Chronology of Milestone Events in Particle Physics - FRETTER 1951
Chronology of Milestone Events in Particle Physics


Fretter, W.B.;
Some Observations on the New Unstable Cosmic-Ray Particles
Phys. Rev. 82 (1951) 294;

Full Text
A large cloud chamber containing several lead plates has been used to observe the unstable particles already reported. The probability of observation has been increased by making the distance between the lead plates two inches instead of 0.75 inch as in our previous experiments. Twenty cases have been seen at sea level where a neutral particle changed into two charged particles in the gas and three cases of sudden changes of direction in the gas have been observed. In one event produced by a neutral, one of the secondary particles was heavily ionizing (estimated at about 4x minimum), passed through a 0.25-inch lead plate without noticeable change in ionization or scattering, and thus must have had a mass larger than that of a -meson. These events all occur in penetrating showers and the findings of the previous observers are generally confirmed.

Accelerator COSM Detectors CLOUD

Related references
Analyse data from
A. J. Seriff et al., Phys. Rev. 78 (1950) 290;
G. D. Rochester and C. C. Butler, Nature 160 (1947) 855;

Data comments
23 events.

  neutral 2charged
  charged charged (neutrals)

Particles studied
  charged ex, mass
  neutral ex, mass

Record comments
Confirmation of the existence of heavy unstable particles.
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