The use of Geant4 for simulations of a plastic beta-detector and its application to efficiency calibration

TL;DR

This paper demonstrates how Geant4 simulations can accurately model a plastic beta-detector's response, aiding in precise efficiency calibration crucial for nuclear physics measurements testing the Standard Model.

Contribution

It introduces a detailed Monte Carlo simulation approach using Geant4 for calibrating plastic beta-detectors, enhancing the accuracy of beta-branching ratio measurements.

Findings

Simulation results agree well with measured beta-spectra

The study improves detector efficiency calibration accuracy

Supports high-precision tests of the Standard Model

Abstract

Precise beta-branching-ratio measurements are required in order to determine ft-values as a part of our program to test the Electroweak Standard Model via unitarity of the Cabibbo-Kobayashi-Moskawa matrix. For the measurements to be useful in this test, their precision must be close to 0.1 %. In a branching-ratio measurement, we position the radioactive sample between a thin plastic scintillator used to detect beta-particles, and a HPGe detector for gamma-rays. Both beta singles and beta-gamma coincidences are recorded. Although the branching ratio depends most strongly on the HPGe detector efficiency, it has some sensitivity to the energy dependence of the beta-detector efficiency. We report here on a study of our beta-detector response function, which used Monte Carlo calculations performed by the Geant4 toolkit. Results of the simulations are compared to measured beta-spectra from several standard beta-sources.