Macro Dark Matter

TL;DR

This paper explores the possibility of macroscopic dark matter candidates, called Macros, which could be composed of Standard Model particles, and discusses observational constraints on their properties and existence.

Contribution

It introduces the concept of Macros as a class of dark matter candidates with specific mass and cross-section ranges, highlighting unexplored parameter space.

Findings

Significant parameter space remains for Macro masses between 55 g and 10^{17} g.

Constraints exclude some low-mass Macros that destabilize matter.

Astrophysical and cosmological observations limit Macro properties.

Abstract

Dark matter is a vital component of the current best model of our universe, $\Lambda$CDM. There are leading candidates for what the dark matter could be (e.g. weakly-interacting massive particles, or axions), but no compelling observational or experimental evidence exists to support these particular candidates, nor any beyond-the-Standard-Model physics that might produce such candidates. This suggests that other dark matter candidates, including ones that might arise in the Standard Model, should receive increased attention. Here we consider a general class of dark matter candidates with characteristic masses and interaction cross-sections characterized in units of grams and cm$^2$, respectively -- we therefore dub these macroscopic objects as Macros. Such dark matter candidates could potentially be assembled out of Standard Model particles (quarks and leptons) in the early universe. A combination of Earth-based, astrophysical, and cosmological observations constrain a portion of the Macro parameter space. A large region of parameter space remains, most notably for nuclear-dense objects with masses in the range $55 - 10^{17}$ g and $2\times10^{20} - 4\times10^{24}$ g, although the lower mass window is closed for Macros that destabilize ordinary matter.