Why are there eight gluons?

Answer 1

Unlike the single photon of QED or the three W and Z bosons of the weak interaction, there are eight independent types of gluon in QCD - Quantum chromodynamics (abbreviated as QCD) is the theory of the strong interaction (colour force), a fundamental force describing the interactions of the quarks and gluons found in hadrons (such as the proton, neutron or pion).

This may be difficult to understand intuitively. Quarks may carry three types of color charge; antiquarks carry three types of anticolor. Gluons may be thought of as carrying both color and anticolor or as describing how quark color changes during interactions.

Technically, QCD is a gauge theory with SU(3) gauge symmetry. Quarks are introduced as spinor fields in Nf flavours, each in the fundamental representation (triplet, denoted 3) of the colour gauge group, SU(3). The gluons are vector fields in the adjoint representation (octets, denoted 8) of colour SU(3). For a general gauge group, the number of force-carriers (like photons or gluons) is always equal to the dimension of the adjoint representation. For the simple case of SU(N), the dimension of this representation is N2−1.

Answer 2

In particle physics, gluons are subatomic particles that cause quarks to interact, and are indirectly responsible for the binding of protons and neutrons together in atomic nuclei.

In technical terms, they are vector gauge bosons that mediate strong color charge interactions of quarks in quantum chromodynamics (QCD). Unlike the neutral photon of quantum electrodynamics (QED), gluons themselves participate in strong interactions. The gluon has the ability to do this as it carries the color charge and so interacts with itself, making QCD significantly harder to analyse than QED.
Gluon
Composition: Elementary particle
Family: Boson
Group: Gauge boson
Interaction: Strong interaction
No. of types: 8
Mass: 0
Electric charge: 0
Spin: 1

Answer 3

Gluons are subatomic particles that cause quarks to interact, and are indirectly responsible for the binding of protons and neutrons together in atomic nuclei.
The experimental evidence of gluons was found in 1979 and at that time only 8 are discovered. So we are also following that.

Answer 4

In particle physics, gluons are subatomic particles that cause quarks to interact, and are indirectly responsible for the binding of protons and neutrons together in atomic nuclei.

In technical terms, they are vector gauge bosons that mediate strong color charge interactions of quarks in quantum chromodynamics (QCD). Unlike the neutral photon of quantum electrodynamics (QED), gluons themselves participate in strong interactions.