Light-cone behavior of hadronic wavefunctions in QCD and experimental consequences

[摘要] NOTE: Text or symbols not renderable in plain ASCII are indicated by [...].Abstract is included in .pdf document.Light-cone behavior of hadronic wavefunctions in QCD and experimental consequences.Predictions are made for the high energy behavior of hadronic structure functions and form factors in Quantum Chromodynamics (QCD). These predictions follow from ladder-approximation calculations of the light-cone behavior of pion and nucleon Bethe-Salpeter wavefunctions. For the pion, some justification for the ladder approximation is found in its agreement with the operator-product expansion of the wavefunction. Our model gives logarithmic corrections to the asymptotic form factor expressions obtained by Brodsky and Farrar and also makes predictions for the threshold behavior of structure functions. We find Ezawa's results, [...], [...] for the pion and nucleon transverse structure functions, respectively, with additional powers of 1n(1-x). A careful examination of the pion result suggests that an infrared singularity in the wavefunction may produce a slower falloff near threshold. For the longitudinal structure functions of the pion and nucleon, we find [...] and [...] threshold behavior, modulo logarithms. In the nucleon structure function calculation, it is noted that photons having momentum near threshold strike only quarks having spin parallel to that of the parent nucleon. This gives W[...](neutron)/W[...](proton) -> 3/7 as x->1. These results are consistent with experiment, although experimental error prevents a convincing test at present. A prediction is made for the magnitude of the asymptotic pion form factor and found to be in reasonable agreement with experiment. We find that the Brodsky-Farrar rules do not automatically give [...] behavior for the N[...] transition form factor. If the amplitudes for a photon to strike quarks with either spin direction are equal, the model gives [...] behavior for the N[...] transition form factor and the neutron F[...] form factor, consistent with experiment.

[发布机构] University:California Institute of Technology;Department:Physics, Mathematics and Astronomy

[关键词] Physics