEP::pi;
  }
 
  return phi;
}
 
#endif