Direct Detection Signatures of Self-Interacting Dark Matter with a Light Mediator

TL;DR

This paper explores how light mediators in self-interacting dark matter models produce distinct nuclear recoil signals in direct detection experiments, offering new ways to identify SIDM signatures and constrain model parameters.

Contribution

It demonstrates that SIDM with a light mediator creates unique recoil spectra and proposes methods to distinguish these signals from traditional dark matter interactions.

Findings

SIDM produces a low-energy peaked recoil spectrum

Different target materials can help identify SIDM signatures

Current experiments place strong bounds on hidden-visible sector mixing

Abstract

Self-interacting dark matter (SIDM) is a simple and well-motivated scenario that could explain long-standing puzzles in structure formation on small scales. If the required self-interaction arises through a light mediator (with mass $\sim 10$ MeV) in the dark sector, this new particle must be unstable to avoid overclosing the universe. The decay of the light mediator could happen due to a weak coupling of the hidden and visible sectors, providing new signatures for direct detection experiments. The SIDM nuclear recoil spectrum is more peaked towards low energies compared to the usual case of contact interactions, because the mediator mass is comparable to the momentum transfer of nuclear recoils. We show that the SIDM signal could be distinguished from that of DM particles with contact interactions by considering the time-average energy spectrum in experiments employing different target materials, or the average and modulated spectra in a single experiment. Using current limits from LUX and SuperCDMS, we also derive strong bounds on the mixing parameter between hidden and visible sector.