List of hypothetical particles

Last updated February 04, 2025

This is a list of hypothetical subatomic particles in physics.

Elementary particles

Some theories predict the existence of additional elementary bosons and fermions that are not found in the Standard Model.

Hypothetical bosons and fermions
Name	Spin	Notes
axion	0	A pseudoscalar particle introduced in Peccei–Quinn theory to solve the strong-CP problem.
dilaton	0	Predicted in some string theories.
graviphoton	1	Also known as "gravivector".^[1] It appears in Kaluza–Klein theory.
graviton	2	Massless boson associated to gravitation. Included in many beyond the Standard Model theories.
dual graviton	2	Has been hypothesized as dual of graviton under electric–magnetic duality in supergravity.
graviscalar	0	Also known as "radion". It appears in Kaluza–Klein theory.
hyperphoton	0	Hypothetical photon-like particle related to CP violations in kaon decay.
inflaton	0	Unidentified scalar force-carrier that is presumed to have physically caused cosmic inflation.
majoron	0	Predicted to understand neutrino masses by the seesaw mechanism.
sterile neutrino	⁠ 1 /2⁠	Right-handed neutrinos are compatible with the Standard Model but have never been observed.
dual photon	1	Dual of the photon under electric–magnetic duality
magnetic photon	1	Hypothetical particle similar to the photon in the presence of magnetic monopoles.
pressuron	0	hypothetical scalar particle which couples to both gravity and matter theorised in 2013.
symmetron	0	Mediates the fifth force of the hypothetical symmetron field.
X and Y bosons	1	These leptoquarks are predicted by Grand Unified Theories to be heavier equivalents of the W and Z.
W′ and Z′ bosons	1	Predicted by several extension of the electroweak interaction.

Particles predicted by supersymmetric theories

Supersymmetry predicts the existence of superpartners to particles in the Standard Model, none of which have been confirmed experimentally. The sfermions (spin-0) include:

squarks
Name	Symbol	Superpartner of	Symbol
sup squark	${\tilde {u}}$	up quark	$u$
sdown squark	${\tilde {d}}$	down quark	$d$
scharm squark	${\tilde {c}}$	charm quark	$c$
sstrange squark	${\tilde {s}}$	strange quark	$s$
stop squark	${\tilde {t}}$	top quark	$t$
sbottom squark	${\tilde {b}}$	bottom quark	$b$

Sleptons
Name	Symbol	Superpartner of	Symbol
selectron	${\tilde {e}}$	electron	$e$
selectron sneutrino	${\tilde {\nu }}_{e}$	electron neutrino	$\nu _{e}$
smuon	${\tilde {\mu }}$	muon	$\mu$
smuon sneutrino	${\tilde {\nu }}_{\mu }$	muon neutrino	$\nu _{\mu }$
stau	${\tilde {\tau }}$	tau	$\tau$
stau sneutrino	${\tilde {\nu }}_{\tau }$	tau neutrino	$\nu _{\tau }$

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 1⁄2) are

Bosinos (superpartners of bosons)
Name	superpartner of:	Notes
axino	axion	Forms a supermultiplet, together with the saxion and axion, in supersymmetric extensions of Peccei–Quinn theory.
dilatino	dilaton
gluino	gluon	Eight gluons and eight gluinos.
gravitino	graviton	Predicted by supergravity (SUGRA).
higgsino	Higgs boson	For supersymmetry there is a need for several Higgs bosons, neutral and charged, according with their superpartners.
photino	photon	Mixing with zino and neutral Higgsinos for neutralinos.
wino, zino	W and Z bosons	The charged wino mixing with the charged Higgsino for charginos, for the zino see line above.

Just as the photon, Z and W^± bosons are superpositions of the B⁰, W⁰, W¹, and W² fields, the photino, zino, and wino^± are superpositions of the bino⁰, wino⁰, wino¹, and wino². 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 (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 fermions produced by the spontaneous breaking of supersymmetry; they are the supersymmetric counterpart of Goldstone bosons.
Sgoldstino, superpartners of goldstinos.

