Counter-top search for macroscopic dark matter

A number of dark matter candidates have been discussed that are macroscopic, of approximately nuclear density, and scatter ordinary matter essentially elastically with approximately their geometric cross section. A wide range of mass and geometric cross section is still unprobed for these “macros.” Macros passing through rock would melt the material in cylinders surrounding their long nearly straight trajectories. Once cooled, the resolidified rock would be easily distinguishable from its surroundings. We discuss how, by visually examining ordinary slabs of rock such as are widely available commercially for kitchen countertops, one could probe an interesting segment of the open macro parameter space.

Figure 1

Illustrative regions of parameter space that could be probed from observations of slabs of ordinary rock are shown in purple. All three regions assume a minimum feature diameter of 1 mm. The region with diagonal hatching assumes a total slab area of $10{\mathrm{m}}^2$, the unhatched region is for a slab of area of $100{\mathrm{m}}^2$ and the horizontal-hatched region assumes a slab area of $1000{\mathrm{m}}^2$. The region currently excluded by examination of ancient mica [11, 12] is shown in yellow with vertical hatching. The grey region is excluded from the effects of cosmic microwave background photons scattering off the macros [19]. The diagonal hatching of this bound in the bottom-left of the parameter space represents the region where the bound may weaken. Lines corresponding to nuclear and atomic density are shown for illustrative purposes.

Figure 2

Illustrative regions of parameter space that could be probed from observations of slabs of ordinary rock are shown in purple. All 3 regions assume a slab area of $1000{\mathrm{m}}^2$. The region with diagonal hatching assumes searches for features with diameter of 0.1 cm or more, the unhatched region is for a minimum feature diameter of 1 cm, and the horizontal-hatched region assumes a minimum feature diameter of 10 cm. The region currently excluded by examination of ancient mica [11, 12] is shown in yellow with vertical hatching. The grey region is excluded from the effects of cosmic microwave background photons scattering off the macros [19]. The diagonal hatching of this bound in the bottom-left of the parameter space represents the region where the bound may weaken. Lines corresponding to nuclear and atomic density are shown for illustrative purposes.