M. Unger

Hadronic Multiparticle Production at Ultra-High Energies and Extensive Air Showers

Studies of the nature of cosmic ray particles at the highest energies are based on the measurement of extensive air showers. Most cosmic ray properties can therefore be obtained only from the interpretation of air shower data and are thus dependent on predictions of hadronic interaction models at ultrahigh energies. We discuss different scenarios of model extrapolations from accelerator data to air shower energies and investigate their impact on the corresponding air shower predictions. To explore the effect of different extrapolations by hadronic interaction models we developed an ad hoc model. This model is based on the modification of the output of standard hadronic interaction event generators within the air shower simulation process and allows us to study the impact of changing interaction features on the air shower development. In a systematic study we demonstrate the resulting changes of important air shower observables and also discuss them in terms of the predictions of the Heitler model of air shower cascades. It is found that the results of our ad hoc modifications are, to a large extent, independent of the choice of the underlying hadronic interaction model.

Report of the Working Group on the Composition of Ultra High Energy Cosmic Rays

For the first time a proper comparison of the average depth of shower maximum (

Proton-Air Cross Section and Extensive Air Showers

X_{\rm max}

On the measurement of the proton-air cross section using air shower data

) published by the Pierre Auger and Telescope Array Observatories is presented. The

The Offline Software Framework of the NA61/SHINE Experiment

X_{\rm max}

Radar reflection off extensive air showers

distributions measured by the Pierre Auger Observatory were fit using simulated events initiated by four primaries (proton, helium, nitrogen and iron). The primary abundances which best describe the Auger data were simulated through the Telescope Array (TA) Middle Drum (MD) fluorescence and surface detector array. The simulated events were analyzed by the TA Collaboration using the same procedure as applied to their data. The result is a simulated version of the Auger data as it would be observed by TA. This analysis allows a direct comparison of the evolution of

Influence of low energy hadronic interactions on air-shower simulations

\langle X_{\rm max} \rangle

Legacy code: Lessons from NA61/SHINE offline software upgrade adventure

with energy of both data sets. The

On the measurement of the proton-air cross section using longitudinal shower profiles

\langle X_{\rm max} \rangle

Mass composition working group report

measured by TA-MD is consistent with a preliminary simulation of the Auger data through the TA detector and the average difference between the two data sets was found to be