Three-particle contributions to the renormalisation of B-meson light-cone distribution amplitudes

We study light-cone distribution amplitudes of heavy-light systems, such as a B-meson. By an explicit computation, we determine how two-parton distribution amplitudes mix with three-parton ones at one loop: phi(+) is shown to mix only into itself, whereas phi-mixes with the difference of three-parton distribution amplitudes Psi(A)-Psi(V). We determine the corresponding anomalous dimension and we check the gauge independence of our result by considering a general covariant gauge. Finally, we comment on some implications of our result for phenomenological models of these distribution amplitudes.