Heavy mesons in two dimensions

The large-mass limit of QCD uncovers symmetries that are not present in the QCD Lagrangian. These symmetries have been applied to physical (finite mass) systems, such as {ital B} and {ital D} mesons. We explore the validity of this approximation in the 't Hooft model (two-dimensional QCD in the large-{ital N} approximation). We find that the large-mass approximation is good, even at the charm mass, for form factors, but it breaks down for the pseudoscalar decay constant.