Chronology of Milestone Events in Particle Physics - ROCHESTER 1947
Chronology of Milestone Events in Particle Physics

ROCHESTER 1947

Rochester, G.D.; Butler, C.C.;
Evidence for the Existence of New Unstable Elementary Particles
Nature 160 (1947) 855;

Reprinted in
R. N. Cahn and G. Goldhaber, The Experimental Foundations of Particle Physics, Cambridge Univ. Press (1991) 69.

Summary
Among some fifty counter-controlled cloud-chamber photographs of penetrating showers which we have obtained during the past year as part of an investigation of the nature of penetrating particles occurring in cosmic ray showers under lead, there are two photographs containing forked tracks of a very striking character. These photographs have been selected from five thousand photographs taken in an effective time of operation of 1,500 hours.
... We conclude, therefore, that the two forked tracks do not represent collision processes, but do represent spontaneous transformations. They represent a type of process with which we are already familiar in the decay of the meson into an electron and an assumed neutrino, and the presumed decay of the heavy meson recently discovered by Lattes, Occhialini and Powell (Nature 160 (1947) 453). (Extracted from the introductory part of the paper.).

Accelerator COSM Detectors CLOUD

Related references
See also
C. M. G. Lattes, G. P. S. Occhialini, and C. F. Powell, Nature 160 (1947) 453;
C. M. G. Lattes, G. P. S. Occhialini, and C. F. Powell, Nature 160 (1947) 486;
J. Daudin, Anneles de Physique, 11e serie, 19(Avril-Juin), 1944;
L. Janossy, G. D. Rochester, and D. Broadbent, Nature 155 (1945) 142;
H. A. Bethe, Phys. Rev. 70 (1946) 821;
L. Leprince-Ringuet and L'heritier, J. Phys. Radium (ser.8) 7 (1947) 66, 69;

Experiment comments
2 events with forked tracks from 5000 photographs.

Reactions
  vee 2charged
  neutral 2charged
  charged charged (neutrals)

Particles studied
  vee ex, mass
  neutral ex, mass
  charged ex, mass

Record comments
First evidence for V events. Confirmation of the existence of a charged unstable particle with a mass between those of the muon and proton.
    
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