THE work of the past ten years has established the existence of a variety of elementary particles of which some of the properties are set out in the accompanying Table. Most of these particles were discovered by experiments with cosmic radiation. But later, the detailed investigations of the properties of the particles, their masses, modes of decay, and the characteristics of their reactions with one another, were actively pursued by means of the controlled beams of particles generated with the great accelerators. The theoretical interpretation of the accumulating body of knowledge about elementary particles has developed rapidly, particularly in the past five years, and it is now possible to give a consistent account of most of the salient features in terms of a number of new conservation laws. The generalized description of the phenomena which has thus been developed suggests that the groups of particles of which the existence has been established, or which are clearly anticipated, form a complete, or nearly complete, set. Some theoreticians have recently suggested that other types, in addition to those included in the Table, are to be expected, but if they exist they are certainly much more elusive than those already known. In this situation, the discovery of any large number of newer particles would represent a radical and immensely important advance. But for the moment there is little experimental evidence for the existence of particles other than those represented in the Table.
A Graph Theoretical Interpretation of Different Types of Energies of Elementary Particles, Atoms and Molecules
