Multimessenger connections of ultra-high energy photons

• Applicant: Professor Dr. Markus Risse
• Subject Area: Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields ; Astrophysics and Astronomy
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 508269468

The era of multimessenger astronomy has started and offers a great potential for further breakthrough discoveries. This has motivated enormous experimental and theoretical efforts. Previous phenomenological studies have focussed on photons and neutrinos up to the observed PeV energies, their production by cosmic rays and links to gravitational waves. In contrast to the case of neutrinos, connections to photons at even higher energies are much less intensely explored so far. This project intends to contribute here and explore, in a phenomenological way, possible multimessenger links of photons in the energy range from roughly 10 PeV to about 100 EeV. Especially, connections of these ultra-high energy photons to the observed PeV photons and PeV neutrinos, and to cosmic rays at the highest energies are to be investigated, leading to three key objectives: (1) Towards exploring the ultra-high energy characteristics of galactic PeV photon sources; (2) Update and extend the GZK photon flux predictions; (3) Constrain the galactic origin of the PeV neutrino flux. Already the present non-observation of ultra-high energy photons provides valuable pieces to the overall multimessenger puzzle. Experimental efforts will allow improved searches for these photons in the coming years, keeping the possibility of actually observing such photons widely open. Thus, it is adequate and timely to explore and exploit the unique multimessenger contributions provided by ultra-high energy photons.

• DFG Programme: Research Grants