LXIV. The energy distribution of cosmic ray particles over northern italy

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Abstract
The energies of 200 multiply-charged particles of the primary cosmic radiation have been determined from measurements of the multiple Coulomb scattering. These particles were found in a stack of emulsions exposed over Northern Italy. The energy determinations have been shown to be reliable up to an energy of at least 3.0 Bev per nucleoli. From these measurements the cut-off energy has been shown to be 1.55±0.06 Bev per nucleon, instead of the 1.05 Bev per nucleon predicted by geomagnetic theory. The integral energy spectrum between 1.8 and 3.0 Bev per nucleon has been shown to be given by N (>E)=370/(m0c2+E)1.50 , and between the above cut-off energy and 800 Bev per nucleon-from a consideration of a-particle produced ‘jets’- to have an exponent of 1.49. A value for the a-particle flux at the top of the atmosphere has been found of 93±8 α-particle/m2/ster/sec.