Why Do Quarks Form Triplets Instead of Larger Groups in the Early Universe?

[cam875]

during the big bang there was said to be at one time a giant soup of quarks for a split of a second before atoms were formed. But why is it quarks always link up in triplets to form protons and neutrons with up and down quarks. Why didnt five or six quarks join up together with the strong nuclear force, transfer of gluons.

 

[Xezlec]

This is a QCD question. Shouldn't this be moved to the high-energy, nuclear, particle physics forum?

 

[malawi_glenn]

i) Quarks must be combined in such a way that the total object (composite particle) is colorless

ii) Only combinations of (3q), (3anti-q) and (q + anti-q) are found in nature today

iii) Assumption that laws of nature is the same for all times (time invariance) -> no such objects back then

 

[stevebd1]

There is the theoretical dibrayon-
http://en.wikipedia.org/wiki/Dibaryon

and the theoretical pentaquark-
http://en.wikipedia.org/wiki/Pentaquark


From 'Neutron Star Interiors and the Equation of State of Superdense Matter' page 9-

3.3 H-matter and exotic baryons

A novel particle that could be of relevance for the composition of neutron star matter is the H-dibaryon $H=([ud][ds][su]))$, a doubly strange six-quark composite with spin and isospin zero, and baryon number two. Since its first prediction in 1977, the H-dibaryon has been the subject of many theoretical and experimental studies as a possible candidate for a strongly bound exotic state. In neutron star matter, which may contain a significant fraction of Λ hyperons, the Λ’s could combine to form H-dibaryons, which could give way to the formation of H-dibaryon matter at densities somewhere above ∼ 4 n₀. If formed in neutron stars, however, H-matter appears to unstable against compression which could trigger the conversion of neutron stars into hypothetical strange stars.

Another particle, referred to as exotic baryon, of potential relevance for neutron stars, could be the pentaquark, $\Theta^+([ud]^2\bar{s})$, with a predicted mass of 1540 MeV. The pentaquark, which carries baryon number one, is a hypothetical subatomic particle consisting of a group of four quarks and one anti-quark (compared to three quarks in normal baryons and two in mesons), bound by the strong color-spin correlation force (attraction between quarks in the color $\overline{\textbf{3}}_c$ channel) that drives color superconductivity. The pentaquark decays according to $\Theta^+(1540)\rightarrow K^+[\bar{s}u]+n[udd]$ and thus has the same quantum numbers as the $K^+n$. The associated reaction in chemically equilibrated matter would imply $\mu^{\Theta^+}=\mu^{K^+}+\mu^n$.

 

[malawi_glenn]

Theoretical and theoretical.. I would call them "hypothetical" (and indeed the wiki articles also call them so)

There are of course many many (infinite) more ways to combine quarks and antiquarks to maintain color neutrality.

 

[Vanadium 50]

Even worse than "theoretical" - there have been many searches for the H, and all have come up dry. There were some early searches for pentaquarks that showed a marginally positive result, however there have been severe difficulties in producing a signal that is both strong and reproducible.