Effective Theories of Gamma-ray Lines from Dark Matter Annihilation
  We explore theories of dark matter in which dark matter annihilations produce mono-energetic gamma rays ("lines") in the context of effective field theory, which captures the physics for cases in which the particles mediating the interaction are somewhat heavier than the dark matter particle itself. Building on earlier work, we explore the generic signature resulting from SU(2)xU(1) gauge invariance that two (or more) lines are generically expected, and determine the expected relative intensities, including the possibility of interference between operators. 
Arvind Rajaraman, Tim M. P. Tait, Alexander M. Wijangco
hep-ph