Quark-quark double scattering in eA DIS and its contribution to quark and antiquark fragmentation functions are investigated with the generalized factorization of the relevant twist-four processes in pQCD. It is shown that the resulting modifications to quark and anti-quark fragmentation functions are different. While the numerical size of these effects cannot be determined from pQCD, the struc...

Modifications to quark and antiquark fragmentation functions due to quark-quark (antiquark) double scattering in nuclear medium are studied systematically up to order O(αs) in deeply inelastic scattering (DIS) off nuclear targets. At the order O(αs), twist-four contributions from quark-quark (antiquark) rescattering also exhibit the Landau-Pomeranchuck-Midgal (LPM) interference feature similar ...

We report on a calculation of one-loop weak corrections to polarized quark-gluon scattering and the corresponding crossed channels. Such contributions are suppressed formally by one power of αs relative to W− or Z−mediated quark-quark scattering, but would enable the spin asymmetry of the gluon distribution to contribute to parity-violating asymmetries that will soon be investigated in polarize...

A review on the requirements of chiral symmetry on effective quark models is presented. The connection between the pion Salpeter amplitude and the mass gap equation is discussed. Hadronic scattering, notably, π π scattering is presented. The constraints imposed by chiral symmetry between difractive quark scattering and quark-quark annihilation is presented. Hadronic coupled channels as a conseq...

I introduce a gauge invariant decomposition of the nucleon spin into quark helicity, quark orbital, and gluon contributions. The total quark (and hence the quark orbital) contribution is shown to be measurable through virtual Compton scattering in a special kinematic region where single quark scattering dominates. This deeply-virtual Compton scattering (DVCS) has much potential to unravel the q...

The high–energy quark–quark scattering amplitude is calculated first in the case of scalar QCD, using Fradkin’s approach to derive the scalar quark propagator in an external gluon field and computing it in the eikonal approximation. The results are then extended to the case of “real” (i.e., fermion) QCD. The high–energy quark–quark scattering amplitude turns out to be described by the expectati...

The high–energy quark–quark scattering amplitude is calculated first in the case of scalar QCD, using Fradkin’s approach to derive the scalar quark propagator in an external gluon field and computing it in the eikonal approximation. The results are then extended to the case of “real” (i.e., fermion) QCD. The high–energy quark–quark scattering amplitude turns out to be described by the expectati...