60 articles
Any Light Particle Search
Any Light Particle Search (ALPS) is a DESY program in Hamburg searching for axions and other weakly interacting light particles; its ALPS II experiment ran its first science campaign in 2024.
Astrophysical and cosmological constraints on WISPs
Astrophysical and cosmological constraints on WISPs covers how stellar cooling, supernova 1987A, cosmic microwave background data, and black-hole superradiance bound axion-like particles, hidden photons, and other very light particles.
Axion
The axion is a hypothetical light, neutral particle proposed in 1977 by Roberto Peccei and Helen Quinn, and a leading candidate for the universe's dark matter.
Axion dark matter
Axion dark matter is the hypothesis that the axion, a particle proposed in 1977 to solve a quantum chromodynamics problem, makes up the universe's dark matter.
Axion-like particle
An axion-like particle (ALP) is a light, weakly coupled pseudoscalar boson not tied to the QCD axion, searched for in stellar cooling, gamma rays, and colliders.
Axiverse
The axiverse is a hypothesized ensemble of many ultralight axion-like particles across a vast range of masses, proposed in 2009 as arising generically from string theory.
Chargino
A chargino is a hypothetical charged fermion predicted by supersymmetry, formed when the superpartners of charged weak gauge bosons and Higgs fields mix into two mass eigenstates.
Composite Higgs model
A composite Higgs model proposes that the Higgs boson is not elementary but a bound state of a new strongly interacting sector near the TeV scale.
Constrained Minimal Supersymmetric Standard Model
The Constrained Minimal Supersymmetric Standard Model (CMSSM) is a restricted version of the Minimal Supersymmetric Standard Model whose particle spectrum is fixed by six universal parameters.
Dark photon
The dark photon, also known as the hidden photon or paraphoton, is a hypothetical gauge boson from a dark sector that kinetically mixes with the ordinary photon.
Dark radiation
Dark radiation is any component of the Universe's radiation energy density made of relativistic particles beyond photons and standard-model neutrinos, measured through the parameter N_eff.
Dark scalar
A dark scalar, also called a dark Higgs boson, is a hypothetical particle whose field breaks a hidden gauge symmetry and gives mass to the dark photon.
Dark sector
A dark sector, also called a hidden sector, is a hypothesized set of particles and forces beyond the Standard Model that couple only feebly to known matter.
Dilaton
The dilaton is a spin-0 scalar field, the partner of the graviton in string theory, that sets coupling strengths and is searched for as a dark matter or dark energy candidate.
Gluino
The gluino is the hypothetical supersymmetric partner of the gluon, a color-charged, electrically neutral Majorana fermion and a central Large Hadron Collider search target, excluded below roughly 2.25 TeV.
Grand Unified Theory
A grand unified theory (GUT), also called grand unification, is a particle-physics framework merging the strong and electroweak forces under one gauge symmetry at extremely high energy.
Gravitino
The gravitino is the hypothetical spin-3/2 superpartner of the graviton predicted by supergravity. It is extremely weakly coupled, possibly stable dark matter, and has never been observed.
Heavy neutral lepton
A heavy neutral lepton, or HNL, is a hypothetical electrically neutral fermion heavier than the known neutrinos, proposed to explain neutrino masses, dark matter, and the matter-antimatter asymmetry.
Hidden valley (physics)
A hidden valley in physics is a beyond-the-Standard-Model scenario where a hidden sector of particles couples weakly to the Standard Model, proposed by Strassler and Zurek in 2006.
Hierarchy problem
The hierarchy problem, also called the gauge hierarchy problem, is the puzzle of why the Higgs boson is so much lighter than the Planck scale.
Higgs portal
The Higgs portal is a class of particle physics models in which dark matter interacts with ordinary particles only through couplings to the Higgs sector.
Higgsino
A higgsino is the hypothetical fermionic superpartner of the Higgs boson in supersymmetric extensions of the Standard Model; none has been observed, though LHC searches continue.
Higher-dimensional supergravity
Higher-dimensional supergravity is supergravity formulated in spacetime dimensions above the four of ordinary general relativity; the eleven-dimensional theory of Cremmer, Julia, and Scherk (1978) is maximal and underlies M-theory.
Inverse seesaw mechanism
The inverse seesaw mechanism is a neutrino mass model, proposed by Mohapatra and Valle in 1986, in which small neutrino masses come from a small lepton-number-violating parameter.
Large extra dimensions
Large extra dimensions are spatial dimensions beyond the familiar three, proposed in 1998 by Arkani-Hamed, Dimopoulos, and Dvali, explaining gravity's weakness as dilution into extra-dimensional volume.
Left-right symmetric model
The left-right symmetric model (LRSM) is a Standard Model extension giving right-handed fermions their own weak interaction, proposed in 1975 to explain parity violation and neutrino mass.
Leptoquark
A leptoquark is a hypothetical particle that couples to both a quark and a lepton, allowing the two to transform into each other; none has been observed.
Light-shining-through-walls experiments
Light-shining-through-walls experiments are laboratory searches for axion-like particles and hidden photons, converting laser photons in a magnetic field and regenerating them behind an opaque barrier.
Lightest supersymmetric particle
The lightest supersymmetric particle (LSP) is the lightest superpartner predicted by supersymmetry. In R-parity-conserving models it is stable and the leading cold dark matter candidate.
List of hypothetical particles
The list of hypothetical particles, also called hypothetical or theoretical particles, covers WIMPs, axions, sterile neutrinos, superpartners, and leptoquarks proposed but not yet confirmed by experiment.