The Bino-Wino Co-Annihilation Scenario

In supersymmetric models with non-universal gaugino masses, it is possible to have opposite-sign $SU(2)$ and $U(1)$ gaugino mass terms. In these models, the gaugino eigenstates suffer little mixing, and can only be brought into accord with the WMAP measured relic density when bino-wino co-annihilation acts to enhance the dark matter annihilation rate. We map out parameter space regions and mass spectra which are characteristic of the bino-wino co-annihilation scenario. Direct and indirect dark matter detection rates are shown to be typically very low. However, in these scenarios, the second lightest neutralino has an enhanced loop decay branching fraction to photons that will lead to unique collider signatures.