Chronology of Milestone Events in Particle Physics - FRY 1956
Chronology of Milestone Events in Particle Physics

FRY 1956

Fry, W.F.; Schneps, J.; Swami, M.S.;
Evidence for a Long-Lived Neutral Unstable Particle
Phys. Rev. 103 (1956) 1904;

Reprinted in
R. N. Cahn and G. Goldhaber, The Experimental Foundations of Particle Physics, Cambridge Univ. Press (1991) 208.

In the course of a scan of emulsion exposed to the Bevatron 90 280 MeV/c momentum K-beam, four events were found which involve the apparent production of a single strange particle in a low-energy interaction. They are interpreted as due to interactions of long-lived neutral K-particles produced in the target with frequency comparable to that of K+-meson production. "Ordinary'' 0 particles would have had to live about 20 mean lifetimes. Energetic neutron stars are rare in the stack. (Science Abstracts, 1957, 2684. R. H. W. Johnston).

Accelerator LBL Detectors EMUL

Related references
More (earlier) information appears in
W. F. Fry, J. Schneps, and M. S. Swami, Phys. Rev. 101 (1956) 1526;
See also
M. Gell-Mann and A. Pais, Phys. Rev. 97 (1955) 1387;
G. A. Snow, Phys. Rev. 103 (1956) 1111;

Data comments
4HeS is the standard PDG name for strange hyperfragment He4.

  p nucleus neutral X 6 GeV (Tlab) angp, p
  neutral nucleus 3HeS X
  3HeS 3He p
  neutral nucleus K X

Particles studied
  KL ex

Record comments
Confirmation of the existence of the KL.
  New Comments List of Comments