Speaker: Saikat Das, Yukawa Institute, Kyoto University, Japan
Abstract: Ultrahigh-energy cosmic rays (UHECRs) are the highest-energy particles observed in the Universe, with their energy spectrum extending beyond a few times 1e20 eV. Their unknown sources can also contribute to the diffuse astrophysical neutrino flux measured by IceCube in the TeV-PeV energy range. By modelling their multi-wavelength energy spectrum, we probe cosmic ray acceleration in high-energy gamma-ray sources such as active galactic nuclei and gamma-ray bursts. In particular, I will discuss models explaining the correlation of a high-energy neutrino event from the direction of the Fermi-LAT gamma-ray blazar TXS 0506+056, and the >10 TeV afterglow emission in GRB 221009A. Using a luminosity-dependent density evolution, I will also present the PeV-EeV diffuse neutrino flux from the entire blazar population. For a generic source distribution, the detection of cosmogenic neutrinos beyond ~0.1 EeV is favourable by upcoming detectors, such as IceCube Gen-2, GRAND and POEMMA, depending on the UHECR mass composition. Lastly, I shall discuss the superheavy dark matter origin of the high-energy cosmic rays, gamma rays, and neutrinos.