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…
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 discovery paves the way for a search for heavier particles of the same type, with one or two charm quarks replaced by bottom quarks. The particle with two bottom quarks is especially interesting: according to calculations, its mass should be smaller than the sum of the masses of any pair of B mesons. This would make the decay not only unlikely, but actually forbidden: the particle would not be able to decay via the strong interaction and would have to do so via the weak interaction instead, which would make its lifetime several orders of magnitude longer than any previously observed exotic hadron.
The new Tcc+, tetraquark is an enticing target for further study. The particles that it decays into are all comparatively easy to detect and, in combination with the small amount of the available energy in the decay, this leads to an excellent precision on its mass and allows the study of the quantum numbers of this fascinating particle. This, in turn, can provide a stringent test for existing theoretical models and could even potentially allow previously unreachable effects to be probed.
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> 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.
This is not the first time a tetraquark has been measured, but instead it's the first time a tetraquark with two charm quarks and no charm antiquarks. That's still nice work, but I was initially confused by the headline ("didn't they discover those already?").
By lisper 2021-07-3111:34 I read it as: "CERN has discovered a new particle, and that new particle is an instance of a known class of particles called tatraquarks". The wording is a little sloppy and ambiguous, but headlines are pretty tightly constrained so I'm willing to cut the writers a little slack on this. I've seen much worse.
By IAmGraydon 2021-07-310:032 reply Like nearly everything from the media, it's a lie designed for clicks.
This sort of comment is actually worse than the thing it is attempting to denigrate. "The media" isn't lying to you. "The media" is a smokescreen that lumps a wildly diverse collection of information purveyors under one, inaccurate and overly generalized, umbrella. Some media seeks to find the truth, some seeks only to manipulate you. Some is built from the ground up to push an agenda (political, religious, etc.), some was built to make money and some was built to speak truth to power. This last should not be lumped in with the rest, even when it disagrees with YOUR personal agenda. There are a great number of journalists that seek to reveal truth, to confront the powerful when they abuse their positions and to attempt to reveal and expose our failings. Don't discount them with inaccurate and dismissive comments like this. The best of them may be the only thing between you and the depredations of those that control our lives and places like the US, where laws provide at least some protection for these journalists and where a tradition of journalistic integrity at least has the possibility of being followed give such journalists a chance to do what they do so well.
By joshmn 2021-07-311:37 This is the kind of echo chamber I am okay with.
By arthurcolle 2021-07-314:061 reply It's not worse - he's stating a fact, and your qualms with his descriptor (i.e. "the media") are secondary to the fact that his statement is an accurate description of 1) the problem and 2) the opponent in question, even if you feel like the secondary component is up for debate.
I'll restate my own adjacent thoughts: If you're a journalist and you are working at a company that performs these sorts of linguistic tricks to optimize for clicks... (and constantly for that matter) then you are equally responsible. Everyone has bills to pay, but everyone who participates has to eventually take responsibility for enabling a broken system.
Truthful descriptions of novel current events, even if they derive less clicks than clickbait, cannot become ancillary goals in the field of journalism. With no exceptions!
I’m sorry, what? Definitively no part of the headline is a lie, nor is any criticism of its factual nature even remotely sensible. “New exotic particle, a type of tetraquark” is completely valid when reduced to “new exotic particle, a tetraquark,” which notably does not say “new exotic particle, the tetraquark.” Collective noun usage, not singular. It’s terse but clear English, quite common in print, and a fantastically weak hill to die on. Watch:
“The junior double whopper, a cheeseburger, is implicated in the coronary event.”
I’d forgive it if it were confusing to someone who learned English as an additional language, not if it’s dishonestly called dishonest.
So no, they are not stating a fact. They’re mad at “the media,” an apparently singular organism, and they believe they’ve found an excuse to bore us all yapping about it for a minute but instead have misunderstood the English language. And you’re right there to back up the same tiresome hooey despite its demonstrably ignorant foundation.
If you’re going to call something a “linguistic trick” it is advisable to master the language, particularly if you’re going to write three paragraphs on the “dishonesty” of a well-written, economical headline about a pretty cool thing science figured out while you were obsessing over the nefarious motivations of people telling the world about it.
By arthurcolle 2021-07-318:371 reply I appreciate your feedback and thank you for sharing your interpretation of my comment.
By key44 2021-07-3116:42 The flagged comment called the headline a lie. You called that a fact. Your comment isn’t up for interpretation; it’s objectively wrong.
Let's not throw baby out with bathwater. This kind of thinking has been so harmful for social cohesion, and we need a cohesive society if we're going to have a prayer of handling the worst problems we've ever faced as a species in a way that future generations will be remotely proud of.
