2-PHOTON PROCESSES IN E+E- CALORIMETRIC EXPERIMENTS AND TESTS OF QUANTUM CHROMODYNAMICS

High-energy two-photon collisions will be responsible for a large fraction of events in e+e- machines such as PETRA, PEP, and LEP. We suggest measuring the energy pattern of the γγ processes, which would provide very interesting information on the interplay between electromagnetic and strong interactions. The angular distribution of the hadronic energy (antenna pattern) is calculated for photon-photon collisions. By using energy-conservation sum rules, we give a model-independent, reliable computation of the corrections due to color confinement, as well as heavy-quark masses and decays. The contributions from the quantum chromodynamics (QCD) structure of the photon, which are characterized by three or four jets in the final state, are taken into account. The energy correlation, i.e.; the hadronic energy radiated through two calorimeters as a function of the relative angle is also calculated. We evaluate the energy pattern and energy correlation for the formation of C-even bound states, and find that an extremely good resolution in the hadronic energy would be needed in order to disentangle the bound-state contribution from the background. We present a detailed discussion of the two-photon processes as a background in the studies of the energy pattern of the e+e- annihilation into hadrons. By requiring that either the total hadronic energy or the invariant hadronic mass is larger than 60% of their maximum value, s, the γγ background should be suppressed enough to allow for the experimental tests of QCD in e+e- annihilation which have been recently proposed. © 1979 The American Physical Society.