Search for dark matter signatures in the cosmic-ray electron and positron spectrum measured by the Fermi Large Area Telescope

Abstract

Over its ten years of mission the Large Area Telescope onboard the Fermi Gamma-ray Space Telescope has collected the largest ever sample of high-energy cosmic-ray electron and positron events. Possible features in their energy spectrum could be a signature of the presence of nearby astrophysical sources or of more exotic sources, such as annihilating or decaying dark matter particles in the Galaxy. In addition, the capture and subsequent annihilation of dark matter particles in the Sun via long-lived dark mediators can yield high-energy electrons and positrons reaching the Earth, which are a probe for the dark matter-nucleon scattering cross section. We present the results of the search for possible features in the cosmic-ray electron and positron spectrum from our Galaxy and towards the Sun. We set constraints on the the velocity-averaged dark matter annihilation cross section and on the dark matter-nucleon scattering cross section up to dark matter masses of 1.7 TeV.

Constraining Time Dependent Dark Matter Signals from the Sun

“…In the generic models scenario we present our results in terms of the annihilation rate (Γ ann ) (instead of the spin-independent or spin-dependent cross sections), which is the most direct and modelindependent way of constraining DM signals from the Sun. We compare some of our results to the limits produced in [36] later in this work at the end of section 4.…”

“…2. We would like to clarify that even though the boosted case is similar to the one considered in [36,48], the threshold case is different from the "delta-like" signals in [36,48].…”

“…This can be mainly attributed to the fact that the exposure of CALET to the Sun is more than the exposure of DAMPE, especially at higher energies. Before we move on to the dark photon model, we would like to compare the results of this section to the ones found in the boosted case ("box-like") from Fermi-LAT data [36] with a signal region defined as 30 0 cone around the Sun. They have set limits on the DM-nucleon cross section, using a cone with aperture of 30 0 pointing towards the Sun as the signal region.…”

“…They have set limits on the DM-nucleon cross section, using a cone with aperture of 30 0 pointing towards the Sun as the signal region. A "box-like" energy spectrum was considered in [36,48] which corresponds to the "boosted" case in this work. Note that the "delta-like" spectrum in [36,48] corresponds to the capture via inelastic scattering and the subsequent annihilation directly to e `e´p airs outside the Sun.…”

“…This work is complementary to the studies of similar models and their signals in Fermi-LAT. A recent analysis of cosmic ray signals in Fermi-LAT from DM annihilation both inside and outside the Sun has been done in [36]. One difference between our work and this reference is that we don't apply any angular cuts.…”