In particle physics, B mesons are mesons composed of a bottom antiquark and either an up (B
), down (B
), strange (B
s) or charm quark (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.