Mystery Meson

X(3872) was found among the decay products of so-called beauty mesons - sub-atomic particles that are produced in large numbers at the Tsukuba "meson factory". It weighs about the same as a single atom of helium and exists for only about one billionth of a trillionth of a second before it decays into other longer-lived, more familiar particles. Although this is extremely short-lived by human standards, scientists say that a billionth of a trillionth of a second is nearly an eternity for a sub-atomic particle this heavy. Particles smaller than the atom are grouped into families depending upon their mass, spin and electric charge. But X(3872) is peculiar in that it does not fit easily into any known particle scheme and, as a result, has attracted a considerable amount of attention from the worlds physics community.
http://news.bbc.co.uk/2/hi/science/nature/3277579.stm