Reheating Temperature and Gauge Mediation Models of Supersymmetry Breaking

For supersymmetric theories with gravitino dark matter, the maximal reheating temperature consistent with big bang nucleosynthesis bounds arises when the physical gaugino masses are degenerate. We consider the cases of a stau or sneutrino next-to-lightest superpartner, which have relatively less constraint from big bang nucleosynthesis. The resulting parameter space is consistent with leptogenesis requirements, and can be reached in generalized gauge mediation models. Such models illustrate a class of theories that overcome the well-known tension between big bang nucleosynthesis and leptogenesis.Comment: 30 pages, 4 figures; v2: refs adde

Hidden Gauginos of an Unbroken U(1): Cosmological Constraints and Phenomenological Prospects.

We study supersymmetric scenarios where the dark matter is the gaugino of an unbroken hidden U(1) which interacts with the visible world only via a small kinetic mixing with the hypercharge. Strong constraints on the parameter space can be derived from avoiding overclosure of the Universe and from requiring successful Big Bang Nucleosynthesis and structure formation. We find that for typical values of the mixing parameter, scenarios with neutralino NLSP are excluded, while scenarios with slepton NLSP are allowed when the mixing parameter lies in the range chi~O(10^(-13) - 10^(-10)). We also show that if the gravitino is the LSP and the hidden U(1) gaugino the NLSP, the bounds on the reheating temperature from long lived charged MSSM relics can be considerably relaxed and we comment on the signatures of these scenarios at future colliders. Finally, we discuss the case of an anomalously small mixing, chi<<10^(-16), where the neutralino becomes a decaying dark matter candidate, and derive constraints from gamma ray experiments.Comment: 32 pages, 6 figure