Speaker
Description
The Geant4 toolkit is widely used for modelling light-nuclei beam fragmentation in human tissue and other radiological studies (see, for example, [1]). Precise and fast modelling of secondary fragments resulting from beam fragmentation in tissue is vital for studying the radiobiological effects of heavy ion therapy [1]. Short $^{16}$O–$^{16}$O and $^{20}$Ne–$^{20}$Ne runs have been conducted at the LHC to study small systems [2]. Spectator fragments with a Z/A ratio similar to $^{16}$O can be transported in the LHC alongside the initial nuclei. The fragmentation of $^{16}$O, particularly the alpha yields, should be modelled to evaluate these effects [3].
A new model for the fragmentation of the light excited nuclei was developed. It can be used both as a fragmentation model in Geant4 and as a separate code to model fragmentation in light nuclei collisions. A model physics performance was validated with FORTRAN77 reference implementation by A. Botvina [4]. The implementation employs modern C++ features and a systematic caching strategy: precomputing valid decay channels indexed by mass ($A$) and charge ($Z$), storing light nuclear properties in a perfect-hashing table, and minimizing dynamic memory allocations through move semantics and lightweight programming patterns. This design ensures thread-safety and adherence to Geant4 coding guidelines while maintaining a memory footprint of under 25 MB. The optimized model achieves significant speed-up along with optimal memory usage compared to the previous version from Geant4 v9.2. After, the revisited code was validated to demonstrate its physics performance. The code has been included in Geant4 v11.4 release.
References
[1] I. Pshenichnov et al., Nucl. Instr. and Meth. B, 268, 604 (2010)
[2] https://home.cern/news/news/accelerators/first-ever-collisions-oxygen-lhc
[3] A. Svetlichnyi et al., Physics 5, 381 (2023)
[4] J.P. Bondorf et al., Physics Reports, 257, 133 (1995)