Comment on “Gauge invariance and kT-factorization of exclusive processes” [arXiv:0807.0296]

Abstract We point out mistakes made in the one-loop calculation of some diagrams for the process π γ ∗ → γ in the preprint arXiv:0807.0296 , and present correct results. Especially, we have difficulty to understand their argument that a highly off-shell gluon generates a light-cone (infrared) singularity. It is shown by means of the Ward identity that the gauge-dependent light-cone singularity found in arXiv:0807.0296 does not exist. It is then shown that a hard kernel derived in the k T factorization of exclusive processes is gauge invariant and free of the light-cone singularity.