In the energy range from a few TeV to 25 TeV, upper bounds on the dark matter decay rate into high-energy monochromatic neutrinos have recently become comparable to those on monochromatic gamma-ray lines. This implies the clear possibility of a future double “smoking gun” as evidence of the dark matter particle, from the observation of both a gamma and a neutrino line at the same energy. In particular, we show that a scenario where both lines are induced from the same dark matter particle decay leads to correlations that can already be tested. We study this “double monochromatic” scenario by considering the complete list of lowest-dimensional effective operators that could induce such a decay. Furthermore, we argue that, on top of lines from decays into two-body final states, three-body final states can also be highly relevant. In addition to producing a distinct hard photon spectrum, three-body final states also produce a linelike feature in the neutrino spectrum that can be searched for with neutrino telescopes.

• Received 26 October 2015

DOI:https://doi.org/10.1103/PhysRevD.93.043535