Editing Preon (section)

{{Short description|Hypothetical subatomic particle}}
{{for multi|the infectious proteins|Prion|the chemical pollutants|Chlorofluorocarbon}}
 
In [[particle physics]], '''preons''' are hypothetical [[point particle]]s, conceived of as sub-components of [[quark]]s and [[lepton]]s.<ref name="D'Souza">
{{cite book
 |last1=D'Souza |first1=I.A.
 |last2=Kalman |first2=C.S.
 |year=1992
 |title=Preons: Models of Leptons, Quarks and Gauge Bosons as Composite Objects
 |publisher=[[World Scientific]]
 |isbn=978-981-02-1019-9
}}</ref> The word was coined by [[Jogesh Pati]] and [[Abdus Salam]], in 1974. Interest in preon models peaked in the 1980s but has slowed, as the [[Standard Model]] of particle physics continues to describe physics mostly successfully, and no direct experimental evidence for lepton and quark compositeness has been found. Preons come in four varieties: plus, anti-plus, zero, and anti-zero. [[W boson]]s have six preons, and quarks and leptons have only three. 

In the [[hadron]]ic sector, some effects are considered anomalies within the Standard Model. For example, the [[proton spin crisis|proton spin puzzle]], the [[EMC effect]], the distributions of electric charges inside the [[nucleon]]s, as found by [[Robert Hofstadter]] in 1956,<ref>{{cite journal |last1=Hofstadter |first1=Robert |date=1 July 1956 |title=Electron Scattering and Nuclear Structure |journal=Reviews of Modern Physics |volume=28 |issue=3 |pages=214–254 |doi=10.1103/RevModPhys.28.214 |bibcode=1956RvMP...28..214H }}</ref><ref>{{cite journal |last1=Hofstadter |first1=R. |last2=Bumiller |first2=F. |last3=Yearian |first3=M.R. |date=1 April 1958 |title=Electromagnetic Structure of the Proton and Neutron |journal=Reviews of Modern Physics |volume=30 |issue=2 |pages=482–497 |doi=10.1103/RevModPhys.30.482 |bibcode=1958RvMP...30..482H  |url=http://www.physics.princeton.edu/~mcdonald/examples/EP/hofstadter_rmp_30_482_58.pdf |archive-url=https://web.archive.org/web/20180223210328/http://www.physics.princeton.edu/~mcdonald/examples/EP/hofstadter_rmp_30_482_58.pdf |archive-date=2018-02-23 |url-status=live}}</ref> and the ad hoc [[CKM matrix]] elements.

When the term "preon" was coined, it was primarily to explain the two families of spin-{{Sfrac|1|2}} fermions: quarks and leptons. More recent preon models also account for spin-1 bosons, and are still called "preons". Each of the preon models postulates a set of fewer fundamental particles than those of the Standard Model, together with the rules governing how those fundamental particles combine and interact. Based on these rules, the preon models try to explain the Standard Model, often predicting small discrepancies with this model and generating new particles and certain phenomena which do not belong to the Standard Model.