Heavy-to-light chromomagnetic matrix element

We report the computation of the matrix element of the chromomagnetic operator of the flavour changing neutral current (FCNC)-type between a B- or D-meson state and a light hadron & an off-shell photon. The computation is carried out by using the light-cone sum rules (LCSR). It is found that the matrix element exhibits large strong phase for which we give a long distance interpretation. The analytic structure of the correlation function in use admits a complex anomalous threshold on the physical sheet. The meaning and handling within the sum rule approach of the latter is discussed. We compare our results to QCD factorisation for which spectator photon emission is end-point divergent.