LIGHT DARK MATTER a

We show how light spin-1 2 or spin-0 particles may be acceptable Dark Matter candidates, provided they annihilate sufficiently strongly through new interactions, such as those induced by a new light neutral spin-1 boson U. The corresponding interaction is stronger than weak interactions at lower energies, but weaker at higher energies. Annihilation cross sections of (axially coupled) spin-1 2 Dark Matter particles, induced by a U vectorially coupled to matter, are the same as for spin-0 particles. In both cases, the cross sections (σann v rel /c) into e + e − automatically include a v 2 dm suppression factor, as desirable to avoid an excessive production of γ rays from residual Dark Matter annihilations. We also relate Dark Matter annihilations with production cross sections in e + e − reactions. As for spin-0, light spin-1 2 Dark Matter particles annihilating into e + e − could be responsible for the bright 511 keV γ ray line observed by INTEGRAL from the galactic bulge.