Pion helicity structure and its consequence for the hard scattering form factor

In a study of the elastic pion form factor for large momentum transfers based on a modified perturbative QCD (PQCD) approach the authors have included, in the light-cone representation, helicity components of the wave function that are customarily neglected. Along with the inclusion of transverse momentum, this gives a large suppression of the form factor from the prediction of the original hard scattering model based on PQCD in the Q2 domain where experimental data are available. They conclude that nonperturbative contributions will dominate in this region