Anticharm

Anticharm refers to the antiquark of the charm quark, denoted c̄. In the Standard Model, quarks carry color charge and have spin 1/2; antiquarks carry the corresponding anti-color and opposite quantum numbers. The charm quark has electric charge +2/3e, so the anticharm carries -2/3e. Like other quarks, it participates in strong, weak, and electromagnetic interactions and combines with other quarks to form hadrons. The baryon number of an antiquark is -1/3.

In hadron spectroscopy, states containing an anticharm quark include mesons such as the anti-D mesons: anti-D^0 (c̄ u) and D^− (c̄ d). Anticharm can also appear in the baryon sector as the antiparticle of charmed baryons, for example in the antiparticles of Λ_c^+ states. Because of confinement, quarks are not found free; anticharm quarks are observed only as parts of hadrons or through the production of charm–anticharm pairs in high-energy processes.

Production and decays: In high-energy collisions, charm and anticharm quark pairs are produced, then hadronize into charmed mesons and baryons. Weak decays of hadrons containing an anticharm contribute to flavor physics and CP violation studies. The term “anticharm” is primarily used in the context of quark flavor notation and is less common in everyday discussions of hadrons compared with the term “charm.”

History and notation: The concept follows from Dirac’s theory of antimatter and the quark model; c̄ is the standard symbol used in particle physics to denote the charm antiquark.