List of hypothetical particles

This is a list of hypothetical particles.

Hypothetical particles are proposed subatomic or composite entities arising in theoretical particle physics and cosmology that have not been experimentally confirmed. They are typically introduced to address limitations of the Standard Model, unify fundamental interactions, or explain unresolved observations such as dark matter, neutrino masses, baryon asymmetry, or cosmic inflation.^[1][2] Many are mathematically well defined within quantum field theory or its extensions and serve as mediators or constituents in speculative but testable frameworks beyond the Standard Model.^[3]

Prominent classes include gauge or symmetry-related particles such as the graviton or graviphoton in quantum gravity and extra-dimensional theories, and supersymmetric partners (e.g., neutralinos or charginos) predicted by supersymmetry.^[4][5] Others address specific phenomena, including hidden-sector bosons such as dark photons or light force carriers proposed to explain nuclear anomalies.^[6]

Hypothetical particles also encompass predicted bound states (e.g., glueballs), topological objects such as magnetic monopoles, and unconventional statistical entities such as anyons or tachyons.^[7][8] Collectively, they form a central component of theoretical model building, guiding experimental searches for physics beyond currently known particles.

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

Supersymmetry predicts the existence of superpartners to particles in the Standard Model, none of which have been confirmed experimentally.^[34] The sfermions (spin is 0) include:

Squarks

Name	Symbol	Superpartner of	Symbol
sup squark	${\displaystyle {\tilde {u}}}$	up quark	${\displaystyle u}$
sdown squark	${\displaystyle {\tilde {d}}}$	down quark	${\displaystyle d}$
scharm squark	${\displaystyle {\tilde {c}}}$	charm quark	${\displaystyle c}$
sstrange squark	${\displaystyle {\tilde {s}}}$	strange quark	${\displaystyle s}$
stop squark[35]	${\displaystyle {\tilde {t}}}$	top quark	${\displaystyle t}$
sbottom squark	${\displaystyle {\tilde {b}}}$	bottom quark	${\displaystyle b}$

Sleptons

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

Another hypothetical sfermion is the saxion, superpartner of the axion. It forms a supermultiplet, together with the axino and the axion, in supersymmetric extensions of Peccei–Quinn theory.^[36]

The predicted bosinos (spin 1⁄2) are

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.

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

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.

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 (in chronological order):

• Cosmon, hypothetical state containing the observable universe before the Big Bang.^[71]
• Diproton (²He), nuclei consisting of two protons and no neutrons.^[72] Observed, but without sufficient evidence.^[73][74]
• Diquark, hypothetical state of two quarks grouped inside a baryon.^[75]
• Geons, electromagnetic or gravitational waves which are held together in a confined region by the gravitational attraction of their own field of energy.^[76]
• Kaluza–Klein towers of particles, predicted by some models of extra dimensions. The extra-dimensional momentum is manifested as extra mass in four-dimensional spacetime.^[77]
• Pomerons, used to explain the elastic scattering of hadrons and the location of Regge poles in Regge theory.^[78] A counterpart to odderons.^[79]

• 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^[80][81]
  • 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.