HOME

TheInfoList



OR:

In
particle physics Particle physics or high energy physics is the study of fundamental particles and forces that constitute matter and radiation. The fundamental particles in the universe are classified in the Standard Model as fermions (matter particles) an ...
, preons are
point particle A point particle (ideal particle or point-like particle, often spelled pointlike particle) is an idealization of particles heavily used in physics. Its defining feature is that it lacks spatial extension; being dimensionless, it does not take up ...
s, conceived of as sub-components of
quarks A quark () is a type of elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. All commonly o ...
and
lepton In particle physics, a lepton is an elementary particle of half-integer spin ( spin ) that does not undergo strong interactions. Two main classes of leptons exist: charged leptons (also known as the electron-like leptons or muons), and neutr ...
s. The word was coined by
Jogesh Pati Jogesh C. Pati (born 1937) is an Indian American theoretical physicist at the SLAC National Accelerator Laboratory. Biography Jogesh Pati started his schooling at Guru Training School, Baripada and then admitted to M.K.C High School where he ...
and
Abdus Salam Mohammad Abdus Salam Salam adopted the forename "Mohammad" in 1974 in response to the anti-Ahmadiyya decrees in Pakistan, similarly he grew his beard. (; ; 29 January 192621 November 1996) was a Punjabi Pakistani theoretical physicist and a ...
, in 1974. Interest in preon models peaked in the 1980s but has slowed, as the
Standard Model The Standard Model of particle physics is the theory describing three of the four known fundamental forces (electromagnetism, electromagnetic, weak interaction, weak and strong interactions - excluding gravity) in the universe and classifying a ...
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 In particle physics, the W and Z bosons are vector bosons that are together known as the weak bosons or more generally as the intermediate vector bosons. These elementary particles mediate the weak interaction; the respective symbols are , , and ...
s have six preons and
quarks A quark () is a type of elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. All commonly o ...
have only three. In the
hadron In particle physics, a hadron (; grc, ἁδρός, hadrós; "stout, thick") is a composite subatomic particle made of two or more quarks held together by the strong interaction. They are analogous to molecules that are held together by the ele ...
ic sector, some effects are considered anomalies within the
Standard Model The Standard Model of particle physics is the theory describing three of the four known fundamental forces (electromagnetism, electromagnetic, weak interaction, weak and strong interactions - excluding gravity) in the universe and classifying a ...
. For example, the proton spin puzzle, the
EMC effect The EMC effect is the surprising observation that the cross section for deep inelastic scattering from an atomic nucleus is different from that of the same number of free protons and neutrons (collectively referred to as nucleons). From this obse ...
, the distributions of electric charges inside the
nucleon In physics and chemistry, a nucleon is either a proton or a neutron, considered in its role as a component of an atomic nucleus. The number of nucleons in a nucleus defines the atom's mass number (nucleon number). Until the 1960s, nucleons were ...
s, as found by Hofstadter in 1956, and the ad hoc CKM matrix elements. When the term "preon" was coined, it was primarily to explain the two families of spin- 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 The Standard Model of particle physics is the theory describing three of the four known fundamental forces (electromagnetism, electromagnetic, weak interaction, weak and strong interactions - excluding gravity) in the universe and classifying a ...
, often predicting small discrepancies with this model and generating new particles and certain phenomena, which do not belong to the Standard Model.