Dark energy candidates

The following hypothetical particles have been proposed to explain dark energy:


Name	Spin	Description
Chameleon	0	Couples to matter more weakly than gravity, with non-linear variable effective mass
Acceleron	0	Particle that relates neutrino masses to dark energy

Dark matter candidates

The following categories are not unique or distinct: For example, either a WIMP or a WISP is also a FIP.


Meaning	Abbreviation	Explanation	Candidates
Feebly interacting particle	FIP	Particles that interacts very weakly with conventional matter	Massive gravitons
Gravitationally interacting massive particle	GIMP	Massive particles that only interact with matter gravitationaly
Lightest supersymmetric particle	LSP	Predictions by supersymmetry	Sneutrino, gravitino, neutralino
Strongly interacting massive particle	SIMP	Particle that interact strongly between themselves and weakly with ordinary matter
Stable massive particles	SMP	Long-lived particle with appreciable mass
Weakly interacting massive particle	WIMP	Heavy particles that only interact with matter weakly	neutralino, sterile neutrino
Weakly interacting slender particle	WISP	Light particles that only interact with matter weakly	axion

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:


Name	Date of anomaly	Origin of the anomaly	Details
750 GeV diphoton	2015	Large Hadron Collider.	Resonance at 750 GeV signature of a bosonic particle
Amaterasu particle	2021	Telescope Array Project	240 EeV cosmic ray
Meshugatron	1989	Fleischmann–Pons experiment	Predicted by Edward Teller in 1989 in an attempt to understand cold fusion claims^[2]
N-ray	1903	Prosper-René Blondlot	An unknown form of radiation.
Oh-My-God particle	1991	High Resolution Fly's Eye Cosmic Ray Detector	320 EeV cosmic ray, most energetic ultra-high-energy cosmic ray detected as of 2015
Oops-Leon	1976	Fermilab	6 GeV resonance
Valentine's day monopole	1982	Blas Cabrera Navarro	Single magnetic monopole detected on February 14, 1982.^[3]
X17 particle	2015	ATOMKI	Hypothesized new vector boson to explain nuclear experiments with beryllium.

Other

Cosmon, hypothetical state containing the observable universe before the Big Bang.
Diproton (He-2), nuclei consisting of two protons and no neutrons. Yet unobserved.
Diquark, hypothetical state of two quarks grouped inside a baryon.
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 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 to be a composite particle.
- Higgs doublets are hypothesized by some theories of physics beyond the standard model.

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.
Elementary particles that are not bosons or fermions:
- Paraparticles, exotic particles that can survive in a 3D-space and follow parastatistics ^[4]^[5]
- Plektons, particles that follow Braid statistics
Exotic particles, particles with exotic properties like negative mass or complex mass.
Exotic hadrons, particles composed of unusual combinations of quarks and gluons.
- Exotic mesons
- Exotic baryons
- Glueball, hypothetical particle that consist of only gluons.
- Quark bound states beyond the pentaquark, like hexaquarks and heptaquarks.
Leptoquark, hypothetical particles that are neither bosons or fermions but carry lepton and baryon numbers.
Magnetic monopole 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, 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, 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.
- Light corpuscles, hypothetical classical particles used to explain optical phenomena.
- Phlogiston, hypothetical combustible content in matter used to explain thermodynamics 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 composed of a top quark 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) and would violate the known laws of causality. A tachyon has an imaginary rest mass.
True muonium, atom composed of a muon 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.

Related Research Articles

In particle physics, an elementary particle or fundamental particle is a subatomic particle that is not composed of other particles. The Standard Model presently recognizes seventeen distinct particles—twelve fermions and five bosons. As a consequence of flavor and color combinations and antimatter, the fermions and bosons are known to have 48 and 13 variations, respectively. Among the 61 elementary particles embraced by the Standard Model number: electrons and other leptons, quarks, and the fundamental bosons. Subatomic particles such as protons or neutrons, which contain two or more elementary particles, are known as composite particles.

