Performance of Geant4 in simulating semiconductor particle detector response in the energy range below 1 MeV

Abstract

Geant4 simulations play a crucial role in the analysis and interpretation of experiments providing low energy precision tests of the Standard Model. This paper focuses on the accuracy of the description of the electron processes in the energy range between 100 and 1000 keV. The effect of the different simulation parameters and multiple scattering models on the backscattering coefficients is investigated. Simulations of the response of HPGe and passivated implanted planar Si detectors to β particles are compared to experimental results. An overall good agreement is found between Geant4 simulations and experimental data.

Measurement of theβ-asymmetry parameter ofCu67in search for tensor-type currents in the weak interaction

“…The angular distribution of the electrons emitted during the β − decay of 67 Cu and 68 Cu was observed with two planar high purity Ge (HPGe) particle detectors with a sensitive diameter of 16 mm and a thickness of 4 mm produced in the Nuclear Physics Institute inŘež, Prague [31][32][33]. Their thickness was selected to fully stop the high endpoint energy β electrons from 68 Cu.…”

“…Detailed models of the HPGe particle detectors were implemented and verified by test measurements [33,50]. The reliability of the simulations was further verified by comparing experimental and simulated isotropic data for both 67 Cu and 68 Cu.…”

Precision Measurement of the β Asymmetry in Spin-Polarized K37 Decay

“…The position of each decay was randomly sampled from the observed distribution, modeled as a Gaussian ellipsoid and included the effects of the cloud's expansion and drift. We used the emstandard opt3 variation of the standard physics lists as well as nondefault values of 1 µm for the cut-for-secondaries parameter and a range factor of f R = 0.002 in order to simulate the low-E β scattering of β + more accurately [34]. The multiple scattering (MSC) of e ± was simulated with the Urban MSC model of Ref.…”

Kinematic sensitivity to the Fierz term ofβ-decay differential spectra

“…For example, atomic effects due to screening are known to be large for low energy β particles from transitions in medium and heavy mass nuclei [39] and require therefore particular attention in precision measurements. On the instrumental side, the effects of scattering of electrons from matter in the setup and their back-scattering from detector surfaces also increases toward lower energies and the description of the processes with current simulation tools [40,41] is not yet sufficiently accurate for competitive measurements of the β spectrum shape. These two criteria tend also to disfavor transitions with small endpoint energies in the selection of candidates.…”