My current research focus is on fundamental physics with neutrons. I work on the future neutron to antineutron search experiment at the European Spallation source (HIBEAM-NNBAR), of which I am one of the co-proposers. I am involved in many aspects of the experiment, but especially on the design of the annihilation detector, which is the main necessary instrumentation to reconstruct the final state arising from an antineutron annihilation with a neutron or a proton in a carbon target. The development of the detector requires detailed simulations, mostly using the Geant4 package, an activity I coordinate in the collaboration