Chronology of Milestone Events in Particle Physics - HODSON 1954
Chronology of Milestone Events in Particle Physics


Hodson, A.L.; Ballam, J.; Arnold, W.H.; Harris, D.R.; Rau, R.R.; Reynolds, G.T.; Treiman, S.B.;
Cloud-Chamber Evidence for a Charged Counterpart of the 0 Particle
Phys. Rev. 96 (1954) 1089;

A photograph obtained in a Wilson cloud chamber, operated in a magnetic field, shows the following unusual event: A positive particle, produced in an interaction above the cloud chamber, decays in flight into a positive particle less massive than a K meson. Four other lightly ionizing particles also originate from the decay point; these appear in the form of two small-angle pairs, each pair consisting of one positive and one negative particle. The observed momenta and ionizations are consistent with three of these four particles being either electrons or mesons; the fourth must be an electron.
The event may be interpreted as the decay: K+ + choose + 0 + Q MeV, followed by the decay of the 0 meson into four electrons (a possible but hitherto unobserved mode of decay): 0 e+ e- e+ e-. This interpretation leads to a remarkable internal consistency of the data and is supported by the following experimental facts:
(i) There is good overall transverse-momentum balance in two mutually perpendicular planes.
(ii) If we assume that all the particles in the above group of four are electrons resulting from the decay of a neutral particle the mass of the latter, determined from energy-momentum balance, is (255-10+15)me, in good agreement with the known mass of the 0 meson.
(iii) A transformation to the rest system of the 0 meson shows that in this frame the four electrons come off as two small-angle pairs traveling in opposite directions. This is the most probable configuration in the four-electron decay of a 0 meson.
The Q values calculated for the K+ decay are: Q(+, 0) = (213+15-10) MeV and Q(+, 0) = (207+15-10) MeV. Comparison of the first Q values with that for the 0 particle Q(+, -) = 214 5 MeV, suggests that the unstable meson observed in this event and designated phenomenologically above as a K+ meson may be a charged counterpart of the 0 particle.
This interpretation may explain at least some of the cases, observed by other workers, in which rays appear to be associated with S particles.
Other possible interpretations of the event are considered.

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Related references
See also
D. R. Harris and A. L. Hodson, Phys. Rev. 95 (1954) 661A;

  K+ + o

Particles studied
  K+ ex

Record comments
Evidence for K+ + o decay.
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