Hard pion chiral perturbation theory for B→π and D→π formfactors

We use one-loop Heavy Meson Chiral Perturbation Theory (HMChPT) as well as a relativistic formulation to calculate the chiral logarithms mπ2log(mπ2/μ2) contributing to the formfactors of the semileptonic B→π decays at momentum transfer q2 away from qmax2=(mB−mπ)2. We give arguments why this chiral behaviour is reliable even in the energy regime with hard or fast pions. These results can be used to extrapolate the formfactors calculated on the lattice to lower light meson masses.