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

For pt. I see ibid., vol. 21, p. 129 (1995). The muon content of EAS has been measured at Haverah Park over an extensive primary energy range ∼5x1014<Ep<1020 eV. Above Ep∼1016 eV the relative muon content has been found to decrease gradually in a smooth fashion up to ∼Ep = 1020 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 3x1015 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 3x1015 eV. Although some groups claim to observe no such a 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 3x1015 eV from below. (author)