  Dark matter may be composed of superWIMPs, superweakly-interacting massive
particles produced in the late decays of other particles. We focus on the case
of gravitinos produced in the late decays of sleptons or sneutrinos and assume
they are produced in sufficient numbers to constitute all of non-baryonic dark
matter. At leading order, these late decays are two-body and the accompanying
energy is electromagnetic. For natural weak-scale parameters, these decays have
been shown to satisfy bounds from Big Bang nucleosynthesis and the cosmic
microwave background. However, sleptons and sneutrinos may also decay to
three-body final states, producing hadronic energy, which is subject to even
more stringent nucleosynthesis bounds. We determine the three-body branching
fractions and the resulting hadronic energy release. We find that superWIMP
gravitino dark matter is viable and determine the gravitino and
slepton/sneutrino masses preferred by this solution to the dark matter problem.
In passing, we note that hadronic constraints disfavor the possibility of
superWIMPs produced by neutralino decays unless the neutralino is photino-like.
