This is a list of hypothetical
subatomic particle
In physics, a subatomic particle is a particle smaller than an atom. According to the Standard Model of particle physics, a subatomic particle can be either a composite particle, which is composed of other particles (for example, a baryon, lik ...
s in
physics
Physics is the scientific study of matter, its Elementary particle, fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge whi ...
.
Elementary particles
Some theories predict the existence of additional elementary bosons and fermions that are not found in the
Standard Model
The Standard Model of particle physics is the Scientific theory, theory describing three of the four known fundamental forces (electromagnetism, electromagnetic, weak interaction, weak and strong interactions – excluding gravity) in the unive ...
.
Particles predicted by supersymmetric theories
Supersymmetry
Supersymmetry is a Theory, theoretical framework in physics that suggests the existence of a symmetry between Particle physics, particles with integer Spin (physics), spin (''bosons'') and particles with half-integer spin (''fermions''). It propo ...
predicts the existence of
superpartner
In particle physics, a superpartner (also sparticle) is a class of hypothetical elementary particles predicted by supersymmetry, which, among other applications, is one of the well-studied ways to extend the Standard Model of high-energy physics.
...
s to particles in the Standard Model, none of which have been confirmed experimentally. The
sfermions (spin-0) include:
Another hypothetical sfermion is the
saxion, superpartner of the axion. Forms a
supermultiplet, together with the axino and the axion, in supersymmetric extensions of
Peccei–Quinn theory.
The predicted bosinos (spin ) are
Just as the photon,
Z and W± bosons are superpositions of the B, W, W, and W fields, the
photino, zino, and wino are superpositions of the bino, wino, wino, and wino. No matter if one uses the original gauginos or this superpositions as a basis, the only predicted physical particles are neutralinos and charginos as a superposition of them together with the Higgsinos.
Other superpartner categories include:
*
Charginos, superpositions of the superpartners of charged Standard Model bosons: charged Higgs boson and W boson. The
Minimal Supersymmetric Standard Model
The Minimal Supersymmetric Standard Model (MSSM) is an extension to the Standard Model that realizes supersymmetry. MSSM is the minimal supersymmetrical model as it considers only "the inimumnumber of new particle states and new interactions ...
(MSSM) predicts two pairs of charginos.
*
Neutralinos, superpositions of the superpartners of neutral Standard Model bosons: neutral Higgs boson, Z boson and photon. The lightest neutralino is a leading candidate for dark matter. The MSSM predicts four neutralinos.
*
Goldstinos are
fermion
In particle physics, a fermion is a subatomic particle that follows Fermi–Dirac statistics. Fermions have a half-integer spin (spin 1/2, spin , Spin (physics)#Higher spins, spin , etc.) and obey the Pauli exclusion principle. These particles i ...
s produced by the spontaneous breaking of
supersymmetry
Supersymmetry is a Theory, theoretical framework in physics that suggests the existence of a symmetry between Particle physics, particles with integer Spin (physics), spin (''bosons'') and particles with half-integer spin (''fermions''). It propo ...
; they are the supersymmetric counterpart of
Goldstone boson
In physics, Goldstone bosons or Nambu–Goldstone bosons (NGBs) are bosons that appear necessarily in models exhibiting spontaneous breakdown of continuous symmetries. They were discovered by Yoichiro Nambu within the context of the BCS superco ...
s.
*
Sgoldstino
A sgoldstino is any of the spin-0 superpartners of the goldstino in relativistic quantum field theories with spontaneously broken supersymmetry. The term ''sgoldstino'' was first used in 1998.
In 2016, Petersson and Torre hypothesized that a s ...
, superpartners of goldstinos.
Dark energy candidates
The following hypothetical particles have been proposed to explain
dark energy
In physical cosmology and astronomy, dark energy is a proposed form of energy that affects the universe on the largest scales. Its primary effect is to drive the accelerating expansion of the universe. It also slows the rate of structure format ...
:
Dark matter candidates
The following categories are not unique or distinct: For example, either a WIMP or a WISP is also a FIP.
Hidden sector theories have also proposed forces that only interact with dark matter, like
dark photons.
