text: Preon - Wikipedia, the free encyclopedia
  In particle physics, preons are "point-like" particles, conceived to be subcomponents of quarks and leptons.[1] 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 the physics mostly successfully, and no direct experimental evidence for lepton and quark compositeness has been found.
  Note that in the hadronic sector there are some intriguing open questions and some effects considered anomalies within the Standard Model. For example, four very important open questions are the proton spin puzzle, the EMC effect, the distributions of electric charges inside the nucleons as found by Hofstadter in 1956, and the ad hoc CKM matrix elements.
  4 Rishon model
  5.1 The mass paradox
  6 Conflicts with observed physics
  Within the Standard Model, there are several different types of particles. One of these, the quarks, has six different types, of which there are three varieties in each (dubbed "colors", red, green, and blue, giving rise to quantum chromodynamics). Additionally, there are six different types of what are known as leptons. Of these six leptons, there are three charged particles: the electron, muon, and tau. The neutrinos comprise the other three leptons, and for each neutrino there is a corresponding member from the other set of three leptons. In the Standard Model, there are also bosons, including the photons; W+, W−, and Z bosons; gluons 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). The quarks, leptons and W boson all have antiparticles with opposite electric charge.
  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. Additionally, mass remains a mystery in the Standard Model. Additionally Kalman [2] notes that according to the concept of atomism, the fundamental building blocks of nature are invisible and indivisible bits of matter that are ungenerated and indestructible. Quarks are not indestructible, some can decay into other quarks. Thus on fundamental grounds- quarks must be composed of 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 recently described very well by the model of de Souza.[3] The Higgs boson explains why particles show inertial mass (but does not explain rest mass).
  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, something that is observably not the case. 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.
  Preon research is motivated by the desire to explain already known facts (retrodiction), which include
  To explain the three generations of fermions.
  To calculate parameters that are currently unexplained by the Standard Model, such as particle masses, electric charges, and color charges, and reduce the number of experimental input parameters required by the Standard Model.
  The desire to make new nontrivial predictions, for example, to provide possible cold dark matter candidates.
  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,[4] alphons, quinks, rishons, tweedles, helons, haplons, Y-particles,[5] and primons.[6] 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.[7] Other attempts include a 1977 paper by Terazawa, Chikashige and Akama,[8] similar, but independent, 1979 papers by Ne'eman,[9] Harari,[10] and Shupe,[11] a 1981 paper by Fritzsch and Mandelbaum,[12] and a 1992 book by D'Souza and Kalman.[1] None of these has gained wide acceptance in the physics world. However, in a recent work[13] de 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,
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