Dynamical Higher-Twist and High x Phenomena: A Window to Quark-Quark Correlations in QCD

Measurements of the power-law corrections to Bjorken scaling and the behavior of structure functions in the highly stressed $x_{bj} \to 1$ regime of electroproduction can lead to new information on the quark-quark correlations controlling the nucleon wavefunction at far-off-shell kinematics. Electroproduction on nuclei at $ A > x_{bj} > 1$ is sensitive to hidden-color components of the nuclear wavefunction. A distinctive dynamical higher-twist ${\cal O}(1/Q^2)$ correction, which is dynamically enhanced at high $x_{bj}$, can arise from the interference of amplitudes where the lepton scatters from two different valence quarks of the target. Measurements of the parity-violating left-right asymmetry $A_{LR}$ in elastic and inelastic polarized electron scattering at large $x_{bj}$ can confirm the structure of the quark-quark correlations and other QCD physics at the amplitude level.