Spectral energy distribution of γ-ray from the Sgr B complex. The grey bands represent the error of the Fermi-LAT measurement and consist of both systematic and statistic errors. The stars (with associated errors) represent the diffuse γ-ray flux discovered by HESS (Aharonian et al. 2006), and the dot-dashed line is the power law obtained using the photon index and normalisation obtained from the original HESS paper reporting its discovery. The dotted line represents the predicted γ-ray spectrum obtained by assuming that the CR spectrum in the Sgr B region is the same as the local CR spectrum measured by PAMELA.