A re-analysis of gravitino dark matter in the constrained MSSM

We re-consider the gravitino as dark matter in the framework of the Constrained MSSM. We include several recently suggested improvements on: (i) the thermal production of gravitinos, (ii) the calculation of the hadronic spectrum from NLSP decay and (iii) the BBN calculation including stau bound-state effects. In most cases we find an upper bound on the reheating temperature T-R less than or similar to a few x 10(7) GeV from over-production of Li-6 from bound state effects. We also find an upper limit on the stau lifetime of 3 x 10(4) sec, which is nearly an order of magnitude larger than the simple limit 5 x 10(3) sec often used to avoid the effect of bound-state catalysis. The bound on T R is relaxed to less than or similar to a few x 10(8) GeV when we use a more conservative bound on Li-6/Li-7, in which case a new region at small stau mass at similar to 100GeV and much longer lifetimes opens up. Such a low stau mass region can be easily tested at the LHC.