Unified TeV Scale Picture of Baryogenesis and Dark Matter

Abstract

We present a simple extension of MSSM which provides a unified picture of cosmological baryon asymmetry and dark matter. Our model introduces a gauge singlet field $N$ and a color triplet field $X$ which couple to the right--handed quark fields. The out--of equilibrium decay of the Majorana fermion $N$ mediated by the exchange of the scalar field $X$ generates adequate baryon asymmetry for $M_N\sim 100$ GeV and $M_X\sim$ TeV. The scalar partner of $N$ (denoted ${\tilde{N}}_1$) is naturally the lightest SUSY particle as it has no gauge interactions and plays the role of dark matter. ${\tilde{N}}_1$ annihilates into quarks efficiently in the early universe via the exchange of the fermionic $\tilde{X}$ field. The model is experimentally testable in (i) neutron--antineutron oscillations with a transition time estimated to be around $10^{10}$ sec, (ii) discovery of colored particles $X$ at LHC with mass of order TeV, and (iii) direct dark matter detection with a predicted cross section in the observable range.

Comments: 10 pages, one reference updated. Version to appear in Phys. Rev. Lett