A VecGeom navigator plugin for Geant4

VecGeom is a geometry modeller library with hit-detection features as needed by particle detector simulation at the LHC and beyond. It was incubated by a Geant-R&D initiative and the motivation to combine the code of Geant4 and ROOT/TGeo into a single, better maintainable piece of software within the EU-AIDA program. So far, VecGeom is mainly used by LHC experiments as a geometry primitive library called from Geant4, where it has had very positive impact on CPU time due to its faster algorithms for complex primitives. In this contribution, we turn to a discussion of how VecGeom can be used as the navigating library in Geant4 in order to benefit from both the fast geometry primitives as well as its vectorized navigation module. We investigate whether this integration provides the speed improvements expected, on top of that obtained from geometry primitives. We discuss and benchmark the application of such a VecGeom-navigator plugin to Geant4 for the use-case of ALICE and show paths towards usage for other experiments. Lastly, an update on the general developments of VecGeom is given. This includes a review of how developments in VecGeom can further benefit from interfacing with external ray-tracing kernels such as Intel-Embree.