Pentaquark Particles: New Doubts Cast on Their Existence in Recent Experiment

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Discussion Overview

The discussion centers around the existence and nature of pentaquark particles, particularly in light of recent experimental findings that cast doubt on their validity. Participants explore theoretical implications, historical context, and related particle configurations, including quark-antiquark pairs and their confinement properties.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants express skepticism about the pentaquark concept, suggesting it feels odd or does not fit well within existing frameworks.
  • Questions arise regarding the existence of particles composed of more than three quarks, with references to potential four-quark states and their historical context.
  • One participant proposes that pentaquarks consist of three quarks and an additional quark-antiquark pair, likening them to a combination of baryons and mesons.
  • Another participant argues that four-quark and five-quark systems can be colorless, challenging the notion that such configurations would lead to color confinement issues.
  • There is a mention of charmonium as a relevant example in the discussion of quark-antiquark pairs and their behavior.

Areas of Agreement / Disagreement

Participants exhibit a mix of skepticism and curiosity regarding pentaquarks, with no clear consensus on their existence or nature. Multiple competing views on the structure and implications of quark configurations remain unresolved.

Contextual Notes

Some claims rely on specific definitions of color confinement and the behavior of quark-antiquark pairs, which may not be universally accepted. The historical context of four-quark states and their disrepute is also noted but not fully resolved.

Who May Find This Useful

Readers interested in particle physics, quark dynamics, and the ongoing debates surrounding exotic hadrons may find this discussion relevant.

humanino
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You said "pentaquark" !?

All right, it is now officially released :
Doubt is cast on pentaquarks
Another dedicated experiment in the same lab is still under the process of data analysis. Let us hope they will agree with each other !
 
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This is good. I always really felt that the pentaquark didn't fit in. I never really liked the idea, it felt quite odd to me to have a pentaquark particle. But I suppose the jury is still out, so I will have to wait and see.
 
Is there any particle made up of more than 3 quarks? I read the Pentaquark link, but didn't I hear news of a suspected 4 quark particle some time back?

Thanks
 
I doubt it. Unless it were two quark-antiquark pairs, which annihilate straight away, color would not be confined.
 
El Hombre Invisible said:
I doubt it. Unless it were two quark-antiquark pairs, which annihilate straight away, color would not be confined.

4-quark and 5-quark systems can be colorless because 2 and 3 quark system are colorless and sums of colorless systems are also colorless.

And quark-antiquark pairs do not necessarily annihilate "straight away". See charmonium.
 
Tell me about charmonium.
 
I think there might be a confusion about language.
"Pentaquark" does not mean 5 quarks.
The PQ is composed of 3 quarks and an additional quark-antiquark pair.
This makes it a bit like a molecule of a baryon and a meson, and not all that exotic.
Its narrow width, if obvserved, is what makes it unusual.
"Four quark" states really mean two quarks and two antiquarks.
They were hot about 20 years ago, and were called "baryonium".
They fell into disrepute, but strong evidence for them was never overturned.
The quarks would not immediately annihilate if they formed two diquarks some distance apart.
 
Well, that's like calling a helium nucleus a dodecaquark!
 

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