Question

The quarks in a particle are confined, meaning individual quarks cannot be directly observed. Are gluons confined as well? Explain

Short answer

A hadron does contain gluons. A meson is exchanged instead of a gluon in hadron-hadron interactions because gluon exchange would violate quark confinement.

Step-by-step solution

Definition of quark particle

A quark is a fundamental constituent of matter and a type of elementary particle. Quarks combine to form composite particles known as hadrons, the most stable of which are protons and neutrons, which form the building blocks of atomic nuclei. Up quarks, down quarks, and electrons make up all commonly observed matter.

Explanation

Quark confinement is a result of color confinement, which is a broader term that states that "colored" particles cannot exist on their own. This also applies to gluons that are colored by nature and are therefore confined to exist within a hadron.

A consequence of this can be seen in hadron-hadron interactions. Strong interactions are mediated by mesons rather than gluons in these cases, as is the case in proton-neutron interactions, which are mediated by a π⁰ -meson.