Prospects for indirect dark matter searches with MeV photons

Abstract

Abstract. Over the past decade, extensive studies have been undertaken to search for photon signals from dark matter annihilation or decay for dark matter particle masses above ∼ 1 GeV. However, due to the lacking sensitivity of current experiments at MeV-GeV energies, sometimes dubbed the 'MeV gap', dark matter models with MeV to sub-GeV particle masses have received little attention so far. Various proposed MeV missions (like, e.g., e-ASTROGAM or AMEGO) are aimed at closing this gap in the mid-or long-term future. This, and the absence of clear dark matter signals in the GeV-TeV range, makes it relevant to carefully reconsider the expected experimental instrumental sensitivities in this mass range. The most common two-body annihilation channels for sub-GeV dark matter are to neutrinos, electrons, pions or directly to photons. Among these, only the electron channel has been extensively studied, and almost exclusively in the context of the 511 keV line. In this work, we study the prospects for detecting MeV dark matter annihilation in general in future MeV missions, using e-ASTROGAM as reference, and focusing on dark matter masses in the range 1 MeV-3 GeV. In the case of leptonic annihilation, we emphasise the importance of the often overlooked bremsstrahlung and in-flight annihilation spectral features, which in many cases provide the dominant gamma-ray signal in this regime.

Prospects for indirect MeV dark matter detection with gamma rays in light of cosmic microwave background constraints

“…In summary, the analysis provided in this paper is similar to that in [24] with a few important exceptions: i) we have considered the additional π + π − channel, ii) we utilize a more accurate computation of the gamma-ray production from the µ + µ − final state, especially for dark matter masses close to the muon mass, iii) we have provided individual constraints for each channel arising from the assumption that the efficiency function is channeldependent, iv) we have performed an analysis on the energy integration range ∆E to optimize the detection limit for each individual channel, resulting in more optimistic results regarding the possible detection, v) we show that the detection limit can vary broadly for different DM density profiles, and we have some cases for which the detection is possible even at the CORE precision level.…”

Dark matter annihilation feedback in cosmological simulations – II. The influence on gas and halo structure

“…where f e f f < 1 is a parameter that relates the energy released that can effectively increase the ionisation fraction, thus strongly restricting the simple s-wave thermal WIMP scenario in the sub-GeV range. A number of missions like e-ASTROGAM and AMEGO will be able to probe the the sub-GeV annihilation products directly today with Fermi Gamma-ray telescope like sensitivity (Bartels et al 2017). Voyager I direct measurements of cosmic ray data however are able to rule out thermal relic WIMPs below about 300 MeV today (Boudaud et al 2017) assuming single decay product annihilations and models of Galactic cosmic ray propagation.…”

Dependence of accessible dark matter annihilation cross sections on the density profiles of dwarf spheroidal galaxies with the Cherenkov Telescope Array

“…The spectra shown in Figure 2 include final state radiations like Bremsstrahlung of charged leptons, which are electroweak corrections different from interactions with external fields. We consider contributions from secondary γ-rays produced during propagations of charged leptons to be negligible [122][123][124][125][126]. The treatment of the secondary γ-rays and the spectra in our calculation would be consistent with those available in Ref.…”