Since the late 1990s, physicists have staged an unprecedented, international effort to determine properties of B mesons--those mesons that contain the second-heaviest type of quark, the bottom or b quark. Large particle accelerators in California and Japan are participating in that work (SN: 3/3/01, p.
So, physicists must turn to theory to distinguish those features due exclusively to the decay of the b quark from the elaborate dance of quarks, antiquarks, and gluons inside a decaying B meson.
Ideally, physicists would study b quarks isolated from all other particles because it's in the details of the disintegrations of those quarks themselves that researchers expect any signs of new phenomena to be most apparent.
Therefore, the systems that are best suited for study in quark models are the heavy quark system which contain c or b quarks
. The bare masses of u, d, and s quarks are 2 MeV, 4 MeV, and 96 MeV, respectively .