  The interaction of ultra-high energy cosmic rays with the atmosphere nuclei
has long been seen as a unique opportunity to study hadronic interactions above
energies attainable by accelerators. However, so far the multiparticle
production properties of the first interaction have been difficult to assess as
they are masked by the many interactions that outline the shower development.
In this work, we demonstrate, that relevant properties of the ultra-high energy
first interaction can be accessed through the analysis of the shower-to-shower
distribution of muons arriving at the ground. In particular, it is shown that
the slope of the low-tail of the number of muon distribution measured at the
ground is a direct link to the high energy spectrum of neutral pions produced
in the interaction of the primary protons. In this presentation, it will also
address the experimental feasibility of such measurements and their connection
with physical quantities being currently measured at the Large Hadron Collider.
