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تسجيل مستخدم جديدFirst direct measurement of positronium hyperfine splitting with sub-THz light
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Positronium is an ideal system for the research of the bound state QED. The hyperfine splitting of positronium (Ps-HFS, about 203 GHz) is an important observable but all previous measurements of Ps-HFS had been measured indirectly using Zeeman splitting. There might be the unknown systematic errors on the uniformity of magnetic field. We are trying to measure Ps-HFS directly using sub-THz radiation. We developed an optical system to accumulate high power (about 10 kW) radiation in a Fabry-Perot resonant cavity and observed the positronium hyperfine transition for the first time.
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Hyperfine splitting of positronium is an important parameter for particle physics. This paper gives experimental techniques and results of R&D studies of our experiment to observe direct hyperfine transition of ortho-positronium to para-positronium.
Positronium is an ideal system for the research of the QED, especially for the QED in bound state. The discrepancy of 3.9sigma is found recently between the measured HFS values and the QED prediction ($O(alpha^3)$). It might be due to the contributio
n of the unknown new physics or the systematic problems in the previous all measurements. We propose new method to measure HFS precisely and directly. A gyrotron, a novel sub-THz light source is used with a high-finesse Fabry-Perot cavity to obtain enough radiation power at 203 GHz. The present status of the optimization studies and current design of the experiment are described.
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