Models of Dark Matter and the INTEGRAL 511 keV line

Two models of dark matter are examined in the context of the bright 511 keV gamma-ray signal observed from the center of the galaxy by the INTEGRAL satellite. A model of annihilating MeV-scale dark matter has been shown by Boehm et al. to be able to provide the required flux of positrons to explain the INTEGRAL signal, and the possible experimental consequences of this model are investigated in rare pion decays. A second possible explanation for INTEGRAL is considered, where TeV-scale WIMPS interacting with a GeV-scale scalar mediator produce positrons through formation and excitation of WIMP-WIMP bound states at the center of the galaxy. It is found that the MeV dark matter model could explain an observed excess in the decay π → e+e−, but that the TeV WIMP model is unable to explain INTEGRAL in the weak-coupling scenario. Brief concluding remarks are made about possible extensions of the TeV WIMP model to strongly coupled systems.