Particle correlation in the cosmic ray showers around the spectral knee

In this paper, we answer the question to what extent the particles in showers initiated by particles with energies of 10¹⁴ – 10¹⁷ eV observed at the edges of extensive air showers, where average particle densities are low (< a few per m²), are correlated. The particle number multiplicity distributions in the surface detectors of the shower arrays are affected by the existence of such a correlation. They are well described by a negative binomial distribution rather than Poisson. Positive correlations cause the distributions to become broader and, in general, the variance of the observed particle number is larger than is usually assumed in the analysis of the shower registration by the Extensive Air Shower experiments. We show how this increase can alter the results of shower axis localisation algorithms.