New Exotic Matter Particle, a Tetraquark, Discovered (phys.org) 26
An anonymous reader quotes a report from Phys.Org: Today, the LHCb experiment at CERN is presenting a new discovery at the European Physical Society Conference on High Energy Physics (EPS-HEP). The new particle discovered by LHCb, labeled as Tcc+, is a tetraquark -- an exotic hadron containing two quarks and two antiquarks. It is the longest-lived exotic matter particle ever discovered, and the first to contain two heavy quarks and two light antiquarks. Quarks are the fundamental building blocks from which matter is constructed. They combine to form hadrons, namely baryons, such as the proton and the neutron, which consist of three quarks, and mesons, which are formed as quark-antiquark pairs. In recent years a number of so-called exotic hadrons -- particles with four or five quarks, instead of the conventional two or three -- have been found. Today's discovery is of a particularly unique exotic hadron, an exotic exotic hadron if you like.
The new particle contains two charm quarks and an up and a down antiquark. Several tetraquarks have been discovered in recent years (including one with two charm quarks and two charm antiquarks), but this is the first one that contains two charm quarks, without charm antiquarks to balance them. Physicists call this "open charm" (in this case, "double open charm"). Particles containing a charm quark and a charm antiquark have "hidden charm" -- the charm quantum number for the whole particle adds up to zero, just like a positive and a negative electrical charge would do. Here the charm quantum number adds up to two, so it has twice the charm! The quark content of Tcc+, has other interesting features besides being open charm. It is the first particle to be found that belongs to a class of tetraquarks with two heavy quarks and two light antiquarks. Such particles decay by transforming into a pair of mesons, each formed by one of the heavy quarks and one of the light antiquarks. According to some theoretical predictions, the mass of tetraquarks of this type should be very close to the sum of masses of the two mesons. Such proximity in mass makes the decay "difficult," resulting in a longer lifetime of the particle, and indeed Tcc+, is the longest-lived exotic hadron found to date.
The new particle contains two charm quarks and an up and a down antiquark. Several tetraquarks have been discovered in recent years (including one with two charm quarks and two charm antiquarks), but this is the first one that contains two charm quarks, without charm antiquarks to balance them. Physicists call this "open charm" (in this case, "double open charm"). Particles containing a charm quark and a charm antiquark have "hidden charm" -- the charm quantum number for the whole particle adds up to zero, just like a positive and a negative electrical charge would do. Here the charm quantum number adds up to two, so it has twice the charm! The quark content of Tcc+, has other interesting features besides being open charm. It is the first particle to be found that belongs to a class of tetraquarks with two heavy quarks and two light antiquarks. Such particles decay by transforming into a pair of mesons, each formed by one of the heavy quarks and one of the light antiquarks. According to some theoretical predictions, the mass of tetraquarks of this type should be very close to the sum of masses of the two mesons. Such proximity in mass makes the decay "difficult," resulting in a longer lifetime of the particle, and indeed Tcc+, is the longest-lived exotic hadron found to date.
Containment (Score:2, Funny)
Just what we need.. (Score:1)
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The "longest lived" lives how long? (Score:3)
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When an article boasts about something as "longest lived", I sure expect that claim to be followed by a concrete number how long that is. The article is suspicious with absence of that information.
I was wondering the same thing. So I did a Google search and found a dozen other articles. All of them mention that the particle has a long life. NONE of them mention what that lifetime is.
So the omission appears to be in the original press release.
Long-lived due to Sharp Peak (Score:5, Informative)
The reason for this is that particles much prefer to decay through the strong interaction if they can but the mass difference is very small between the tetraquark and the D mesons it can decay into. This means there is not much energy left over to give to those mesons which makes the decay slower than it would otherwise be.
I suspect the reason there is no clear lifetime value yet is that they have not done a detailed analysis to find a reliable number. However, if the mass peak is much narrower than other tetraquarks you can still say the lifetime is much longer while still not having a reliable number.
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Theoretically estimated to be about 7.6 picoseconds
https://arxiv.org/pdf/1912.064... [arxiv.org]
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Wait, what about the fact that it is alive?
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yocto is better but its a bit harder to deal with.
if they wanted a faster answer, they should have gone buildroot.
(wait, wut?)
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Believe me, I know longest lived when I see it. I have nose for these things, I'm a powerful genius. There are no short things on me at all, everyone says so. I know all about protons and croutons, talk to them every day.
Tetras video game. (Score:2)
Tetraquark ... an exotic hadron containing two quarks and two antiquarks.
Arrange quarks and antiquarks of different shapes/colors to form a Tetraquark, clear the row and get points ... :-)
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Melted (Score:2)
My brain just melted a little it reading that. I guess it was a catalyst for some charming tetraquark decay...
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Impressed. (Score:2)
I'm impressed. They got through the summary and even the article itself without mentioning the Standard Model at all in any context.
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Because it is part of the Standard Model, the 1964 paper proposing the quark model by Gell-Mann and Zweig predicted four and five quark particles.
how long? (Score:2)
They say several times that it's so long-lived.
But they don't say HOW MANY microseconds that is. :-(
Nothing at CERN, either (Score:2)
This is a media blurb, we may have to wait for the pre-print.
https://lhcb-public.web.cern.ch/Welcome.html#Tcc/ [web.cern.ch]
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Will be on the order of picoseconds, estimated by theory to be less than 7.6
https://arxiv.org/pdf/1912.064... [arxiv.org]
I don't understand any of this (Score:1)
Where's the Ferengi Quark? (Score:1)
Exciting (Score:2)
This is giving me a hadron