WISP (particle physics)

Although left-chiral neutrinos and right-chiral antineutrinos (“active” neutrinos) are known to exist – and active neutrinos do technically satisfy the definition of the term – “WISP” is most often used to refer to a low-mass hypothetical particles which are still dark matter candidates. Examples include:[1]

• Axion – long standing hypothetical strong force related light particle
• Sterile neutrino – never-observed particles explicitly excluded from weak interactions (if they exist) as well as the strong and electromagnetic forces
• Supersymmetric particles, particularly the lightest supersymmetric particle which might be a
  • Chargino – supersymmetric fermions that are electrically charged composites of superpartners to bosons, or perhaps a
  • Neutralino – supersymmetric fermions that are electrically neutral composites of superpartners to bosons

All WISPs are dark matter candidates, except for conventional, active neutrinos, whose cumulative density could not be sufficient to account for the observed effects of dark matter, based on current estimated limits on their numbers and mass.[1]

The various sources of WISPs could possibly include, hot astrophysical plasma and energy transport in stars.[1] Note however, that since they remain hypothetical (except neutrinos) the means of creation of WISPs depends on the theoretical framework used to propose them.

WISPs are the low-mass counterpart of weakly interacting massive particles (WIMPs).

• Axion
• Hot dark matter
• Light dark matter
• Lightest supersymmetric particle (LSP)
• Sterile neutrino
• Weakly Interacting Massive Particle (WIMP)