Heavy- to light-meson transition form factors

Semileptonic heavy -> heavy and heavy -> light meson transitions are studied as a phenomenological application of a heavy-quark limit of Dyson-Schwinger equations. Employing two parameters: E, the difference between the mass of the heavy meson and the effective-mass of the heavy quark; and Lambda, the width of the heavy-meson Bethe-Salpeter amplitude, we calculate f_+(t) for all decays on their entire kinematically accessible t-domain. Our study favours f_B in the range 0.135-0.17 GeV and with E=0.44 GeV and 1/Lambda = 0.14 fm we obtain f_+^{B pi}(0) = 0.46. As a result of neglecting 1/m_c-corrections, we estimate that our calculated values of \rho^2 = 0.87 and f_+^{DK}(0)=0.62 are too low by approximately 15%. However, the bulk of these corrections should cancel in our calculated values of Br(D -> \pi l nu)/Br(D -> K l nu)=0.13 and f_+^{D pi}(0)/f_+^{DK}(0) = 1.16.