The “wow” is about the size of the headline. Not about the particle.
There are particles, and there are particles. This isn’t a new elementary particle. It isn’t a new object built from new and unknown elementary particles. It’s yet another hadron — a particle built from well-known and well-understood quarks, antiquarks and gluons — of which we know hundreds, including the neutron and proton. In fact, this particular hadron is a new member of a well-known family, and was fully expected.
So this is a nice little discovery, but not very newsworthy. (And it won’t help with the Higgs search in any appreciable or meaningful way, despite the BBC’s attempt to make a link between them.)
If you remember hydrogen from freshman year in college, you can quickly understand what this new “particle” is — by some measures it is not really a new particle at all, but rather a new configuration of old particles. Do you remember that hydrogen has quantum numbers n and l (principal and orbital)? And that there are all sorts of “orbitals”, or “energy levels”, labeled by n and l? A sketch of their energies versus n and l is given in the figure.
Well, now imagine this: if instead of calling these “orbitals” or “states” or “levels” of an atom, you called each of those a different “particle”; the n=1, l=0 state is one “particle”, the n=2, l=0 is a second particle, and the n=2, l=1 state is a third particle, and so on.
That’s basically what’s happening in the context of today’s news, except that instead of an atom built from a proton and an electron and held together by the electric force, this is an “atom” built from a bottom quark and a bottom anti-quark and held together by the strong nuclear force. (A few people still call “bottom quarks” by the name“beauty quarks”, but the name is dying out.) We call this atom “bottom quarkonium”, or sometimes “bottomonium”. And instead of calling the different energy levels of this atom “states” or “orbitals”, we call them “particles.” That may seem a little odd until you realize that historically we often discover particles and give them names long before we realize that they’re actually made from something else… and also in some cases it can get rather ambiguous as to what is made from what, and whether intuition about atoms really applies to complicated objects such as the proton. This certainly can lead to a lot of confusion in the press and public about what kinds of new “particles” are really big news.
So what happened here is that the ATLAS experiment has identified a new state of bottomonium. [Actually, these are three states, so close together in mass that they can't be separated by the experimental methods --- so really there are three new particles that have been discovered. I hope you are now three times as excited.] We already knew lots of them, going back as far as 1977; see the figure, (which I’ve taken from B. Fulsom’s talk at the Blois 2011 conference), and on which I’ve marked the new “particle(s)”. Their masses are pretty much what had been expected from calculations based on earlier data.
I wrote a whole nice post about quarkonium and hydrogen explaining the details of how these were found, but my word processor program crashed and refuses to recover the document, so apologies for the brevity of today’s explanation.