View source for List of hypothetical particles

{{For|all particles|List of particles}}
{{Short description|none}}

This is a list of hypothetical [[subatomic particle]]s in [[physics]].

== Elementary particles ==

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

{|class="wikitable"
|+ Hypothetical bosons and fermions
|-
! scope=col | Name
! scope=col | Spin
! scope=col | Notes
|-
| [[axion]] || {{center|0}} || A pseudoscalar particle introduced in [[Peccei–Quinn theory]] to solve the [[strong-CP problem]].
|-
| [[dilaton]] || {{center|0}} || Predicted in some string theories.
|-
| [[graviphoton]] || {{center|1}} || Also known as "gravivector".<ref>
{{cite journal
 |last=Maartens |first=R.
 |date=2004
 |title=Brane-world gravity
 |journal=[[Living Reviews in Relativity]]
 |volume=7 |issue=1 |pages=7
 |bibcode=2004LRR.....7....7M |pmc=5255527
 |doi=10.12942/lrr-2004-7 |doi-access=free
 |pmid=28163642
 |arxiv=gr-qc/0312059
 |url=http://www.emis.de/journals/LRG/Articles/lrr-2004-7/download/lrr-2004-7BW.pdf
}}
</ref> It appears in [[Kaluza–Klein theory]].
|-
|[[graviton]] || {{center|2}} || Massless boson associated to [[gravitation]]. Included in many [[Physics beyond the Standard Model|beyond the Standard Model]] theories.
|-
| [[dual graviton]] || {{center|2}} || Has been hypothesized as dual of [[graviton]] under [[electric-magnetic duality|electric–magnetic duality]] in [[supergravity]].
|-
| [[graviscalar]] || {{center|0}} || Also known as "radion". It appears in [[Kaluza–Klein theory]].
|-
|[[hyperphoton]]
|{{center|0}}
|Hypothetical photon-like particle related to [[CP violation|CP violations]] in [[kaon]] decay. 
|-
| [[inflaton]] || {{center|0}} || Unidentified scalar force-carrier that is presumed to have physically caused [[cosmic inflation]].
|-
| [[majoron]] || {{center|0}} || Predicted to understand [[neutrino]] masses by the [[seesaw mechanism]].
|-
|[[sterile neutrino]]
|{{center| {{sfrac| 1 |2}} }}
|Right-handed neutrinos are compatible with the Standard Model but have never been observed. 
|-
|[[dual photon]]
|{{center|1}}
| Dual of the [[photon]] under [[Montonen–Olive duality|electric–magnetic duality]] 
|-
| [[magnetic photon]] || {{center|1}}|| Hypothetical particle similar to the photon in the presence of [[Magnetic monopole|magnetic monopoles]].
|-
|[[pressuron]]
|{{center|0}}
|hypothetical [[scalar particle]] which couples to both gravity and matter theorised in 2013.
|-
|[[symmetron]]
|{{center|0}}
|Mediates the fifth force of the hypothetical symmetron field.
|-
| [[X and Y bosons]] || {{center|1}} || These [[leptoquark]]s are predicted by [[Grand Unified Theory|Grand Unified Theories]] to be heavier equivalents of the W and Z.
|-
| [[W′ and Z′ bosons]] || {{center|1}} ||Predicted by several extension of the [[electroweak interaction]].
|}

=== Particles predicted by supersymmetric theories ===
[[Supersymmetry]] predicts the existence of [[superpartner]]s to particles in the Standard Model, none of which have been confirmed experimentally. The [[sfermion]]s (spin-0) include:

{|class=wikitable style="text-align:center;"
|+squarks
|-
!Name
!Symbol
!Superpartner of
!Symbol
|-
| sup squark
| <math>\tilde{u}</math>
| [[up quark]]
| <math>u</math>
|-
| sdown squark
| <math>\tilde{d}</math>
| [[down quark]]
| <math>d</math>
|-
| scharm squark
| <math>\tilde{c}</math>
| [[charm quark]]
| <math>c</math>
|-
| sstrange squark
| <math>\tilde{s}</math>
| [[strange quark]]
| <math>s</math>
|-
| [[stop squark]]
| <math>\tilde{t}</math>
| [[top quark]]
| <math>t</math>
|-
| sbottom squark
| <math>\tilde{b}</math>
| [[bottom quark]]
| <math>b</math>
|}