<span class="mw-page-title-main">Fermion</span> Type of subatomic particle

In particle physics, a fermion is a subatomic particle that follows Fermi–Dirac statistics. Fermions have a half-odd-integer spin and obey the Pauli exclusion principle. These particles include all quarks and leptons and all composite particles made of an odd number of these, such as all baryons and many atoms and nuclei. Fermions differ from bosons, which obey Bose–Einstein statistics.

<span class="mw-page-title-main">Hadron</span> Composite subatomic particle

In particle physics, a hadron is a composite subatomic particle made of two or more quarks held together by the strong interaction. They are analogous to molecules, which are held together by the electric force. Most of the mass of ordinary matter comes from two hadrons: the proton and the neutron, while most of the mass of the protons and neutrons is in turn due to the binding energy of their constituent quarks, due to the strong force.

Particle physics or high-energy physics is the study of fundamental particles and forces that constitute matter and radiation. The field also studies combinations of elementary particles up to the scale of protons and neutrons, while the study of combination of protons and neutrons is called nuclear physics.

The Standard Model of particle physics is the theory describing three of the four known fundamental forces in the universe and classifying all known elementary particles. It was developed in stages throughout the latter half of the 20th century, through the work of many scientists worldwide, with the current formulation being finalized in the mid-1970s upon experimental confirmation of the existence of quarks. Since then, proof of the top quark (1995), the tau neutrino (2000), and the Higgs boson (2012) have added further credence to the Standard Model. In addition, the Standard Model has predicted various properties of weak neutral currents and the W and Z bosons with great accuracy.

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, or an elementary particle, which is not composed of other particles. Particle physics and nuclear physics study these particles and how they interact. Most force-carrying particles like photons or gluons are called bosons and, although they have quanta of energy, do not have rest mass or discrete diameters and are unlike the former particles that have rest mass and cannot overlap or combine which are called fermions. The W and Z bosons, however, are an exception to this rule and have relatively large rest masses at approximately 80 GeV and 90 GeV respectively.

Supersymmetry is a theoretical framework in physics that suggests the existence of a symmetry between particles with integer spin (bosons) and particles with half-integer spin (fermions). It proposes that for every known particle, there exists a partner particle with different spin properties. There have been multiple experiments on supersymmetry that have failed to provide evidence that it exists in nature. If evidence is found, supersymmetry could help explain certain phenomena, such as the nature of dark matter and the hierarchy problem in particle physics.

In supersymmetry, the neutralino is a hypothetical particle. In the Minimal Supersymmetric Standard Model (MSSM), a popular model of realization of supersymmetry at a low energy, there are four neutralinos that are fermions and are electrically neutral, the lightest of which is stable in an R-parity conserved scenario of MSSM. They are typically labeled $N͂ 01$ , $N͂ 02$ , $N͂ 03$ and $N͂ 04$ although sometimes $is also used when is used to refer to charginos.$

In particle physics, a gauge boson is a bosonic elementary particle that acts as the force carrier for elementary fermions. Elementary particles whose interactions are described by a gauge theory interact with each other by the exchange of gauge bosons, usually as virtual particles.

A photino is a hypothetical subatomic particle, the fermion WIMP superpartner of the photon predicted by supersymmetry. It is an example of a gaugino. Even though no photino has ever been observed so far, it is one of the candidates for the lightest supersymmetric particle in the universe. It is proposed that photinos are produced by sources of ultra-high-energy cosmic rays.

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 [minimum] number of new particle states and new interactions consistent with "Reality". Supersymmetry pairs bosons with fermions, so every Standard Model particle has a superpartner. If discovered, such superparticles could be candidates for dark matter, and could provide evidence for grand unification or the viability of string theory. The failure to find evidence for MSSM using the Large Hadron Collider has strengthened an inclination to abandon it.

In particle physics, a superpartner 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.

In supersymmetry theories of particle physics, a gaugino is the hypothetical fermionic supersymmetric field quantum (superpartner) of a gauge field, as predicted by gauge theory combined with supersymmetry. All gauginos have a spin of 1/2, except for the gravitino, which has a spin of 3/2.