From experimental anomalies
These hypothetical particles were claimed to be found or hypothesized to explain unusual experimental results. They relate to experimental anomalies but have not been reproduced independently or might be due to experimental errors:
Other
*
Cosmon, hypothetical state containing the observable universe before the
Big Bang
The Big Bang is a physical theory that describes how the universe expanded from an initial state of high density and temperature. Various cosmological models based on the Big Bang concept explain a broad range of phenomena, including th ...
.
*
Diproton
Helium (He) ( standard atomic weight: ) has nine known isotopes, but only helium-3 (He) and helium-4 (He) are stable. All radioisotopes are short-lived; the longest-lived is He with half-life . The least stable is He, with half-life (), though He ...
(He-2), nuclei consisting of two protons and no neutrons. Yet unobserved.
*
Diquark, hypothetical state of two
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 ...
grouped inside a
baryon
In particle physics, a baryon is a type of composite particle, composite subatomic particle that contains an odd number of valence quarks, conventionally three. proton, Protons and neutron, neutrons are examples of baryons; because baryons are ...
.
*
Geons are electromagnetic or gravitational waves which are held together in a confined region by the gravitational attraction of their own field of energy.
*
Kaluza–Klein towers of particles are predicted by some models of extra dimensions. The extra-dimensional momentum is manifested as extra mass in four-dimensional spacetime.
*
Pomerons, used to explain the
elastic scattering
Elastic scattering is a form of particle scattering in scattering theory, nuclear physics and particle physics. In this process, the internal states of the Elementary particle, particles involved stay the same. In the non-relativistic case, where ...
of hadrons and the location of
Regge poles in
Regge theory. A counterpart to
odderons.
By type
*
Branons, scalar fields predicted in brane world models.
*
Composite Higgs, models that consider 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 excited state, quantum excitation of the Higgs field,
one of the field (physics), fields in particl ...
to be a composite particle.
**
Higgs doublets are hypothesized by some theories of
physics beyond the standard model
Physics beyond the Standard Model (BSM) refers to the theoretical developments needed to explain the deficiencies of the Standard Model, such as the inability to explain the fundamental parameters of the standard model, the strong CP problem, neut ...
.
*
Continuous spin particle are hypothetical massless particles related to the classification of the representations of the
Poincaré group.
*
Cryptons, any particle from the dark sector of
string theory landscape
In string theory, the string theory landscape (or landscape of vacua) is the collection of possible false vacua,The number of metastable vacua is not known exactly, but commonly quoted estimates are of the order 10500. See M. Douglas, "The stat ...
.
*Elementary particles that are not bosons or fermions:
**Paraparticles, exotic particles that can survive in a 3D-space and follow
parastatistics
In quantum mechanics and statistical mechanics, parastatistics is a hypothetical alternative to the established particle statistics models (Bose–Einstein statistics, Fermi–Dirac statistics and Maxwell–Boltzmann statistics). Other alterna ...
**Plektons, particles that follow
Braid statistics
In mathematics and theoretical physics, braid statistics is a generalization of the Spin–statistics theorem, spin statistics of bosons and fermions based on the concept of braid group. While for fermions (bosons) the corresponding statistics ...
*
Exotic particles, particles with exotic properties like negative mass or complex mass.
*
Exotic hadrons
Exotic hadrons are subatomic particles composed of quarks and gluons, but which – unlike "well-known" hadrons such as protons, neutrons and mesons – consist of more than three valence quarks. By contrast, "ordinary" hadrons contain just two or ...
, particles composed of unusual combinations of quarks and gluons.
**
Exotic mesons
**
Exotic baryons
**
Glueball, hypothetical particle that consist of only
gluons
A gluon ( ) is a type of massless elementary particle that mediates the strong interaction between quarks, acting as the exchange particle for the interaction. Gluons are massless vector bosons, thereby having a spin of 1. Through the s ...
.
**Quark bound states beyond the
pentaquark
A pentaquark is a human-made subatomic particle, consisting of four quarks and one antiquark bound together; they are not known to occur naturally, or exist outside of experiments specifically carried out to create them.
As quarks have a bar ...
, like
hexaquarks and
heptaquarks.
*
Leptoquark, hypothetical particles that are neither bosons or fermions but carry
lepton
In particle physics, a lepton is an elementary particle of half-integer spin (Spin (physics), spin ) that does not undergo strong interactions. Two main classes of leptons exist: electric charge, charged leptons (also known as the electron-li ...
and
baryon numbers.
