Robust constraints and novel gamma-ray signatures of dark matter that interacts strongly with nucleons

Dan Hooper,Samuel D Mcdermott

doi:10.1103/physrevd.97.115006

Abstract

Due to shielding, direct detection experiments are in some cases insensitive to dark matter candidates with very large scattering cross sections with nucleons. In this paper, we revisit this class of models and derive a simple analytic criterion for conservative but robust direct detection limits. While large spin-independent cross sections seem to be ruled out, we identify potentially viable parameter space for dark matter with a spin-dependent cross section with nucleons in the range of ${10}^{\ensuremath{-}27}\text{ }\text{ }{\mathrm{cm}}^{2}\ensuremath{\lesssim}{\ensuremath{\sigma}}_{\mathrm{DM}\ensuremath{-}p}\ensuremath{\lesssim}{10}^{\ensuremath{-}24}\text{ }\text{ }{\mathrm{cm}}^{2}$. With these parameters, cosmic-ray scattering with dark matter in the extended halo of the Milky Way could generate a novel and distinctive gamma-ray signal at high galactic latitudes. Such a signal could be observable by Fermi or future space-based gamma-ray telescopes.

Highlights

If the particles that make up the dark matter of our Universe interact strongly with the Standard Model, such interactions would be expected to generate large event rates in direct detection experiments, assuming that the dark matter is able to reach the detectors with a standard velocity distribution
By “robust,” we mean that in the regions of parameter space we indicate it is not possible for the number of scattering events from dark matter to be smaller than the number used to set the lower limit. This region should be ruled out regardless of the manner in which multiply scattering particles are included. To obtain such limits on the dark matter scattering cross section, we propose that the results of direct detection experiments be interpreted as follows
For the smaller value of D adopted in the left frame, the cosmic-ray halo is largely concentrated within the innermost few tens of kpc, where dark matter particles are abundant, generating a substantial fraction of the isotropic gamma-ray background (IGRB)

Summary

INTRODUCTION

If the particles that make up the dark matter of our Universe interact strongly with the Standard Model, such interactions would be expected to generate large event rates in direct detection experiments, assuming that the dark matter is able to reach the detectors with a standard velocity distribution. In this way, such shielding could render dark matter with large scattering cross sections invisible at direct detection experiments For these reasons, qualitatively different theoretical and experimental considerations are necessary when considering dark matter candidates with very strong interactions with the Standard Model. We revisit the constraints on nonannihilating dark matter with a large scattering cross section with nucleons and discuss the astrophysical gamma-ray signatures in this class of models. Throughout this study, we will refer to dark matter as ψ, and we will assume it does not annihilate in the present epoch

CONSTRAINTS ON DARK MATTER WITH LARGE SCATTERING CROSS SECTIONS WITH NUCLEI

BBN and CMB

Direct detection

GAMMA-RAY SIGNATURES OF COSMIC-RAY INTERACTIONS WITH DARK MATTER

Findings

CONCLUSIONS