I was interviewed briefly on ABC's PM program yeterday, to cover this discovery, and LHC-related news more generally. A technical account of the work can be found in the paper LHCb submitted to Phys. Rev. Lett., which is available on the arXiv.
(What I've written simplifies things considerably: for example, these cascade-b's are negatively charged; there's also a matching set of neutral cascade-b's, each with an up quark in place of the down. And why are there three related states close in mass? As well as being an empirical observation, such patterns can be understood by considering the possible ways to combine quarks with various flavours and spins, taking into account the symmetry of the resulting wavefunction in each case. Readers with a considerable amount of university physics should be able to follow the PDG's discussion of the charmed baryons: baryons carrying one unit of “beauty” are an analogous case.)