particle physics Particle physics or high energy physics is the study of fundamental particles and forces that constitute matter and radiation. The fundamental particles in the universe are classified in the Standard Model as fermions (matter particles) an ...

, 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 Dark matter is a hypothetical form of matter thought to account for approximately 85% of the matter in the universe. Dark matter is called "dark" because it does not appear to interact with the electromagnetic field, which means it does not a ...

candidate, and is essentially synonymous with '' axion-like particle'' (ALP). With the exception of “active”

neutrino A neutrino ( ; denoted by the Greek letter ) is a fermion (an elementary particle with spin of ) that interacts only via the weak interaction and gravity. The neutrino is so named because it is electrically neutral and because its rest mass ...

s, all WISPs are

hypothetical particles This is a list of known and hypothesized particles. Elementary particles Elementary particles are particles with no measurable internal structure; that is, it is unknown whether they are composed of other particles. They are the fundamental ob ...

. 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, a WIMP is a new elementary particle which interacts via gra ...

s (WIMPs).

Discussion

Except for conventional, active

neutrinos A neutrino ( ; denoted by the Greek letter ) is a fermion (an elementary particle with spin of ) that interacts only via the weak interaction and gravity. The neutrino is so named because it is electrically neutral and because its rest mass is ...

, 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 (plural hypotheses) is a proposed explanation for a phenomenon. For a hypothesis to be a scientific hypothesis, the scientific method requires that one can test it. Scientists generally base scientific hypotheses on previous obser ...

particles which are viable

candidates. Examples include: * Axion – long standing hypothetical

strong force The strong interaction or strong force is a fundamental interaction that confines quarks into proton, neutron, and other hadron particles. The strong interaction also binds neutrons and protons to create atomic nuclei, where it is called the ...

related light particle *

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

– never-observed particles explicitly excluded from

weak interaction In nuclear physics and particle physics, the weak interaction, which is also often called the weak force or weak nuclear force, is one of the four known fundamental interactions, with the others being electromagnetism, the strong interaction ...

s (if they exist) as well as the strong and

electromagnetic force In physics, electromagnetism is an interaction that occurs between particles with electric charge. It is the second-strongest of the four fundamental interactions, after the strong force, and it is the dominant force in the interactions o ...

s * Supersymmetric particles, particularly the lightest supersymmetric particle 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 In a supersymmetric theory the equations for force and the equations for matter are identical. In theoretical and mathematical physics, any theory with this property has the principle of supersymmetry (SUSY). Dozens of supersymmetric theories ...

fermions 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 odd half-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 (''kheir''), "hand", a familiar chiral object. An object or a system is ''chiral'' if it is distinguishable from i ...

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 Astrophysical plasma is plasma outside of the Solar System. It is studied as part of astrophysics and is commonly observed in space. The accepted view of scientists is that much of the baryonic matter in the universe exists in this state. When ...

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