B meson

In particle physics, B mesons are mesons composed of a bottomantiquark and either an up (B
), down (B
), strange (B
_s) or charmquark (B
_c). The combination of a bottom antiquark and a top quark is not thought to be possible because of the top quark's short lifetime. The combination of a bottom antiquark and a bottom quark is not a B meson, but rather bottomonium, which is something else entirely.

Each B meson has an antiparticle that is composed of a bottom quark and an up (B
), down (B
), strange (B
_s) or charm (B
_c) antiquark respectively.