The Galactic $\gamma$-ray diffuse emission is produced by the interaction of cosmic rays (CRs) with ambient gas and radiation fields. Studying this radiation helps us to reconstruct particle transport and distribution in the Galaxy. We will present the analysis of HAWC (High Altitude Water-Cherenkov) data to measure the spectrum and the angular distribution of the diffuse emission from the Galactic Plane.
In the future, we will use these HAWC measurements to constrain particle transport properties in different regions of the Galactic Plane, such as close to the Galactic Centre, comparing them to the predictions of transport models implemented with the DRAGON code, which solves the CR transport equation in the Galaxy under general conditions including inhomogeneous and anisotropic diffusion. In particular, we use HAWC results to scrutiny a model based on inhomogeneous diffusion which - better than conventional models - provides a good description of the diffuse emission measured by Fermi-LAT and Milagro along the inner Galactic plane and in the Galactic center region.