Leptophilic dark matter in Galactic Center excess

Abstract

Herein we explore the possibility of explaining a gamma-ray excess in the Galactic Center with the dark matter scenario. After taking into account the constraints from both the AMS-02 experiment and the gamma-ray observation on dwarf spheroidal satellite galaxies in Fermi-LAT, we find that the $\ensuremath{\tau}$ lepton channel is the only permissive channel for the interpretation of the Galaxy center excess. Tau leptophilic dark matter provides a well-motivated framework in which the dark matter can dominantly couple to $\ensuremath{\tau}$ lepton at tree-level. We describe the interactions with a general effective field theory approach by using higher-dimensional operators, and this approach provides for a model independent analysis. We consider the constraints from the measurement of the DM relic density in the Planck experiment and the AMS-02 cosmic rays experiment, and find that most of the interaction operators except ${\mathcal{O}}_{7}$, ${\mathcal{O}}_{9}$ and ${\mathcal{O}}_{12}$ have been excluded. Due to the quantum fluctuations, even in such a scenario there are loop induced dark matter-nucleon interactions. We calculate the dark matter-nucleon scattering cross-section at loop-level, and if the limits on the dark matter-nucleon scattering cross-section from direct detection experiments are also taken into account, we find that the operators remaining available for accounting for the Galaxy center excess are ${\mathcal{O}}_{9}$ and ${\mathcal{O}}_{12}$.