gluoni

Gluoni is the Italian term for gluons, the gauge bosons of quantum chromodynamics (QCD), the theory of the strong interaction. They are massless, spin-1 particles that carry color charge and act as the force carriers between quarks. Unlike photons in quantum electrodynamics, gluons themselves carry color and can interact with each other, a consequence of the non-Abelian SU(3) gauge symmetry of QCD.

There are eight independent gluon states, corresponding to the eight generators of SU(3). In practical terms, gluons come in eight color-anticolor combinations; they couple to quarks with the strong coupling constant g_s. The QCD Lagrangian includes a term for the gluon field strength F^a_{μν} and a covariant derivative D_μ that contains the gluon fields, describing quark-gluon and gluon-gluon interactions.

Gluons are massless, so they propagate at the speed of light. However, they cannot be observed in isolation due to color confinement: color-charged particles and their carriers are not found free in nature. At short distances, asymptotic freedom makes the strong force weaker, enabling perturbative calculations in high-energy processes.

In high-energy experiments, gluons participate in scattering and radiation, and can split into quark-antiquark pairs, contributing to jet production. The discovery of three-jet events in electron-positron annihilation and subsequent jet studies provided indirect evidence for gluons. To date, no free gluon has been observed; gluons have been inferred from the behavior of hadrons and from parton showers in collider experiments.