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

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.Comment: 11 pages, 6 figure

Addendum to "On an unverified nuclear decay and its role in the DAMA experiment''

We reply to the critiques of our paper arXiv:1210.5501 by the DAMA collaboration which appeared in arXiv:1210.6199 and arXiv:1211.6346. Our original claim that the observed background levels are likely to require a large modulation fraction of any putative signal holds. In fact, in light of DAMA's recent comment our claim is further corroborated. We identify the source of the discrepancy between our own analysis and DAMA's claimed levels of unmodulated background. Our analysis indicates that the background in the signal region as reported by DAMA is indeed likely underestimated.Comment: 6 pages, 2 figures; replacement of the original reply to arXiv:1210.6199 to include a response to the second critique in arXiv:1211.6346. A fit to the unmodulated rate including signal is presented. No change in the conclusion

On an unverified nuclear decay and its role in the DAMA experiment

The rate of the direct decay of 40K to the ground state of 40Ar through electron capture has not been experimentally reported. Aside from its inherent importance for the theory of electron capture as the only such decay known of its type (unique third-forbidden), this decay presents an irreducible background in the DAMA experiment. We find that the presence of this background, as well as others, poses a challenge to any interpretation of the DAMA results in terms of a Dark Matter model with a small modulation fraction. A 10ppb contamination of natural potassium requires a 20% modulation fraction or more. A 20ppb contamination, which is reported as an upper limit by DAMA, disfavors any Dark Matter origin of the signal. This conclusion is based on the efficiency of detecting 40K decays as inferred from simulation. We propose measures to help clarify the situation.Comment: 8 pages, 3 figures; v2 - published version; results unchanged; an addendum can be found in http://arxiv.org/abs/arXiv:1210.754