{|class=wikitable style="text-align:center;"
|+Sleptons
|-
!Name
!Symbol
!Superpartner of
!Symbol
|-
| selectron
| <math>\tilde{e}</math>
| [[electron]]
| <math>e</math>
|-
| selectron sneutrino
| <math>\tilde{\nu}_e</math>
| [[electron neutrino]]
| <math>\nu_e</math>
|-
| smuon
| <math>\tilde{\mu}</math>
| [[muon]]
| <math>\mu</math>
|-
| smuon sneutrino
| <math>\tilde{\nu}_\mu</math>
| [[muon neutrino]]
| <math>\nu_\mu</math>
|-
| stau
| <math>\tilde{\tau}</math>
| [[Tau (particle)|tau]]
| <math>\tau</math>
|-
| stau sneutrino
| <math>\tilde{\nu}_\tau</math>
| [[tau neutrino]]
| <math>\nu_\tau</math>
|}

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 {{frac|1|2}}) are 
{| class="wikitable"
|+Bosinos (superpartners of bosons)
|-
! scope="col" | Name
! scope="col" | superpartner of:
! scope="col" | Notes
|-
|[[axino]]
|[[axion]]
|Forms a [[supermultiplet]], together with the [[saxion]] and axion, in supersymmetric extensions of Peccei–Quinn theory.
|-
|[[dilatino]]
|[[dilaton]]
|
|-
| [[gluino]] || gluon|| Eight [[gluon]]s and eight gluinos. 
|-
| [[gravitino]] || [[graviton]]|| Predicted by [[supergravity]] ([[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. 
|-
| [[gaugino|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, [[W and Z bosons|Z and W<sup>±</sup> bosons]] are superpositions of the B{{sup|0}}, W{{sup|0}}, W{{sup|1}}, and W{{sup|2}} fields, the [[photino]], zino, and wino{{sup|±}} are superpositions of the bino{{sup|0}}, wino{{sup|0}}, wino{{sup|1}}, and wino{{sup|2}}. 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:

* [[Chargino|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.
* [[Neutralino|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.
* [[Goldstino]]s are [[fermion]]s produced by the spontaneous breaking of [[supersymmetry]]; they are the supersymmetric counterpart of [[Goldstone boson]]s.
* [[Sgoldstino]], superpartners of goldstinos.

== Dark energy candidates ==
{{See also|Dark energy#Theories of dark energy}}The following hypothetical particles have been proposed to explain [[Dark energy|dark energy:]]
{| class="wikitable"
|+
!Name
!Spin
!Description
|-
|[[Chameleon particle|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 ==
{{See also|Dark matter#Composition}}
The following categories are not unique or distinct: For example, either a WIMP or a WISP is also a FIP.
{| class="wikitable"
|+
!Meaning
!Abbreviation
!Explanation
!Candidates
|-
|[[Feebly interacting particle]]
|FIP
|Particles that interacts very weakly with conventional matter 
|[[Massive gravity|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]]
|-
|[[WISP (particle physics)|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 photon]]s.

== 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:
{| class="wikitable"
|+
!Name
!Date of anomaly
!Origin of the anomaly
!Details
|-
|[[750 GeV diphoton excess|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
|[[Cold fusion|Fleischmann–Pons experiment]]
|Predicted by [[Edward Teller]] in 1989 in an attempt to understand [[cold fusion]] claims<ref>{{Cite book |last=Huizenga |first=John R. (John Robert) |url=https://archive.org/details/coldfusionscient0000huiz/mode/2up?q=teller |title=Cold fusion : the scientific fiasco of the century |date=1992 |publisher=Rochester, N.Y., U.S.A. : University of Rochester Press |others=Internet Archive |isbn=978-1-878822-07-9}}</ref>
|-
|[[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.<ref>{{Cite journal |last=Brumfiel |first=Geoff |date=2004-05-01 |title=The waiting game |url=https://www.nature.com/articles/429010a |journal=Nature |language=en |volume=429 |issue=6987 |pages=10–11 |doi=10.1038/429010a |pmid=15129249 |issn=1476-4687}}</ref>
|-
|[[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 [[Quark|quarks]] grouped inside a [[baryon]].
* [[Geon (physics)|Geon]]s 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 theory|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.
* [[Pomeron]]s, used to explain the [[elastic scattering]] of hadrons and the location of [[Regge pole]]s in [[Regge theory]]. A counterpart to [[Odderon|odderons]].