*
Magnetic monopole
In particle physics, a magnetic monopole is a hypothetical particle that is an isolated magnet with only one magnetic pole (a north pole without a south pole or vice versa). A magnetic monopole would have a net north or south "magnetic charge". ...
is a generic name for particles with non-zero magnetic charge. They are predicted by Grand Unification Theories. These may include:
**
Dirac monopoles, monopole that would allow charge quantization.
**
't Hooft–Polyakov monopoles, Dirac monopole but without
Dirac strings.
**
Wu–Yang monopoles, point-like monopole with potential of the form 1/''r''.
**
Dyons, extensions of the idea of a magnetic monopole.
*
Majorana fermions, fermions that are their own anti-particle
*
Mesonic molecule
A mesonic molecule is a set of two or more mesons bound together by the strong force. Unlike baryonic molecules, which form the nuclei of all elements in nature save hydrogen-1, a mesonic molecule has yet to be definitively observed. The X(3872 ...
, two mesons bound together by strong force.
*
Micro black hole, sub-atomic sized black holes.
**
Black hole electron, microscopic black hole with the properties of an electron.
*
Minicharged particle are hypothetical subatomic particles charged with a tiny fraction of the electron charge.
*
Mirror particles are predicted by theories that restore
parity symmetry.
*
Neutronium
Neutronium (or neutrium, neutrite, or element zero) is a hypothetical substance made purely of neutrons. The word was coined by scientist Andreas von Antropoff in 1926 (before the 1932 discovery of the neutron) for the hypothetical "element of ...
, hypothetical nuclei consisting only of
neutrons (more than one). Examples include the
tetraneutron.
*
Preons were suggested as subparticles of quarks and leptons, but modern
collider experiments have all but ruled out their existence.
** Rishons, particles from the
Rishon model of preons.
* From superseded and obsolete theories
**
Caloric rays used until the 19th century to explain
thermal radiation
Thermal radiation is electromagnetic radiation emitted by the thermal motion of particles in matter. All matter with a temperature greater than absolute zero emits thermal radiation. The emission of energy arises from a combination of electro ...
.
**
Light corpuscles, hypothetical classical particles used to explain optical phenomena.
**
Phlogiston, hypothetical combustible content in matter used to explain
thermodynamics
Thermodynamics is a branch of physics that deals with heat, Work (thermodynamics), work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these quantities is governed b ...
before the 18th century.
** Ultramundane corpuscles, from
Le Sage's theory of gravitation, used to explain gravitational phenomena.
*
Strangelet, hypothetical particle that could form matter consisting of
strange quarks.
*
R-hadron, bound particle of a quark and a supersymmetric particle.
*
T meson, hypothetical
mesons
In particle physics, a meson () 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, the ...
composed of a
top
Top most commonly refers to:
* Top, a basic term of orientation, distinguished from bottom, front, back, and sides
* Spinning top, a ubiquitous traditional toy
* Top (clothing), clothing designed to be worn over the torso
* Mountain top, a moun ...
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 nucleus, atomic nuclei ...
and one additional subatomic particle. Examples include the
theta meson, formed by a top and an anti-top.
*
Tachyons is a hypothetical particle that travels
faster than the speed of light so they would paradoxically experience time in reverse (due to inversion of the
theory of relativity
The theory of relativity usually encompasses two interrelated physics theories by Albert Einstein: special relativity and general relativity, proposed and published in 1905 and 1915, respectively. Special relativity applies to all physical ph ...
) and would violate the known laws of
causality. A tachyon has an
imaginary rest mass.
*
True muonium, atom composed of a
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 ''ħ'', but with a much greater mass. It is classified as a ...
and an anti-muon. Yet unobserved.
*
Unparticles, hypothetical particles that are massless and scale invariant.
*
Weyl fermions, hypothetical spin-1/2 massless particles, only found as a
quasiparticle
In condensed matter physics, a quasiparticle is a concept used to describe a collective behavior of a group of particles that can be treated as if they were a single particle. Formally, quasiparticles and collective excitations are closely relate ...
.
See also
References
{{Particles
Particles
In the physical sciences, a particle (or corpuscle in older texts) is a small localized object which can be described by several physical or chemical properties, such as volume, density, or mass.
They vary greatly in size or quantity, from s ...
Subatomic particles
Particles
Unsolved problems in physics
*