Momentum Distribution of Charged Cosmic-Ray Particles at Sea Level

Abstract

A new measurement of the momentum distribution of high energy charged cosmic-ray particles at sea level has been made with a magnetic spectrograph which uses two counter-controlled cloud chambers and a large electromagnet. The spectrum is extended beyond previous determinations to a momentum of 80 Bev/c. For the 1547 measureable sets of tracks recorded the positive-negative ratio is 1.26±0.06. Up to the highest momenta measured the differential spectrum can be represented by an expression of the form $\frac{1}{p^s}$ with $s=1.9\mathrm{}$. The positive excess and positive-negative ratio appear to be functions of momentum with the positives predominating at about 1.3 Bev/c. Except for this the positive and negative spectra are very similar. Although the effect is barely outside statistical uncertainty there seems to be an anomalous dip in the momentum distribution at about 3 Bev/c. There seems to have been a small diurnal variation in the spectrum during the time occupied by the experiment, 1 Bev/c particles being favored during the day, and 3 Bevc and 6 Bev/c particles being favored at night. These effects are discussed and the present results are compared with data of other experimenters.