Goals of preon models

Preon research is motivated by the desire to: *Reduce the large number of particles, many that differ only in charge, to a smaller number of more fundamental particles. For example, the
electron The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no kn ...
and
positron The positron or antielectron is the antiparticle or the antimatter counterpart of the electron. It has an electric charge of +1 '' e'', a spin of 1/2 (the same as the electron), and the same mass as an electron. When a positron collides ...
are identical except for charge, and preon research is motivated by explaining that electrons and positrons are composed of similar preons with the relevant difference accounting for charge. The hope is to reproduce the reductionist strategy that has worked for the
periodic table of elements The periodic table, also known as the periodic table of the (chemical) elements, is a rows and columns arrangement of the chemical elements. It is widely used in chemistry, physics, and other sciences, and is generally seen as an icon of c ...
. *Explain the three
generation A generation refers to all of the people born and living at about the same time, regarded collectively. It can also be described as, "the average period, generally considered to be about 20–⁠30 years, during which children are born and gr ...
s of
fermions In particle physics, a fermion is a particle that follows Fermi–Dirac statistics. Generally, it has a half-odd-integer spin: spin , spin , etc. In addition, these particles obey the Pauli exclusion principle. Fermions include all quarks and ...
. *Calculate parameters that are currently unexplained by the Standard Model, such as particle
mass Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different elementar ...
es,
electric charge Electric charge is the physical property of matter that causes charged matter to experience a force when placed in an electromagnetic field. Electric charge can be ''positive'' or ''negative'' (commonly carried by protons and electrons respe ...
s, and
color charge Color charge is a property of quarks and gluons that is related to the particles' strong interactions in the theory of quantum chromodynamics (QCD). The "color charge" of quarks and gluons is completely unrelated to the everyday meanings of ...
s, and reduce the number of experimental input parameters required by the Standard Model. *Provide reasons for the very large differences in energy-masses observed in supposedly fundamental particles, from the
electron neutrino The electron neutrino () is an elementary particle which has zero electric charge and a spin of . Together with the electron, it forms the first generation of leptons, hence the name electron neutrino. It was first hypothesized by Wolfgang Pauli ...
to the
top quark The top quark, sometimes also referred to as the truth quark, (symbol: t) is the most massive of all observed elementary particles. It derives its mass from its coupling to the Higgs Boson. This coupling y_ is very close to unity; in the Standard ...
. *Provide alternative explanations for the
electro-weak In particle physics, the electroweak interaction or electroweak force is the unified description of two of the four known fundamental interactions of nature: electromagnetism and the weak interaction. Although these two forces appear very differe ...
symmetry breaking In physics, symmetry breaking is a phenomenon in which (infinitesimally) small fluctuations acting on a system crossing a critical point decide the system's fate, by determining which branch of a bifurcation is taken. To an outside observe ...
without invoking a
Higgs field The Higgs boson, sometimes called the Higgs particle, is an elementary particle in the Standard Model of particle physics produced by the quantum excitation of the Higgs field, one of the fields in particle physics theory. In the Stand ...
, which in turn possibly needs a
supersymmetry In a supersymmetric theory the equations for force and the equations for matter are identical. In theoretical and mathematical physics, any theory with this property has the principle of supersymmetry (SUSY). Dozens of supersymmetric theories e ...
to correct the theoretical problems involved with the Higgs field. Supersymmetry itself has theoretical problems. *Account for neutrino oscillation and mass. *Make new nontrivial predictions, such as
cold dark matter In cosmology and physics, cold dark matter (CDM) is a hypothetical type of dark matter. According to the current standard model of cosmology, Lambda-CDM model, approximately 27% of the universe is dark matter and 68% is dark energy, with only a sm ...
candidates. *Explain why there exists only the observed variety of particle species, and give a model with reasons for producing ''only'' these observed particles (since the prediction of non-observed particles is a problem with many current models, such as
supersymmetry In a supersymmetric theory the equations for force and the equations for matter are identical. In theoretical and mathematical physics, any theory with this property has the principle of supersymmetry (SUSY). Dozens of supersymmetric theories e ...
).


