Hypothetical Alternative Energy Sources for the ‘Second Meson’ Events


IN the paper toy Lattes, Occhialini and Powell*, it is shown that cosmic ray mesons coming to the end of their track in a photographic emulsion rather frequently give rise to a secondary meson of kinetic energy about 4 MeV., and no other visible particle. This observation appears to demand for its interpretation the existence of two sorts of meson, the source of the observed kinetic energy of the secondary-residing in the mass difference between the two. In view of the importance of this conclusion, we have tried to consider all reasonably imaginable processes to explain the observations without introducing a new elementary particle; processes, that is, in which the energy is derived from the material of the photographic emulsion instead of from the meson. Reasons are given below for the confident rejection of all such processes.

Author information

Rights and permissions

Reprints and Permissions

About this article

Cite this article

FRANK, F. Hypothetical Alternative Energy Sources for the ‘Second Meson’ Events. Nature 160, 525–527 (1947). https://doi.org/10.1038/160525a0

Download citation

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.