In many respects the resonons are similar to "excited" elementary particles—they possess a definite spin, isospin, and parity; on the other hand, they are in a way similar to systems of coupled particles. A task of prime importance is the thorough investigation of the resonons together with the old, well-behaved particles. The discovery of the resonons has complicated matters, and shows once again the inexhaustible content of matter; at the same time, this will surely provide the means of solving ^^me central problems in our understanding of the inner structure of particles and the ways in which they are related, and bring us a little closer to the formulation of a unified interpretation of all the kinds of matter as we know it.
In order to throw things into their proper historical perspective, let us recall that the new elementary particles were first discovered in the laboratory (the electron, the proton, and the neutron), successively in 1897 (J. J. Thomson), in 1911 (E. Rutherford), and in 1932 (J. Chadwick). Following this, particles were discovered in cosmic rays, specifically primary particles (mainly protons, but also deuterons and nuclei of helium and other elements) with tremendous energies, ranging in the vicinity of 3 billion electron-volts (as observed in the middle latitudes); at that time terrestrial accelerators did not yield such energies., Detected in cosmic rays were the positron (1932, Anderson-Blackett-Occhialini), the p mesons (1935, Anderson), the pions (1947-1950, Powell), some of the K mesons or "kaons" (1941-1947, Leprince-Ringuet, O' Ceallaigh, and others), and some of the hyperons, viz. A, E+, (from 1947 on, Rochester and Butler, Levi-Setti,. and others). Later it was possible to obtain high particle fluxes by means of powerful proton accelerators and to discover new particles (p, n, K , and the resonons.
In particular, in 1960 were discovered all the members of the antisigma hyperon family, viz., the particles (the Alvarez group in Berkeley, U. S. A. ), (the Van Ganchan group, and V. I. Veksler in Dubna), E+ (the Amaldi and Manfredini group in Rome, in the analysis of photographic plates irradiated at Berkeley).
In order to give a picture of the efforts being devoted to probing into matter, let us list the most important accelerators operating in the world today, starting with theprotonmachines: we have the American "Cosmotron", of 3.5 Bev; the American "Bevatron" , of 7 Bev; the Soviet machine of 10 Bev
at Dubna (with an electromagnet weighing about 30,000 tons and weak focusing); and the French installation "Saturn", of 2.5 Bev. In 1960 a record-breaking proton accelerator, of 28 Bev (with a magnet weighing only about 3000 tons, strong focusing), was put into operation in Geneva, at the European Organization for Nuclear Research (CERN). A similar accelerator, of 33 Bev, was put into operation in 1962 at Brookhaven.
In 1961 the Soviet 7 Bev proton accelerator (strong focusing) was built in Moscow, and it will serve as a model for a proton machine of 50-70 Bev: Machines of up to 1000 Bev are now being planned.
Certainly further advances in the detection of new particles and resonons and of their properties may be expected from the most powerful accelerators, and not only from the proton synchrotrons but also the electron synchrotrons.
To this point we have been discussing only circular proton accelerators, in which the protons are pushed to high speeds by a combination of electric and magnetic fields. Let us now list the existing top-energy electron accelerators. There are two machines in the U. S.A. , at the California Institute of Technology and at Cornell University, and a high-flux machine at Frascati, near Rome, imparting to the electrons energies in excess of 1 Bev (1100-1200 Mev). In the fall of 1962 an electron synchrotron of about 2 Bev was put into operation, which is planned to be brought up to 6 Bev (U.S.A.). In addition, there is a linear electron accelerator of 1 Bev at Stanford University (U.S.A.), where construction has also been started of a high-flux linear electron accelerator, two miles long, with an energy of about 30 Bev.
The proton accelerators have made it possible to further considerably our knowledge of the nature of the strong interactions among nucleons, hyperons, and mesons. On the other hand, by scattering high electron fluxes from a linear accelerator on protons and deuterons, Hofstadter was able to explore for the first time the structure of the elementary particles, measure the size of the proton and the neutron = 0.8. cm), and even determine the way in which the charge is distributed within them. This is essentially a new development of the methods employed by Rutherford, who used helium nuclei to probe into the atom and thus discover its core, the atomic nucleus.