In particle physics, the chargino is a hypothetical particle which refers to the mass eigenstates of a charged superpartner, i.e. any new electrically charged fermion predicted by supersymmetry. They are linear combinations of the charged wino and charged higgsinos. There are two charginos that are fermions and are electrically charged, which are typically labeled C͂^±
₁ and C͂^±
₂, although sometimes $and are also used to refer to charginos, when is used to refer to neutralinos. The heavier chargino can decay through the neutral Z boson to the lighter chargino. Both can decay through a charged W boson to a neutralino:$

In particle physics, preons are hypothetical point particles, conceived of as sub-components of quarks and leptons. 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 bosons have six preons, and quarks and leptons have only three.

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, neutrino oscillations, matter–antimatter asymmetry, and the nature of dark matter and dark energy. Another problem lies within the mathematical framework of the Standard Model itself: the Standard Model is inconsistent with that of general relativity, and one or both theories break down under certain conditions, such as spacetime singularities like the Big Bang and black hole event horizons.

In particle physics, a stop squark, symbol t͂, is the superpartner of the top quark as predicted by supersymmetry (SUSY). It is a sfermion, which means it is a spin-0 boson. While the top quark is the heaviest known quark, the stop squark is actually often the lightest squark in many supersymmetry models.

This page is a glossary of terms in string theory, including related areas such as supergravity, supersymmetry, and high energy physics.

The idea that matter consists of smaller particles and that there exists a limited number of sorts of primary, smallest particles in nature has existed in natural philosophy at least since the 6th century BC. Such ideas gained physical credibility beginning in the 19th century, but the concept of "elementary particle" underwent some changes in its meaning: notably, modern physics no longer deems elementary particles indestructible. Even elementary particles can decay or collide destructively; they can cease to exist and create (other) particles in result.

References

↑ Maartens, R. (2004). "Brane-world gravity" (PDF). Living Reviews in Relativity . 7 (1): 7. arXiv: gr-qc/0312059 . Bibcode:2004LRR.....7....7M. doi: 10.12942/lrr-2004-7 . PMC 5255527 . PMID 28163642.
↑ Huizenga, John R. (John Robert) (1992). Cold fusion : the scientific fiasco of the century. Internet Archive. Rochester, N.Y., U.S.A. : University of Rochester Press. ISBN 978-1-878822-07-9.
↑ Brumfiel, Geoff (2004-05-01). "The waiting game". Nature. 429 (6987): 10–11. doi:10.1038/429010a. ISSN 1476-4687. PMID 15129249.
↑ Wang, Zhiyuan; Hazzard, Kaden R. A. (January 2025). "Particle exchange statistics beyond fermions and bosons". Nature. 637 (8045): 314–318. arXiv: 2308.05203 . Bibcode:2025Natur.637..314W. doi:10.1038/s41586-024-08262-7 . Retrieved 2025-01-19.
↑ "Mathematical methods point to possibility of particles long thought impossible". Archived from the original on January 9, 2025. Retrieved 2025-01-19.

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[1] Maartens, R. (2004). "Brane-world gravity" (PDF). Living Reviews in Relativity . 7 (1): 7. arXiv: gr-qc/0312059 . Bibcode:2004LRR.....7....7M. doi: 10.12942/lrr-2004-7 . PMC 5255527 . PMID 28163642.

[2] Huizenga, John R. (John Robert) (1992). Cold fusion : the scientific fiasco of the century. Internet Archive. Rochester, N.Y., U.S.A. : University of Rochester Press. ISBN 978-1-878822-07-9.

[3] Brumfiel, Geoff (2004-05-01). "The waiting game". Nature. 429 (6987): 10–11. doi:10.1038/429010a. ISSN 1476-4687. PMID 15129249.

[4] Wang, Zhiyuan; Hazzard, Kaden R. A. (January 2025). "Particle exchange statistics beyond fermions and bosons". Nature. 637 (8045): 314–318. arXiv: 2308.05203 . Bibcode:2025Natur.637..314W. doi:10.1038/s41586-024-08262-7 . Retrieved 2025-01-19.

[5] "Mathematical methods point to possibility of particles long thought impossible". Archived from the original on January 9, 2025. Retrieved 2025-01-19.

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