The Role of Wino Content in Neutralino Dark Matter * Disclaimer

We investigate the dark matter prospects of supersymmetric models with nonuniversal gaug-ino masses. We find that for very particular values of the ratio of soft supersymmetry-breaking gaugino masses, M 2 /M 1 , an enhanced coannihilation efficiency between the lightest chargino and the lightest neutralino occurs, allowing for scalars with masses well above the normally accepted limits for viable dark matter in the universal case. As a specific example, we investigate models of hidden sector gaugino condensation. These models exhibit high scalar masses, previously thought dangerous, and the requisite freedom in the ratio of gaugino masses. The cos-mologically viable regions of parameter space are investigated, allowing very specific statements to be made about the content of the supersymmetry-breaking hidden sector. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof of The Regents of the University of California and shall not be used for advertising or product endorsement purposes. Lawrence Berkeley Laboratory is an equal opportunity employer. ii It has long been held that one of the prime virtues of supersymmetry as an explanation of the hierarchy problem is that it tends to also provide a solution to the dark matter problem as a nearly automatic consequence of R-parity conservation. The lightest supersymmetric particle (LSP) is then stable and, as it tends to be a neutral gaugino, it will typically have the right mass and annihilation rate in the early universe to provide sufficient mass density today to account for observations suggesting ρ tot ≃ ρ crit [1]. This paper initially investigates the dark matter implications of the most widely studied benchmark in supersymmetric phenomenology, the constrained Minimal Supersymmetric Standard Model (cMSSM). We emphasize that the cMSSM fails to solve the dark matter problem over most of its parameter space with the exception of certain very special patterns of soft supersymmetry-breaking terms. These patterns must constrain the neutralino (a fermion) to have a very specific mass relationship to an unrelated boson such as the lightest Higgs or the stau. Barring these fine-tuned relationships, the cMSSM predicts too much dark matter – thus bringing it into conflict with direct measurements of the age of the universe [2, 3]. We find this failure to be due, in part, to the cMSSM constraint on the gaugino mass ratio M 2 /M 1. Eliminating this assumption of universal gaugino masses …