Abstract
An experiment was carried out at Mt. Evans, Colorado (altitude 4300 m) to study the development of extensive air showers in the atmosphere. Showers with cores striking near a cloud-chamber-hodoscope arrangement were selected, and the differential energy spectrum of the shower particles determined by observing their transition effect in six \textonehalf{}-in. lead plates with a 68-counter hodoscope. Each shower can be assigned an age classification on the basis of this energy spectrum. The lateral structure function between 2 m and 8 m from the core was obtained from measurements of the particle densities at four extension trays containing 50 counters with a total area of 1.34 ${\mathrm{m}}^{2}$. It was found from the hodoscope data that the lateral structure function of the showers of various ages does not agree well with the predictions of the single-particle cascade theory. The observed structure function for showers at and beyond the cascade maximum is less steep than expected near the axis; this is consistent with multiple production of shower-producing particles in the primary collision. It was also found that the lateral distribution of showers past the cascade maximum varies only slowly with age; this tendency is predicted in a general way by the cascade theory, but only at a much later stage of development than observed and with quite a different slope of the distribution curve. The interpretation of this effect as the result of a "rejuvenation" of the shower by the continuous transfer of energy from the nucleonic cascade to the electron cascade is therefore more likely.
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