Antitriplets

Antitriplets are a term used in quantum chromodynamics to denote the anti-fundamental representation of the color SU(3) group. In this context, quarks transform as the fundamental triplet 3 of SU(3) color, while antiquarks transform as its complex conjugate, the anti-triplet 3̄. The anti-triplet and triplet share the same dimension, three, but they transform oppositely under color rotations.

In practical terms, an antiquark carries an anticolor corresponding to one of the three colors: anti-red, anti-green, or anti-blue. The color representations combine to form color-neutral, observable states. For example, the combination 3 ⊗ 3̄ decomposes into a color singlet and an octet: 1 ⊕ 8. This underpins the formation of mesons, which are color-singlet quark–antiquark pairs. Baryons, consisting of three quarks, achieve a color-singlet state through the appropriate combination of three triplets, which includes a totally antisymmetric component.

Mathematically, in SU(3) language, the triplet is the fundamental representation with Dynkin label (1,0) and the anti-triplet is its complex conjugate with label (0,1). In particle physics, antitriplets are essential for describing antiquarks and their participation in hadron structure, as well as interactions mediated by gluons, which carry color charge.

Antitriplets are distinct from antiquarks in separate flavor space; in color space they provide the necessary conjugate representation to pair with triplets. The concept is central to the quark model, color confinement, and the description of mesons and baryons.