FINALIST: New Measurement of the Electron Magnetic Moment and a New Dark Photon/Axion Search

The electron’s magnetic moment in Bohr magnetons is newly determined to be g/2 = 1.001 159 652 180 59 (13)[1].

This new and most accurate determination of a property of an elementary particle was carried out to allow the most stringent test the most precise prediction of the Standard Model (SM).

The new measurement, with SM calculations, provides the fine structure constant α, with 1/ α = 137.035 999 166 (15).

This value is critical given that the only two independent measurements of this constant with comparable precision currently disagree by 5 standard deviations[2,3].

New ideas and methods to use a trapped electron as a qubit for better measurements will be discussed.

These include the use of a quantum-limited detector for QND detection, detector backaction circumvention[4], and cryogenic gas He3 NMR.

Finally, a 75-times lower limit on 0.6 meV dark photons has been set using the trapped electron as a background-free quantum detector[5].

The promising prospects of making a broad search for 0.1 to 1 meV dark photons and axions will be discussed.

[1] X. Fan, T. G. Myers, B. A. D. Sukra, G. Gabrielse, Phys. Rev. Lett. 130, 071801 (2023)

[2] L. Morel, Z. Yao, P. Cladé, and S Guellati-Khélifa Nature 588, 61 (2020).

[3] R. H. Parker, C. Yu, W. Zhong, B. Estey, H. Müller, Science 360, 191 (2018)

[4] X. Fan and G. Gabrielse, Phys. Rev. Lett. 126, 070402 (2021)

[5] X. Fan, G. Gabrielse, P. W. Graham, R. Harnik, T. G. Myers, H. Ramani, B. A. D. Sukra, S. S. Y. Wong, Y. Xiao, Phys. Rev. Lett. 129, 261801 (2023)