Logarithmic approximations, quark form factors, and quantum chromodynamics

Abstract

The structure of perturbative quantum chromodynamics in kinematic regimes characterized by two large but different mass scales is investigated. The double-leading-logarithm approximation is reviewed, and the roles of the various elements of this approximation are emphasized. In particular, the question of whether a suppression of cross sections in the limit of small angles and large ratios of kinematic variables is predicted by the theory is treated at various levels of approximation. Improved analysis suggests that no suppression is predicted. It is argued, however, that a definitive answer can only arise from an exact analysis.