Positronium rare annihilation experiment with a positron beam-line using permanent magnets

Positronium Ps. is a bound state of an electron and a positron, which annihilates into photons. It is a suitable place to study the quantum electrodynamics QED.since strong and weak interactions are negligibly small in the annihilation processes. Our experimental group has been measuring rare annihilation processes from Ps using a multi-g-ray spectrometer called UNI which consists of 32 NaI Tl. 3 in.f=4 in.. scintillation counters. We had detected the 4g and 5g annihilation processes for the first time in the world. In the experiment, ;200 4-g events and one 5-g event have been collected, respectively, until today. Since these processes do not include any lower order of Feynman graphs, we can study a 7 and a 8 a : fine structure constant.processes almost purely, which is unexplored region of the QED higher order processes. We are planning to utilize a positron beam line using permanent magnets. By employing EGS4 code system for simulating electromagnetic processes and Runge–Kutta method for solving equations of motion, detection efficiency of our detector and transport efficiency of the beam line have been simulated. q1999 Published by Elsevier Science B.V. All rights reserved