Chiral expansion for lattice computations of B⁺ → D⁰K⁺(π⁺) and B⁺ → D⁰K⁺(π⁺) amplitudes

In this work, we suggest that hard-pion chiral perturbation theory may be applicable to the real parts of nonleptonic B⁺ → D⁰P⁺ and B⁺ → D⁰P⁺ (P = K,π) decay amplitudes. These amplitudes play an important role in the extraction of the angle γ in the b−d unitarity triangle of the CKM matrix, and their real parts can be computed using lattice QCD. We construct the leading-order operator in the chiral expansion for these nonleptonic decays, and discuss the generic features of the next-to-leading-order terms.