In
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) and ...
, 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 ab ...
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.
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 ...
, all WISPs are candidate
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 ab ...
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
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 ab ...
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 – 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 interact ...
s (if they exist) as well as the 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 Sta ...
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 – 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 theorie ...
fermion
In particle physics, a fermion is a particle that follows Fermi–Dirac statistics. Generally, it has a half-odd-integer spin: spin , spin , etc. In addition, these particles obey the Pauli exclusion principle. Fermions include all quarks and ...
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
Excluded active neutrinos
Although ordinary “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 ...
(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 ...
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 ...
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 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 ab ...
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.
]
See also
* Axion
* Hot dark matter
* Light dark matter
* Lightest supersymmetric particle (LSP)
* Sterile neutrino
* 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 ...
(WIMP)
References
Dark matter
Hypothetical elementary particles
category:Physics beyond the Standard Model
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