Hard processes in quantum chromodynamics

Dokshitzer, Dyakonov, Troyan.

The use of Quantum Chromodynamics (QCD) in treating the hadronic world has become an overwhelming trend in particle physics. Owing to the asymptotic freedom of QCD, one can use perturbative methods to describe hard hadronic processes, i.e. those in which small distances as compared to hadron size are important. This paper is devoted to an improved perturbative QCD analysis of a wide class of hard processes. We start with the deep inelastic lepton-hadron scattering and the inclusive e+e~ annihilation to hadrons, and show how and to what extent QCD imitates the parton model. We move further to hard semi-inclusive processes, and demonstrate that in this case the QCD predictions differ drastically from those of the parton model. The approach outlined in the paper paves the ‘ way for a detailed quantitative description of hard processes (provided QCD is the right theory). Special attention is given to the underlying physics. In particular, a possible influence of the hitherto unknown confinement mechanism on perturbative QCD analysis is discussed.