The analytic behavior of the heavy-light meson form factor is investigated using several relativistic examples including unconfined, weakly confined, and strongly confined mesons. It is observed that confinement erases the anomalous threshold singularity and also induces an essential singularity at the normal annihilation threshold. In the weak confinement limit, the would-be anomalous threshold contribution is identical to that of the real singularity on its spacelike side.

• Received 31 January 1997

DOI:https://doi.org/10.1103/PhysRevD.56.238