Geant4 Simulations for the Radon Electric Dipole Moment Search at

10000
1000
2
χ red
= 1.21
t 1/2
= 24.300(6) min
Counts
100
10
0 50 100 150 200
Time (min)
Figure 3.2: Geant4 simulation of the decay of 10 8 223 Rn nuclei detected by a ring of
eight GRIFFIN detectors in their highest efficiency mode with the radiation emitted
isotropically into 4π. The times were binned into seconds and the function used to
fit was y = A 1 + A 2 e −ln(2)t
A 3 , where A 1 is due to background, A 2 is initial count rate
and A 3 is the half-life (t 1/2 ).
simulation. The two options for the emission of radiation were an isotropic distribution
or an angle dependent distribution based on the initial and final states of the
nucleus and the orientation of the nuclear spin in space, described by its magnetic
substate populations.
To generate an isotropic distribution, emitting the radiation evenly into a solid
angle of 4π, the following equations for θ and φ were utilized:
φ = 2πχ 1
θ = cos −1 (1.0−{χ 2 [1.0−cos(α)]})
Where χ i are random numbers generated using the drand48 function and α is the
maximum angle of emission (α = π for emission into 4π radians).
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