Ultrahigh energy cosmic ray (UHECR) protons produced by uniformly distributed astrophysical sources contradict the energy spectrum measured by both the AGASA and HiRes experiments, assuming the small scale clustering of UHECRs observed by AGASA is caused by pointlike sources. In that case, the small number of sources leads to a sharp exponential cutoff at the energy $E<\mathrm{}{10}^{20}\mathrm{eV}$ in the UHECR spectrum. New hadrons with a mass of 1.5–3 GeV can solve this cutoff problem. For the first time we discuss the production of such hadrons in proton collisions with infrared or optical photons in astrophysical sources. This production mechanism, in contrast with proton-proton collisions, requires the acceleration of protons only to energies $E\lesssim {10}^{21}\mathrm{eV}.$ The diffuse gamma-ray and neutrino fluxes in this model obey all existing experimental limits. We predict large UHE neutrino fluxes well above the sensitivity of the next generation of high energy neutrino experiments. As an example we study hadrons containing a light bottom squark. This model can be tested by accelerator experiments, UHECR observatories, and neutrino telescopes.

• Received 6 March 2003

DOI:https://doi.org/10.1103/PhysRevD.68.043005