Clock comparisons reduce upper limits on the mass of "Dark Matter" particles

[RedshiftDrift]

Still no dark-matter particle detection. "A search for oscillations in the frequencies of optical clocks has come up empty, implying new bounds on ultralight dark matter particles." https://physics.aps.org/articles/v16/s87; the original paper is on arXiv:2301.03433.

The possible mass of bosonic dark-matter particles has to be extremely small. This excludes by orders of magnitude bosons that have a mass-energy comparable to CMB photons (which have an energy of $\approx 6 \times 10^{-4}$ eV).

Image taken from arXiv:2301.03433.