Speaker
Akira Ishida
(University of Tokyo (JP))
Description
Positronium (Ps) is an ideal system for precision test of bound-state Quantum Electrodynamics (QED). The hyperfine splitting (HFS) of the ground-state Ps has a discrepancy of 16 ppm (4.5 $\sigma$) between the averaged previous experimental value and the theoretical calculation with $O(\alpha^3)$ corrections. A new experiment which reduced possible systematic uncertainties, which are Ps thermalization effect and non-uniformity of magnetic field, was performed to check the discrepancy. It revealed that the Ps thermalization effect was as large as 10$\pm$2 ppm, which could have been underestimated as a systematic uncertainty in the previous experiments. Treating this effect correctly, a new independent experimental result of $203.3942 \pm 0.0016 ({\mathrm{stat.}}, 8.0~{\mathrm{ppm}}) \pm 0.0013 ({\mathrm{syst.}}, 6.4~{\mathrm{ppm}})~{\mathrm{GHz}}$ was obtained. This result is consistent with the QED prediction within 1.1 $\sigma$, whereas it disfavours the previous experimental average by 2.6 $\sigma$. It shows that the Ps thermalization effect is crucial for precision measurement of HFS. In this presentation, I will explain the details of the new experiment. Future prospects for improved precision will be also briefly discussed.
Author
Akira Ishida
(University of Tokyo (JP))
Co-authors
Akira Yamamoto
(High Energy Accelerator Research Organization (JP))
Dr
Haruo Saito
(The University of Tokyo)
Dr
Kenichi Tanaka
(High Energy Accelerator Research Organization)
Mitsuhiro Yoshida
(High Energy Research Organization)
Shoji Asai
(University of Tokyo (JP))
Tomio Kobayashi
(University of Tokyo (JP))
Dr
Toshio Namba
(The University of Tokyo)
