Gluino NLSP, Dark Matter via Gluino Coannihilation, and LHC Signatures

The possibility that the gluino is the next to the lightest supersymmetric particle (GNLSP) is discussed and it is shown that such models are realized in the context of nonuniversal SUGRA within a significant part of the parameter space under all known experimental bounds. It is then shown that the GNLSP models lead to a compressed sfermion spectrum with the sleptons often heavier than the squarks at least for the first two generations. The relic density here is governed by gluino coannihilation implying a near degeneracy of the gluino and neutralino masses. Thus the GNLSP class of models is very predictive first because the SUSY production cross sections at the LHC are dominated by gluino production and second because the gluino production itself proceeds dominantly through a single channel which allows for a direct determination of the gluino mass and an indirect determination of the neutralino mass due to the near degeneracy. A detailed analysis of these models shows that the jet production and tagged b-jets from the gluino production can be discriminated from the standard model background with appropriate cuts. It is found that the GNLSP models can be tested with just 10 fb$^{-1}$ of integrated luminosity and may therefore be checked with low luminosity runs in the first data at the LHC. Thus if a GNLSP model is realized, the LHC will turn into a gluino factory through a profuse production of gluinos with typically only a small fraction $\lesssim 5%$ of total SUSY events arising from other production modes over the allowed GNLSP model parameter space.