Production of Four-Prong Final States in Photon-Photon Collisions

摘要

This thesis describes the measurement, analysis and discussion of the reaction gamma gamma -> X, where X is a hadronic final state with four charged particles. In particular, we have investigated the states 2 pi /sup +/2 pi /sup -/, K/sup +-/ pi /sup -+/ pi /sup +/ pi /sup -/, K/sup +/K/sup -/ pi /sup +/ pi /sup -/, 2K/sup +/2K/sup -/ and panti p pi /sup +/ pi /sup -/. The experiment was performed with the TPC/Two-Gamma facility at the e/sup +/e/sup -/ collider PEP at the Standford Linear Accelerator Center. The process gamma gamma -> 2 pi /sup +/2 pi /sup -/ had been measured in the beginning of this decade. The shape of the measured cross section suggested the presence of a resonance in this channel, and many such interpretations were brought forth in the following years. In ch. 2, these interpretations and theories are reviewed and a motivation is given for the investigation of states similar to 2 pi /sup +/2 pi /sup -/, but containing kaons and protons. Also, the existing data from related experiments in radiative J/psi decays and hadronic collisions are listed. In the last section of the chapter, the outstanding features of the TPC/Two-Gamma detector for the measurement of four-prong events are emphasized. Ch. 3 is a very brief overview of the kinematical properties of the two-photon initial state, which is brought about by the exchange of two photons by the colliding electron and positron. In ch. 4 the details of the detector system are given, and the method used to measure and analyze events from exclusive four-particle final states is outlined. The results of the measurements are given in ch. 5. Ch. 6 concludes with a discussion of the results, and an interpretation of the measurements. 89 refs.; 68 figs.; 12 tabs. (Atomindex citation 19:004140)