THEORETICAL ANALYSIS OF EXTENSIVE AIR SHOWERS .4. MUON SHOWERS DEEP UNDERGROUND

For Pt. III see ibid vol.2, No.3, (1969) 354-64. Studies of muon showers deep underground by the Utah group have stimulated an extension of the previous calculations of the present authors into the region covered by the underground experiment: viz. muon threshold energies of the order of 1000 gev and zenith angles in the region of 60 degrees . The effect of varying some of the more important parameters of the high- energy nucleon-air-nucleus collision has been examined, and it is concluded that a multiplicity law of the form E p1/4 is preferred to an Ep1/2 law and that there is no evidence for a significantly greater mean transverse momentum than the value of 0.4 Gev/c, which relates to the parents of muons of lower energy. An increase in the fraction of kaons generated with increasing nucleon energy is not favoured. Concerning the mass spectrum of the primary particles, there is some support for the contention that the primaries above 1015 ev are largely protons, but none for the conclusion of Grigorov et al. in 1967 that the proportion of heavy nuclei commences to increase at 1012 ev. However, a problem that affects all the conclusions is that significantly fewer multiple events are observed than expected.