Explaining PAMELA and WMAP data through Coannihilations in Extended SUGRA with Collider Implications

Abstract

The PAMELA positron excess is analyzed within the framework of nonuniversal SUGRA models with an extended $U(1)^n$ gauge symmetry in the hidden sector leading to neutralino dark matter with either a mixed Higgsino-wino LSP or an essentially pure wino dominated LSP. The Higgsino-wino LSP can produce the observed PAMELA positron excess and satisfy relic density constraints in the extended class of models due to a near degeneracy of the mass spectrum of the extended neutralino sector with the LSP mass. The simultaneous satisfaction of the WMAP relic density data and the PAMELA data is accomplished through a co-annihilation mechanism ($B_{\rm Co}-mechanism$), and leads to predictions of a neutralino and a chargino in the mass range (180-200) GeV as well as low lying sparticles accessible at colliders. We show that the models are consistent with the antiproton constraints from PAMELA as well as photon flux data from EGRET and FERMI-LAT. Predictions for the scalar neutralino proton cross section relevant for the direct detection of dark matter are also discussed and signatures at the LHC for these PAMELA inspired models are analyzed. It is shown that the mixed Higgsino-wino LSP model will be discoverable with as little as 1 fb$^{-1}$ of data and is thus a prime candidate for discovery in the low luminosity runs at the LHC.