SELEX at Fermilab Discovers New Particle

sellthesedownfalls writes "Scientists at the Department of Energy's Fermi National Accelerator Laboratory will announce on Friday, June 18 the observation of an unexpected new member of a family of subatomic particles called 'heavy-light' mesons. The new meson, a combination of a strange quark and a charm antiquark, is the heaviest ever observed in this family, and it behaves in surprising ways -- it apparently breaks the rules on decaying into other particles. See the Fermilab Press Release."

Comments

Re:Slashdot Reader Discovers New Oxymoron

[p3tersen]

It's a bound state of two quarks. The charm quark is "heavy", i.e. relatively massive, while the the strange quark is less so.

Re:118?

[geeber]

Victor Ninov at Lawerence Berkley National Laboratory.

Let's hope Fermilab is more certain about this discovery.

Not a stupid question!

[benhocking]

Actually, they do occur in nature. Specifically, they occur when a sufficiently energetic cosmic ray strikes our atmosphere.

This is the same reason that many physicists laugh off the idea that they're going to create a mini-black hole that would sink to the earth's core and destroy us all. The universe is constantly running even higher-energy experiments in our atmosphere all the time - we just haven't placed our detectors in the right place! (To be fair to our hard-working particle physicists, you would need a VERY large detector hovering high in the air if you wanted to catch these things in nature.)

Re:Not a stupid question!

[barawn]

I wouldn't think there would be an absolute cutoff there, but a (granted very steep) curve; which means that some very tiny fraction of particles *could* make it here with those energies (and who's to say what original energy level that particle started off with?)

No, of course it's not an absolute cutoff - however, the slope is somewhere in the neighborhood of E^-10 or so, which may as well be an absolute cutoff. No matter how hard you try, you basically can't get much above 6 x 10^19 for more than about 50 megaparsecs. If the GZK cutoff really does exist (which... well, it better, it's very basic physics) then in the absence of sources we don't understand (which is what we think we have), we never should've seen these particles. The "normal" processes which generate particles less than 6E-19, convolved with the GZK effect, would've produced a flux so freaking low we never would've seen it.

what are the odds that the particle in question could have resulted from the Big Bang energies once protons and neutrons started to form from the 'soup'? I realize it would have been traveling for quite a while and the odds would be infinitely small, but still, the mw background is just an average temperature, is it not?)

Actually stuff that's formed from recombination era would be microwave background energies - because, well, that's what the microwave background is. :)

But anyway, it's not just that we saw one particle, because the thing is, the detectors didn't run for that long, and they weren't that large (i.e. their acceptance was quite low). They would've had to have gotten astro-freaking-phenomenally lucky in order to see one that far away from the expected. It gets even worse when you have other detectors come online that also see those energy events.

It's not the individual particles that interest us. It's the fact that there seems to be a real spectrum out there - there's something actually producing these energies, and either A) it's close, or B) we don't understand interactions at high energies, or C) all of the cosmic ray physics people are smoking something. Considering B) basically implies that one of the fundamental tenets of relativity is wrong - which would be bad , I'd like for it to be A, but I've got a feeling it'll turn out to be C. :)

If they haven't been seen before...

[Anomalous Canard]

...it's a new discovery!

We certainly expected that there would be a strange-anticharm meson, but until it was observed, there was no way to tell it's mass (except in a very broad range of likely masses for members of the heavy-light mesons) and it's lifetime. Quantum chromodynamics, while in many respects a remarkably precise theory, still has to have the masses of the particles put into the equations. In a real Theory of Everything, we'd be able to calculate the mass of such a meson before we'd seen it.

These particles certainly exist in nature, but because their lifetime is so short, you'd have to be right where they were created to be able to see them before they decayed. Since our detector-on-the-surface-of-a-neutron-star project (affectionately called the DOTSOAN project) has had its funding denied again, the only place we can be observing right where they were created is right here on Earth in the accellerators.

Re:I like the way humans think

[aducore]

The rules are just the way we understand things. When something breaks the rules, it means we need to put the rules back together so that they aren't broken as easily.

There's a difference between defying human theories of physics, and defying nature.

Re:What, no pictures?

[Pi_0's don't shower]

This is definitely "order of magnitude" a typical strong decay.

There are two things which are unusual about this, however:

1) It's a strong decay, and the particle is more massive than other exotic (with more than just down/up quarks) mesons, but this one lives longer than light mesons in its family. Whether this means it's longer lived than charm-down or charm-up mesons or longer lived than a lighter resonance of charm-strange isn't enunciated here, but either way, that's a surprise. There may be some type of parity conservation at work.

(NB - strong interactions conserve parity)

2) It decays into an eta particle much more often (6x more) than decay into a kaon. This is unusual, because more phase space is available for kaons (they have less mass than etas, therefore it's energetically favorable). Again, this could be related to parity issues, like pion decay (prefers muons over less-massive electrons), but that isn't enunciated here either.

It just goes to show that there's a lot left to investigate just in the basic standard model -- something that a lot of the SUSY/string-loving public forgets quite often. (IAAP, btw)

Re:Somebody's having a lot of fun at work...

[heyitsme]

It's a wonder they got any work done that day...

With 6800 acres of buffalo, trails, and lakes, not to mention a swimming pool, basketball and tennis courts, a rec center and bar (the alcoholic type) its a wonder we ever get any work done around here :)

Re:False Alarm

[worst_name_ever]

The alleged story is indeed mostly true (reference here) although apparently it was two Heineken bottles, and the the theory of how they got there is that it was a prank, not an oversight during construction.