Non-thermal WIMPs as Dark Radiation

Abstract

It has been thought that only light species could behave as radiation and account for the dark radiation observed recently by Planck, WMAP9, South Pole and ATACAMA telescopes. In this work we will show that GeV scale WIMPs can plausibly account for the dark radiation as well. Heavy WIMPs might mimic the effect of a half neutrino species if some of their fraction were produced non-thermally after the thermal freeze-out. In addition, we will show how BBN, CMB and Structure Formation bounds might be circumvented.