Muons in extensive air showers .2. The muon content of EAS as a function of primary energy

The muon content of EAS has been measured at Haverah Park over an extensive primary energy range similar to 5 x 10(14) < E(p) < 10(20) V. Above E(p) similar to 10(16) eV the relative muon content has been found to decrease gradually in a smooth fashion up to similar to E(p) = 10(20) eV. This suggests to us that there is no major change in primary mass composition or the nature of nuclear interactions throughout these energies. Below 3 x 10(15) eV, however, there does appear to be a significant change in the muon content characteristics. Observations, reported in this paper, indicate a more rapid reduction in the proportion of muons with increasing energy in the decade of primary energy below 3 x 10(15) eV. Although some groups claim to observe no such muon feature in this energy region, there is some support for our conclusion. If such a change is attributed to a change in primary mass composition then the implication must be a change to a smaller mean mass at energies approaching 3 x 10(15) eV from below.