NEW PHOTOGRAPHS OF HEAVY MESOTRONS IN A WILSON CHAMBER

In the fifth issue of the Bulletin of the American Physical Society for 1948, a brief communication was published on the work of Gitalak and Brode^1, who measured the mass of mesotrons at sea level. The authors used a Wilson chamber in a magnetic field of 4750 oersteds. To determine the ranges, several metal plates were placed in the chamber. The strong magnetic field, and also the fact that the masses were determined using tracks of slow mesotrons (the measured values of the momenta lie within the limits 50–600 MeV), ensured a high accuracy in the determination of the mass. The authors indicate that the total error in the mass determination, caused by distortion of the radius of curvature by turbulent flows in the chamber and by scattering, lies within the limits 4.5–11%. In all, 41 mass determinations were made. In 37 cases the mass of the mesotrons was determined within the limits of error with a value of \(192m_e\). In the remaining four photographs the following mass values were obtained:

\[ 547m_e;\qquad 558m_e;\qquad 568m_e;\qquad 717m_e. \]

These mass values once again confirm the existence of a multiplicity of mesotron masses, established in the works of A. Alikhanyan, A. Alikhanov and A. Weisenberg^2 and of S. Nikitin^3 in 1946 and confirmed in 1947 byך

work of A. Alikhanian, A. Alikhanov, V. Morozov, G. Muskeishvili, and A. Khrimian[^4]. Let us recall that in the latter work the existence was established of particles with masses \(200m_e\), \(350m_e\), \(500—600m_e\), \(950m_e\), and with large masses.

In the next communication, placed in the same issue of the Bulletin and belonging to Brode, it is stated that the author has constructed an apparatus installed on an airplane and specially intended for measuring the masses of mesotrons at high altitudes. The apparatus consists of a permanent magnet, giving a field with an intensity of 5000 oersteds, and three Wilson chambers, of which one is placed above the gap of the magnet, and two others—one below it, the other above the second. The chambers, placed directly above and below the gap of the magnet, form a magnetic analyzer, making it possible to determine with great accuracy the change in the direction of the trajectory caused by the action of the magnetic field, and consequently the momentum of the particle. The third chamber, in which 15 lead plates of total thickness 9 cm are placed, serves to determine the range of the particles. Such a system is completely analogous to the magnetic mass spectrograph used in the study of the mesotron mass spectrum by A. Alikhanov, A. Alikhanian, and their collaborators, but has a considerably smaller aperture. It is to be expected that in the near future, with the aid of the described instrument, the other mass values discovered by Soviet physicists will also be confirmed.

A. Weissenberg

CITED LITERATURE

1. Bulletin of the American Physical Society, No. 1, 1948.
2. A. Alikhanian, A. Alikhanov, and A. Weissenberg, Journal of Physics, vol. XI, No. 2.
3. S. Nikitin, Journal of Physics, vol. XI, No. 2.
4. A. Alikhanian, A. Alikhanov, V. Morozov, G. Muskeishvili, and A. Khrimian, Doklady AN SSSR, vol. LVIII, p. 1331.