IMPLICATIONS OF GLUON RADIATION EFFECTS AND SOFT TRANSVERSE MOMENTA FOR THE NUCLEON SUBSTRUCTURE IN QCD

Abstract

The proton and neutron helicity-conserving form factors in the spacelike region are studied within a convolution scheme which takes into account: (i) soft-gluon radiative corrections via Sudakov-type form factors, and (ii) the intrinsic k⊥-dependence of the nucleon wave function. Results are presented for a complete set of nucleon distribution amplitudes which comply with QCD sum rules. Implications for the end point behavior of nucleon distribution amplitudes are discussed in the context of Appell decompositions. The calculated leading-order perturbative contribution to both form factors falls short compared to the existing data, indicating substantial higher-order perturbative corrections (i.e. a large K factor) and/or sizeable soft contributions, e.g., higher-twist effects, at presently accessible momentum-transfer values.