Photon-Photon Collisions, a New Area of Experimental Investigation in High-Energy Physics

Abstract

The purpose of this paper is to show that the conditions of photon-photon collisions at high energy can be almost perfectly reproduced by using the "quasi-real" photon spectra originating from electron-positron colliding beams. We show that (a) the problem of background elimination can be properly solved by detecting both the outgoing electron and positron at very small angles with respect to their incident directions; (b) in spite of this very stringent restriction on phase space, and of possible additional restrictions due to experimental conditions, reasonably high counting rates will be achieved with the new electron-positron storage rings (of beam energy 2-3 GeV and of luminosity ∼${10}^{32}$ ${\mathrm{cm}}^{-2\mathrm{}}$ ${\sec }^{-1\mathrm{}}$) now planned or under construction; and (c) these counting rates increase with rising beam energy. We discuss a number of applications: particle-pair creation ($e^{-}{e}^{+},{\mu }^{-}{\mu }^{+},{\pi }^{-}{\pi }^{+},K^{-}{K}^{+},p\overline{p},\dots$) or single-particle creation (${\pi }^0,\eta ,{\eta }^{\prime }$). Angular distributions of particles produced are also shown.