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

ARMENTEROS 1955

Armenteros, R.; Gregory, B.P.; Hendel, A.; Lagarrigue, A.; Leprince-Ringuet, L.; Muller, F.; Peyrou, C.;
Further Discussion of the K Decay Mode
Nuovo Cim. 1 (1955) 915;

Summary
After a description of the methods used in the measurements of momentum and range, the data on 46 S-events obtained with a double cloud-chamber experiment are examined. Momentum-range measurements on 22 positive S's give a mass consistent with a single value at (928 13) me. The analysis of the ranges of the secondaries shows, however, that not all S-events can be explained by a single decay mode. A large proportion of the secondaries correspond to a light meson of unique range (75.7 1.7) g cm-2 Cu. The comparison of this range with the measured masses of the primary particles proves that these secondaries are -mesons. The accompanying neutral secondary is shown at the same time to be a particle of zero mass. The absence of cascade showers associated with S-events with long range secondaries shows that the neutral secondary is a neutrino. The decay mode K previously proposed is more firmly established. Two independent mass estimates are obtained for the K-particle. One - from momentum-range measurements - gives directly (90 6 27) me. Another - from the mode of decay and the range of the -secondary - gives indirectly (941 11) me. A final best mass of (935 15) me is obtained by the combination of the two estimates after taking into account possible additional errors. The K particle is then shown to be essentially positive and to constitute (66 18)% of the S's which passed through the top chamber. No precise information can be obtained as to the mode of decay of S-particles which are known not to belong to the K-decay mode.

Accelerator COSM Detectors CLOUD

Related references
See also
M. Annis, W. Cheston, and H. Primakoff, Rev. of Mod. Phys. 25 (1953) 818;
R. Armenteros et al., Nuovo Cim. Suppl. 12 (1954) 327;
H. A. Bethe, Phys. Rev. 70 (1946) 821;
H. S. Bridge et al., Nuovo Cim. 12 (1954) 81;
R. H. Brown et al., Nature 163 (1949) 82;
V. A. Regener, Phys. Rev. 84 (1951) 161;
B. P. Gregory et al., Nuovo Cim. 11 (1954) 292;
A. L. Hodson et al., Phys. Rev. 96 (1954) 1089;
M. G. K. Menon and C. O'Ceallaigh, Proc. Roy. Soc. A221 (1954) 292;
C. O'Ceallaigh, Phil. Mag. 42 (1951) 1032;
M. W. Friedlander, D. Keefe, M. G. K. Menon, and L. van Rossum, Phil. Mag. 45 (1954) 1043;

Reactions
  K
  K+ +

Particles studied
  K+ ex, mass, qn
  K ex, mass, qn

Record comments
Confirmation of the existence of the K+.
    
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