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T: Teilchenphysik

T 407: Kosmische Strahlung III

T 407.9: Talk

Wednesday, March 29, 2006, 18:20–18:35, HG2-HS3

Photons at the end of the cosmic-ray spectrum? — •Markus Risse^1,2, Piotr Homola², Ralph Engel¹, Dariusz Gora^2,3, Dieter Heck¹, Jan Pekala², Barbara Wilczynska², and Henryk Wilczynski² — ¹Forschungszentrum Karlsruhe, Institut für Kernphysik, 76021 Karlsruhe — ²Institute of Nuclear Physics PAN, 31-342 Krakow, Poland — ³Universität Karlsruhe, Institut für Experimentelle Kernphysik, 76021 Karlsruhe

Photons above 10 EeV might provide a key for understanding the origin of cosmic rays. Substantial fluxes of these ultrahigh-energy (UHE) photons are predicted in top-down models of cosmic-ray origin. UHE photons are also produced by the GZK process of resonant photoproduction of pions, in analogy to GZK neutrinos. Experimentally, UHE photons can be discriminated from nuclear primaries due to differences in the expected air shower signatures. So far, no photon detection has been claimed. In this work, recent results on upper limits to the fraction of photons are presented. The statistics collected so far already allows us to constrain some top-down models. With increasing data statistics from the Pierre Auger Observatory, further constraints are expected.