Perturbative QCD of hard and soft processes

TL;DR

This paper examines the application of perturbative QCD to high energy processes, analyzing higher order corrections for hard processes and summing contributions for soft processes to understand their behaviors.

Contribution

It provides a detailed analysis of higher order and higher twist corrections in perturbative QCD and connects soft process summations to Regge-like amplitudes.

Findings

Higher order and higher twist effects are crucial for pion form factor behavior.

Summing lowest twist operators yields Regge-like amplitudes.

Perturbative QCD can describe both hard and soft high energy processes.

Abstract

We discuss some problems concerning the application of perturbative QCD to high energy processes. In particular for hard processes, we analyze higher order and higher twist corrections. It is argued that these effects are of great importance for understanding the behaviour of pion electromagnetic form factor at moderately large momentum transfers. For soft processes, we show that summing the contributions of the lowest twist operators leads to a Regge-like amplitude.