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Phys. Rev. Lett. 130, 071801 (2023) - Measurement of the Electron Magnetic Moment
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Measurement of the Electron Magnetic Moment

X. Fan, T.?G. Myers, B.?A.?D. Sukra, and G. Gabrielse
Phys. Rev. Lett. 130 , 071801 ? Published 13 February 2023
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Abstract

The electron magnetic moment, ? μ / μ B = g / 2 = 1.001   159  652   180  59  ( 13 ) [0.13?ppt], is determined 2.2 times more accurately than the value that stood for fourteen years. The most precisely determined property of an elementary particle tests the most precise prediction of the standard model (SM) to 1 part in 10 12 . The test would improve an order of magnitude if the uncertainty from discrepant measurements of the fine structure constant α is eliminated since the SM prediction is a function of α . The new measurement and SM theory together predict α ? 1 = 137.035  999  166  ( 15 ) [0.11?ppb] with an uncertainty 10 times smaller than the current disagreement between measured α values.

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  • Received 27 September 2022
  • Revised 7 December 2022
  • Accepted 7 December 2022

DOI: https://doi.org/10.1103/PhysRevLett.130.071801

ⓒ 2023 American Physical Society

Physics Subject Headings (PhySH)

  1. Research Areas
Quantum nondemolition measurement
  1. Properties
Magnetic moment
  1. Techniques
Cyclotron resonance Penning traps
Atomic, Molecular & Optical Particles & Fields General Physics

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Searching for New Physics with the Electron’s Magnetic Moment

Published 13 February 2023

Measurements of the magnetic moment of the electron have achieved unprecedented accuracy, showing great potential for the search for physics beyond the standard model.

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Authors & Affiliations

X. Fan 1,2,* , T.?G. Myers 2 , B.?A.?D. Sukra 2 , and G. Gabrielse 2,†

  • 1 Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
  • 2 Center for Fundamental Physics, Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208, USA

  • * xing.fan@northwestern.edu
  • † gerald.gabrielse@northwestern.edu

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Vol. 130, Iss. 7 ? 17 February 2023

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Images

  • Figure 1
    Figure 1

    This Northwestern determination (red) and our 2008 Harvard determination (blue) [ 37 ]. SM predictions (solid and open black points for slightly differing C 10 [ 40, 41 ]) are functions of discrepant α measurements [ 38, 39 ]. A ppt is 10 ? 12 .

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  • Figure 2
    Figure 2

    (a)?Cryogenic system supports a 50?mK electron trap upon a 4.2?K solenoid to provide a very stable B . (b)?Silver electrodes of a cylindrical Penning trap. (c)?Quantum spin and cyclotron energy levels used for measurement.

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  • Figure 3
    Figure 3

    Quantum jump cyclotron (a) and anomaly (b)?line shapes that are measured (points), predicted (dashed line) and fit (solid line) vs fractional drive detunings from f ? c ( 1 + ε ) and ν ? a ( 1 + ε ) (defined later in the text). (c)?A dip in Johnson noise reveals ν ? z .

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  • Figure 4
    Figure 4

    (a)?Measured g / 2 ? 1.001  159  652  180  59 before (white) and after (red) cavity-shift correction. (b)?Measurements take place in valleys of the cyclotron damping rate where spontaneous emission is inhibited.

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  • Figure 5
    Figure 5

    SM prediction of α using μ / μ B from this Northwestern measurement (red), and from our 2008 Harvard measurement (blue), with solid and open points for slightly differing C 10 [ 40, 41 ]. The α measurements (black) were made with Cs at Berkeley [ 38 ] and Rb in Paris [ 39 ]. A ppb is 10 ? 9 .

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