Chronology of Milestone Events in Particle Physics - ILOFF 1955
Chronology of Milestone Events in Particle Physics

ILOFF 1955

Iloff, E.L.; Chupp, W.W.; Goldhaber, G.; Goldhaber, S.; Lannutti, J.E.; Pevsner, A.; Ritson, D.M.;
Mean Lifetime of Positive K Mesons
Phys. Rev. 99 (1955) 1617;

Mean lifetimes for heavy mesons from cosmic rays have been reported by various groups using cloud chambers and Cerenkov counters. (L. Mezetti and J. W. Keufel, Phys. Rev. 95 (1954) 859; Barker et al., Phil. Mag., (7) 46 (1955) 307) We have carried out a measurement of the mean lifetime of artificially produced K+ mesons by making use of their decay in flight in nuclear emulsion.
"Along the track'' scanning of K+ mesons in nuclear emulsions has shown a number of interactions in flight; in addition, 19 events have been found in which there is a single outgoing track of grain density less than that of the incoming K+ meson. In each of these events the mass of the incoming particle was determined by grain counting and multiple-scattering measurements and its identity as a K+ particle was thus established. If these events were due to interactions in flight, one would expect to find some stars with a lightly ionizing track coming out together with one or more black evaporation prongs. No such stars were observed. Also, none of the interactions in flight so far seen give off a visible L meson. It therefore seems reasonable to identify all events of this type as the decay of K+ mesons in flight. From the number of decays in flight found and the proper slowing-down time of all the K+ mesons followed, a mean lifetime is obtained....
From the 19 decays in flight observed we find a mean lifetime for K+ mesons of K+ = 1.01-0.21+0.33 x 10-8 sec. (Extracted from the introductory part of the paper.).

Accelerator LBL Detectors EMUL

Related references
See also
L. Mezetti and J. W. Keuffel, Phys. Rev. 95 (1954) 859;
L. T. Kerth, D. H. Stork, R. P. Haddock, and M. M. Whitehead, Phys. Rev. 99 (1955) 641;
K. H. Barker et al., Phil. Mag. 46 (1955) 307;

  K+ charged X 335-360,390-450 MeV (Plab)

Particles studied
  K+ qn, w

Record comments
K+ lifetime measurements from decays in flight.
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