keVmass

KeVmass is a term used in particle physics and cosmology to denote particle rest masses on the kilo-electronvolt scale, expressed in the commonly used unit keV/c^2. It is not an official unit, but a way to refer to masses around a few keV rather than to specify a precise value. When scientists speak of keVmass they are emphasizing the mass scale, which has particular implications for production mechanisms and decay channels.

In theoretical models, keV-scale masses arise for light fermions such as sterile neutrinos, which are candidates for warm dark matter. The keV mass range loosely covers 1–50 keV, though some models extend beyond. These particles would have very small mixing with standard model neutrinos, making them difficult to detect directly, but they could decay and emit X-ray photons.

Units and conversions: 1 keV/c^2 corresponds to about 1.78×10^-33 kg. The electron rest mass is 0.511 MeV/c^2, i.e., about 511 keV/c^2, illustrating that keV-scale masses are much smaller than the electron mass. Observational constraints from X-ray astronomy constrain the mixing angles and densities of keV-scale sterile neutrinos.

Related topics include sterile neutrinos, warm dark matter, and keV-scale physics.