Mesotron (Intermediate Particle) as a Name for the New Particles of Intermediate Mass

C. D. Anderson and S. H. Neddermeyer

Editor’s Note

In 1936, Carl Anderson and Seth Neddermeyer at the California Institute of Technology found evidence in cosmic-ray experiments for a particle having mass intermediate between those of the electron and proton. The particle carried one unit of charge, and penetrated matter much more strongly than the electron. Here the particle’s discoverers propose a name for it. As its intermediate mass seemed the key property, they suggest the term “mesotron”. This was later shortened to “meson”, although the particle Anderson and Neddermeyer had discovered was actually what physicists today call the muon, a massive relative of the electron. The term meson later became used for intermediate-mass “hadrons” such as the pion or kaon, which are comprised of two quarks.　　中文

THE existence of particles intermediate in mass between protons and electrons has been shown in experiments on the cosmic radiation1. Since at present so little is known concerning the properties of these particles, for example, the exact value of the mass, the laws governing their production, their stability against disintegration, etc., it may yet be too early to assign to them a name. But inasmuch as several names have already been suggested, namely, dynatron, penetron, barytron, heavy electron, yukon and x-particle, it may be wise to consider the matter at this time.　　中文

The property which so far serves to distinguish the new particles from the other two types of particles which carry the same magnitude of electric charge, namely, the proton and the electron, seems to be the magnitude of their mass. Although from the experiments so far performed, it is not possible to say definitely whether the new particles exist with a unique mass only, or whether they occur with a range of masses, it does appear quite certain that the mass, whether unique or not, is greater than that of an electron and less than that of a proton. One must consider then three types of particles all carrying electric charges of equal magnitude: electrons, the new particles and protons. We should like to suggest therefore the word “mesotron” (intermediate particle) as a name for the new particles. It appears quite likely that the appropriateness of this name will not be lost, whatever new facts concerning these particles may be learned in the future.　　中文

(142, 878; 1938)

Carl D. Anderson and Seth H. Neddermeyer: California Institute of Technology, Pasadena, Sept. 30.

Reference:

1. For historical summary see Wentzel, G., Naturwiss., 26, 273 (1938); and Bowen, Millikan and Neher, footnote, Phys. Rev., 53, 219 (1938).