Composite Inelastic Dark Matter

TL;DR

This paper proposes that the DAMA dark matter signal is due to hyperfine transitions in a composite meson dark matter particle, involving a new gauge boson that induces inelastic scattering.

Contribution

It introduces a novel composite dark matter model with hyperfine transitions explaining DAMA's annual modulation signal.

Findings

Hyperfine transitions can produce inelastic scattering signals.

A QCD-like sector can host meson dark matter with relevant energy splittings.

Kinetic mixing with a U(1) gauge boson facilitates the inelastic transitions.

Abstract

Peaking consistently in June for nearly eleven years, the annual modulation signal reported by DAMA/NaI and DAMA/LIBRA offers strong evidence for the identity of dark matter. DAMA's signal strongly suggest that dark matter inelastically scatters into an excited state split by O(100 keV). We propose that DAMA is observing hyperfine transitions of a composite dark matter particle. As an example, we consider a meson of a QCD-like sector, built out of constituent fermions whose spin-spin interactions break the degeneracy of the ground state. An axially coupled U(1) gauge boson that mixes kinetically with hypercharge induces inelastic hyperfine transitions of the meson dark matter that can explain the DAMA signal.