An universal description of the particle flux distributions in extended air showers

It is shown that the electromagnetic and muonic fluxes in extended air showers (EAS) can be described using a simple model incorporating attenuation and geometrical dispersion. The model uses a reduced set of parameters including the primary energy E, the position of shower maximum X{sub max} relative to the ground, and a muon flux normalization N{sub {mu}}. To a good approximation, this set of three physical parameters is sufficient to predict the variability of the particle fluxes due to systematic differences between different models of composition and hadronic interactions, and due to statistical event-by-event differences in shower development. Measurements of these three physical observables are therefore unbiased and very nearly model-independent, in contrast with standard measurement techniques. The theoretical problem of determining primary composition is thus deconvolved from the measurement procedure, and may be approached in a subsequent analysis of the measured distributions of (E, X{sub max}, N{sub {mu}})