Minicharged particles (or milli-charged particles) are a proposed type of subatomic particle. They are charged, but with a tiny fraction of the
charge of the electron
The elementary charge, usually denoted by , is a fundamental physical constant, defined as the electric charge carried by a single proton (+1 ''e'') or, equivalently, the magnitude of the negative electric charge carried by a single electron, w ...
. They weakly interact with matter. Minicharged particles are not part of the
Standard Model
The Standard Model of particle physics is the Scientific theory, theory describing three of the four known fundamental forces (electromagnetism, electromagnetic, weak interaction, weak and strong interactions – excluding gravity) in the unive ...
. One proposal to detect them involved photons tunneling through an opaque barrier in the presence of a perpendicular magnetic field, the rationale being that a pair of oppositely charged minicharged particles are produced that curve in opposite directions, and recombine on the other side of the barrier reproducing the photon again.
Minicharged particles would result in vacuum magnetic
dichroism
In optics, a dichroic material is either one which causes visible light to be split up into distinct beams of different wavelengths (colours) (not to be confused with Dispersion (optics), dispersion), or one in which light rays having different P ...
,
and would cause energy loss in
microwave cavities.
Photons from the
cosmic microwave background
The cosmic microwave background (CMB, CMBR), or relic radiation, is microwave radiation that fills all space in the observable universe. With a standard optical telescope, the background space between stars and galaxies is almost completely dar ...
would be dissipated by galactic-scale magnetic fields if minicharged particles existed, so this effect could be observable.
In fact the dimming observed of remote supernovae that was used to support
dark energy
In physical cosmology and astronomy, dark energy is a proposed form of energy that affects the universe on the largest scales. Its primary effect is to drive the accelerating expansion of the universe. It also slows the rate of structure format ...
could also be explained by the formation of minicharged particles.
Tests of Coulomb's law can be applied to set bounds on minicharged particles.
References
Hypothetical particles
Dark matter
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