Why Mesons Can't Be Made of 2 Quarks Alone

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Discussion Overview

The discussion revolves around the composition of mesons and the conditions under which they can exist, specifically questioning why mesons are formed from quark-antiquark pairs rather than just two quarks. The scope includes theoretical considerations of particle physics and the properties of hadrons.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant notes that mesons are typically composed of a quark-antiquark pair, questioning why a meson cannot consist of two quarks, such as an up-down pair.
  • Another participant states that hadrons must be color neutral, which can only occur with three quarks or a quark-antiquark pair.
  • A later reply reiterates the requirement for color neutrality in hadrons, suggesting that other combinations like pentaquarks or tetraquarks exist but have not been conclusively observed.
  • One participant expresses interest in whether a "crippled meson" could exist and seeks conditions under which it might be possible, particularly in the context of quark-gluon plasma transitions.
  • Another participant asserts that a "crippled meson" is not possible, referencing the earlier points about color neutrality.

Areas of Agreement / Disagreement

Participants generally agree that mesons require a quark-antiquark pair for color neutrality, but there is disagreement regarding the possibility of alternative configurations, such as a "crippled meson." The discussion remains unresolved on this point.

Contextual Notes

The discussion includes assumptions about color charge and the properties of hadrons, which may not be fully explored or defined. The concept of a "crippled meson" is not clearly defined, leading to ambiguity in the responses.

Achim
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As far as I know a Baryon is made of three Quarks (eg uud, udd etc) and a Meson of two Quarks, a Quark/Antiquark pair. As I am not a student / scholar in Physics but very deeply interested in this field, I couldn't find any explanation, why a Meson is omly made up by a Quark/Antiquark pair. What hinders a Meson to be made of, let's say an up-down Quark pair? Pauli only forbids constructions like up-up or down-down as both involved Quarks cannot be differed in this. So, can anyone please help my fault in thinking and grant me a hint, on why two Quarks cannot form a Meson WITHOUT an Anti-Quark / third Quark?
Add-on question: if such ud-Quark is not possible, would such construction MAYBE possible in a process when glasma becomes Quark-Gluon-Plasma?
This is not a question for a scientific work, neither homework etc. this is just a question to ease my always chatting mind at night as I am very sich, struck with central apnea sleeping disorder and hence my mind ventures into all sorts of science to keep my spirit going. I apologise for any error I made in constructing my question. Thank you.
 
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Drakkith said:
I think hadrons (baryons and mesons) are required to be color neutral, something which can only happen if you have 3 quarks or a quark-antiquark pair.

http://hyperphysics.phy-astr.gsu.edu/hbase/forces/color.html
Thank you, I understand the status-quo. My question's intention is different, I am after "is a crippled meson possible or not" plus "if it is possible, what condition could produce it". That why I mentioned the glasma -> quark-gluon-plasma transition.

Thoughts?
 
Achim said:
, I am after "is a crippled meson possible or not"

And the answer is "no", for the reasons explained above.
 
Drakkith said:
I think hadrons (baryons and mesons) are required to be color neutral, something which can only happen if you have 3 quarks or a quark-antiquark pair.
Or with 4 quarks and one antiquark ("pentaquark"), with two quarks or two antiquarks ("tetraquark"), with no valence quarks at all ("glueball") or with even more exotic combinations, but those things have not been observed yet (at least not conclusively).
Achim said:
I am after "is a crippled meson possible or not"
No.
 

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