CR propagation in the Galaxy with numerical codes.
The precise measurement of cosmic-ray (CR) fluxes at the top of the atmosphere allows us to constrain propagation models very effectively due to its direct dependency on the grammage seen by the particles during their transport in the Galaxy. The knowledge of the processes related to the propagation makes it possible to reconstruct the cosmic-ray source spectrum and thus to constrain the acceleration processes, but also to test the existence of exotic contributions such as the annihilation of dark-matter (DM) particles. In the last years, a fleet of ground-based, balloon-borne, and spacecraft instruments have measured CR species fluxes and $\gamma$-rays emissions produced during their propagation with unprecedented accuracy. Exploiting the data collected by these experiments requires reliable and detailed calculations using numerical models. In my talk I will present DRAGON2 a new code to simulate CR propagation, including realistic models of the Galaxy and all the relevant transport processes.