Eun-joo Ahn

The Pierre Auger Observatory located in Argentina is designed to observe high energy cosmic rays. Fortuitously, the Observatory is able to search for high energy neutrinos where its detection capabilities are comparable to that of neutrino-dedicated observatories. Due to the small cross section, neutrino-induced air showers are likely to occur deep in the atmosphere. Hence,… More »

Despite 100 years since the first discovery of cosmic rays, we still do not know what these particles are at the highest energy. The Pierre Auger Observatory in Argentina is able to detect cosmic rays above 1017 eV with high accuracy due to its hybrid detection technique. Studying the distribution of Xmax, the position in… More »

The Pierre Auger Observatory measures the longitudinal air shower profile of ultra high energy cosmic rays which gives information on composition and hadronic interaction properties. Eun-Joo Ahn and colleagues use this data to obtain the proton-air cross section. Preliminary results show a surprising rise in the cross section with energy, which is not predicted by… More »