Measuring the Cosmic Ray Decoherence Curve

The spatial correlation between the particles in an extensive air shower depends on the lateral profile of the shower. A quantity which is often measured is the cosmic ray decoherence curve, giving the probability to detect two particles as a function of their distance. Such a measurement, although on a reduced distance scale, may be carried out by means of simple Geiger counters. General considerations about designing such an experiment are given, and an example is reported making use of four small Geiger counters.