Measurement of the fine-structure constant as a test of the Standard Model
By Richard H. Parker, Chenghui Yu, Weicheng Zhong, B. Estey, H. Müller. Science, 2018
855 citations recorded by the source corpus.
Refining the fine-structure constant The fine-structure constant, α, is a dimensionless constant that characterizes the strength of the electromagnetic interaction between charged elementary particles. Related by four fundamental constants, a precise determination of α allows for a test of the Standard Model of particle physics. Parker et al. used matter-wave interferometry with a cloud of cesium atoms to make the most accurate measurement of α to date. Determining the value of α to an accuracy of better than 1 part per billion provides an independent method for testing the accuracy of quantum electrodynamics and the Standard Model. It may also enable searches of the so-called “dark sector” for explanations of dark matter. Science, this issue p. 191 Atom interferometry provides a precise measurement of the fine-structure constant. Measurements of the fine-structure constant α require methods from across subfields and are thus powerful tests of the consistency of theory and experiment in physics. Using the recoil frequency of cesium-133 atoms in a matter-wave interferometer, we recorded the most accurate measurement of the fine-structure constant to date: α = 1/137.035999046(27) at 2.0 × 10−10 accuracy. Using multiphoton interactions (Bragg diffraction and Bloch oscillations), we demonstrate the largest phase (12 million radians) of any Ramsey-Bordé interferometer and control systematic effects at a level of 0.12 part per billion. Comparison with Penning trap measurements of the electron gyromagnetic anomaly ge − 2 via the Standard Model of particle physics is now limited by the uncertainty in ge − 2; a 2.5σ tension rejects dark photons as the reason for the unexplained part of the muon’s magnetic moment at a 99% confidence level. Implications for dark-sector candidates and electron substructure may be a sign of physics beyond the Standard Model that warrants further investigation.
Subfields: Atomic and Molecular Physics, and Optics, Nuclear and High Energy Physics
View Paper: https://www.semanticscholar.org/paper/324ac67c6fc93fab71d8176043fe5be21141d5d5
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Citations in the corpus
- Theory of the Anomalous Magnetic Moment of the Electron (2019, background): “The values of α currently available are from the Rb atom [48] and Cs atom [49] measurements of h / m X and are obtained as α − 1 ( Cs ) = 137.035 999 046 ( 27 ) .”
- Three-pion contribution to hadronic vacuum polarization (2019, background): “Note that for (g − 2)μ it does not matter if α is taken from (g− 2)e [97] or Cs interferometry [98], but the tension between the two at the level of 2.”
- Measurement of the anomalous precession frequency of the muon in the Fermilab Muon g−2 Experiment (2021, background): “Recent discrepancies in the measurement of the fine structure constant [8, 9] do not significantly affect the muon g − 2 prediction.”
- Dark matter, millicharges, axion and scalar particles, gauge bosons, and other new physics with LDMX (2018, background): “For electrophilic pseudoscalars and leptophilic scalars, we have also highlighted relevant parameter space that is favored by the recent anomalies in the measurements of the electron [111] and muon [7, 108–110] magnetic moments.”