Using Field Theory in Hadron Physics

Abstract

This decade has seen a marvelous return to quantum field theory among theorists in high energy physics. The compelling beauty of non-Abelian gauge theories, the striking empirical support for spontaneous symmetry breaking in weak interaction theories, the deep connection between asymptotic freedom and the approximate scaling in inelastic lepton scattering on hadrons, the entrancing suggestion of quark confinement-all this and more has drawn our focus once again on quantum field theories. We have learned to view field theory as providing us with fundamental degrees of freedom rather than thinking that each new particle or resonance as requiring a new field for its description. Indeed the idea that some small set of degrees of freedom (quarks and gluons) provides the basis for all observed mesons and baryons seems to be a concrete realization of the ideas of “nuclear democracy” advocates of the last decade. [Increasing numbers of them have been seen with path integrals and Lagrangians lately.] It makes explicit the concept that all hadrons are composites; not of each other, though through unitarity all the hadrons can become the other hadrons within the restrictions of conservation of charge, baryon number, isospin, etc. It is a deeper way: they are all composites of quarks and gluons.