Constraining Very Heavy Dark Matter Using Diffuse Backgrounds of Neutrinos and Cascaded Gamma Rays

TL;DR

This paper uses gamma-ray and neutrino observations to place new constraints on very heavy dark matter, exploring its potential to explain high-energy background features and emphasizing the importance of multi-messenger data for robust limits.

Contribution

It introduces a combined gamma-ray and neutrino analysis to constrain very heavy dark matter properties across a wide mass range, extending previous bounds to higher masses.

Findings

VHDM could explain the VHE excess in gamma-ray background.

Combined gamma-ray and neutrino data provide stronger constraints on VHDM.

Constraints on VHDM extend to higher masses than previous studies.

Abstract

We consider multi-messenger constraints on very heavy dark matter (VHDM) from recent Fermi gamma-ray and IceCube neutrino observations of isotropic background radiation. Fermi data on the diffuse gamma-ray background (DGB) shows a possible unexplained feature at very high energies (VHE), which we have called the "VHE Excess" relative to expectations for an attenuated power law extrapolated from lower energies. We show that VHDM could explain this excess, and that neutrino observations will be an important tool for testing this scenario. More conservatively, we derive new constraints on the properties of VHDM for masses of 10^3-10^10 GeV. These generic bounds follow from cosmic energy budget constraints for gamma rays and neutrinos that we developed elsewhere, based on detailed calculations of cosmic electromagnetic cascades and also neutrino detection rates. We show that combining both gamma-ray and neutrino data is essential for making the constraints on VHDM properties both strong and robust. In the lower mass range, our constraints on VHDM annihilation and decay are comparable to other results; however, our constraints continue to much higher masses, where they become relatively stronger.