A Democratic Gauge Model for Dark/Visible Matter Symmetry
  We develop a model for visible matter-dark matter interaction based on the exchange of a weakly interacting massive gauge boson called herein the WIMG. Our model hinges on the assumption that all known particles in the visible matter have their counterparts in the dark matter. We postulate six families of particles five of which are dark. This leads to the unavoidable postulation of six parallel worlds, the visible one and five invisible worlds. We give arguments on particle decays and lifetimes that set a limit on the mass of the WIMG, the gray boson responsible for the very meager communication among these worlds. The 5:1 ratio of dark to visible matter is taken for granted. 
O. Oliveira, C. A. Bertulani, M. S. Hussein, W. de Paula and T.   Frederico
hep-ph