Editing Preon (section)

==Background==
Before the Standard Model was developed in the 1970s (the key elements of the Standard Model known as [[quark]]s were proposed by [[Murray Gell-Mann]] and [[George Zweig]] in 1964), physicists observed hundreds of different kinds of particles in [[particle accelerator]]s. These were organized into relationships on their physical properties in a largely ad-hoc system of hierarchies, not entirely unlike the way [[Taxonomy (biology)|taxonomy]] grouped animals based on their physical features. Not surprisingly, the huge number of particles was referred to as the "[[particle zoo]]".

The Standard Model, which is now the prevailing model of particle physics, dramatically simplified this picture by showing that most of the observed particles were [[meson]]s, which are combinations of two [[quark]]s, or [[baryon]]s which are combinations of three quarks, plus a handful of other particles. The particles being seen in the ever-more-powerful accelerators were, according to the theory, typically nothing more than combinations of these quarks.

===Comparisons of quarks, leptons, and bosons===
Within the Standard Model, there are [[List of particles|several classes of particles]]. One of these, the [[quark]]s, has six types, of which there are three varieties in each (dubbed "[[Color charge|colors]]", red, green, and blue, giving rise to [[quantum chromodynamics]]).

Additionally, there are six different types of what are known as [[lepton]]s. Of these six leptons, there are three [[charged particle]]s: the [[electron]], [[muon]], and [[tau (particle)|tau]]. The [[neutrino]]s comprise the other three leptons, and each neutrino pairs with one  of the three charged leptons.

In the Standard Model, there are also [[boson]]s, including the [[photon]]s and [[gluon]]s; [[W and Z bosons|W{{sup|+}}, W{{sup|−}}, and Z bosons]]; and the [[Higgs boson]]; and an open space left for the [[graviton]]. Almost all of these particles come in "left-handed" and "right-handed" versions (see '' [[Chirality (physics)|chirality]]''). The quarks, leptons, and W boson all have [[antiparticle]]s with opposite electric charge (or in the case of the neutrinos, opposite [[weak isospin]]).

===Unresolved problems with the Standard Model===
The Standard Model also has a number of problems which have not been entirely solved. In particular, no successful theory of [[gravitation]] based on a particle theory has yet been proposed. Although the Model assumes the existence of a graviton, all attempts to produce a consistent theory based on them have failed.

Kalman<ref>{{cite journal |last=Kalman |first=C.S. |year=2005 |title=Why quarks cannot be fundamental particles |journal=Nuclear Physics B: Proceedings Supplements |volume=142 |pages=235–237 |doi=10.1016/j.nuclphysbps.2005.01.042 |arxiv=hep-ph/0411313 |bibcode=2005NuPhS.142..235K |s2cid=119394495 }}</ref> asserts that, according to the concept of [[atomism]], fundamental building blocks of nature are indivisible bits of matter that are ungenerated and indestructible. Neither leptons nor quarks are truly indestructible, since some leptons can decay into other leptons, some quarks into other quarks. Thus, on fundamental grounds, quarks are not themselves fundamental building blocks, but must be composed of other, fundamental quantities—preons. Although the mass of each successive particle follows certain patterns, predictions of the [[rest mass]] of most particles cannot be made precisely, except for the masses of almost all baryons which have been modeled well by de&nbsp;Souza (2010).<ref>{{cite journal |last=de&nbsp;Souza |first=Mario Everaldo  |year=2010 |title=Calculation of almost all energy levels of baryons |journal=[[Papers in Physics]] |volume=3 |pages=030003–1 |doi=10.4279/PIP.030003 |url=http://www.papersinphysics.org/papersinphysics/article/download/64/pdf64 |doi-access=free }}</ref>

The Standard Model also has problems predicting the large scale structure of the universe. For instance, the SM generally predicts equal amounts of matter and [[antimatter]] in the universe. A number of attempts have been made to "fix" this through a variety of mechanisms, but to date none have won widespread support. Likewise, basic adaptations of the Model suggest the presence of [[proton decay]], which has not yet been observed.

===Motivation for preon models===
Several models have been proposed in an attempt to provide a more fundamental explanation of the results in experimental and theoretical particle physics, using names such as "[[Parton (particle physics)|parton]]" or "preon" for the hypothetical basic particle constituents.

