In this paper we present the recent developments in the Geant4 hadronic framework, as well as in some of the existing physics models.
Geant4 is the main simulation toolkit used by the LHC experiments and therefore a lot of effort is put into improving the physics mod els in order for them to have more predictive power. As a consequence, the code complexity increases, which requires constant improvement and optimisation on the programming side. At the same time, we would like to review and eventually reduce the complexity of the hadronic software framework.
As an example, a factory design pattern has been applied in Geant4 to avoid duplications of objects, like cross sections, which can be used by several processes or physics models. This approach has been applied also for physics lists, to provide a flexible configuration mechanism at run-time, based on macro files. Moreover, these developments open the future possibility to build Geant4 with only a specified sub-set of physics models.
Another technical development focused on the reproducibility of the simulation, i.e. the possibility to repeat an event once the random generator status at the beginning of the event is known. This is crucial for debugging rare situations which may occur after long simulations. Moreover, reproducibility in normal, sequential Geant4 simulation is an important prerequisite to verify the equivalence with multi-threaded Geant4 simulations.