Are ultrahigh energy cosmic rays a signal for supersymmetry?

We investigate the possibility that cosmic rays of energy larger than the Greisen-Zatsepin-Kuzmin cutoff are not nucleons, but a new stable, massive, hadron that appears in many extensions of the standard model. We focus primarily on the $S^0$, a $\mathrm{uds}$-gluino bound state. The range of the $S^0$ through the cosmic background radiation is significantly longer than the range of nucleons, and therefore $S^0$’s can originate from sources at cosmological distances.