Resummation of threshold logarithms in deeply-virtual Compton scattering

I derive an all-order resummation formula for the logarithmically enhanced contributions proportional to $\frac{\alpha_s^n}{x \pm \xi} \log (\frac{\xi \pm x}{2\xi})^k$ in the coefficient function of deeply-virtual-Compton scattering and the pion-photon transition form factor in momentum space. The resummation is performed at the next-to-next-to-leading logarithmic accuracy. The key observation is that the non-singlet coefficient function itself factorizes in the $x \rightarrow \pm \xi$ limit, which allows for a resummation using renormalization group equations