Q-ball candidates for self-interacting dark matter

TL;DR

It is shown that nontopological solitons, known as Q-balls, are promising candidates for self-interacting dark matter, and can satisfy the cross-section requirements for a broad range of masses.

Abstract

We show that non-topological solitons, known as Q-balls, are promising candidates for self-interacting dark matter. They can satisfy the cross-section requirements for a broad range of masses. Unlike previously considered examples, Q-balls can stick together after collision, reducing the effective self-interaction rate to a negligible value after a few collisions per particle. This feature modifies predictions for halo formation. We also discuss the possibility that Q-balls have large interaction cross-sections with ordinary matter.

Figures (1)

• Figure 1: Empirical constraints (shades of grey) on Q-ball/proton cross section and mass assuming $\phi$ interacts through an intermediate boson $Z'$ with $M_{Z'} \approx 1$ TeV and $g \approx 0.1$. Experiments are described in Ref. last. The most likely range for Q-balls is enclosed by hatched boundary (either Type I with $\phi_0/\mu$ within a few orders of magnitude of unity or Type II). White regions are currently unconstrained experimentally. If no restriction is placed on $\phi_0/\mu_0$, the predicted range for Q-balls expands to the dot-dashed boundary, including even more untested territory.