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GREGORY 1954

Gregory, B.P.; Lagarrigue, A.; Leprince-Ringuet, L.; Muller, F.; Peyrou, C.;
Etude des Mesons K Charges, au Moyen de Deux Chambres de Wilson Superposées / Study of Charged K-mesons by means of two Superposed Wilson Chambers
Nuovo Cim. 11 (1954) 292;

Summary
In this paper we present some results on charged heavy mesons. They were obtained with an experimental arrangement consisting essentially of two large cloud-chambers placed one above the other. The top chamber had a magnetic field while the bottom chamber was of the multiplate type. The contents of the different sections of the paper can be summarized as follows:

1. The double cloud-chamber method is compared with other more conventional methods.
2. The apparatus is briefly described.
3. The behaviour in the multiplate chamber of the charged secondaries of V^±-decays occurring in the top chamber is discussed. π-mesons have been identified through their nuclear interactions. The presence of μ-mesons is also strongly suggested by: (a) the long mean-free-path of the secondaries and (b) one direct mass measurement.
4. S and slow V^±-events observed in the multiplate chamber are discussed. It is shown that one should distinguish between two groups of decays: One with secondaries of range smaller than 20 g/cm² of Pb, the other with larger range secondaries. Although the first group can be due to τ-mesons, the second group cannot be so explained, at least not phenomenologically.
5. The results of mass measurements - from range and momentum - on the primaries of the second group of events are presented. The measurements agree with a unique value of (914 ± 20) m_e; which appears to be different from the τ-mass.
6. We show that some, and probably most, of the secondaries of this second group of events are μ-mesons. This conclusion is based on the dynamics of the decay and results from the measured mass of the primary particle and the observed ranges of the secondaries. The observation of one large angle scattering indicates, however, that π-mesons may also be present among the secondaries.
7. The data on the range of the charged secondaries are analysed. If we exclude the possible π^– secondary, our results are in good agreement with a μ-meson of unique momentum. However, a continuous spectrum, sharply peaked in the high momentum region, is not excluded.
8. The almost complete absence of negative primaries for S-events is reported.
9. The results are compared with those obtained elsewhere. They agree with other cloud-chamber results assuming the existence of π-secondaries with a range of 66 g/cm² of Pb. The spectrum obtained for the μ-secondaries does not fit with that of the secondaries of k-particles found in photographic emulsions.
10. The conclusions are summarized.

Accelerator COSM Detectors CLOUD

Related references
Analyse data from
G. D. Rochester and C. C. Butler, Nature 160 (1947) 855;
M. Annis et al., Nuovo Cim. 9 (1952) 624;
C. O'Ceallaigh, Phil. Mag. 42 (1951) 1032;
R. W. Thompson, A. V. Buskirk, C. J. Karzmark, and R. H. Rediker, Phys. Rev. 92 (1953) 209;
E. Amaldi et al., Nuovo Cim. 10 (1953) 937;
W. B. Fretter et al., Phys. Rev. 92 (1953) 1583;
H. S. Bridge and M. Annis, Phys. Rev. 82 (1951) 445;
R. H. Brown et al., Nature 163 (1949) 82;
D. Lal, Y. Pal, and B. Peters, Phys. Rev. 92 (1953) 438;

Reactions

	K– μ– ν
	K+ μ+ ν

Particles studied

	K+	mass
	K–	mass

Record comments
Confirmation of the decays K^± → μ^± neutral.

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