Color Exchange in Near-forward Hard Elastic Ecattering

Abstract

We study the large-$t$ small angle behavior of quark-quark elastic scattering. We employ a factorization procedure previously developed for fixed angle scattering, which depends on the color structure of the factorized hard subprocess. We find an evolution in $t$ that (in leading logarithmic approximation) becomes diagonal in a singlet-octet basis in the $t$-channel as $s\rightarrow \infty$. Octet exhange in the hard scattering is associated with the familiar `reggeized', $s^{\alpha_g(t)}$ behavior, which arises from $s$-dependence in Sudakov suppression. In contrast, Sudakov suppression for $t$-channel singlet exchange in the hard scattering is $s$-independent. In general, these contributions are mixed by soft corrections, which, however, cancel in many experimental amplitudes and cross sections.