The NAP flux at mountain altitude 735 g cm-2

Abstract

The energy spectrum of nuclear active particles (NAP) with energy Sigma Egamma greater than 3 TeV is obtained from an analysis of thick emulsion chamber (140 cu of Pb) exposed on Mount Norikura at 2770 m above sea level and the vertical flux is estimated to be (1.4+or-0.1)*10-10 cm-2 s-1 sr-1. Assuming that the energy spectrum and the zenith angle distribution of NAP are expressed by power functions proportional to E-( gamma +1) and cosn-2 theta respectively in differential form, the exponents gamma and n are obtained as 2.3+or-0.1 and 7.3+or-0.5 respectively. The collision mean free path and the ratio of constituents of NAP are discussed.