Search for dark matter cosmic-ray electrons and positrons from the Sun with the Fermi Large Area Telescope

Abstract

We use 7 years of electron and positron Fermi-LAT data to search for a possible excess in the direction of the Sun in the energy range from 42 GeV to 2 TeV. In the absence of a positive signal we derive flux upper limits which we use to constrain two different dark matter (DM) models producing e + e − fluxes from the Sun. In the first case we consider DM model being captured by the Sun due to elastic scattering and annihilation into e + e − pairs via a long-lived light mediator that can escape the Sun. In the second case we consider instead a model where DM density is enhanced around the Sun through inelastic scattering and the DM annihilates directly into e + e − pairs. In both cases we perform an optimal analysis, searching specifically for the energy spectrum expected in each case, i.e., a box-like shaped and line-like shaped spectrum respectively. No significant signal is found and we can place limits on the spin-independent cross-section in the range from 10 −46 cm 2 to 10 −44 cm 2 and on the spin-dependent cross-section in the range from 10 −43 cm 2 to 10 −41 cm 2 . In the case of inelastic scattering the limits on the cross-section are in the range from 10 −43 cm 2 to 10 −41 cm 2 . The limits depend on the life time of the mediator (elastic case) and on the mass splitting value (inelastic case), as well as on the assumptions made for the size of the deflections of electrons and positrons in the interplanetary magnetic field. PACS numbers: 95.35.+d, 95.85.Ry

Status, Challenges and Directions in Indirect Dark Matter Searches

“…If the dark matter "world" is coupled to our usual world through long lived mediators that can escape the Sun interior and decay into Standard Model particles in-flight to the Earth, then other techniques can also search for dark matter accumulated in the Sun. In such models of secluded dark matter [175], an excess of gamma-rays or cosmic-rays from the direction of the Sun could also be interpreted as a signature of dark matter annihilations inside it [176][177][178][179]. Secluded dark matter models also present advantages for neutrino searches.…”

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

“…Therefore, to take into account the effect of heliomagnetic field, in the present analysis we have chosen as signal region a cone with aperture of 30 • pointing towards the Sun (see Ref. [9] for alternative RoIs).…”

“…In this work, we performed a comprehensive analysis of the CRE data [6] collected by the Fermi Large Area Telescope (LAT) [7] to search for possible features in the spectrum originating either from the direct annihilation of DM particles in the Galactic halo into e + e − pairs [8] or towards the Sun, where we searched for either delta-like lines or box-like spectral edges [9].…”

Search for dark matter signatures in the gamma-ray emission towards the Sun with the Fermi Large Area Telescope

“…The standard solar emission mechanisms are expected to yield a smooth gamma-ray spectrum, while both the DM scenarios illustrated above are expected to yield some characteristic features in the spectrum. In particular, if gamma rays are produced through a mediator, the spectrum should exhibit a box-like feature [22,23]; on the other hand, if gamma rays are produced directly in DM annihilations, a line-like feature is expected [24].…”