Letter | Published:

Large Cosmic Ray Showers and Mesons

Nature volume 145, pages 103104 (20 January 1940) | Download Citation



IT has been pointed out recently by Bhabha, Carmichael and Chou1 that a meson may produce a large cosmic ray shower by knocking on an atomic electron in a close collision; this electron then produces a shower by the ordinary cascade process. Previously, Bhabha2 had come to the conclusion that large knock-on showers are comparatively unimportant; but he had based his argument on the assumption that the scattering of mesons by electrons could be described by the Dirac relativistic theory. However, Massey and Corben3 have shown that the effect of the spin of the meson is greatly to increase the scattering for high energies of the incident meson and the knocked-on electron. Using Massey and Corben's formula, Bhabha, Carmichael and Chou have shown that the experimental results of Carmichael and Chou4 can be reasonably well explained, whereas the previous theory predicted too few large showers.

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  1. 1.

    , and , Proc. Indian Acad., A, 10, 221 (1939).

  2. 2.

    , Proc. Roy. Soc., A, 164, 257 (1938).

  3. 3.

    and , Proc. Camb. Phil. Soc., 35, 463 (1939).

  4. 4.

    and , NATURE, 144, 325 (1939).

  5. 5.

    , Proc. Roy. Soc., A, 173, 91 (1939).

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Author information


  1. Trinity College, Cambridge.

    • A. H. WILSON
  2. Clare College, Cambridge. Dec. 22.

    • F. BOOTH


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