Low Energy Electron Positron Physics at Jefferson Lab

Phase-sensitive spectroscopy of n=2 positronium fine-structure intervals

Not scheduled

20m

F113 (CEBAF CENTER)

Speaker

Donovan Newson (University College London)

Description

Precise measurements of energy intervals of positronium, the bound-state of an electron and a positron, can be used to test quantum electrodynamics theory and constrain parameters related to physics not included in the framework [1]. Despite this promise current measurements of the n=2 fine-structure intervals of positronium are around an order of magnitude less precise than the corresponding calculations; limited by the significant 50 MHz natural line width of the 2P levels and frequency-dependent microwave power variations. Here we describe a new measurement using a variation of Ramsey’s methods of separated oscillatory fields and an energetic source of metastable positronium atoms [2]. We present our latest results [3] and discuss possible improvements to reach the next frontier of experimental precision in positronium spectroscopy.

[1] Precision spectroscopy of positronium: Testing bound-state QED theory and the search for physics beyond the Standard Model, G. S. Adkins, D. B. Cassidy, J. Perez-Rios, Phys. Rep. 975, 1 (2022)

[2] An energy tunable continuous 23S1 positronium beam, D. M. Newson, T. J. Babij, and D. B. Cassidy, Rev. Sci. Instrum. 94, 083201 (2023)

[3] Phase-variation Ramsey spectroscopy of the 23S1-23P2 interval in positronium, D. M. Newson and D. B. Cassidy, Phys. Rev. Lett. 136, 033001 (2026)