=== By type ===

*[[Brane cosmology|Branons]], scalar fields predicted in brane world models.
*[[Composite Higgs models|Composite Higgs,]] models that consider the [[Higgs boson]] to be a composite particle.
**[[Two-Higgs-doublet model|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]].
*[[Crypton (particle)|Cryptons]], any particle from the dark sector of [[String theory landscape|string theory landscape.]]
*Elementary particles that are not bosons or fermions:
**Paraparticles, exotic particles that can survive in a 3D-space and follow [[parastatistics]]<ref>{{Cite journal|first1=Zhiyuan|last1=Wang|first2=Kaden R. A.|last2=Hazzard|date=January 2025|title=Particle exchange statistics beyond fermions and bosons|journal=Nature|volume=637|issue=8045|pages=314–318|language=en-US|access-date=2025-01-19|doi=10.1038/s41586-024-08262-7|arxiv=2308.05203 |bibcode=2025Natur.637..314W |url=https://www.nature.com/articles/s41586-024-08262-7}}</ref><ref>{{Cite web|language=en-US|url=https://news.rice.edu/news/2025/mathematical-methods-point-possibility-particles-long-thought-impossible|title=Mathematical methods point to possibility of particles long thought impossible|access-date=2025-01-19|archive-url=https://web.archive.org/web/20250109103702/https://news.rice.edu/news/2025/mathematical-methods-point-possibility-particles-long-thought-impossible|archive-date=January 9, 2025|url-status=live}}</ref>
**Plektons, particles that follow [[Braid statistics]]
*[[Exotic matter|Exotic particles]], particles with exotic properties like negative mass or complex mass.
*[[Exotic hadron|Exotic hadrons]], particles composed of unusual combinations of quarks and gluons.
**[[Exotic meson|Exotic mesons]]
**[[Exotic baryon|Exotic baryons]]
**[[Glueball]], hypothetical particle that consist of only [[Gluon|gluons]].
**Quark bound states beyond the [[pentaquark]], like [[Hexaquark|hexaquarks]] and [[Heptaquark|heptaquarks]].
*[[Leptoquark]], hypothetical particles that are neither bosons or fermions but carry [[Lepton number|lepton]] and [[Baryon number|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:
**[[Magnetic monopole#Dirac quantization|Dirac monopoles]], monopole that would allow charge quantization.
**[['t Hooft–Polyakov monopole|'t Hooft–Polyakov monopoles]], Dirac monopole but without [[Dirac string]]s.
**[[Wu–Yang monopole|Wu–Yang monopoles]], point-like monopole with potential of the form 1/''r''.
**[[Dyon]]s, extensions of the idea of a magnetic monopole.
*[[Majorana fermion|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 matter|Mirror particles]] are predicted by theories that restore [[Parity (physics)|parity symmetry]].
* [[Neutronium]], hypothetical nuclei consisting only of [[Neutron|neutrons]] (more than one). Examples include the [[tetraneutron]].
* [[Preon]]s 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 theory|Caloric rays]] used until the 19th century to explain [[thermal radiation]].
** [[Corpuscular theory of light|Light corpuscles]], hypothetical classical particles used to explain optical phenomena.
** [[Phlogiston theory|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 quark|strange quarks]].
* [[R-hadron]], bound particle of a quark and a supersymmetric particle.
* [[T meson]], hypothetical [[Meson|mesons]] composed of a [[Top quark|top]] [[quark]] and one additional subatomic particle. Examples include the [[theta meson]], formed by a top and an anti-top.
* [[tachyon|Tachyons]] is a hypothetical particle that travels [[Faster-than-light|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 [[Mass#Tachyonic particles and imaginary (complex) mass|imaginary rest mass]].
* [[True muonium]], atom composed of a [[muon]] and an anti-muon. Yet unobserved.
* [[Unparticle physics|Unparticles]], hypothetical particles that are massless and scale invariant.
* [[Weyl equation|Weyl fermions]], hypothetical spin-1/2 massless particles, only found as a [[quasiparticle]].

== See also ==
{{columns-list|colwidth=30em|* [[Alternatives to the Standard Higgs Model]]
* [[Chronon]]
* [[Chirality (physics)|Chirality]] and [[Helicity (particle physics)|helicity]]
* [[List of fictional elements, materials, isotopes and subatomic particles]]
* [[Timeline of particle discoveries]]
* [[List of particles]]
}}

== References ==
{{reflist}}

{{Particles}}

[[Category:Physics-related lists|Particles]]
[[Category:Subatomic particles]]
[[Category:Particles]]
[[Category:Unsolved problems in physics]]
[[Category:Hypothetical particles|*]]