123 lines
4.5 KiB
C++
123 lines
4.5 KiB
C++
//$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$//*
|
|
// LOW ENERGY MUON SPIN RELAXATION, ROTATION, RADIATION Geant4 SIMULATION
|
|
// ID : LEMuSRMuonDecayChannel.hh , v 1.0
|
|
// AUTHOR: Taofiq PARAISO based on G4MuonDecayChannel $Id$
|
|
// DATE : 2004-07-13 11:15
|
|
//
|
|
//$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$//
|
|
//
|
|
// & &&&&&&&&&& &&&&&&& &&&&&&&&
|
|
// & & && && & &&
|
|
// & & & & & & &&
|
|
// & &&&&&&& & & &&&&&& &&&&&&&&
|
|
// & & & && & & &&
|
|
// & & && & & && && & &
|
|
// &&&&&&&&&& &&&&&&&&&& & &&&&& && &&&&&&& & &&
|
|
// &
|
|
// &
|
|
// &
|
|
// &
|
|
// MUON DECAY CHANNEL.HH
|
|
//$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$//
|
|
|
|
/**
|
|
* The LEMuSRMuonDecayChannel class contains the implementation of the asymmetric muon decay. The process is applicable to muon (positive or negative) and muonium.
|
|
*
|
|
* It was inspired from the G4MuonDecayChannel method, which did not take into account the spin polarization of the muon.
|
|
*
|
|
* One should notice that recent versions of Geant4 feature a G4MuonDecayChannelWithSpin class, whose role is identical to the class we are describing.
|
|
*
|
|
* The two caracteristics of this process are
|
|
* - The Michel spectrum for e+ energy distribution
|
|
* \image html michel.gif Michel's Spectrum.
|
|
* - The cardioidal angular distribution as a function of the positron energy
|
|
* \image html kardio.gif Cardioid.
|
|
* .
|
|
* The angular direction of the positron emission is in relation with the energy of
|
|
* the positron.
|
|
* The more energy the positron has, the smaller the angle of emission with respect
|
|
* to the muon spin is. The V-A theory predicts the positron rate to be
|
|
* \f[ \mbox{d}\Gamma^2(w,\theta)= \frac{1}{\tau n(w)\left[1+ D(w)cos\theta \right]}\mbox{d}w \mbox{d}(\cos \theta),\f]
|
|
* \f$w\f$ being the ratio between the energy of the emitted positron and the
|
|
* maximal energy, and \f$\theta\f$ the angle between the muon spin and the
|
|
* positron momentum.
|
|
*
|
|
* The distribution \f$n(w)\f$ along energy is given by the Michel's spectrum
|
|
* \f[ n(w)= w^2(3-2w)\f] and the asymmetric factor is given by
|
|
* \f[D(w) = \frac{2w-1}{3-2w}.\f] We assume, here, that the muons are fully
|
|
* polarized.
|
|
*
|
|
* The distribution along energies becomes, for \f$\Theta=0\f$,
|
|
* \f[n(w)+n(w)D(w)= 2w^2\f]
|
|
* and for \f$\Theta = \pi\f$,
|
|
* \f[n(w)-n(w)D(w)= 4(w^2-w^3)\f]
|
|
*
|
|
* The asymmetry can be derived integrating the rate \f$d\Gamma^2\f$,
|
|
* and one should get
|
|
* \f[A(w_{min}, \Theta_0) = \frac{1+\cos\Theta_0}{6}\frac{1+2w_{min}^3-3w_{min}^4}{1-2w_{min}^3+w_{min}^4}\f]
|
|
* where \f$\Theta_0\f$ is the opening angle of the solid angle.
|
|
* This means that if one select all positron energies, \f$w_{min}\simeq 0\f$
|
|
* - \f$A \simeq\frac{1}{3}\f$ for small solid angles
|
|
* - \f$A \simeq\frac{1}{6}\f$ for large solid angles
|
|
|
|
*/
|
|
|
|
#ifndef LEMuSRMuonDecayChannel_h
|
|
#define LEMuSRMuonDecayChannel_h 1
|
|
|
|
|
|
#include "G4ios.hh"
|
|
#include "globals.hh"
|
|
#include "G4VDecayChannel.hh"
|
|
#include "G4DynamicParticle.hh"
|
|
#include "Randomize.hh"
|
|
#include "G4ThreeVector.hh"
|
|
#include "G4Transform3D.hh"
|
|
|
|
class LEMuSRMuonDecayChannel : public G4VDecayChannel
|
|
{
|
|
|
|
// Class Decription
|
|
|
|
public:
|
|
//!Constructor.
|
|
LEMuSRMuonDecayChannel(const G4String& theParentName,
|
|
G4double theBR);
|
|
//! Destructor.
|
|
~LEMuSRMuonDecayChannel();
|
|
|
|
static LEMuSRMuonDecayChannel* pointer;
|
|
static LEMuSRMuonDecayChannel* GetInstance();
|
|
|
|
|
|
void finalize();
|
|
|
|
public: // With Description
|
|
//! \mm
|
|
virtual G4DecayProducts *DecayIt(G4double);
|
|
HepRandomEngine* theEngine;
|
|
G4ThreeVector emomdir;
|
|
|
|
//! Angles.
|
|
G4double alpha,sinalpha, cosalpha, delta, sindelta, cosdelta;
|
|
//! Sines and cosines.
|
|
G4double costheta, sintheta, phi, sinphi, cosphi, theta;
|
|
|
|
inline G4double GetTheta(){return theta;};
|
|
inline G4double GetPhi(){return phi;};
|
|
|
|
|
|
//! Polarized decay
|
|
/*!
|
|
* Gets the muon polarization and launch the Decay it method.
|
|
*/
|
|
G4DecayProducts *DecayItPolarized(G4double,G4ThreeVector polar);
|
|
|
|
|
|
private:
|
|
|
|
|
|
};
|
|
|
|
#endif
|