Large - Q 2 behavior of the pion electromagnetic form factor *

We study the largeQ 2 behavior of the electromagnetic form factor of the pion, which is viewed as a quarkantiquark bound state in a (nongauge) quantum field theory. When the pion's Bethe-Salpeter wave function is expanded in 0(4) partial waves, it is found that the information needed about the partial-wave amplitudes is their scaling behavior at large momentum and the locations of their poles in the complex J plane. This information is determined by using the operator-product expansion, conformal invariance at short distances, and a regularity property that holds at least in the ladder model. The resulting behavior of the form factor is roughly F( Q 2)( Q 2)1, with corrections due to anomalous dimensions.