NEGATIVE PION AND MUON FLUXES IN ATMOSPHERIC CASCADES AT A DEPTH OF 5G CM(-2)

This paper reports observations of the absolute momentum differential fluxes of negative pions and muons between 4 and 15 GeV/c and between 0.3 and 15 GeV/c, respectively, at an atmospheric depth of 5 g cm(-2). The data have been collected by the balloon-borne experiment MASS (ma tter-antimatter space spectrometer) launched from Prince Albert (Canad a) where the geomagnetic cut-off is 650 MV/c. The instrument was flown on the 5th of September 1989, the duration of the flight was 5.5 hour s at an altitude of more than 117000 ft. The measured fluxes are compa red to calculations. The muon spectrum follows a power law in momentum with a spectral index of 2.36 above 2 GeV/c.