Slashdot Mirror
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.
My blog
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.
I'm guessing: E=mc^2.
See for instance here
Who knows? Perhaps that's why they're yet to be discovered: that we haven't reached the right energies. Well, the LHC will reach far higher energies than anything else on earth. Every time there's been a substantial step up in collision energies, all manner of new particles fall out. That alone makes the LHC favourite to dominate the field for the foreseeable future. That's before you consider the fact that a project of this scale, with absolutely enormous long-term funding, attracts everyone. The best particle physicists in the world are going to be attracted to working on the LHC, or on analysis of the data it produces.
There'll still be discoveries made elsewhere, but for the headline stuff, watch CERN.
Real Daleks don't climb stairs - they level the building.
From wikipedia:
The mass of the proton is the sum of masses of its quarks + the energy of the gluon field that holds the quarks together.
IANAP
In nature, quarks are always found bound together in groups like this, and never in isolation, because of a phenomenon known as confinement.
I think the problem with "real" -vs- "theoretical" is that we are talking about the things that make-up matter. So even the idea of "real" doesn't apply. People want something they can see and touch and interact with, and if that is what it means to be real, then quarks are not real. But scientifically, they exist and they can be seen and measured indirectly.
(Although, thanks to the magic of the internet, there is no way to know that I exist either)
I think it's more accurate to say that it is "starting", and will continue to start for a while. These things don't just turn on, and the LHC has actually been pretty much on-target with the exception of that magnet blowing up.
He's talking about the energy levels produced at CERN. While scientists anywhere will be making discoveries, it will likely be with data produced from experiments at CERN.
Oh man, you get my Dutch Grammar Nazi going on ;-)
I assume you meant something like:
"Dit is waarschijnlijk een van de laatste opvallende subatomische ontdekkingen die ergens anders gemaakt worden dan CERN, aangezien de LHC op het punt staat de jacht op het Higgs-deeltje te beginnen, dat ongrijpbaar blijft zelfs voor het experiment dat zojuist het Omega-sub-b deeltje heeft ontdekt..."
Yeah, that sentence is a b*tch in Dutch too...
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.
Ever since deep inelastic scattering experiments revealed that the proton is not a pointlike charge at sufficiently small electron wavelengths, but rather scatters electrons as if it contained three pointlike (at that scale) charges (+2/3, +2/3, and -1/3), quarks have generally been considered real. Prior to these experiments, there most certainly was ontological debate about quarks. There was also similar debate about atoms for quite some time (see Ernst Mach).
SIGSEGV caught, terminating
wait... not that kind of sig.
no, An Idiot.
Wow, sent an e-mail as suggested when clicking on "use classic" banner, and got a fast response that addressed my msg
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
Of course they are sharing the raw data. But understanding the raw data means understanding a great deal about the physical structure of the detector. Basically, if you know enough about that, you are part of the CERN team, whether you are physically there or not. Relatively few of the thousands of scientists working "at" CERN are physically there at any time: most spend most of their time connected only electronically. Why do you think the WWW was invented there?
Consciousness is an illusion caused by an excess of self consciousness.
The mass of new particles can be predicted with extreme precision using quantum theory. Lattice chromodynamics predicts new particles using theorized hyperspatial symmetries that we have extrapolated from the symmetries in known particles. Because these symmetries are extremely complicated, the masses of these postulated particles are calulated by computer. If the computer prediction matches up to the measured mass of a new particle, that's one step toward verifying the theory.
And yes, I know that even though all of that is accurate, it often sounds like it could have been made up on the spot. :)
Genocide Man -- Life is funny. Death is funnier. Mass murder can be hilarious.
What you get after anti-matter/matter collide is lots of energy. E=mc^2 so you can also get particles.
Strange quarks have a mass of 95MeV, bottom has 4.2GeV so the total mass of the Omega-sub-b would be 4.39GeV Up quarks have a mass of 3MeV, down has 6MeV so the total mass of a Proton would be 0.012GeV
It's not quite so simple. The masses of the baryons are usually dominated by the binding energy (i.e. in the 'gluon' field) and not by the masses of the constituent quarks. The proton/neutron are the extreme case where almost all their mass is from binding energy. Estimating the mass of the quarks themselves is a very tricky business; since you cannot observe free quarks, you have to infer their effective mass in bound systems. An up quark in a baryon (bound system of 3 quarks) has a different effective mass than when it is part of a meson (bound system of two quarks). The masses of the up and down quarks you quote are their effective masses in baryons; the mass of the proton is 0.938 GeV, which is clearly MUCH larger than the sum of the quark masses. The same goes for this new baryon (Omega_b), but to a lesser degree.
Actually, the question of the masses of particles can be considered a little bit moot (or not, depending on what you're studying); in the Standard Model, all elementary particles are massless, and pick up effective masses only through their coupling to the Higgs field, similar to the way the proton has its mass due to the quarks coupling to the gluon fields. But at the moment, no one has been able to calculate what the effective particle masses (of any particle) should be, since we don't know enough about the Higgs field (should it exist) to be able to work out the couplings to various particles.
IAAPP
There are three fundamental forces that matter in a particle collider: the strong force, the weak force, and the electro-magnetic force. When the interactions are through the strong force (which is described by the theory of quantum chromodynamics [QCD]), the result is either things start to stick together or you create a pairs of quarks (a quark and its anti-quark, to conserve charge). These quark pairs can, in turn, either produce new pairs of quarks or they can stick and produce new particles. So, strong interactions can produce strange quarks out of nothing if you supply enough energy, but they'll always come in a strange/anti-strange pair. Given that the \omega_b has both a strange and an anti-strange quark in it, I'm guessing that it probably is coming out of a series of strong nuclear interactions.
At low energies, electro-magnetic forces deal with the interactions of particles and photons, which is important but kinda boring (at high enough energies life is more complicated and EM forces become a kind of weak force, but that's getting off track).
The final force, the weak force doesn't interact very strongly with particles (hence its name), so weak events are much less common than strong events. On the other hand, because they obey different symmetries, weak events can do some things that strong events can't do. In particular, weak events can change the flavor of quarks, for example, from a down quark to a strange quark. So, the second way you can get a strange quark from a bunch of up and down quarks is through a weak interaction that changes the flavor of one or more quarks.
-JS
Vanity of vanities, all is vanity...