Effective field theory approach to the Galactic Center gamma-ray excess

We explore the possibility of explaining a gamma-ray excess in the Galactic center, originally pointed out by Hooper, collaborators, and other groups, in an effective field theory framework. We assume that dark matter annihilation is mediated by particles heavy enough to be integrated out and that such particles couple to all quark families. We calculate the effective coupling required to explain the annihilation signal in the Galactic center and compare with bounds from direct detection, collider searches, and the requirement that the dark matter particles make up the appropriate fraction of the universal energy budget. We find that only a very small set of operators can explain the gamma-ray excess while being consistent with other constraints. Specifically, for scalar dark matter, the viable options are one scalar-type coupling to quarks and one interaction with gluons, while for fermionic (Dirac) dark matter, the viable options are two scalartype dimension-7 operators or a dimension-6 vector-type operator. in all cases, future searches with the Large Hadron Collider should probe the relevant operators' effective energy scale, while all viable interactions should escape direct detection experiments.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)U.S. Department of EnergyFundacao de Amparao a Pesquisa do Estado de São PauloUniversidade Federal de São Paulo, Dept Ciencias Exatas & Terra, BR-09972270 Diadema, SP, BrazilUniv Calif Santa Cruz, Dept Phys, Santa Cruz, CA 95064 USAUniv Calif Santa Cruz, Santa Cruz Inst Particle Phys, Santa Cruz, CA 95064 USAUniversidade Federal de São Paulo, Dept Ciencias Exatas & Terra, BR-09972270 Diadema, SP, BrazilU.S. Department of Energy: SC0010107Fundacao de Amparao a Pesquisa do Estado de São Paulo: 2013/22079-8Web of Scienc