Geant4 Simulations for the Radon Electric Dipole Moment Search at

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Chapter 4 Results This chapter presents the results from the RnEDM Geant4 simulations and outlinesthesensitivityoftheexperiment. Thesensitivitiesarederivedfromthesimulated precession frequencies fit with a function which describes the physics involved in the simulation using a chi-squared minimization method. This method used a maximum likelihood technique specific for counting experiments which are based on the Poisson distribution. The achievable EDM sensitivity according to the Geant4 simulations is discussed. 4.1 γ-Ray Spectroscopy The results from the Geant4 simulations were analyzed using γ-ray spectroscopy techniques. One dimensional γ-ray energy spectra and two dimensional γ-ray energytime matrices were constructed from the Geant4 simulated data. Preserving all energies, times and interaction locations in the output binary data files allowed for a complete reconstruction of the data into spectra and matrices during the sorting process. Sorting the data had three main tasks, firstly to remove any rejected hits 60
(user-defined option), secondly toapply arealisticenergyresolution responsefunction for the detectors (see Section 3.6.2), and finally to generate the output spectrum and matrix files for subsequent analysis. The GRIFFIN detectors can be operated in two different modes to accept “good” events, namely, the suppressed and unsuppressed mode. In the unsuppressed mode, all γ-ray energies deposited in the detectors are accepted as valid hits and recorded in the output files. In the suppressed mode, however, a GRIFFIN detector which registered a γ-ray event in a germanium crystal in coincidence with any of the BGO detectors surrounding that detector would not be included in the output files. This mode significantly reduces the background in the spectrum by suppressing Compton scattering in which a γ-ray scatters out of an HPGe detector without depositing its fullenergy. AlltheanalysispresentedinthisChapterwasconductedinthesuppressed mode. 4.1.1 Efficiencies The first characteristic studied using the Geant4 simulations was the absolute γ- ray photopeak efficiency for the RnEDM experiment. The absolute efficiency of a ring of eight GRIFFIN detectors in both the forward and back configurations is presented in Figure 4.1. The detectors in their highest efficiency mode have an efficiency of 26.3% at 100 keV and 9.7% at 1 MeV, while in the fully suppressed mode they have anefficiencyof17.5%at100keVand6.5%at1MeV.Theremainderofthesimulations were performed with the GRIFFIN detectors in the forward position to maximize the number of counts detected. The efficiency of the entire RnEDM apparatus is lower relative to Figure 4.1 due to the increased probability of γ-ray scattering inside the EDM cell, oven, magnet and shielding. Figure 4.2 studies the decrease in efficiency 61
Page 1 and 2:
GEANT4 SIMULATIONS FOR THE RADON EL
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Dictated but not read. i
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Contents Acknowledgements ii 1 Intr
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4 Results 60 4.1 γ-Ray Spectroscop
Page 9 and 10:
List of Figures 1.1 An illustration
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Chapter 1 Introduction Thesearchfor
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ˆP ր ˆT ց Figure 1.1: An illust
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1.1.1 CP Violation Following the ob
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Figure 1.2: Experimental upper limi
Page 19 and 20: Figure 1.3: Illustration of the dou
Page 21 and 22: Chapter 2 RnEDM Experiment at TRIUM
Page 23 and 24: Figure 2.1: A schematic of the ISAC
Page 25 and 26: a measurement cell. The RnEDM exper
Page 27 and 28: NMR techniques, and supplementing s
Page 29 and 30: Occupied Orbitals Fine Structure Hy
Page 31 and 32: energy levels are separated accordi
Page 33 and 34: (σ + ) along the axis of the B fie
Page 35 and 36: atom and absorbed by another. Radia
Page 37 and 38: anaverageof120kHzphotopeakcountrate
Page 39 and 40: Figure 2.7: One GRIFFIN/TIGRESS HPG
Page 41 and 42: (a) One GRIFFIN detector in the HPG
Page 43 and 44: 3.1 Introduction 3.1.1 Previous Wor
Page 45 and 46: energies, branching ratios, emissio
Page 47 and 48: used around the measurement cell in
Page 49 and 50: 3.2.5 Simulated Data Thecodewaswrit
Page 51 and 52: lower its total energy. Internal co
Page 53 and 54: 10000 1000 2 χ red = 1.21 t 1/2 =
Page 55 and 56: as [47] I(E) = G 2π 3 7 c 6 | M i
Page 57 and 58: was to use an average X-ray energy
Page 59 and 60: 1.5 1.4 1.3 1.2 P = 100% P = 75% P
Page 61 and 62: where (a b c d | e f) are Clebsch-G
Page 63 and 64: 2 2 1.5 J i = 5/2, J f = 5/2 J i =
Page 65 and 66: of radius 10 cm, allowing the GRIFF
Page 67 and 68: (a) Screenshot showing the detector
Page 69: 3.6.2 Output Data and Sort Codes Th
Page 73 and 74: 30 Absolute Efficiency (%) 25 20 15
Page 75 and 76: 11 10 9 8 7 6 5 4 3 2 1 0 1e+06 Cou
Page 77 and 78: 4.2.1 Multipolarity Effects The sha
Page 79 and 80: Figure 4.7: The time projections an
Page 81 and 82: distribution, this average intensit
Page 83 and 84: Table 4.1: The fit results for the
Page 85 and 86: 12 10 linear regression: y = 0.2243
Page 87 and 88: 15 Linear Counts (e+04) 10 5 0 1e+0
Page 89 and 90: Chapter 5 Conclusions and Future Di
Page 91 and 92: simulated given sufficient parent a
Page 93 and 94: Appendix A Figure A.1: Simulated de
Page 95 and 96: Figure A.3: Simulated decay scheme
Page 97 and 98: Figure A.5: Simulated decay scheme
Page 99 and 100: 6 out = (1/(1+∆ˆ2))*(f(k,jf,L1,L
Page 101 and 102: 44 return; 45 end 46 if abs(m) > j
Page 103 and 104: 1 % LegendreP.m 2 function P = Lege
Page 105 and 106: 39 xx(i+1,j+1) = r(i+1,1)*sin((i*re
Page 107 and 108: 11 %warning('m1 + m2 + m3 must equa
Page 109 and 110: 23 end 24 % ////////// 25 j1 = J1;
Page 111 and 112: 33 if L1 == L2 && ∆ == 0 34 title
Page 113 and 114: Bibliography [1] J. M. Pendlebury a
Page 115 and 116: [25] P. G. Bricault, M. Dombsky, Je
Page 117: [47] RichardA.Dunlap. An introducti
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