Exotic energy injection with ExoCLASS: application to the Higgs portal model and evaporating black holes

Abstract

We devise a new user-friendly tool interfaced with the Boltzmann code CLASS to deal with any kind of exotic electromagnetic energy injection in the universe and its impact on anisotropies of the Cosmic Microwave Background. It makes use of the results from standard electromagnetic cascade calculations develop in the context of WIMP annihilation, generalized to incorporate any injection history. We first validate it on a specific WIMP scenario, the Higgs Portal model, confirming that the standard effective on-the-spot treatment is accurate enough. We then analyze the more involved example of evaporating Primordial Black Holes (PBHs) with masses in the range [3 × 10 13 , 5 × 10 16 ]g, for which the standard approximations break down. We derive robust CMB bounds on the relic density of evaporating PBHs, ruling out the possibility for PBHs with a monochromatic distribution of masses in the range [3 × 10 13 , 2.5 × 10 16 ]g to represent all of the Dark Matter in our Universe. Remarkably, we confirm with an accurate study that the CMB bounds are several orders of magnitude stronger than those from the galactic gamma-ray background in the range [3×10 13 , 3×10 14 ]g. A future CMB experiment like CORE+, or an experiment attempting at measuring the 21 cm signal from the Dark Ages could greatly improve the sensitivity to these models.

The synergy between CMB spectral distortions and anisotropies

“…Our results are shown in Figure 9. The blue region corresponds to the Planck+ FIRAS case, and can be compared with the dashed-dotted lines for previous CMB anisotropy bounds (black for [45], red for [144], orange for [91], and yellow for [186]), with the dotted line for previous SDs constrains, and finally with dahsed lines for previous BBN constraints.…”

“…Note also that our current numerical implementation assumes a single initial PBH mass, but would be easy to generalize to extended spectra. In the monochromatic case, and assuming that PBHs account for a fraction f frac of DM, the energy injection rate can be calculated as [91,144] Q = ρ cdm f frac f effṀ M .…”

“…As a general remark, it is important to underline the fact that many of the modifications discussed here rely on the work already performed by different groups and previous public codes. First, our implementation of the thermal history in presence of energy injection is based on a previous public branch of class specifically designed for the precise treatment of exotic energy injections, called ExoCLASS [91], which incorporates itself some previous numerical results, in particular from [84].…”

CMB anisotropy and BBN constraints on pre-recombination decay of dark matter to visible particles

“…The CMB is sensitive to new physics such as dark matter self interactions [2,3], dark matter-dark radiation interactions [4,5], decay of long-lived unstable particles [6,7], evaporating primordial black holes [8,9], and annihilation of dark matter to standard model particles [10][11][12]. The physics in the dark sector can affect CMB both gravitationally [5,13,14] and electromagnetically [6,7,9,10]. In particular, there are many particle physics motivated scenarios where dark matter can annihilate or decay to standard model particles [6,[15][16][17][18][19][20][21][22], see [23,24] for reviews.…”

Evaporating primordial black holes as varying dark energy

“…The reasons are two: 1) the CMB shift parameters have been evaluated using only the TT modes of the CMB which is particular insensitive to the PBH physics as also evidenced by [44]; 2) the effective dark energy equation In Fig. 2 we show the 68.3% and 95.4% confidence contours for the ΛCDM and the PBH models, respectively, along with the 1D marginalized likelihoods for various parameter combinations.…”