Speaker
Description
Positronium, a bound state composed of an electron and a positron, is a pure lepton system. Depending on the total spin, there are para-positronium (p-Ps) and ortho-positronium (o-Ps), which eventually annihilate into two photons and three photons, respectively. Due to minimal hadronic effects, experimental measurement of the continuous spectrum of three-photon annihilation of o-Ps can be used to verify the accuracy of high-order perturbation corrections in bound-state quantum electrodynamics (QED). In terms of theoretical calculations, Adkins in his two articles from 2005 [1] and 2000 [2] theoretically calculated the first-order correction O(𝛼) and the second-order correction O($𝛼^2$) of the three-photon annihilation energy spectrum of o-Ps. In 2014, an experiment at the University of Tokyo obtained a result [3,4] consistent with theoretical calculations [1], but with large uncertainties. This experiment aimed to measure the three-photon annihilation energy spectrum of o-Ps with higher experimental accuracy. At the same time, through Geant4 simulation, the theoretical energy spectrum, including O(𝛼) and O($𝛼^2$) corrections, was generated and compared with the experimental data to verify the degree of conformity. We will present the current status of simulations and experiments, as well as the future goals of research and measurements.
[1] G. S. Adkins, Analytic Evaluation of the Amplitudes for Orthopositronium Decay to Three Photons to One-Loop Order, Phys. Rev. A 72, 032501 (2005)
[2] G. S. Adkins, R.N. Fell, J Sapirstein, Order A2 Corrections to the Decay Rate of Orthopositronium, Phys. Rev. Lett. 84, 22 (2000)
[3] S. Adachi, First Verification of Higher-Order Corrections in the Energy Spectrum of Orthopositronium Decay Gamma Rays, Master Thesis, University of Tokyo (2015)
[4] S. Adachi et al., J. Phys.: Conf. Ser. 618 012007 (2015)
