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A CASE OF NUCLEAR INTERACTION OF BOTH DECAY PRODUCTS OF A NEUTRAL MESON
Among the photographs obtained in observations of the passage of penetrating showers of cosmic rays through a large Wilson chamber (altitude above sea level 3.5 km), several cases of the decay of neutral \(V\)-mesons were discovered[^1]. In one photograph it was noted that both charged particles produced in the decay formed stars. The stereoscopic photograph of this case, presented by the authors, is shown schematically in the figure: the neutral meson decayed at point \(A\); the particles produced in the decay (apparently mesons) passed through three lead plates, each 8 mm thick, and formed two stars in the fourth plate. The stars are situated in a well-illuminated part of the chamber, and stereoscopic analysis of the photograph shows that the components of each star converge at a common point. Therefore the presence of two stars seems quite convincing.
As is known, the decay scheme of the neutral \(V\)-meson has not yet been definitively established. However, any of the schemes currently being discussed[^2][^3] requires the presence of \(\pi\)- or \(\mu\)-mesons among the decay products.
The photograph obtained is a very strong argument in favor of the fact that there are no \(\mu\)-mesons among the decay products of \(V\)-mesons. Indeed, \(\mu\)-mesons practically do not form stars that could be detected with the aid of a Wilson chamber. As for \(\pi\)-mesons, they form stars with an effective cross section close to the geometrical cross section of the nucleus. Therefore the authors consider that the stars shown in the figure were produced by a proton and a \(\pi\)-meson, or by two \(\pi\)-mesons of different signs.
A. V.
References
- H. Bridge, H. Courant, B. Rossi, Phys. Rev. 85, 159 (1952).
- Armentoros, Nature 167, 501 (1951).
- Leighton, Phys. Rev. 83, 843 (1951).