SINCE 1937, the evidence from the study of cosmic rays has increasingly pointed to the existence of a particle about a hundred times more massive than the electron, giving support to a suggestion of Yukawa's in 1935 that the forces binding protons and neutrons together in atomic nuclei might be connected with particles of about that mass. Since Yukawa's first paper, much theoretical work has been done and the subject has now reached a stage when a general survey is possible. Unluckily the new particle does not readily lend itself to direct laboratory investigation, and there are still many possible formulations of the theory, all of which have to be elaborated until further indirect comparison with experiment is possible.
Theory of Heavy Quanta
Door Frederik Jozef Belinfante. Pp. xii + 126. ('s-Gravenhage: Martinus Nijhoff, 1939.)