First test of O(α) correction on the energy spectrum in the orthopositronium decay

[摘要] Positronium(Ps) is an ideal system for the precision test of quantum electrodynamics (QED) in bound state. Orthopositronium(o-Ps) decays into three gamma rays dominantly, and their energy spectrum has detail information on bound-state QED. The purpose of this study is to check the spectrum at the O(α) level accuracy. We constructed a setup for the precise measurement. Ps is created at silica aerogel in a vacuum chamber, and its decay gamma rays are measured with a LaBr3(Ce) scintillator. In this setup, the materials around the Ps assembly and the detector are well-controlled, and all their responses are coded in a GEANT4 simulator in detail. After the measurement for 100 days, the obtained spectrum is compared with the expected spectrum from the QED calculations and the GEANT4 simulator. The obtained spectrum is consistent with O(a) calculation and excludes the lowest-order calculation at 92% C.L.

[发布机构] Department of Physics, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo; 113-0033, Japan^1;International Center for Elementary Particle Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo; 113-0033, Japan^2

[效力级别] 化学

[关键词] Energy spectra;Ideal systems;Orthopositronium;Precise measurements;QED calculation;Quantum electrodynamics;Silica aerogels;Vacuum chambers