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New exotic matter particle, a tetraquark, discovered at CERN

phys.org

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Re: New exotic matter particle, a tetraquark, discovered at CERN

#201

Post by dukwon »

akomtu wrote: post #2

The article (light on details, as usual) mentions that a slightly different configuration of a tetraquark would be very stable (again, not sure if that means nanoseconds or hours). If such stable multiquarks exist, without an electric charge they would be effectively untraceable, right? The only way to see such a particle would be to hit it precisely with an even smaller particle and get it to bounce back.

A stable heavy-quark tetraquark shouldn't live longer than, say, the B_c meson, which has a lifetime of about 5×10^-13 s

Re: New exotic matter particle, a tetraquark, discovered at CERN

#202

Post by amelius »

geertj wrote: post #190
gizmo686 wrote: post #189

Earlier quoted context omitted.

> 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…

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.

Perhaps the structure becomes visible at higher energies?

Re: New exotic matter particle, a tetraquark, discovered at CERN

#203

Post by dukwon »

im3w1l wrote: post #151
whatshisface wrote: post #11

Earlier quoted context omitted.

The resonance width is inversely proportional to the lifetime, and if the resonance width is about 400keV, the particle would live for about 10^-21 seconds. For comparison, neutrons decay via the weak force in about 800 seconds, and delta baryons, a randomly chosen strong force decay, live for 10^-24 seconds. That makes this tetraquark long-lived for a strong decay, but that's way, way faster than a weak decay. https…

Despite free neutrons decaying in 800s, there are many stable elements containing neutrons. Would it be possible to imagine a tetraquark as an ingredient of a stable particle?

No. The presence of a valence antiquark guarantees it will decay at some point.

Re: New exotic matter particle, a tetraquark, discovered at CERN

#204

Post by dukwon »

rkagerer wrote: post #173

Neat! What can you imagine might be applications for exotic particles like this? (even if if it's a stretch or fictional)

In the world of double-open-heavy-flavour hadrons (to which this particular tetraquark belongs), you get bullshit headlines like this https://www.sciencealert.com/new-quark-fusion-releases-signi...

Re: New exotic matter particle, a tetraquark, discovered at CERN

#205

Post by im3w1l »

amai wrote: post #196
im3w1l wrote: post #148

Earlier quoted context omitted.

The highest possible charge is 2/3 + 2/3 + 1/3 + 1/3 = 2. Every swap of a quark to a lower charge one reduces the total charge by 1. So the possibilities are 2, 1, 0, -1, -2.

But a combination like 2/3 + 2/3 + 1/3 + (-1/3) = 4/3. Are these not possible?

That's not exactly two antiquarks.

Re: New exotic matter particle, a tetraquark, discovered at CERN

#206

Post by ShinyRice »

BurningFrog wrote: post #165
whatshisface wrote: post #11

Earlier quoted context omitted.

The resonance width is inversely proportional to the lifetime, and if the resonance width is about 400keV, the particle would live for about 10^-21 seconds. For comparison, neutrons decay via the weak force in about 800 seconds, and delta baryons, a randomly chosen strong force decay, live for 10^-24 seconds. That makes this tetraquark long-lived for a strong decay, but that's way, way faster than a weak decay. https…

Then I wonder if this "particle" is just some components that takes 10^-21 seconds to bounce away from each other after colliding?

They don't just "bounce away", some of its quarks turn into different ones through interactions, and that is enough to class that process as a decay.

Also, quarks can't bounce away from each other. Lone quarks do not and cannot exist in nature, as far as we know.

Re: New exotic matter particle, a tetraquark, discovered at CERN

#207

Post by lisper »

spxtr wrote: post #59

> 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 qua…

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.

Re: New exotic matter particle, a tetraquark, discovered at CERN

#208

Post by dukwon »

oldspleen wrote: post #7

someone please ELI5 and how this discovery is important for furthering our understanding of quantum numbers

It won't improve our understanding of quantum numbers in general (a quantum number is just a discrete conserved quantity). The final paragraph mentions measuring the quantum numbers of this particular particle, namely its angular momentum and parity.

Re: New exotic matter particle, a tetraquark, discovered at CERN

#209

Post by ASalazarMX »

rnjesus wrote: post #120
ASalazarMX wrote: post #83

Earlier quoted context omitted.

Super spoiler below: Their tri-solar system was too unstable to terraform, they needed a stable solar system to migrate to. Of course ours was the nearest with an habitable planet (otherwise there wouldn't be much of a story), so they can immediately colonize Earth, and probably begin the centuries-long process of terraforming the neighboring planets.

an aside: i really wish hn had a redaction-style, click-to-reveal spoiler system. not that i don’t appreciate the spoiler warning here — it’s quite kind that people mark their comments as-such — but even when i’ve seen “spoiler warnings” for other content that i’d rather not be spoiled on, it’s very hard to not skim the next few proceeding lines out of habit (especially on mobile). i can’t imagine i’m the only one wh…

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Let's see...

.stenalp gnirobhgien eht gnimrofarret fo ssecorp gnol-seirutnec eht nigeb ylbaborp dna ,htraE ezinoloc yletaidemmi nac yeht os ,)yrots a fo hcum eb t'ndluow ereht esiwrehto( tenalp elbatibah na htiw tseraen eht saw sruo esruoc fO .ot etargim ot metsys ralos elbats a dedeen yeht ,mrofarret ot elbatsnu oot saw metsys ralos-irt riehT

Oh god no, forget this.

Re: New exotic matter particle, a tetraquark, discovered at CERN

#210

Post by key44 »

arthurcolle wrote: post #198
key44 wrote: post #195

Earlier quoted context omitted.

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 fantastica…

I appreciate your feedback and thank you for sharing your interpretation of my comment.

The flagged comment called the headline a lie. You called that a fact. Your comment isn’t up for interpretation; it’s objectively wrong.
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