Cosmic-Ray Air Showers at Sea Level

An investigation at sea level of cosmic-ray showers with sizes from 5×{}10⁵ to over 10⁹ particles is described. The core locations, arrival directions, and particle density distributions of several thousand showers whose cores landed within an area of 10⁵ m² were determined by the techniques of fast-timing and density sampling. The most important results are as follows: (1) The existence of primary particles with energies greater than 10¹⁸ ev is established by the observation of one shower with more than 10⁹ particles. (2) The function f(r)=0.45(NR₀²)r^-0.7(1+r)^-3.2, where r=RR₀ and R₀=79 m, describes the lateral distribution of particles at distances in the range 50 m<R<400 m and for showers with sizes in the range 5×10⁵<N<10⁸. (3) At distances greater than 50 m from the core the density fluctuations in individual showers have a Poisson distribution. (4) The size and zenith angle distribution can be represented by the formula s(N, x)=s₀(10⁶N)^Γ+1exp[-(x-x₀)Λ], where x=x₀secθ, x₀=1040 g cm^-2, s₀=(6.6±1.0)×10^-8 cm^-2 sec^-1 sterad^-1, Γ=1.9±0.1, Λ=(113±9) g cm^-2, x₀<x<1.3x₀, and 7×10⁵<N<7×10⁸. (5) No evidence is found of anisotropy in the arrival directions or of a break in the energy spectrum of the primaries up to the largest energies observed. (6) Assuming a specific model for shower development and taking into account fluctuations in the depth of the first interaction, the integral energy spectrum of the primaries is J(E)=J₀(10¹⁵E)^γ, where J₀=(8.1±3.1)×10^-11 cm^-2 sec^-1 sterad^-1, γ=2.17±0.1, and 3×10¹⁵ ev<E<10¹⁸ ev.