$D^*D\pi$ form factor revisited

Abstract

The $D^*D\pi$ form factor is evaluated in a QCD sum rule calculation for both $D$ and $\pi$ off-shell mesons. We study the Borel sum rule for the three-point function of one pseudoscalar, one axial and one vector meson currents. We find that the momentum dependence of the form factors is very different if the $D$ or the $\pi$ meson is off-shell, but they lead to the same coupling constant in the $D^*D\pi$ vertex.