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21 - Gauge theories, QCD and the renormalization group

Published online by Cambridge University Press:  04 August 2010

Elliot Leader
Affiliation:
Birkbeck College, University of London
Enrico Predazzi
Affiliation:
Università degli Studi di Torino, Italy
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Summary

In the previous chapter we studied the general ideas of renormalization of a field theory, in particular, the freedom in the choice of a renormalization scheme and the consequences thereof as embodied in the renormalization group. For simplicity we talked mainly in terms of scalar φ4 theory. But we did illustrate the very important property of asymptotic freedom that emerges when these results are used in QCD.

In this chapter we show how to extend these ideas to the realistic case of gauge theories, and especially to QCD. We begin with a general outline of gauge theories and point out some of their subtleties, highlighting differences between QCD and QED. We then extend the renormalization group results of Chapter 20 to the case of QCD.

Introduction

In earlier chapters, and in those to follow, we constantly quote QCD corrections to naive quark–parton model estimates in various processes. It is felt at present that QCD is a serious candidate for the theory of strong interactions. QCD has many beautiful properties. It is a non-Abelian gauge theory describing the interaction of massless spin ½ objects, the ‘quarks’, which possess an internal degree of freedom called colour, and a set of massless gauge bosons (vector mesons), the ‘gluons’ which mediate the force between quarks in much the same way that photons do in QED. Loosely speaking, the quarks come in three colours and the gluons in eight.

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Publisher: Cambridge University Press
Print publication year: 1996

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