The Strong Interactions

2021 ◽  
pp. 422-441
Author(s):  
J. Iliopoulos ◽  
T.N. Tomaras

For many years strong interactions had a well-deserved reputation for complexity. Their apparent strength rendered perturbation theory inapplicable. However, in the late 1960s a series of experiments studying the deep inelastic electron–nucleon scattering showed that at a more fundamental level, the strong interactions among the constituent quarks can be described perturbatively by an asymptotically free gauge theory. We present the theory of quantum chromodynamics, the unbroken gauge theory of the colour SU(3) group. We show how we can compute its predictions in the kinematic regions in which perturbation theory is applicable, but also in the strong coupling regime through numerical simulations on a space-time lattice.

1994 ◽  
Vol 05 (02) ◽  
pp. 195-200
Author(s):  
CARLETON DeTAR

Through numerical simulations over the past decade we have made significant progress toward solving quantum chromodynamics (QCD), the widely accepted theory of the strong interactions. Quantitatively respectable results are beginning to emerge. We are also gaining new qualitative insights into the workings of the theory that will assist in the design and analysis of experiment. I give a few examples of recent progress in lattice QCD and discuss goals and prospects for computations using the coming generation of teraflops-scale supercomputers.


2021 ◽  
Vol 36 (21) ◽  
pp. 2130012
Author(s):  
Michael Creutz

Quantum chromodynamics (QCD), the theory of the strong interactions, involves quarks interacting with non-Abelian gluon fields. This theory has many features that are difficult to impossible to see in conventional diagrammatic perturbation theory. This includes quark confinement, mass generation and chiral symmetry breaking. This paper is a colloquium level overview of the framework for understanding how these effects come about.


2005 ◽  
Vol 20 (22) ◽  
pp. 5202-5213
Author(s):  
MAX KLEIN

HERA is the world's only accelerator to study inelastic electron-proton scattering at the energy frontier which uniquely allows the partonic structure of the proton and the theory of strong interactions, QCD, to be deeply explored. A review is given here of recent results from the HERA ep collider experiments H1 and ZEUS and the fixed target eN spin experiment HERMES as was presented to the 32nd Rochester conference at Beijing in summer 2004. The summary comprises new results on the quark and gluon structure of the proton, on the strong coupling constant αs, on the production of charm and beauty particles and on hard diffractive scattering. New ideas and developments in HERA physics are presented as are the first measurements with the upgraded polarised ep collider.


2019 ◽  
Vol 34 (25) ◽  
pp. 1950144 ◽  
Author(s):  
Weihua Yang

Quantum chromodynamics is a non-Abelian gauge theory of strong interactions, in which the parity symmetry can be violated by the nontrivial [Formula: see text]-vacuum tunneling effects. The [Formula: see text]-vacuum induces the local parity-odd domains. Those reactions that occur in these domains can be affected by the tunneling effects and quantities become parity-odd. In this paper we consider the fragmentation process where parity-odd fragmentation functions are introduced. We present the fragmentation functions by decomposing the quark–quark correlator. Among the total 16 fragmentation functions, eight of them are parity conserved, and the others are parity violated. They have a one-to-one correspondence. Positivity bounds of these one-dimensional fragmentation functions are shown. To be explicit, we also introduce an operator definition of the parity-odd correlator. According to the definition, we give a proof that the parity-odd fragmentation functions are local quantities and vanish when sum over all the hadrons [Formula: see text].


Author(s):  
John Iliopoulos

All ingredients of the previous chapters are combined in order to build a gauge invariant theory of the interactions among the elementary particles. We start with a unified model of the weak and the electromagnetic interactions. The gauge symmetry is spontaneously broken through the BEH mechanism and we identify the resulting BEH boson. Then we describe the theory known as quantum chromodynamics (QCD), a gauge theory of the strong interactions. We present the property of confinement which explains why the quarks and the gluons cannot be extracted out of the protons and neutrons to form free particles. The last section contains a comparison of the theoretical predictions based on this theory with the experimental results. The agreement between theory and experiment is spectacular.


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