On the fraction of dark matter in charged massive particles (CHAMPs)

TL;DR

This paper derives upper bounds on the fraction of dark matter in the form of charged massive particles (CHAMPs) using cosmological and astrophysical constraints, showing that CHAMPs constitute a very small part of dark matter.

Contribution

It provides the first comprehensive bounds on the fraction of dark matter in CHAMPs considering multiple astrophysical and terrestrial constraints.

Findings

The fraction of dark matter in CHAMPs must be less than 1.4%.

Decaying neutral dark matter must have a lifetime greater than 0.9-3.4 thousand Gyr.

Magnetic field coupling cannot solve the cuspy halo problem in dwarf galaxies.

Abstract

From various cosmological, astrophysical and terrestrial requirements, we derive conservative upper bounds on the present-day fraction of the mass of the Galactic dark matter (DM) halo in charged massive particles (CHAMPs). If dark matter particles are neutral but decay lately into CHAMPs, the lack of detection of heavy hydrogen in sea water and the vertical pressure equilibrium in the Galactic disc turn out to put the most stringent bounds. Adopting very conservative assumptions about the recoiling velocity of CHAMPs in the decay and on the decay energy deposited in baryonic gas, we find that the lifetime for decaying neutral DM must be > (0.9-3.4)x 10^3 Gyr. Even assuming the gyroradii of CHAMPs in the Galactic magnetic field are too small for halo CHAMPs to reach Earth, the present-day fraction of the mass of the Galactic halo in CHAMPs should be < (0.4-1.4)x 10^{-2}. We show that redistributing the DM through the coupling between CHAMPs and the ubiquitous magnetic fields cannot be a solution to the cuspy halo problem in dwarf galaxies.