Exotic massive hadrons and ultrahigh energy cosmic rays - art. no. 015021

We investigate the proposal that primary cosmic rays of energy above the Gr eisen-Zatsepin-Kuzmin cutoff are exotic massive strongly interacting partic les (uhecrons). We study the properties of air showers produced by uhecrons and find that masses in excess of about 50 GeV are inconsistent with the h ighest energy event observed. We also estimate that with sufficient statist ics a uhecron of mass as low as 10 GeV may be distinguished from a proton.