On the relic abundance of light photinos

We solve the coupled Boltzmann equation for the system of light photinos interacting with pions and $R^0$'s (the gluon-gluino bound state) to determine the relic abundance of light photinos in the light gaugino scenario. Cosmology bounds the ratio r of the R^0 mass to the photino mass to be less than about 1.8. We also use a model Lagrangian embodying crossing symmetry between the $R^0 \leftrightarrow \photino \pi \pi$ and $R^0 \pi \leftrightarrow \photino \pi$ reactions to identify cosmologically favored regions of $R^0$ lifetime as a function of $R^0$ and photino masses.