Background

Before the Standard Model was developed in the 1970s (the key elements of the Standard Model known as
quark A quark () is a type of elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. All commonly o ...
s were proposed by
Murray Gell-Mann Murray Gell-Mann (; September 15, 1929 – May 24, 2019) was an American physicist who received the 1969 Nobel Prize in Physics for his work on the theory of elementary particles. He was the Robert Andrews Millikan Professor of Theoretical ...
and
George Zweig George Zweig (; born May 30, 1937) is a Russian-American physicist. He was trained as a particle physicist under Richard Feynman. He introduced, independently of Murray Gell-Mann, the quark model (although he named it "aces"). He later turned his ...
in 1964), physicists observed hundreds of different kinds of particles in
particle accelerator A particle accelerator is a machine that uses electromagnetic fields to propel charged particles to very high speeds and energies, and to contain them in well-defined beams. Large accelerators are used for fundamental research in particle ...
s. These were organized into relationships on their physical properties in a largely ad-hoc system of hierarchies, not entirely unlike the way
taxonomy Taxonomy is the practice and science of categorization or classification. A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...
grouped animals based on their physical features. Not surprisingly, the huge number of particles was referred to as the "
particle zoo In particle physics, the term particle zoo is used colloquially to describe the relatively extensive list of known subatomic particles by comparison to the variety of species in a zoo. In the history of particle physics, the topic of particles wa ...
". 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 In particle physics, a meson ( or ) is a type of hadronic subatomic particle composed of an equal number of quarks and antiquarks, usually one of each, bound together by the strong interaction. Because mesons are composed of quark subparticles ...
s, which are combinations of two
quark A quark () is a type of elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. All commonly o ...
s, or
baryon In particle physics, a baryon is a type of composite subatomic particle which contains an odd number of valence quarks (at least 3). Baryons belong to the hadron family of particles; hadrons are composed of quarks. Baryons are also classified ...
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 several classes of particles. One of these, the
quark A quark () is a type of elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. All commonly o ...
s, has six types, of which there are three varieties in each (dubbed "
colors Color (American English) or colour (British English) is the visual perceptual property deriving from the spectrum of light interacting with the photoreceptor cells of the eyes. Color categories and physical specifications of color are associa ...
", red, green, and blue, giving rise to
quantum chromodynamics In theoretical physics, quantum chromodynamics (QCD) is the theory of the strong interaction between quarks mediated by gluons. Quarks are fundamental particles that make up composite hadrons such as the proton, neutron and pion. QCD is a type ...
). Additionally, there are six different types of what are known as
lepton In particle physics, a lepton is an elementary particle of half-integer spin ( spin ) that does not undergo strong interactions. Two main classes of leptons exist: charged leptons (also known as the electron-like leptons or muons), and neutr ...
s. Of these six leptons, there are three
charged particle In physics, a charged particle is a particle with an electric charge. It may be an ion, such as a molecule or atom with a surplus or deficit of electrons relative to protons. It can also be an electron or a proton, or another elementary particle, ...
s: the
electron The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no kn ...
,
muon A muon ( ; from the Greek letter mu (μ) used to represent it) is an elementary particle similar to the electron, with an electric charge of −1 '' e'' and a spin of , but with a much greater mass. It is classified as a lepton. As wi ...
, and
tau Tau (uppercase Τ, lowercase τ, or \boldsymbol\tau; el, ταυ ) is the 19th letter of the Greek alphabet, representing the voiceless dental or alveolar plosive . In the system of Greek numerals, it has a value of 300. The name in English ...
. The
neutrino A neutrino ( ; denoted by the Greek letter ) is a fermion (an elementary particle with spin of ) that interacts only via the weak interaction and gravity. The neutrino is so named because it is electrically neutral and because its rest mass ...
s 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
boson In particle physics, a boson ( ) is a subatomic particle whose spin quantum number has an integer value (0,1,2 ...). Bosons form one of the two fundamental classes of subatomic particle, the other being fermions, which have odd half-integer s ...
s, including the
photon A photon () is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are massless, so they always ...
s; W+, W, and Z bosons;
gluon A gluon ( ) is an elementary particle that acts as the exchange particle (or gauge boson) for the strong force between quarks. It is analogous to the exchange of photons in the electromagnetic force between two charged particles. Gluons bind q ...
s and the
Higgs boson The Higgs boson, sometimes called the Higgs particle, is an elementary particle in the Standard Model of particle physics produced by the quantum excitation of the Higgs field, one of the fields in particle physics theory. In the Stand ...
; and an open space left for the
graviton In theories of quantum gravity, the graviton is the hypothetical quantum of gravity, an elementary particle that mediates the force of gravitational interaction. There is no complete quantum field theory of gravitons due to an outstanding mathem ...
. Almost all of these particles come in "left-handed" and "right-handed" versions (see ''
chirality Chirality is a property of asymmetry important in several branches of science. The word ''chirality'' is derived from the Greek (''kheir''), "hand", a familiar chiral object. An object or a system is ''chiral'' if it is distinguishable from ...
''). The quarks, leptons, and W boson all have
antiparticle In particle physics, every type of particle is associated with an antiparticle with the same mass but with opposite physical charges (such as electric charge). For example, the antiparticle of the electron is the positron (also known as an antie ...
s with opposite electric charge.


