  We calculate the transition form factor of the neutral pion where one photon
is virtual and another photon is real in the model where the light constituent
quark mass and the quark-pion vertex are taken to be momentum independent.
Radiative corrections to the lowest order triangle quark Feynman amplitude are
calculated. The resummation of the lowest radiative corrections to the virtual
photon vertex is done by applying the Sudakov exponential hypothesis. Using
fitting parameters, the quark mass and the strong coupling constant, the
results on the pion transition form factor are compared with existing data
published by CELLO, CLEO, BaBar and Belle collaborations.
