Speaker
Description
O Deligny1, I Lhenry-Yvon1, Q Luce2, M Roth2, D Schmidt2 and A A Watson3
1 IJClab (Laboratoire de Physique des 2 Infinis Irène Joliot-Curie), CNRS/IN2P3, Université Paris-Saclay, Orsay, France 2 Institut für Astroteilchenphysik (IAP), Karlsruhe Institute of Technology, Karlsruhe, Germany 3 School of Physics and Astronomy, University of Leeds, LS2 9JT, UK
When analysing data from air-shower arrays, it has become common practice to use the signal at a considerable distance from the shower axis (r_opt) as a surrogate for the size of the shower. This signal, S(r_opt), can then be related to the primary energy in a variety of ways. After a brief review of the reasons for the introduction of r_opt, made in a seminal paper by Hillas in 1969, it will be shown that r_opt is a more effective tool when the detectors are laid out on a triangular grid than when the detectors are deployed on a square grid. This result may have implications for explaining the differences of flux observed above 10 EeV by the Auger and Telescope Collaborations. Additionally, this finding should be kept in mind when designing new shower arrays.
