Getting a charge out of dark matter

We consider the possibility that dark matter is in the form of charged massive particles. Several constraints are discussed: (a) the absence of heavy-hydrogen-like atoms in water; (b) the agreement between the observed cosmic abundance of the elements and standard big-bang nucleosynthesis predictions; (c) the observed properties of galaxies, stars, and planets; (d) their nonobservation in $\gamma$-ray and cosmic-ray detectors, and the lack of radiation damage to space-borne electronic components. We find that integer-charged particles less massive than ${10}^3$ TeV are probably ruled out as dark matter; but note briefly that there is a slim chance they could be blown out of the halo by supernovae. Above this mass the freeze-out abundance of these particles would overclose the Universe; thus their discovery would be evidence for inflation (or other late-time entropy dumping) below $m_{\mathrm{ch}}$. We indicate where one should consider looking for charged massive dark matter.