QUARK STRUCTURE OF THE PION AND PION FORM-FACTOR

We consider the pion structure in the region of low and moderately high momentum transfers: at low Q(2), the pion is treated as a composite system of constituent quarks; at moderately high momentum transfers, Q(2) = 10-25 GeV2, the pion form factor is calculated within perturbative QCD taking into account one-gluon hard exchange. Using the data on the pion form factor at Q(2) < 3 GeV2 and the pion axial-vector decay constant, we reconstruct the pion wave function in the soft and intermediate regions. This very wave function combined with the one-gluon hard scattering amplitude allows a calculation of the pion form factor in the hard region Q(2) = 10-25 GeV2. A specific feature of the reconstructed pion wave function is a quasizone character of the q ($) over bar q excitations. On the basis of the obtained pion wave function and the data on deep inelastic scattering off the pion, the valence quark distribution in a constituent quark is determined.