QCD

Asymptotic freedom

In previous sections, wave functions of some baryons in terms of quark fields have been discussed. Originally, in the 1960's, quarks have been introduced as some kind of "bookkeeping device" in order to construct hadrons (mesons and baryons) from them and to deduce the multiplet structure of these bound states. Only later, in the 1970's, QCD has been established as the theory underlying the so far merely poorly understood strong force. In QCD, quarks and antiquarks play the role of the matter fermions, interacting through the excvange of gauge bosons, the gluons. In contrast to its archetype, QED, however, in QCD the quanta of field theory cannot be found as free particles. They always are confined in hadrons. This striking contrast can be traced back to the structure of the Lagrangian, in particular to the fact that QCD is a non-Abelian gauge theory. The new effect here is a phenomenon known as asymptotic freedom.
  1. The effect of hadrons as bound states of quarks (and gluons?)
  2. Asymptotic freedom: The "what" and the "why"
  3. How to measure &alphas