QCD Phenomena and the Light-Cone Wavefunction of Hadrons

Light-cone Fock-state wavefunctions encode the properties of a hadron in terms of its fundamental quark and gluon degrees of freedom. A recent experiment at Fermilab, E791, demonstrates that the color coherence and shape of light-cone wavefunctions in longitudinal momentum fraction can be directly measured by the high energy diffractive jet dissociation of hadrons on nuclei. Given the proton's light-cone wavefunctions, one can compute not only the quark and gluon distributions measured in deep inelastic lepton-proton scattering, but also the multi-parton correlations which control the distribution of particles in the proton fragmentation region and dynamical higher twist effects. First-principle predictions can be made for structure functions at small and large light-cone momentum fraction $x$. Light-cone wavefunctions also provide a systematic framework for evaluating exclusive hadronic matrix elements, including timelike heavy hadron decay amplitudes and form factors. In principle, light-cone wavefunctions can be computed in nonperturbative QCD by diagonalizing the light-cone Hamiltonian using the DLCQ method, as in dimensionally reduced collinear QCD.