MUONS (GREATER-THAN-OR-EQUAL-TO-1 GEV) IN LARGE EXTENSIVE AIR SHOWERS OF ENERGIES BETWEEN 10(16.5)EV AND 10(19.5)EV OBSERVED AT AKENO

The properties of muons (greater than or equal to 1 GeV) in giant air showers between 10(16.5) eV, and 10(19.5) eV are measured by the Akeno 1 km(2), 20 km(2) and 100 km(2) air shower arrays. The lateral distribution of muons is well fitted by the formula given by Greisen with parameters beta = 2.52+/-0.02 and log(R(0)) = (0.58+/-0.04)(sec theta-1)+(2.39+/-0.05) between 10(16.5) eV and 10(19.0) eV within 800 m of the air shower axis, where theta is the zenith angle of the shower arrival direction. The relation between the total number of muons (N-mu) and the total number of electrons (N-e) derived using these parameters is expressed on average as N-mu = (2.6+/-1.3) x 10(5.0+a)(N-e/10(7))(b), where a = (1.07+/-0.13)(sec theta - 1) and b = (0.77+/-0.02) - (0.17+/-0.02)(sec theta - 1). The lateral distribution of muons becomes steeper than expected from extrapolation of the above formula for core distances > 800 m and is expressed as rho(mu) = N mu(C'(mu)/R(0)(2))r(-0.75)(1+r)(-beta){1+(R/800 m)(3)}(-delta) (r = R/R(0), where R is a core distance). No deviation from this formula has been observed for sec theta < 2.0 up to 10(19.0) eV. The relation between the muon density (rho mu (600)) and the charged-particle density on the ground at 600 m from the core (S(600)) is studied between 10(16.5) eV and 10(19.0) eV. A systematic change in the chemical composition of cosmicrays from a predominantly heavy to a predominantly light composition above 10(17.5) eV claimed by the Fly's Eye group has not been detected beyond the present experimental uncertainties. The present experiment suggests a much smaller rate of change of composition between 10(17.5) eV and 10(18.5) eV than that from the Fly's Eye experiment Fly's Eye experiment.