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Question Beta Decay 

Keywords: Beta Decay
Forum: Physics List
Date: 01 Dec, 2003
From: <jelenas1@hotmail.com>

Hi

I am trying to model free neutron beta decay. However, the G4 model for beta decay is too simple for my purposes, and I have to modify quite a bit of it. For instance, the present model assumes the proton momentum to be zero, and works mainly with the electron and anti-neutrino in implementing conservation laws. I need to include the proton into the calculations also.

Unfortunitely, the present model is not very explicit, and some parts of it are quite difficult to understand, which also makes modifying it quite difficult.

I think I've managed to decipher most of it, but the while loop in the code segment below from G4NeutronBetaDecayChannel is giving me a lot of trouble. I think it's performing some sort of Von Neumann rejection.

Below, xmax is the mass difference between the parent and daughters, and aENuCorr is the electron-antineutrino correlation factor, -0.102.

  // calcurate electron energy
  G4double x;                    // Energy of electron
  G4double p;                    // momentum of electron
  G4double m = daughtermass[0];  //Mass of electron
  G4double w;                    // cosine of electron-neutrino angle
  G4double r;  
  G4double r0;
  do {
      x = xmax*G4UniformRand();
      p = sqrt(x*(x+2.0*m));
      w = 1.0-2.0*G4UniformRand();
      r = p*(x+m)*(xmax-x)*(xmax-x)*(1.0+aENuCorr*p/(x+m)*w);
      r0 = G4UniformRand()*(xmax+m)*(xmax+m)*xmax*xmax*(1.0+aENuCorr);
  } while (r < r0);   

I have looked in the physics reference manual, but this doesn't have a lot of information. Any help, therefore, on the code segment above, or any additional information on the workings of the neutron decay class would be highly appreciated.

Thanks,

Jelena

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1 None: Re: Beta Decay   (Wellisch, J.P. - 09 Dec, 2003)
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