Non-thermal WIMPs as "Dark Radiation" in Light of ATACAMA, SPT, WMAP9 and Planck

TL;DR

This paper proposes that the extra radiation suggested by recent cosmic microwave background data can be explained by non-thermal WIMP dark matter particles, which are mostly cold but include a relativistic component, aligning with observational constraints.

Contribution

It introduces a novel explanation for dark radiation using non-thermal WIMPs, supported by theoretical models and consistency with cosmological bounds.

Findings

Non-thermal WIMPs can mimic dark radiation effects.

Parameter space is consistent with BBN, CMB, and structure formation.

Explicit models demonstrate the scenario's viability.

Abstract

The Planck and WMAP9 satellites, as well as the ATACAMA and South Pole telescopes, have recently presented results on the angular power spectrum of the comic microwave background. Data tentatively point to the existence of an extra radiation component in the early universe. Here, we show that this extra component can be mimicked by ordinary WIMP dark matter particles whose majority is cold, but with a small fraction being non-thermally produced in a relativistic state. We present a few example theories where this scenario is explicitly realized, and explore the relevant parameter space consistent with BBN, CMB and Structure Formation bounds.