Direct Measurement of Positronium HyperFine Structure: ∼ A New Horizon of Precision Spectroscopy Using Gyrotrons ∼

Abstract

Positronium is an ideal system for research on QED, especially in a bound state. A discrepancy (3.9σ ) is found recently between measured HFS values and the QED prediction (including up-to O(α 3 log α −1 ), where α is the fine-structure constant.). It might be due to a contribution of unknown new physics or common systematic problems in all the previous measurements. A new method to measure HFS directly is performed using a high power gyrotron. The transition from ortho-positronium to para-positronium has been observed with 5 σ CL, which is the first observation of M1 transition in (sub)Terahertz region. New technologies of high power gyrotrons are developed for precision spectroscopy.

The Direct Spectroscopy of Positronium Hyperfine Structure Using a Sub-THz Gyrotron

“…As mentioned in Ref. [5], there are two possible uncertainties in this method. The first is due to a non-uniformity of the static magnetic field, and the second is due to the non-thermalization of positronium in gas, similar to effects seen in lifetime measurements of o-Ps [6].…”

“…However, the Fabry-Pérot resonator has a significant advantage when we consider Ps formation. A positron source is used to form Ps with an electron in a gas molecule [5]. Since the optical path of the ring cavity is split into two separate paths, positronium cannot be efficiently formed in both.…”

The Gyrotrons as Promising Radiation Sources for THz Sensing and Imaging

“…The energy splitting between o-Ps and p-Ps, i.e., the HFS is about 203.4 GHz. A significant discrepancy of 3.9 standard deviations between the measured HFS values and the theoretical prediction of the quantum electrodynamics (QED) motivated the development of a novel method for the direct and precise evaluation of HFS [73]. In contrast to the previous indirect methods (e.g., measuring the Zeeman splitting in a static magnetic field) that are prone to systematic errors, the new approach relies on a stimulated transition between o-Ps and p-Ps states induced by irradiation with Analogously to DNP-NMR, the sensitivity of the ESR spectroscopy increases significantly, advancing toward higher intensities of the magnetic field and correspondingly to higher frequencies.…”

Gyrotrons for High-Power Terahertz Science and Technology at FIR UF

“…Zeeman splitting in a static magnetic field), however, do not agree well with the theoretical predictions. The observed significant discrepancy of 3.9 (15 ppm) has motivated the development of a novel and precise technique for evaluation of the HFS [43]. It is based on a stimulated transition from o-Ps to p-Ps induced by means of irradiation by a strong electromagnetic wave with a frequency of about 203 GHz.…”