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 In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stron ...
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 asserts that, according to the concept of atomism, fundamental building blocks of nature are indivisible bits of matter that are ungenerated and indestructible. Quarks are not truly indestructible, since some can decay 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 The invariant mass, rest mass, intrinsic mass, proper mass, or in the case of bound systems simply mass, is the portion of the total mass of an object or system of objects that is independent of the overall motion of the system. More precisely, i ...
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. 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 modern physics, antimatter is defined as matter composed of the antiparticles (or "partners") of the corresponding particles in "ordinary" matter. Antimatter occurs in natural processes like cosmic ray collisions and some types of radioac ...
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 In particle physics, proton decay is a hypothetical form of particle decay in which the proton decays into lighter subatomic particles, such as a neutral pion and a positron. The proton decay hypothesis was first formulated by Andrei Sakharov ...
, 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" 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 The periodic table, also known as the periodic table of the (chemical) elements, is a rows and columns arrangement of the chemical elements. It is widely used in chemistry, physics, and other sciences, and is generally seen as an icon of ch ...
in Chemistry, which reduced 94 naturally occurring elements to combinations of just three building-blocks (proton, neutron, electron). Likewise, the
Standard Model The Standard Model of particle physics is the theory describing three of the four known fundamental forces (electromagnetism, electromagnetic, weak interaction, weak and strong interactions - excluding gravity) in the universe and classifying a ...
later organized the "particle zoo" of
hadrons In particle physics, a hadron (; grc, ἁδρός, hadrós; "stout, thick") is a composite subatomic particle made of two or more quarks held together by the strong interaction. They are analogous to molecules that are held together by the ele ...
by reducing several dozen particles to combinations at a more fundamental level of (at first) just three
quarks A quark () is a type of elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. All commonly o ...
, consequently reducing the huge number of arbitrary constants in mid-twentieth-century particle physics prior to the
Standard Model The Standard Model of particle physics is the theory describing three of the four known fundamental forces (electromagnetism, electromagnetic, weak interaction, weak and strong interactions - excluding gravity) in the universe and classifying a ...
and
quantum chromodynamics In theoretical physics, quantum chromodynamics (QCD) is the theory of the strong interaction between quarks mediated by gluons. Quarks are fundamental particles that make up composite hadrons such as the proton, neutron and pion. QCD is a type ...
. 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'', ''alphons'', ''quinks'', '' rishons'', ''tweedles'', ''helons'', ''haplons'', ''Y-particles'', and ''primons''. ''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 ''Physical Review'' is a peer-reviewed scientific journal established in 1893 by Edward Nichols. It publishes original research as well as scientific and literature reviews on all aspects of physics. It is published by the American Physical S ...
''. Other attempts include a 1977 paper by Terazawa, Chikashige and Akama, similar, but independent, 1979 papers by Ne'eman, Harari, and Shupe, a 1981 paper by Fritzsch and Mandelbaum, and a 1992 book by D'Souza and Kalman. None of these have gained wide acceptance in the physics world. However, in a recent work 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 The Nobel Prizes ( ; sv, Nobelpriset ; no, Nobelprisen ) are five separate prizes that, according to Alfred Nobel's will of 1895, are awarded to "those who, during the preceding year, have conferred the greatest benefit to humankind." Alfr ...
acceptance lecture,
Hans Dehmelt Hans Georg Dehmelt (; 9 September 1922 – 7 March 2017) was a German and American physicist, who was awarded a Nobel Prize in Physics in 1989, for co-developing the ion trap technique (Penning trap) with Wolfgang Paul, for which they shared one-h ...
described a most fundamental elementary particle, with definable properties, which he called the ''
cosmon Cosmon or Cosmonium is a hypothetical form of matter. The idea was originally proposed by Georges Lemaître, who suggested the concept of a 'primeval atom’ (''L'Hypothèse de l'Atome Primitif'') 1946. He illustrated the idea by imagining an obje ...
'', as the likely end result of a long but finite chain of increasingly more elementary particles.


Composite Higgs

Many preon models either do not account for the
Higgs boson The Higgs boson, sometimes called the Higgs particle, is an elementary particle in the Standard Model of particle physics produced by the quantum excitation of the Higgs field, one of the fields in particle physics theory. In the Stand ...
or rule it out, and propose that electro-weak symmetry is broken not by a scalar Higgs field but by composite preons. 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.