By IAmGraydon 2021-07-310:38 Yes, my comment was a bit hyperbolic. However, if we're going to have a prayer of handling the worst problems we've ever faced as a species in a way that future generations will be remotely proud of, we need a media that doesn’t profit from the exact opposite occurrence.
By 8bitsrule 2021-07-315:50 Reminds me of an ad in the Sunday, Dec. 27 1969 New York Times that read:
"War is over - if you want it."
By z3ncyberpunk 2021-07-310:17 Yes, because yellow journalism making a comeback means that somehow the readers fault for distrusting the journalists... Classic GN shilling
We have no hope of facing those problems if our social cohesion is so fragile that it can't even handle calling an article out as clickbait.
There's a very big difference between calling something clickbait and saying "everything from the media is a lie".
"Quarks are the fundamental building blocks from which matter is constructed."
I sometimes wish would include "In our current model", "We now think that", or some other qualifier.
Such absolute statements have been made frequently prior to our current understanding.
I have no special knowledge to lead me to believe that quarks are not the end all of parties.
But I was happy with atom being the fundamental thing, and then electrons, neutrons, protons were the thing as well.
The other day I read about Fractons "quasiparticles or Partial Particles", so now I have to figure those out as well.
I have lost track if the graviton has been found yet. I dont think it has.
From a purely layman's sense of esthetics the current model for particle physics is messy and a little spooky.
I have an odd hobby. I collect old paper encyclopedias from pre 1970 For every language that I speak. It takes up MASSIVE amounts of space.
The oldest I have been able to acquire on a limited budget Is 1880.
It is always fun to track concepts over time.
They all state what the world is like, and how it works as bombastic facts.
Yet over time, most of it gets replaced or at least highly refined and things are removed.
Particle physics is an active field with much still to learn or figure out. Let us keep that in mind.
"We now think that" is the qualifier on the entirety of physics. It's redundant.
By abainbridge 2021-07-318:272 reply Haha. True. Some parts of physics are way shakier than others though. For example, the whole big bang, dark matter, dark energy area needs the qualifier of, "We know we've got something wrong here, but its the best we've got". (eg see https://en.wikipedia.org/wiki/Big_Bang#Problems_and_related_...). I'm trying not to be controversial here. I'm just using this as an example of physics with well known problems.
Regarding, "Quarks are the fundamental building blocks", do we actually think that? If so, why? I'm genuinely curious. Is it just because we haven't seen anything more fundamental? That would violate your "We now think that" qualifier - ie if that is the reason, the qualifier should be "We have NO reason to think that...".
By brianpan 2021-08-015:44 It's much worse than you think.
In physics there is 1) we know this is definitely wrong but it's useful and 2) this is very right so far and it's probably going to be wrong. I'm only a little bit joking. Now, I am not a physicist but I have been in a physics rabbit hole for a few months now.
The absolute best most experimentally verified theories we have are: general relativity and quantum mechanics. These are the pinnacle of physics. And they are incompatible with each other. So we know for sure that one is wrong. Or both are wrong.
String theory might be the resolution of that, making strings the most fundamental thing. But we've been working on it for 50 years with basically nothing to show for it so far. And there may be more beyond strings, who knows.
Of course there are many things in physics we can say with great confidence. But in terms of fundamental understanding there is ONLY "we now think that".
By ThinkBeat 2021-07-3116:42 There is a theory about Preons.
This theory has fallen out of fashion.
"In particle physics, preons are point particles, conceived of as sub-components of quarks and leptons."
By h2odragon 2021-07-313:27 I'll certainly give the authors of the papers the benefit of a presumption of humility; it's the people "translating into layman's terms" and "passing on knowledge" that introduce Authority, and other errors, as part of the process.
"Think for yourself, schmuck" is the only dogma worth petting.
By complexmango 2021-07-3118:06 If only epidemiologists had such humility
> I sometimes wish would include "In our current model", "We now think that", or some other qualifier.
There is actually good reason to think quarks aren't fundemental. Even ignoring the empirical shortcomings of the standard model (specifically the incompatibility with General Relativity), it just doesn't "look" like a fundemental model.
Specifically, it is essentially a periodic table of elementary particles, with 3 "generations" of matter particles. Like the periodic table of the elements, this structure is highly suggestive that there is some deeper underlying structure.
I agree that we don’t know. But there is also evidence that quarks are fundamental. Based on all our measurement, they are point like particles with no internal structure or size.
By whatshisface 2021-07-3017:10 Two more technical treatments:
https://cerncourier.com/a/new-tetraquark-a-whisker-away-from... https://lhcb-public.web.cern.ch/Welcome.html#Tcc
