UV Completions of Magnetic Inelastic Dark Matter and RayDM for the Fermi Line(s)

TL;DR

This paper investigates UV-complete models for magnetic inelastic dark matter and RayDM to explain the Fermi gamma-ray line, analyzing higher order corrections and their impact on annihilation rates and observational signatures.

Contribution

It provides a detailed analysis of UV completions for magnetic inelastic dark matter and RayDM, including higher order corrections, and explores their viability in explaining the Fermi line.

Findings

Rayleigh operators dominate present-day gamma-ray signatures.

Moderately strong coupling models can explain the Fermi line.

Pure Majorana WIMP models require very strong coupling and light messengers.

Abstract

Models that seek to produce a line at ~130 GeV as possibly present in the Fermi data face a number of phenomenological hurdles, not the least of which is achieving the high cross section into gamma gamma required. A simple explanation is a fermionic dark matter particle that couples to photons through loops of charged messengers. We study the size of the dimension 5 dipole (for a pseudo-Dirac state) and dimension 7 Rayleigh operators in such a model, including all higher order corrections in 1/M_{mess}. Such corrections tend to enhance the annihilation rates beyond the naive effective operators. We find that while freezeout is generally dominated by the dipole, the present day gamma-ray signatures are dominated by the Rayleigh operator, except at the most strongly coupled points, motivating a hybrid approach. With this, the Magnetic inelastic Dark Matter scenario provides a successful explanation of the lines at only moderately strong coupling. We also consider the pure Majorana WIMP, where both freezeout and the Fermi lines can be explained, but only at very strong coupling with light (~200 - 300 GeV) messengers. In both cases there is no conflict with non-observation of continuum photons.