particle physics Particle physics or high-energy physics is the study of Elementary particle, fundamental particles and fundamental interaction, forces that constitute matter and radiation. The field also studies combinations of elementary particles up to the s ...

, the acronym WISP refers to a largely hypothetical weakly interacting sub-eV particle, or ''weakly interacting ''slender'' particle'', or ''weakly interacting ''slim'' particle'' – low-mass particles which rarely interact with conventional particles. The term is used to generally categorize a type of

dark matter In astronomy, dark matter is an invisible and hypothetical form of matter that does not interact with light or other electromagnetic radiation. Dark matter is implied by gravity, gravitational effects that cannot be explained by general relat ...

candidate, and is essentially synonymous with '' axion-like particle'' (ALP). WISPs are generally

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. Particles predicted by supersy ...

. WISPs are the low-mass counterpart of

weakly interacting massive particle Weakly interacting massive particles (WIMPs) are hypothetical particles that are one of the proposed candidates for dark matter. There exists no formal definition of a WIMP, but broadly, it is an elementary particle which interacts via gravity an ...

s (WIMPs).

Discussion

Except for conventional, active

neutrinos A neutrino ( ; denoted by the Greek letter ) is an elementary particle that interacts via the weak interaction and gravity. The neutrino is so named because it is electrically neutral and because its rest mass is so small ('' -ino'') that it ...

, all WISPs are candidate

constituents, and many proposed experiments to detect WISPs might possibly be able to detect several different kinds. "WISP" is most often used to refer to a low-mass

hypothetical A hypothesis (: hypotheses) is a proposed explanation for a phenomenon. A scientific hypothesis must be based on observations and make a testable and reproducible prediction about reality, in a process beginning with an educated guess or tho ...

particles which are viable

candidates. Examples include: *

Axion An axion () is a hypothetical elementary particle originally theorized in 1978 independently by Frank Wilczek and Steven Weinberg as the Goldstone boson of Peccei–Quinn theory, which had been proposed in 1977 to solve the strong CP problem ...

– long-standing hypothetical

strong force In nuclear physics and particle physics, the strong interaction, also called the strong force or strong nuclear force, is one of the four known fundamental interactions. It confines quarks into protons, neutrons, and other hadron particles, an ...

related light particle *

Sterile neutrino Sterile neutrinos (or inert neutrinos) are hypothetical particles (neutral leptons – neutrinos) that interact only via gravity and not via any of the other fundamental interactions of the Standard Model. The term ''sterile neutrino'' is used to ...

– never-observed particles explicitly excluded (if they exist) from the

weak Weak may refer to: Songs * Weak (AJR song), "Weak" (AJR song), 2016 * Weak (Melanie C song), "Weak" (Melanie C song), 2011 * Weak (SWV song), "Weak" (SWV song), 1993 * Weak (Skunk Anansie song), "Weak" (Skunk Anansie song), 1995 * "Weak", a son ...

strong Strong may refer to: Education * The Strong, an educational institution in Rochester, New York, United States * Strong Hall (Lawrence, Kansas), an administrative hall of the University of Kansas * Strong School, New Haven, Connecticut, United ...

and

electromagnetic In physics, electromagnetism is an interaction that occurs between particles with electric charge via electromagnetic fields. The electromagnetic force is one of the four fundamental forces of nature. It is the dominant force in the interacti ...

interactions * Supersymmetric particles, particularly the

lightest supersymmetric particle In particle physics, the lightest supersymmetric particle (LSP) is the generic name given to the lightest of the additional hypothetical particles found in supersymmetric models. In models with R-parity conservation, the LSP is stable; in other w ...

which might be a **

Neutralino 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 ...

–

supersymmetric 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 ...

fermion In particle physics, a fermion is a subatomic particle that follows Fermi–Dirac statistics. Fermions have a half-integer spin (spin 1/2, spin , Spin (physics)#Higher spins, spin , etc.) and obey the Pauli exclusion principle. These particles i ...

s that are electrically ''neutral'' composites of

superpartner In particle physics, a superpartner (also sparticle) 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. ...

s to

bosons In particle physics, a boson ( ) is a subatomic particle whose spin quantum number has an integer value (0, 1, 2, ...). Bosons form one of the two fundamental classes of subatomic particle, the other being fermions, which have half odd-integer ...

Excluded active neutrinos

Although ordinary "active"

(left-

chiral Chirality () is a property of asymmetry important in several branches of science. The word ''chirality'' is derived from the Greek language, Greek (''kheir''), "hand", a familiar chiral object. An object or a system is ''chiral'' if it is dist ...

and right-chiral antineutrinos) are particles known to exist, and though active neutrinos do indeed technically satisfy the description of the term, they are often excluded from lists of "WISP" particles. The reason that active neutrinos are often ''not'' included among WISPs is that they are no longer viable dark matter candidates: current estimated limits on their number density and mass indicate that their cumulative mass-density could not be high enough to account for the amount of

inferred from its observed effects, although they certainly do make some ''small'' contribution to dark matter density.

Sources

The various sources of WISPs could possibly include hot astrophysical plasma and energy transport in stars. Note however, that since they remain hypothetical (except for active neutrinos), the means of creation of WISPs depends on the theoretical framework used to propose them.

References

Dark matter Hypothetical elementary particles category:Physics beyond the Standard Model {{particle-stub

Discussion

Excluded active neutrinos

Sources

See also

References