Thermal and annihilation radiation in the quark nugget model of dark matter

Abstract

The quark nugget (QN) model of dark matter suggests that the dark matter may consist of compact composite objects of quark matter. Although such composite particles can strongly interact with visible matter, they may remain undetected because of a small cross section to mass ratio. We focus on anti-QNs made of antiquarks since they are heated by annihilation with visible matter and radiate. We study the radiation spectrum and power from anti-QNs in our Galaxy and compare them with satellite observations. Thermal radiation from anti-QN is produced by fluctuations of the positron density. We calculate the thermal radiation of anti-QNs with the use of the Mie theory and found its ratio to the black-body radiation. This allows us to find the equilibrium temperature of anti-QNs in the interstellar medium and determine their contribution to the observed diffuse background radiation in our Galaxy in different frequency intervals, from radio to UV. We also consider nonthermal radiations from anti-QNs, which are produced by products of annihilations of particles of the interstellar gas with anti-QNs. Such radiations include photons from decays of ${\ensuremath{\pi}}^{0}$ mesons, synchrotron, bremsstrahlung, and transition radiations from ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$ mesons, electrons, and positrons. Synchrotron radiation in MHz frequency range and flux of photons from ${\ensuremath{\pi}}^{0}$ decays may be above the detection threshold in such detectors as Fermi-LAT.