A B-meson is a type of meson so-called because it's composed of one bottom (b) antiquark and one up, down, strange, or charm quark. Its antiparticle, the B-bar meson, consists of a bottom quark and an up, down, strange, or charm antiquark. The B meson is a heavy particle; its mass of 5.28 GeV/c2 (due mostly the high mass of the bottom quark that it contains) is five times greater than that of the proton.


B mesons exhibit CP violation, which makes them ideal particles for studying the tiny differences between matter and antimatter and understanding why there is such a preponderance of matter over antimatter in the present-day universe.