Rishon model

The '' rishon model'' (RM) is the earliest effort (1979) to develop a preon model to explain the phenomenon appearing in the
Standard Model The Standard Model of particle physics is the theory describing three of the four known fundamental forces (electromagnetism, electromagnetic, weak interaction, weak and strong interactions - excluding gravity) in the universe and classifying a ...
(SM) of
particle physics Particle physics or high energy physics is the study of fundamental particles and forces that constitute matter and radiation. The fundamental particles in the universe are classified in the Standard Model as fermions (matter particles) an ...
. It was first developed by
Haim Harari use both this parameter and , birth_date to display the person's date of birth, date of death, and age at death) --> , death_place = , death_cause = , body_discovered = , resting_place = , resting_place_coordinates ...
and Michael A. Shupe (independently of each other), and later expanded by Harari and his then-student
Nathan Seiberg Nathan "Nati" Seiberg (; born September 22, 1956) is an Israeli American theoretical physicist who works on quantum field theory and string theory. He is currently a professor at the Institute for Advanced Study in Princeton, New Jersey, United ...
. The model has two kinds of fundamental particles called rishons (ראשונים) (which means "First" in
Hebrew Hebrew (; ; ) is a Northwest Semitic language of the Afroasiatic language family. Historically, it is one of the spoken languages of the Israelites and their longest-surviving descendants, the Jews and Samaritans. It was largely preserved ...
). They are T ("Third" since it has an electric charge of ⅓  ''e'', or Tohu (תוהו) which means "Chaos") and V ("Vanishes", since it is electrically neutral, or Vohu which means "void"). All
lepton In particle physics, a lepton is an elementary particle of half-integer spin ( spin ) that does not undergo strong interactions. Two main classes of leptons exist: charged leptons (also known as the electron-like leptons or muons), and neutr ...
s and all flavours of
quark A quark () is a type of elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. All commonly o ...
s are three-rishon ordered triplets. These groups of three rishons have
spin-½ In quantum mechanics, spin is an intrinsic property of all elementary particles. All known fermions, the particles that constitute ordinary matter, have a spin of . The spin number describes how many symmetrical facets a particle has in one ful ...
. The Rishon model illustrates some of the typical efforts in the field. Many of the preon models theorize that the apparent imbalance of matter and antimatter in the universe is in fact illusory, with large quantities of preon-level antimatter confined within more complex structures.


Criticisms


The mass paradox

One preon model started as an internal paper at the Collider Detector at
Fermilab Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a United States Department of Energy national laboratory specializing in high-energy particle physics. Since 2007, Fermilab has been operat ...
(CDF) around 1994. The paper was written after an unexpected and inexplicable excess of jets with energies above 200 
GeV GEV may refer to: * ''G.E.V.'' (board game), a tabletop game by Steve Jackson Games * Ashe County Airport, in North Carolina, United States * Gällivare Lapland Airport, in Sweden * Generalized extreme value distribution * Gev Sella, Israeli-Sou ...
were detected in the 1992–1993 running period. However,
scattering Scattering is a term used in physics to describe a wide range of physical processes where moving particles or radiation of some form, such as light or sound, are forced to deviate from a straight trajectory by localized non-uniformities (including ...
experiments have shown that quarks and leptons are "point like" down to distance scales of less than 10−18 m (or of a proton diameter). The
momentum In Newtonian mechanics, momentum (more specifically linear momentum or translational momentum) is the product of the mass and velocity of an object. It is a vector quantity, possessing a magnitude and a direction. If is an object's mass an ...
uncertainty Uncertainty refers to epistemic situations involving imperfect or unknown information. It applies to predictions of future events, to physical measurements that are already made, or to the unknown. Uncertainty arises in partially observable or ...
of a preon (of whatever mass) confined to a box of this size is about 200 GeV/c, which is 50,000 times larger than the (model dependent)
rest mass The invariant mass, rest mass, intrinsic mass, proper mass, or in the case of bound systems simply mass, is the portion of the total mass of an object or system of objects that is independent of the overall motion of the system. More precisely, i ...
of an up-quark, and 400,000 times larger than the rest mass of an electron. Heisenberg's
uncertainty principle In quantum mechanics, the uncertainty principle (also known as Heisenberg's uncertainty principle) is any of a variety of mathematical inequalities asserting a fundamental limit to the accuracy with which the values for certain pairs of physic ...
states that \operatorname x \cdot \operatorname p \ge \tfrac\hbar and thus anything confined to a box smaller than \operatorname x would have a momentum uncertainty proportionally greater. Thus, the preon model proposed particles smaller than the elementary particles they make up, since the momentum uncertainty \operatorname p should be greater than the particles themselves. So the preon model represents a mass paradox: How could quarks or electrons be made of smaller particles that would have many orders of magnitude greater mass-energies arising from their enormous momenta? One way of resolving this paradox is to postulate a large binding force between preons that cancels their mass-energies. recursor to color charge?


