Geant3s

Geant3s refers to a family of detector simulation software projects based on the GEANT3 framework. In this sense, Geant3s are not a single package but a collection of applications developed by various high-energy physics experiments to model the interaction of particles with matter and the response of detectors. They typically rely on the legacy Fortran-based GEANT3 core, augmented with experiment-specific geometry, materials, magnetic fields, and digitization steps.

Geant3s emerged from the widespread adoption of GEANT3 in particle and nuclear physics during the late 1980s and 1990s. They were configured to reflect individual detector layouts, incorporating geometry builders, material libraries, and tailored physics lists to simulate electromagnetic and hadronic processes, energy deposition, scattering, decays, and secondary particle production. Output from these simulations often fed into reconstruction algorithms and performance studies, enabling optimization of detector design and data analysis strategies.

Architecturally, a Geant3s workflow centers on defining a detector model, loading a magnetic field map, running particle transport and interactions through materials, and producing hit information and digitized signals that resemble real experimental data. Because the core code was written in Fortran and designed for flexibility, many Geant3s included substantial customization by collaboration-specific teams, making each Geant3s instance somewhat unique.

Legacy and transition: with the advent of Geant4 in the early 2000s, many experiments migrated toward newer, object-oriented toolkits. Some Geant3s projects were retired or rewritten, while others were maintained for archival data reprocessing or compatibility. Geant3s remain of historical interest for understanding early detector simulations and the evolution of particle-transport software.