Anomalous Longitudinal Shower Profiles and Hadronic Interactions
  The bulk of air showers initiated by very high energy cosmic rays exhibits a longitudinal development in depth with a single well-defined shower maximum. However, a small fraction of showers has a profile that differs considerably from this average behaviour. In extreme cases, such anomalous longitudinal profiles can even have two distinct shower maxima. We discuss the properties of the primary interactions that lead to such profiles. Simulations are used to estimate the rate of anomalous profiles in dependence of primary energy, mass, and characteristic features of hadronic multiparticle production at very high energies. 
Colin Baus and Ralph Engel and Tanguy Pierog and Ralf Ulrich and   Michael Unger
astro-ph.HE