Is astronomy possible with neutral ultrahigh energy cosmic ray particles existing in the standard model?

The recently observed correlation between HiRes stereo cosmic ray events with energies E ∼ 10¹⁹ eV and BL Lacertae objects occurs at an angle that strongly suggests that the primary particles are neutral. We analyze whether this correlation, if not a statistical fluctuation, can be explained within the Standard Model, i.e., assuming only known particles and interactions. We have not found a plausible process that can account for these correlations. The mechanism that comes closest—the conversion of protons into neutrons in the IR background of our Galaxy—still underproduces the required flux of neutral particles by about two orders of magnitude. The situation is different at E ∼ 10²⁰ eV, where the flux of cosmic rays at the Earth may contain up to a few percent of neutrons, indicating their extragalactic sources. The text was submitted by the authors in English.