antistrange

The antistrange quark, denoted as s-bar (s̄), is the antiparticle of the strange quark in the Standard Model. Like the strange quark, it is a spin-1/2 fermion that carries color charge and participates in the strong, electromagnetic, and weak interactions. Its mass is similar to that of the strange quark, and it combines with other quarks to form hadrons just as s does.

In flavor quantum numbers, the antistrange quark carries baryon number B = -1/3 and strangeness S = +1 (the strange quark has S = -1). It has the same magnitude of electric charge as the strange quark but with the opposite sign, giving s-bar an electric charge of +1/3 e. As an antiparticle, s-bar is part of color-anticolor configurations in hadrons.

Antistrange quarks appear in various hadrons. In mesons, they are found in kaons such as K+ (u s-bar) and K0 (d s-bar), and in their antiparticles K- (s u-bar) and anti-K0 (s-bar d-bar). In baryons, they contribute to antiparticles such as anti-Lambda (anti-u, anti-d, anti-s). The presence of s-bar in these states determines their strangeness content and affects their decays and interactions.

Production and interactions: antistrange quarks are produced in high-energy processes through quark-antiquark pair creation in strong or electromagnetic interactions. Weak decays can change flavor and alter the strange content of hadrons containing s-bar. The study of systems with strange and antistrange quarks, including K0–anti-K0 mixing and kaon decays, has been central to flavor physics and tests of CP violation and the Standard Model.