Conflicts with observed physics

Preon models propose additional unobserved forces or dynamics to account for the observed properties of elementary particles, which may have implications in conflict with observation. For example, now that the
LHC The Large Hadron Collider (LHC) is the world's largest and highest-energy particle collider. It was built by the European Organization for Nuclear Research (CERN) between 1998 and 2008 in collaboration with over 10,000 scientists and hundre ...
's observation of a
Higgs boson The Higgs boson, sometimes called the Higgs particle, is an elementary particle in the Standard Model of particle physics produced by the quantum excitation of the Higgs field, one of the fields in particle physics theory. In the Stand ...
is confirmed, the observation contradicts the predictions of many preon models that did not include it. Preon theories require quarks and leptons to have a finite size. It is possible that the
Large Hadron Collider The Large Hadron Collider (LHC) is the world's largest and highest-energy particle collider. It was built by the European Organization for Nuclear Research (CERN) between 1998 and 2008 in collaboration with over 10,000 scientists and hundred ...
will observe this after it is upgraded to higher energies.


In popular culture

* In the 1948 reprint/edit of his 1930 novel ''
Skylark Three ''Skylark Three'' is a science fiction novel by American writer E. E. Smith, the second in his ''Skylark'' series. Originally serialized through the ''Amazing Stories'' magazine in 1930, it was first collected in book form in 1948 by Fantasy P ...
'',
E. E. Smith Edward Elmer Smith (May 2, 1890 – August 31, 1965), publishing as E. E. Smith, Ph.D. and later as E. E. "Doc" Smith, was an American food engineer (specializing in doughnut and pastry mixes) and science-fiction author, best known for the '' ...
postulated a series of 'subelectrons of the first and second type' with the latter being fundamental particles that were associated with the gravitation force. While this may not have been an element of the original novel (the scientific basis of some of the other novels in the series was revised extensively due to the additional eighteen years of scientific development), even the edited publication may be the first, or one of the first, mentions of the possibility that electrons are not fundamental particles. * In the novelized version of the 1982 motion picture '' Star Trek II: The Wrath of Khan'', written by
Vonda McIntyre Vonda Neel McIntyre () was an American science fiction writer and biologist. Early life and education Vonda N. McIntyre was born in Louisville, Kentucky, the daughter of H. Neel and Vonda B. Keith McIntyre, who were born in Poland, Ohio. She ...
, two of Dr. Carol Marcus' Genesis project team, Vance Madison and Delwyn March, have studied sub-elementary particles they've named "boojums" and "snarks", in a field they jokingly call "kindergarten physics" because it is lower than "elementary" (analogy to school levels). * James P. Hogan's 1982 novel ''
Voyage from Yesteryear ''Voyage from Yesteryear'' is a 1982 science fiction novel by British writer James P. Hogan. Origins According to Hogan, the idea for the book originated around 1976 when he was asked by a friend about whether there was a solution to "the Tro ...
'' discussed preons (called ''tweedles''), the physics of which became central to the plot.


See also

*
Technicolor (physics) Technicolor theories are models of physics beyond the Standard Model that address electroweak gauge symmetry breaking, the mechanism through which W and Z bosons acquire masses. Early technicolor theories were modelled on quantum chromodynam ...
* Preon star *
Preon-degenerate matter Degenerate matter is a highly dense state of matter, state of Fermion, fermionic matter in which the Pauli exclusion principle exerts significant pressure in addition to, or in lieu of, thermal pressure. The description applies to matter composed ...
* Rishon model


References


Further reading

* * {{particles Hypothetical elementary particles