Quantum chromodynamics

Definition

Quantum Chromodynamics (QCD) is the theory describing the strong interaction, one of the fundamental forces in particle physics, which acts between quarks and gluons. It explains how quarks are held together within protons, neutrons, and other hadrons.

5 Must Know Facts For Your Next Test

1. QCD is a part of the Standard Model of particle physics.
2. Quarks come in six flavors: up, down, charm, strange, top, and bottom.
3. The force carriers in QCD are gluons, which themselves carry color charge.
4. Color confinement means that quarks cannot be isolated as single particles; they are always found in groups forming hadrons.
5. Asymptotic freedom describes how quarks interact more weakly at high energies or short distances.

Review Questions

• What particles are affected by Quantum Chromodynamics?
• Explain the concept of color confinement in QCD.
• What is asymptotic freedom and how does it relate to the behavior of quarks at high energies?

Related terms

Gluon:

A massless elementary particle that acts as the exchange particle for the strong force between quarks.

Hadrons:

Composite particles made up of quarks held together by the strong force; includes protons and neutrons.

Standard Model:

The theory describing three of the four known fundamental forces (electromagnetic, weak, and strong interactions) and classifying all known elementary particles.