Time dispersion of muons in EAS

Describes the results and conclusions from an experiment set up to measure the time spread of muons in extensive air showers (EAS) detected at the Haverah Park EAS detector array, UK. The pulse risetimes (T₇₀) from 10% to 70% amplitude of the responses from 3*10 m² muon detectors are studied, and the anomalous pulse structure is investigated. The mean T₇₀ is studied as a function of shower size, zenith angle and core distance and its dependence on shower size is related to the elongation length of the EAS. Fluctuations in T₇₀ are studied as a method of yielding the mass composition of the primary particles. The measured fluctuations in T₇₀ are related to fluctuations in the depth of the electromagnetic cascade maximum. The results yield the same value for both the elongation rate and the fluctuation in the depth of maximum sigma (X_m) of 58(+or-23) g cm^-2. The results are consistent with simulation studies that assume protons are still the dominant component of cosmic rays in the energy range 10¹⁷ to 10¹⁸ eV.