The Double Scattering Contribution to $b_1(x,Q^2)$ in the Deuteron

Abstract

We study the tensor structure function $b_1\text{xq}$ in deep inelastic scattering (DIS) of an electron from a polarized deuteron target. We model the electron-nucleon cross section at the starting point for $Q^2$ evolution by vector-meson-dominance (VMD). Shadowing due to the double-scattering of vector mesons, along with the presence of a d-state admixture in ground state deuteron wave function gives rise to a non-vanishing contribution to $b_1\text{xq}$. Although significant at large Bjorken $x$, the restoration of rotational symmetry for small $x$ ($\le 10^{-3}$) requires that $b_1^{(2)}\text{xq}$ approach zero as $x\to 0$ in this model. If the model is valid, it should apply within the range of present fixed target experiments.

Comments: 15 pages, 5 figures, BoxedEPS, REVTeX; correspondence to jaffe@mitlns.mit.edu ; discussion of impact parameter dependence of shadowing has been corrected, confirming a more significant enhancement of $b_1$ at small-x, figures have been changed