The Q/sup 2/ and transverse momentum dependence of jet production in photon-photon interactions

The results of an experimental study of jet production in photon-photon interactions are presented. The study is based on single-tagged events collected with the PLUTO detector at PETRA and covers the ranges 0.1 ≤ Q/sup 2/ ≤ 18 GeV/sup 2/ and measured jet rho/sub T/ ≤ 5 GeV/c. At all Q/sup 2/, the data show a high rho/sub T/ tail characteristic of hard, point-like interactions. The jet production cross section approaches the standard Quark-Parton Model (QPM) expectation from above as either jet rho/sub T/ or Q/sup 2/ increases. Overall, the data are described in both total cross-section and event topology by the incoherent sum of a vector dominance model (which accounts for the low rho/sub T/ jets) and the QPM (which predicts high rho/sub T/ jets). At Q/sup 2/ ≤ 1 GeV/sup 2/ and 1.5 ≤ jet rho/sub T/ ≤ 4 GeV/c, the data lie systematically above this simple sum. The thrust distribution of the events in this kinematic region looks less two-jet-like than expected for quark jets with standard Feynman-Field fragmentation. This excess is compared to predictions for higher-order QCD processes and the gauge theory of integrally charged quarks