ar X iv : h ep - p h / 06 12 12 1 v 1 1 1 D ec 2 00 6 Heavy meson semileptonic decays in two dimensions in the large N c

We study QCD in 1 + 1 dimensions in the large Nc limit using light-front Hamiltonian perturbation theory in the 1/Nc expansion. We use this formalism to exactly compute hadronic transition matrix elements for arbitrary currents at leading order in 1/Nc, which we use to write the semileptonic differential decay rate of a heavy meson and its moments. We then compare with the results obtained using an effective field theory approach based on perturbative factorization, with the intention of better understanding quark-hadron duality. A very good numerical agreement is obtained between the exact result and the result using effective theories.