List of hypothetical particles

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

Template:See alsoThe 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

Template:See also 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
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.
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
  • 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.