Abstract
KM2A is one of the main sub-arrays of LHAASO, working on gamma ray astronomy and cosmic ray physics at energies above 10 TeV. Detector simulation is the important foundation for estimating detector performance and data analysis. It is a big challenge to simulate the KM2A detector in the framework of Geant4 due to the need to track numerous photons from a large number of detector units (>6000) with large altitude difference (30 \(\mathrm m\)) and huge coverage (1.3 \(\mathrm km^{2}\)). In this paper, the design of the KM2A simulation code G4KM2A based on Geant4 is introduced. The process of G4KM2A is optimized mainly in memory consumption to avoid memory overflow. Some simplifications are used to significantly speed up the execution of G4KM2A. The running time is reduced by at least 30 times compared to full detector simulation. The particle distributions and the core/angle resolution comparison between simulation and experimental data of the full KM2A array are also presented, which show good agreement.
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Acknowledgements
We would like to thank all staff members who work at the LHAASO site above 4400 meters above sea level year-round to maintain the detector and keep the water recycling system, electricity power supply and other components of the experiment operating smoothly. We are grateful to Chengdu Management Committee of Tianfu New Area for the constant financial support for research with LHAASO data. We deeply appreciate the computing and data service support provided by the National High Energy Physics Data Center for the data analysis in this paper. This research work is also supported by the following grants: The National Key R &D program of China under grants 2018YFA0404201, by the National Natural Science Foundation of China (NSFC) No. 12022502, No. 12205314, No. 12105301, No. 12261160362, No. 12105294, No. U1931201, No. 12393851, No. 12393854. In Thailand, support was provided by the National Science and Technology Development Agency (NSTDA) and the National Research Council of Thailand (NRCT) under the High-Potential Research Team Grant Program (N42A650868).
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Cao, Z., Aharonian, F., An, Q. et al. LHAASO-KM2A detector simulation using Geant4. Radiat Detect Technol Methods (2024). https://doi.org/10.1007/s41605-024-00467-8
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DOI: https://doi.org/10.1007/s41605-024-00467-8