antibottom

Antibottom refers to the antiparticle of the bottom quark, denoted b̄. Like the bottom quark, the antibottom carries spin 1/2 and participates in the strong, weak, and electromagnetic interactions, but its quantum numbers are opposite in certain respects. The electric charge of the antibottom is +1/3 e (opposite to the bottom quark’s −1/3 e). Its mass is effectively the same as that of the bottom quark, with a value around 4.18 GeV/c^2 in common schemes. In quantum chromodynamics, the antibottom also carries anti-color charge, reflecting its status as an antiparticle of a colored quark.

In bound states, antibottom quarks appear primarily in mesons when paired with light quarks. Examples include the B+ (u b̄), B0 (d b̄), and B̄0_s (s b̄) mesons, where the antibottom combines with a light quark. The corresponding antiparticles of these mesons contain a bottom quark instead of an antibottom. Antibottom quarks also occur in antibaryons containing an anti-b quark, such as anti-Lambda_b^0. Free quarks do not exist due to confinement; the antibottom is always found within hadrons.

Production and decay: antibottom quarks are produced in high-energy collisions alongside bottom quarks, forming bb̄ pairs in processes governed by quantum chromodynamics. They decay via the weak interaction through transitions described by the CKM matrix, commonly leading to final states that include charm or up quarks, leptons, and neutrinos. The lifetimes of hadrons containing bottom or antibottom quarks are on the order of 1 picosecond to a few picoseconds.

Significance: studying systems with antibottom quarks, especially B mesons and anti-b baryons, provides insight into CP violation, the CKM matrix, and tests of the Standard Model in heavy-flavor physics and QCD.