Observe Gamma-Rays and Neutrinos Associated with Ultra-High Energy Cosmic Rays

IceCube measures a diffuse neutrino flux comparable to the Waxman-Bahcall bound, which suggests the possibility that the ultra-high energy cosmic rays (UHECRs) have a common origin with diffuse high energy neutrinos. We propose high energy gamma-ray and/or neutrino observations toward the arrival directions of UHECRs to search for the sources and test this possibility. We calculate the detection probability of gamma-ray/neutrino sources, and find that the average probability per UHECR of >10 EeV is similar to 10% if the sensitivity of the gamma-ray or neutrino telescope is similar to 10(-)(12) erg cm(-2) s(-1) and the source number density is similar to 10(-5) Mpc(-3). Future gamma-ray and neutrino observations toward UHECRs, e.g., by LHAASO-WCDA, CTA, IceCube/Gen2, are encouraged to constrain the density of UHECR sources or even identify the sources of UHECRs.

Automated summary

IceCube measures a diffuse neutrino flux comparable to the Waxman-Bahcall bound, indicating the potential common origin of ultra-high energy cosmic rays with high energy neutrinos. Future observations are encouraged to constrain the density of UHECR sources or identify the sources of UHECRs.