Impact of Geant4's Electromagnetic Physics Constructors on Accuracy and Performance of Simulations for Rare Event Searches

TL;DR

This paper evaluates how different electromagnetic physics constructors in Geant4 affect the accuracy and computational performance of simulations for rare event searches, crucial for background prediction in low background physics experiments.

Contribution

It provides a systematic comparison of Geant4 electromagnetic physics constructors' impact on simulation accuracy and performance in rare event search scenarios.

Findings

Physics constructor choice influences total energy deposition predictions.

Different constructors vary in computational efficiency.

Results guide optimal constructor selection for specific experimental setups.

Abstract

A primary objective in contemporary low background physics is the search for rare and novel phenomena beyond the Standard Model of particle physics, e.g. the scattering off of a potential Dark Matter particle or the neutrinoless double beta decay. The success of such searches depends on a reliable background prediction via Monte Carlo simulations. A widely used toolkit to construct these simulations is Geant4, which offers the user a wide choice of how to implement the physics of particle interactions. For example, for electromagnetic interactions, Geant4 provides pre-defined sets of implementations: physics constructors. As decay products of radioactive contaminants contribute to the background mainly via electromagnetic interactions, the physics constructor used in a Geant4 simulation may have an impact on the total energy deposition inside the detector target. To facilitate the selection of physics constructors for simulations of experiments that are using CaWO$_4$ and Ge targets, we quantify their impact on the total energy deposition for several test cases. These cases consist of radioactive contaminants commonly encountered, covering energy depositions via $\alpha$, $\beta$, and $\gamma$ particles, as well as two examples for the target thickness: thin and bulky. We also consider the computing performance of the studied physics constructors.