Chiral perturbation theory for SU(3) breaking in heavy-meson systems.

The SU(3)-breaking effects due to light-quark masses on heavy-meson masses, decay constants ({ital F}{sub {ital D}},{ital F}{sub {ital D}{ital s}}), and the form factor for semileptonic {ital {bar B}}{r arrow}{ital D}{sup (*)}{ital l}{bar {nu}}{sub {ital l}} transitions are formulated in chiral perturbation theory, using a heavy-meson effective Lagrangian and expanding in inverse powers of the heavy-meson mass. To leading order in this expansion, the leading chiral logarithms and the required counterterms are determined. At this level, a nonanalytic correction to the mass splittings of {ital O}({ital p}{sup 3}) appears, similar to the one found in light baryons. The correction to {ital F}{sub {ital D}{ital s}}/{ital F}{sub {ital D}} is roughly estimated to be of the order of 10% and, therefore, experimentally accessible, while the correction to the form factor is likely to be substantially smaller. We explicitly check that the heavy-quark symmetry is preserved by the chiral loops.