An interpretation of a simple portal dark matter model on Fermi-LAT gamma-ray excess

Abstract

Dark matter is one of the main components of the universe. Due to its weak interaction with other particles, dark matter cannot be identified as a particle that we know of. We are interested in a simple particle physics scenario where dark matter is identified with the fermion in the dark sector and the standard model sector is connected to dark matter via the portal scalar field. One of the promising signals from these models are gamma-rays from dark matter annihilation processes. In 2016, the Fermi-LAT collaboration detected a gamma-ray excess signal coming from Milky Way’s galactic center which was immediately regarded as a possible candidate for the first detection of dark matter. In this project, we study an interpretation of the signal from Fermi-LAT as a dark matter annihilation from portal dark matter model. First, we calculated gamma-ray fluxes from dark matter annihilations as subsequent decays of portal scalars where the astrophysical factor is calculated from the Navarro-Frenk-White (NFW) dark matter density profile. We found that the simplest model does not fit adequately with chi-squared per degree of freedom, . We proposed that a part of the Fermi-LAT excess might come from another source of gamma-ray. The dark matter model combined with an unknown astrophysical source is then studied. The combined model is able to provide a reasonable fit indicating that scalar mass is 130 GeV, where dark matter mass is in the range of 150 − 350 GeV and 〈σν〉 is around 7 × 10−26 cm3/s.