  We compute the imaginary part of the 2-loop vertex corrections in the QCD
Factorization framework for hadronic two-body decays as B -> pi pi. This
completes the NNLO calculation of the imaginary part of the topological tree
amplitudes and represents an important step towards a NNLO prediction of direct
CP asymmetries in QCD Factorization. Concerning the technical aspects, we find
that soft and collinear infrared divergences cancel in the hard-scattering
kernels which demonstrates factorization at the 2-loop order. All results are
obtained analytically including the dependence on the charm quark mass. The
numerical impact of the NNLO corrections is found to be significant, in
particular they lead to an enhancement of the strong phase of the
colour-suppressed tree amplitude.

High Energy Physics - Phenomenology