The Production of Mesons in Very High Energy Collisions
When nuclear encounters take place at very high energies, say of 100 GeV or more, then usually many mesons are produced. This does not necessarily mean that already in a nucleon-nucleon collision many mesons are produced because it might be that a production of many mesons takes place through a cascade process inside a nucleus. This was the view which was for a long time held by Heitler. On the other hand, I think there has recently been pretty good evidence that also in a single nucleon-nucleon collision many mesons can be produced. Best evidence for this are perhaps the jets which are occasionally observed and in which there are great numbers of shower tracks without the appearance of any heavy tracks. Although it is in most cases not probable that these events are actually simple nucleon-nucleon collisions one may say that even if they constitute reactions with nucleons at the surface of a nucleus the nucleus cannot have participated in the process very much since else one would have observed the evaporation of particles. That such events are possible has been emphasized by the theory long ago and the attempts have also started very early to connect the theoretical estimates with experiment. I remind you of the papers by Wataghin — but it was only in recent years that one has tried to give a more detailed theoretical description. Such description was given by Fermi and myself and recently by Landau. In the following I shall not repeat the details of Fermi’s and my own papers but I will give a survey of Landau’s work which is perhaps not generally accessible since it was published in Russian. At the end I will compare the results of the three theories with recent experiments. Landau’s paper appeared after those of Fermi and myself and tries to improve on the angular distribution of the particles as found by Fermi.
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