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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."
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.
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.)
Ben Hocking
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...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.
Anomalous: deviating from what is usual, normal, or expected
Canard: a false or unfounded repor
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)
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.
In Soviet Rush, today's Tom Sawyer gets high on you.