Exclusive chromomagnetism in heavy-to-light FCNCs

We compute matrix elements of the chromomagnetic operator, often denoted by O-8, between B/D states and light mesons plus an off-shell photon by employing the method of light-cone sum rules at leading twist-2. These matrix elements are relevant for processes such as B -> K*l(+)l(-) and they can be seen as the analogues of the well-known penguin form factors T-1,T-2,T-3 and f(T). We find a large CP-even phase for which we give a long-distance interpretation. We compare our results to QCD factorization for which the spectator photon emission is end-point divergent. The analytic structure of the correlation function used in our method admits a complex anomalous threshold on the physical sheet. The meaning and handling within the sum rule approach of the anomalous threshold is discussed. DOI: 10.1103/PhysRevD.87.074008