Novel Nuclear Effects in QCD: The Non-Universality of Nuclear Antishadowing and the Implications of Hidden Color

Abstract

The shadowing and antishadowing of nuclear structure functions in the Gribov‐Glauber picture is due to the destructive and constructive interference of amplitudes arising from the multiple‐scattering of quarks in the nucleus, respectively. The diffractive contributions to deep inelastic scattering includes Pomeron and Odderon contributions from multi‐gluon exchange as well as Reggeon quark‐exchange contributions. The coherence of multi‐step nuclear processes leads to shadowing and antishadowing of the electromagnetic nuclear structure functions in agreement with measurements. This picture also leads to substantially different antishadowing for charged and neutral current reactions, thus affecting the extraction of the weak‐mixing angle θW. The fact that Reggeon couplings depend on the quantum numbers of the struck quark implies non‐universality of nuclear antishadowing for charged and neutral currents as well as a dependence of antishadowing on the polarization of the beam and target. The implications of hidden color degrees of freedom in the nuclear wavefunction is also briefly discussed.