Talk:Exotic baryon

Comments

Not enough material here for an independent page. Bambaiah 17:34, Jun 9, 2005 (UTC)

Blow it out your butt. It's enough information, and it's good information. Aside, which article would you have it rather be on?

I think that Bambaiah made this comment when this page was completely different. At that time there was probably a large overlap with the page on pentaquarks and he decided to make this page a redirect to that page. I deleted the redirect and wrote most of the current page, Bambaiah also made some edits.Count Iblis 16:17, 12 December 2005 (UTC)[reply]

The article doesn't actually define what an exotic baryon is, just one criterion that must be true. A bound state of 51 quarks and 6 antiquarks would not be an exotic baryon. A bound state of 30 quarks and 27 antiquarks would be. Can you discern why, based on the information in this article? No. So, still not enough material for an independent page. Maybe someone who actually knows what they're talking about can waste their precious time rewriting the article, instead of the jokers above. --76.224.69.253 13:50, 5 November 2007 (UTC)[reply]

I think the article is pretty clear about what exotic baryons are. Now, I'm a physicist and I think Bambaiah is too, so we are certainly not "jokers" who don't know what they are talking about. A rigorous clear cut defintion would be nonsensical, because "exotic" is inherently an imprecise term. The article simply reflects this and is therefore accurate. This is something we encouter often when writing about physics. Even when writing in peer reviewed journals, you'll often prefer to use inaccurate vague language over of very rigorous precise language to make the text easier to read. Count Iblis 14:08, 5 November 2007 (UTC)[reply]

Proposed rename to "Exotic hadron"

There is an inconsistency across our articles on subatomic particles. Here are some definitions in the present articles:

From lede to Hadron:
"In particle physics ... hadrons are categorized into ... baryons, made of three quarks and mesons ... made of [two quarks] ... Hadrons containing more than three quarks (exotic hadrons) have been discovered in recent years ... [continues discussing "tetraquark state (an exotic meson)" and "two pentaquark states (exotic baryons)..."]

From lede to Baryon:
"A baryon is a composite subatomic particle made up of three quarks ... as distinct from mesons, which are composed of [two quarks]. Baryons and mesons belong to the hadron family of particles, which are the quark-based particles."

If our main articles on these particles state that a meson is defined as a 2-quark hadron, and a baryon as a 3-quark hadron, then by definition a hadron with 4 or 5 quarks can't be a baryon, it's something else.

I do see online, that some papers refer to hadrons with >3 quarks as exotic baryons, while other papers refer to them as exotic hadrons. Whatever various authors might individually call these particles, our articles should be consistent - we can't/shouldn't tell a reader that a baryon is defined as having 3 quarks, and also that baryons can have 4 or 5 quarks. Tentatively, it looks like the majority of WP:RS tend to prefer this kind of nomenclature:

2 quarks - meson
3 quarks - baryon
4 quarks - tetraquark AKA exotic something
5 quarks - pentaquark AKA exotic something

I think the last 2 would be best described as "exotic hadrons", since there doesn't seem to be a consensus among reliable sources overturning decades of definitions of a baryon as being a hadron that has 3 quarks.

There's a possibly related inconsistency over at Chronology of the universe, where the article states that baryogenesis took place long before the first hadrons were able to form (states baryons able to form [baryogenesis] at about 10^-11 sec, but also says that the first hadrons "can form" only at about 10^-6 to 1 sec). That's got to be incorrect - if anyone can work out what it's trying to say, please do fix it!

To fix the inconsistency generally, would other editors be OK if we standardize by renaming this article to "Exotic hadron", which appears more correct (and is already used in our article "Hadron"), and similarly correcting elsewhere?

FT2 ^{(Talk | email)} 18:13, 24 September 2018 (UTC)[reply]

Wikipedia doesn't get to dictate how words are defined. Tetraquarks are exotic mesons, pentaquarks are exotic baryons. Defining mesons as two-quark states and baryons as three-quark states is technically incorrect, but very common. Please look at the first paper to propose the quark model^[1], which states "Baryons can now be constructed from quarks by using the combinations (qqq), (qqqqq̅), etc., while mesons are made out of (qq̅), (qq̅qq̅), etc.", as well as the PDG^[2]^[3]^[4] if you want a more modern source. BTW, there is already a page called exotic hadron. — dukwon (talk) (contribs) 21:57, 24 September 2018 (UTC)[reply]

dukwon - in that case, since the discovery of tetraquark quark hadrons, it sounds like the practical definition of a baryon has extended to cover "a hadron with an odd number >= 3 of quarks", and of a meson as "a hadron with an even number >= 2 of quarks", with >= 4 sometimes qualified as "exotic". Is that more in line with recent usage? FT2 ^{(Talk | email)} 03:40, 30 September 2018 (UTC)[reply]

Almost. A glueball (no quarks) would be an exotic meson, as would a qq̅ state with a valence glue component (hybrid meson). The most general definition is that mesons are hadrons that are bosons, baryons are hadrons that are fermions. Exotic hadrons are anything that doesn't fit in the "standard" qq̅ or qqq pictures. — dukwon (talk) (contribs) 08:56, 30 September 2018 (UTC)[reply]

References

[1] ttps://doi.org/10.1016/S0031-9163(64)92001-3

[2] ttp://pdg.lbl.gov/2018/reviews/rpp2018-rev-non-qqbar-mesons.pdf

[3] ttp://pdg.lbl.gov/2018/reviews/rpp2018-rev-pentaquarks.pdf

[4] ttp://pdg.lbl.gov/2018/reviews/rpp2018-rev-naming-scheme-hadrons.pdf

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