Related papers: QCD beyond diagrams
These lectures provide an overview of Quantum Chromodynamics (QCD), the $SU(3)_C$ gauge theory of the strong interactions. After briefly reviewing the empirical considerations which lead to the introduction of {\it colour}, the QCD…
We discuss a set of recently discovered quadratic relations between gauge theory amplitudes. Such relations give additional structural simplifications for amplitudes in QCD. Remarkably, their origin lie in an analogous set of relations that…
Systematic approaches to building up gauge invariant descriptions of charged fields, such as electrons or quarks, are described. Physically relevant descriptions must then be singled out from a multiplicity of possibilities and to this end…
Charge symmetry breaking in the strong interaction occurs because of the difference between the masses of the up and down quarks. At present the Standard Model can't explain the observed mass pattern (M(n), M(p), m(u), m(d) etc.) and their…
In this talk we review relations and representations of primitive QCD tree amplitudes. Topics covered include the BCJ relations, the CHY representation, and the KLT relations. We will put a special emphasis on how these relations and…
QCD in a five-dimensional sliced bulk with chiral extra-quarks on the boundaries is generically free from the strong CP problem. Accidental axial symmetry is naturally present except for suppressed breaking interactions, which plays a role…
Heavy quark bound state systems, mesons and hybrids, are discussed in the framework of the QCD effective field theory called potential Non-Relativistic QCD.
The standard model of strong interactions invokes the quantum chromodynamics (QCD) of quarks and gluons interacting within a fluid. At sufficiently small length scales, the effective interactions between the color charged particles within…
Several topics in hadron physics at different scales of resolution are discussed. First, deep-inelastic scattering from nucleons and nuclei is viewed in a light-cone coordinate space picture. Then the smooth transition from parton to hadron…
Quantum Chromodynamics (QCD) predicts that topological charge changing transitions will take place in hot quark matter. Such transitions induce P- and CP-violating effects. We will show that in the presence of a magnetic field these…
Just as Quantum Electrodynamics describes how electrons are bound in atoms by the electromagnetic force, mediated by exchange of photons, Quantum Chromodynamics (QCD) describes how quarks are bound inside hadrons by the strong force,…
Vacuum of Quantum Chromodynamics in very strong (hadron-scale) magnetic fields exhibits many interesting nonperturbative effects. Some of these effects can be studied with the help of lattice simulations in quenched QCD. We review our…
In the physical vacuum of QCD, the energy density of light-quark fields strongly coupled to slowly varying gluon fields can be negative. The states that drive this energy density lowest are condensates of pairs of quarks and antiquarks of…
QCD perturbation theory using quark and gluon propagators that have an extra term at zero four-momentum is equivalent to standard PQCD in the presence of massless quark and gluon pairs in the perturbative vacuum. We verify at low orders in…
The cross sections of heavy quark production in $pp$ collision and for their photo- and electroproduction are calculated in the framework of QCD. The virtual nature of the interacting gluons as well as their transverse motion and different…
String theory has been initially derived from motivations coming from strong interaction phenomenology,but its application faced deep conceptual and practical difficulties. The strong interactions found their theoretical foundation…
Physics is an experimental science; and a constructive feedback between theory and extant and forthcoming experiments is necessary if an understanding of nonperturbative QCD is to be achieved. The Dyson-Schwinger equations connect…
We construct a model for the quark-gluon vertex of Landau gauge QCD. This is of twofold interest: on the one hand the quark-gluon interaction is at the heart of quark confinement, on the other hand it is a central element in hadron…
The aim of this introductory lecture is to review the arguments, according to which the symmetry properties of the strong interaction reveal themselves at low energies. I first discuss the symmetries of QCD, then sketch the method used to…
This is a written version of two lectures given at the First School on Field Theory and Gravitation in Vitoria (Brasil) April 15-19, 1997. We discuss the foundation of QCD as the theory of strong interactions and the perturbative analysis…