Bibliography

“Heavy Unstable Particles.” Problems of Modern Physics, collection of translations and review articles of periodical literature. Issue 4, 1955. Foreign Literature Publishing House, Moscow, p. 214, price 10 rubles 50 kopecks.

The collections Problems of Modern Physics, issued by the Foreign Literature Publishing House, make it possible to acquaint a broad circle of scientific workers and students with original foreign works in the most rapidly developing fields of physics.

Such collections, provided that carefully selected and thoughtfully arranged material is included, can serve as a valuable aid for study and reference.

The collection under review consists of translations of original articles and the most important reviews on heavy unstable particles published in 1953–1954. As is known, the problem of heavy unstable particles, which began with investigations in 1947–1948, proved extraordinarily complex, and at present dozens of laboratories in many countries are engaged in solving it. The results of the early work are presented in the collection by a review by Rochester and Butler, systematizing all the experimental material accumulated by 1953.

Later investigations of 1953–1954 made it possible to refine the old results and obtain new data. During this period significant advances were achieved thanks to the application of a new research method—emulsion chambers—and the further development and accumulation of data from Wilson chambers. Finally, it became possible to obtain heavy unstable particles under laboratory conditions at accelerators.

The most important works of this period are given either in full or in the form of abridged translations.

Thus, the collection in fact reflects the state of the problem from the time of the first discoveries of heavy unstable particles up to approximately the middle of 1954; its publication appears more than timely.

In the first section—“General Reviews”—there are review articles by Rochester and Butler, “New Unstable Particles in Cosmic Radiation” (1953), and by Pauli, “Hyperons and Heavy Mesons” (1954). The first review is the most detailed of those available; it collects and systematizes all data on new unstable particles with masses of 400–2200 \(m_e\), obtained by the beginning of 1953. Pauli’s review is brought up to the beginning of 1954 and includes data on spontaneous nuclear disintegration (discovered in 1953) and the first results with emulsion chambers. It should be noted that the content of both reviews not only reflects the state of the problem at the time they were written, but almost completely

retains its significance at the present time as well. These works serve as an introduction to its remaining sections.

The second section contains works on neutral unstable particles. In its first part are collected works performed with Wilson chambers and devoted mainly to \(\Theta^0(V_1^0)\)-decays and anomalous decays that do not agree with the schemes of \(\Lambda^0\)- and \(\Theta^0\)-decays. Studies on \(\Lambda^0\)-particles are not included here, but they have found sufficiently complete reflection in the reviews by Rochester and Butler and by Păuză.

The second part of the section includes works on \(\Lambda^0\)-particles registered in photoemulsions and reported at the conference in Bagnères-de-Bigorre. These works refine the data obtained by means of Wilson chambers.

The third section, “Charged Unstable Particles,” begins with works on \(\tau\)-mesons. In addition to the works confirming the usual scheme of \(\tau\)-decay, data are given on anomalous \(\tau\)-decays in photoemulsions and decays in flight in a Wilson chamber. The second part of the section, devoted to \(K\)-particles, contains reports (and partly the discussion) at the conference in Bagnères-de-Bigorre. It is useful that two important methodological works are presented here: on the technique of using emulsion chambers and on the method of constant sagitta.

Works on \(S\)-particles (\(K\)-decays in a multiplate Wilson chamber) are set apart in a separate group and are represented by the articles of Bridge et al., “Results of the Latest Investigations of \(S\)-Particles,” and of Fretter et al., “Measurement of the Mass of \(S\)-Particles by the Pulse–Range Method.”

The concluding part of the third section contains the work of York, Leighton, and Bjørnerud on charged \(V\)-particles, carried out with two Wilson chambers. In this work, in particular, the question of short-lived charged hyperons is discussed (lifetime \(t = 3 \cdot 10^{-10}—10^{-11}\) sec.).

Works on the lifetime of heavy unstable particles are set apart in the fourth section of the collection. In the article by Newth, the existing methods for determining the mean lifetime of various unstable particles (\(\Lambda^0\), \(\Theta^0\), \(K^{\pm}\), and \(\tau^{\pm}\)), whose decay is observed in a Wilson chamber, are discussed, and the data obtained are summarized. In the cited work by Mazetti and Keil, the decay curve of stopped unstable cosmic particles was measured for the first time with the aid of a liquid scintillation counter and Cherenkov-radiation counters. Let us note that this method found application in subsequent works of 1955 in the development of new methods for selecting \(S\)-particles and measuring their lifetimes.

The last, fifth section of the collection includes works on heavy unstable particles obtained on accelerators in the bombardment of targets with negative \(\pi\)-mesons. Here, in particular, data are given on the pair production of hyperons and \(K\)-mesons—the most important result obtained in the first months of operation of the Brookhaven cosmotron.

The brief review given of the contents of the collection shows that it embraces all the principal directions of research on heavy unstable particles and is therefore a useful and necessary aid. The clear systematization of the works in the collection facilitates acquaintance with the material and its use for reference purposes. In our opinion, however, in such collections one should not limit oneself to complete or abridged translations of the principal works, but should also include, where possible, a complete bibliography of all works carried out during the period surveyed by the collection. The presence of a complete bibliography would considerably increase the value of these collections and would eliminate almost inevitable gaps in coverage.

During the past year, investigations in the field of heavy unstable particles continued on a broad front; in a number of countries large teams of physicists have been brought into them. New data have been obtained on spontan-

... decay of fragments, on the interactions of heavy negative unstable particles with matter, on pair production of particles, and so forth. Because of the novelty of these works and the lack of space, they are reflected in the volume only in part. Therefore, while noting here the great positive significance of the collection under review, we wish to draw attention to the advisability of promptly taking into account the rapidly accumulating new data. In addition to original works that require coverage in subsequent collections, attention should be paid to the most important lectures from the cycle delivered at the “Varenna School of Physics” by Fermi, Rossi, Leprince-Ringuet, and other researchers. Alongside original works, these lectures are an extremely valuable aid in the study of the rapidly developing field of heavy unstable particles.

M. Daion