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Physicists Discover "Doubly Strange" Particle
Tsalg writes "Physicists have discovered a new particle made of three quarks, the Omega-sub-b. The particle contains two strange quarks and a bottom quark (s-s-b). It is an exotic relative of the much more common proton and weighs about six times the proton mass. This is probably one of the last noticeable sub-atomic discoveries made somewhere else than at CERN since LHC is about to start the hunt for the Higgs particle that remains elusive even for the experiment that just discovered the Omega-sub-b."
Sure. Quarks are one of the two basic building blocks of matter, the other being the lepton. This particular particle -- a baryon, since it is comprised of three quarks -- consists of two strange quarks and one bottom quark. Strange quarks and bottom quarks are both very unstable. Another example of a baryon is the proton, which contains two up quarks and and a down quark. Up and down quarks are generally, by comparison, very stable. The instability of the quarks make this particular baryon difficult to detect.
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Yes, it's been seen before. There's an ungodly amount of particles (even if you restrict yourself to baryons), in fact, including many weird ones - see http://en.wikipedia.org/wiki/List_of_baryons for instance, or locate a copy of the Physics Letters B/Review of Particle Physics, which dedicates ~150 pages to listing baryons (in my 2004 copy, that is; chances are it's even more today).
So I am obviously not understanding how the masses of the quarks correlate to the masses of the fermions. What am I missing here?
IANAPP (particle physicist), but I guess you're missing the equivalent to the "binding energy". Just like the mass of an atomic nucleus isn't equal to the sum of the masses of the protons and neutrons in it.
Won't happen. We're hard at work on it right now (except when we're reading slashdot...), and we're making some amazing leaps forward in analysis techniques, but we simply won't have enough data to be sufficiently sensitive to the Higgs by the time the accelerator shuts down. We might find evidence or even strong evidence, but not strong enough to call it discovery. We do have enough data to exclude certain mass ranges, however. When you combine our data with D0's (the experiment that did the analysis in TFA), we have enough sensitivity to say that the Higgs, if it is the standard model Higgs (and the lightest SUSY Higgs is sufficiently similar that this holds for it, too), does not have a mass quite close to 170 GeV (which is pretty close to the mass of the top quark, incidentally). http://www-d0.fnal.gov/Run2Physics/WWW/results/prelim/HIGGS/H64/
SIGSEGV caught, terminating
wait... not that kind of sig.
The proton weighs a little under a GeV, most of which is binding energy. Since the u and d quarks have so little mass, you can effectively ignore it and look at the dynamical relationship of 3 bound quarks. This is why early models which treated protons and neutrons as different states of the same particle (called isospin symmetry) worked so well. The equation's not all that simple, since binding energy is itself a function of the masses of the quarks involved. The only real theoretical calculations are heavily computational lattice QCD simulations, and experiments like this are a good test of those calculations.
As a sidenote, the headline makes very little sense. We observed a "triply-strange" particle, the original Omega, ages ago. What makes this special aren't the two s quarks per se, but their appearance alongside a bottom quark.
IAAPP