P.E. Hodgson

CXVI. Nuclear disintegrations caused by 50–125 mev protons: I

Summary The results of measurements on nuclear disintegrations caused by 50–125 mev protons in photographic emulsion are given. The relative numbers and the angular and energy distributions of the secondary alpha-particles and protons have been found and the collision mean free path for protons in emulsion deduced.

XV. Some features of nuclear disintegrations caused by cosmic rays

Summary Cosmic ray stars in light and heavy elements have been investigated by the photographic plate method. The angular distribution of the particles from stars in heavy elements is shown to be isotropic, while that of those from light elements is not. Possible explanations of this are discussed. The numbers of stars with various numbers of alpha particles and protons are shown to be in accordance with a random distribution. This indicates that the emission of one charged particle has no influence on the nature of a subsequent charged particle. The emission of excited beryllium eight nuclei is also investigated and their frequency found to agree with the evaporation theory.

VIII The disintegration of lead nuclei by cosmic rays

Summary Cosmic-ray stars in lead have been investigated by means of photographic plates in close contact with lead foil. The energy distributions of protons and alpha-particles from lead stars have been determined and are compared with the prediction of the evaporation theory. The mean ratio of doubly to singly charged particles is estimated, and an approximate value of the rate of star production in lead deduced.

IX. The production of τ-mesons in ice

Summary Nuclear-research emulsion has been exposed to the cosmic radiation under various thicknesses of ice. Three events interpreted as the decay of τ-mesons have been observed, and measurements on their tracks show that these particles decay into three π-mesons of total kinetic energy (73±6) Mev and have mass (965±12)me . They are found with a frequency of about 0·0008 τ-mesons per star in emulsion exposed under ice. The emulsion was examined for nuclear disintegrations produced by heavy mesons, and for τ-mesons decaying in flight, but no such events were found. The life time is shown to be longer than 10-9 sec.

XC. The energy distribution of alpha-particles emitted from nuclear disintegrations

Summary The energy distributions of the alpha-particles emitted from small nuclear disintegrations caused by the cosmic radiation in photographic emulsion have been found. These are analysed into the parts due to the light and the heavy elements of the emulsion, and the variation of nuclear temperature and effective potential barrier height with star size found for each.

THE EMISSION OF Li

Summary Lithium 8 nuclei ejected from cosmic-ray induced disintegrations have been investigated using the photographic plate method. Earlier work has been confirmed, and the frequency and energy distribution of the Li8 nuclei determined and compared with the predictions of the evaporation theory. Some nuclear reactions involving the production of Li8 have been identified.

sup 8

Summary A calculation has been made of the consequences of assuming that stars are produced in a cascade process by charged and uncharged particles according to a very simple law. The constants in this law can be chosen to give agreement with experiment to the extent to which the quantities are known and also fall within the ranges that are a priori permissible. It does not appear possible to determine them with much accuracy from existing data, but it seems that a fair proportion of the stars with less than five prongs are due to primaries of fairly high energy.