Preon theory is motivated by a desire to replicate in particle physics the achievements of the [[periodic table]] in Chemistry, which reduced 94&nbsp;naturally occurring elements to combinations of just three building-blocks (proton, neutron, electron). Likewise, the [[Standard Model]] later organized the "particle zoo" of [[hadrons]] by reducing several dozen particles to combinations at a more fundamental level of (at first) just three [[quarks]], consequently reducing the huge number of arbitrary constants in mid-twentieth-century particle physics prior to the [[Standard Model]] and [[quantum chromodynamics]].

However, the particular preon model discussed below has attracted comparatively little interest among the particle physics community to date, in part because no evidence has been obtained so far in collider experiments to show that the fermions of the Standard Model are composite.

===Attempts===
A number of physicists have attempted to develop a theory of "pre-quarks" (from which the name ''preon'' derives) in an effort to justify theoretically the many parts of the Standard Model that are known only through experimental data. Other names which have been used for these proposed fundamental particles (or particles intermediate between the most fundamental particles and those observed in the Standard Model) include ''prequarks'', ''subquarks'', ''maons'',<ref>
{{cite news
 |last=Overbye |first=D. |author-link=Dennis Overbye
 |date=5 December 2006
 |title=China pursues major role in particle physics
 |newspaper=[[The New York Times]]
 |url=https://www.nytimes.com/2006/12/05/science/05china.html
 |access-date=2011-09-12
}}
</ref> ''alphons'', ''quinks'', ''[[Rishon model|rishon]]s'', ''tweedles'', ''helons'', ''haplons'', ''Y-particles'',<ref>
{{cite journal
 |last1=Yershov |first=V.N.
 |year=2005
 |title=Equilibrium configurations of tripolar charges
 |journal=[[Few-Body Systems]]
 |volume=37 |issue=1–2 |pages=79–106
 |arxiv=physics/0609185 |bibcode = 2005FBS....37...79Y
 |doi=10.1007/s00601-004-0070-2 |s2cid=119474883
}}
</ref> and ''primons''.<ref>
{{cite journal
 |last1=de Souza |first1=M.E.
 |year=2005
 |title=The ultimate division of matter
 |journal=[[Scientia Plena]]
 |volume=1 |issue=4 |pages=83
}}
</ref> ''Preon'' is the leading name in the physics community.

