Observations on the Production of Mesons by Cosmic Radiation


IN examining photographic plates ‘exposed' to cosmic radiation at a height of about 10,000 ft. on the Jungfraujoch and the Pic du Midi, and at about 18,000 ft. on Kilimanjaro and Chacaltaya, we have now observed twenty nuclear ‘explosions' which are accompanied by the emission of slow mesons. In this communication we give a number of photomicrographs of the tracks of these ‘ejected' mesons. An analysis of the observed secondary effects which they produce enables us to show that at least the majority of them interact with nuclei and are therefore negatively charged ; and that on the average they produce more vigorous nuclear disintegrations than most of the negative mesons which stop in the emulsions after being generated outside it. The main features of our present knowledge of charged mesons, with masses in the interval from 100 me to 400 me, can be accounted for in terms of two types of particles of different mass1'2, which can be either positively or negatively charged, the heavier being generated in processes associated with the explosive disintegration of nuclei, and decaying spontaneously to produce the lighter ones. The possibility is not excluded, however, that the phenomena are more complicated than has been visualized hitherto.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.


  1. 1

    Marshak and Bethe, Phys. Rev., 72, 506 (1947).

    ADS  CAS  Article  Google Scholar 

  2. 2

    Lattes, Muirhead, Occhialini and Powell, Nature, 159, 694 (1947). Lattes, Occhialini and Powell, Nature, 160, 453 and 486 (1947).

    ADS  CAS  Article  Google Scholar 

  3. 3

    Powell and Rosenblum, Nature, 161, 473 (1948).

    ADS  CAS  Article  Google Scholar 

  4. 4

    Fermi, Teller and Weisskopf, Phys. Rev., 71, 314 (1947).

    ADS  CAS  Article  Google Scholar 

  5. 5

    Frölich, Nature, 180, 235 (1947).

    Google Scholar 

  6. 6

    Gardner and Lattes, Science, March 12, 1948.

  7. 7

    Conversi, Pancini and Piccioni, Phys. Rev., 71, 209 (1947). Anderson, Adams, Lloyd and Rau, Phys. Rev., 72, 724 (1947).

    ADS  CAS  Article  Google Scholar 

  8. 8

    Klein, Nature, 161, 897 (1948).

    ADS  CAS  Article  Google Scholar 

  9. 9

    Lattes, Occhialini and Powell, Proc. Phys. Soc. (in the press). Goldschmidt-Clermont, King, Muirhead and Ritson, Proc. Phys. Soc. (in the press).

Download references

Author information



Rights and permissions

Reprints and Permissions

About this article

Cite this article

OCCHIALINI, G., POWELL, C. Observations on the Production of Mesons by Cosmic Radiation. Nature 162, 168–173 (1948). https://doi.org/10.1038/162168a0

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.


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing