Muons in extensive air showers of size 10(^4) to 10(^7) particles

Abstract

Using the Durham spectrograph and Small Extensive Air Shower Array situated 40 m. above sea level, the rate of single muons and muonpairs of momentum in the range 20 GeV/c to 1000 GeV/c in air showers of size 10(^4) to 10(^7) particles have been measured. The rate of unassociated muon pairs has also been recorded. The large solid iron spectrograph (MARS) is of toroidal design having two distinct halves, which both have a maximum detectable momentum2of about 3000 GeV/c, and an acceptance of 487 cm(^2)sr for single air shower accompanied muons. Both halves are triggered by scintillation counters, whilst muon track location is achieved by digitised neon flash tubes on the Eastern half, and by photography of the flash tubes on the Westernhalf. The air shower array (SARA) has 14 plastic scintillation counters having areas varying from 0.26 m(^2) . to 2.0 m(^2). and placed in an hexagonal geometry around the spectrograph. The array has a characteristic radius of 60 m. and is sensitive to showers of size 10(^5) to 3 10(^6) particles. The measured rates of single and double muons accompanied by air showers are compared to the predictions of semi-empirical electron and muon structure functions. Broad support is found for the structure of muons for small radial distances ≤ 100 m.) as predicted by the expression introduced by Greisen (l960) including an extrapolation to muons of momentum above 1000 GeV/c. A comparison is also made with the predictions of both the CKP, and Feynman scaling model of high energy particle interactions as applied to extensive air showers by Goned (1975) and Fishbane, et al.,(l974). Evidence is found to support the suggestion (Gaisser and Maurer (1972) Fishbane, et al.,(1974),Wdowczyk and Wolfendale (1973)) that the combination of a scaling particle interaction model and an assumed primary spectrum dominated by protons predicts too low a ratio of muons to electrons in air showers at sea level. In contrast the predictions of the CKP model largely coincide with the experimental data. Some evidence is also found for coincident muon pairs at sea level unaccompanied by shower particles.