Efforts to develop a substructure date at least as far back as 1974 with a paper by Pati and Salam in ''[[Physical Review]]''.<ref>
{{cite journal
 |last1=Pati  |first1=J.C.
 |last2=Salam |first2=A.
 |year=1974
 |title=Lepton number as the fourth "color"
 |journal=[[Physical Review D]]
 |volume=10 |issue=1 |pages=275–289
 |bibcode = 1974PhRvD..10..275P |doi=10.1103/PhysRevD.10.275
 |s2cid=17349483
 |url=http://pdfs.semanticscholar.org/21fb/f9d49acf3e3f07098ca686ae4058c38dbd03.pdf
 |url-status=dead
 |archive-url=https://web.archive.org/web/20190220013017/http://pdfs.semanticscholar.org/21fb/f9d49acf3e3f07098ca686ae4058c38dbd03.pdf
 |archive-date=2019-02-20
}}<br/>Erratum:
{{cite journal
 |last1=Pati  |first1=J.C.
 |last2=Salam |first2=A.
 |year=1975
 |title=Erratum: Lepton number as the fourth "color"
 |journal=[[Physical Review D]]
 |volume=11 |issue=3 |page=703
 |bibcode = 1975PhRvD..11..703P |doi=10.1103/PhysRevD.11.703.2
|doi-access=free}}
</ref>
Other attempts include a 1977 paper by Terazawa, Chikashige, and Akama,<ref>
{{cite journal
 |last1=Terazawa   |first1=H.
 |last2=Chikashige |first2=Y.
 |last3=Akama      |first3=K.
 |year=1977
 |title=Unified model of the Nambu-Jona-Lasinio type for all elementary particles
 |journal=[[Physical Review D]]
 |volume=15 |issue=2 |pages=480–487
 |bibcode = 1977PhRvD..15..480T  |doi=10.1103/PhysRevD.15.480
}}
</ref> similar, but independent, 1979 papers by Ne'eman,<ref>
{{cite journal
 |last=Ne'eman |first=Y.
 |year=1979
 |title=Irreducible gauge theory of a consolidated Weinberg-Salam model
 |journal=[[Physics Letters B]]
 |volume=81 |issue=2 |pages=190–194 
 |bibcode = 1979PhLB...81..190N  |osti=6534180
 |doi=10.1016/0370-2693(79)90521-5
 |url=https://www.osti.gov/biblio/6534180
}}
</ref>
Harari,<ref name=harari1>
{{cite journal
 |last=Harari |first=H.
 |year=1979
 |title=A schematic model of quarks and leptons
 |url=http://www.slac.stanford.edu/cgi-wrap/getdoc/slac-pub-2310.pdf
 |journal=[[Physics Letters B]]
 |volume=86 |issue=1 |pages=83–86
 |bibcode = 1979PhLB...86...83H |osti=1447265 
 |doi=10.1016/0370-2693(79)90626-9
}}</ref>
and Shupe,<ref>
{{cite journal
 |last=Shupe |first=M.A.
 |year=1979
 |title=A composite model of leptons and quarks
 |journal=[[Physics Letters B]]
 |volume=86 |issue=1 |pages=87–92
 |bibcode=1979PhLB...86...87S
 |doi=10.1016/0370-2693(79)90627-0
}}
</ref> a 1981 paper by Fritzsch and Mandelbaum,<ref>
{{cite journal
 |last1=Fritzsch   |first1=H.
 |last2=Mandelbaum |first2=G.
 |year=1981
 |title=Weak interactions as manifestations of the substructure of leptons and quarks
 |journal=[[Physics Letters B]]
 |volume=102 |issue=5 |pages=319
 |bibcode = 1981PhLB..102..319F
 |doi=10.1016/0370-2693(81)90626-2
}}
</ref>
and a 1992 book by D'Souza and Kalman.<ref name="D'Souza"/> None of these have gained wide acceptance in the physics world. However, in a recent work<ref>
{{cite journal
 |last=de&nbsp;Souza |first=M.E.
 |year=2008
 |title=Weak decays of hadrons reveal compositeness of quarks
 |journal=[[Scientia Plena]]
 |volume=4 |issue=6 |pages=064801–1
}}</ref>
de&nbsp;Souza has shown that his model describes well all weak decays of hadrons according to selection rules dictated by a quantum number derived from his compositeness model. In his model leptons are elementary particles and each quark is composed of two ''primons'', and thus, all quarks are described by four ''primons''. Therefore, there is no need for the Standard Model Higgs boson and each quark mass is derived from the interaction between each pair of ''primons'' by means of three Higgs-like bosons.

In his 1989 [[Nobel Prize]] acceptance lecture, [[Hans Georg Dehmelt|Hans Dehmelt]] described a most fundamental elementary particle, with definable properties, which he called the ''[[cosmon]]'', as the likely result of a long but finite chain of increasingly more elementary particles.<ref>
{{cite web
 |last=Dehmelt |first=H.G.
 |year=1989
 |title=Experiments with an isolated subatomic particle at rest
 |series=Nobel lecture
 |publisher=[[The Nobel Foundation]]
 |url=https://www.nobelprize.org/nobel_prizes/physics/laureates/1989/dehmelt-lecture.html
}} See also references therein.
</ref>

===Composite Higgs===
{{See also|Composite Higgs models|Two-Higgs-doublet model}}{{update|date=July 2019}}
Many preon models either do not account for the [[Higgs boson]] or rule it out, and propose that electro-weak symmetry is broken not by a scalar Higgs field but by composite preons.<ref>{{cite arXiv |last1=Dugne |first1=J.-J. |last2=Fredriksson |first2=S. |last3=Hansson |first3=J. |last4=Predazzi |first4=E. |year=1997 |title=Higgs pain? Take a preon! |eprint=hep-ph/9709227}}</ref>  For example, Fredriksson preon theory does not need the Higgs boson, and explains the electro-weak breaking as the rearrangement of preons, rather than a Higgs-mediated field. In fact, the Fredriksson preon model and the de Souza model predict that the Standard Model Higgs boson does not exist.